bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Heterogeneous Network Edge Prediction: A Data Integration Approach to Prioritize Disease-Associated Genes 1 1,2, Daniel S. Himmelstein , Sergio E. Baranzini ∗ 1 Biological & Medical Informatics, UCSF, San Francisco, California, USA 2 Neurology, UCSF, San Francisco, California, USA ∗ E-mail: [email protected]
1 Abstract
2 The first decade of Genome Wide Association Studies (GWAS) has uncovered a wealth of disease-
3 associated variants. Two important derivations will be the translation of this information into a multiscale
4 understanding of pathogenic variants, and leveraging existing data to increase the power of existing and
5 future studies through prioritization. We explore edge prediction on heterogeneous networks—graphs
6 with multiple node and edge types—for accomplishing both tasks. First we constructed a network
7 with 18 node types—genes, diseases, tissues, pathophysiologies, and 14 MSigDB (molecular signatures
8 database) collections—and 19 edge types from high-throughput publicly-available resources. From this
9 network composed of 40,343 nodes and 1,608,168 edges, we extracted features that describe the topology
10 between specific genes and diseases. Next, we trained a model from GWAS associations and predicted the
11 probability of association between each protein-coding gene and each of 29 well-studied complex diseases.
12 The model, which achieved 132-fold enrichment in precision at 10% recall, outperformed any individ-
13 ual domain, highlighting the benefit of integrative approaches. We identified pleiotropy, transcriptional
14 signatures of perturbations, pathways, and protein interactions as fundamental mechanisms explaining
15 pathogenesis. Our method successfully predicted the results (with AUROC = 0.79) from a withheld mul-
16 tiple sclerosis (MS) GWAS despite starting with only 13 previously associated genes. Finally, we combined
17 our network predictions with statistical evidence of association to propose four novel MS genes, three
18 of which (JAK2, REL, RUNX3 ) validated on the masked GWAS. Furthermore, our predictions provide
19 biological support highlighting REL as the causal gene within its gene-rich locus. Users can browse all
20 predictions online (http://het.io). Heterogeneous network edge prediction effectively prioritized genetic
21 associations and provides a powerful new approach for data integration across multiple domains. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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22 Author Summary
23 For complex human diseases, identifying the genes harboring susceptibility variants has taken on medical
24 importance. Disease-associated genes provide clues for elucidating disease etiology, predicting disease
25 risk, and highlighting therapeutic targets. Here, we develop a method to predict whether a given gene
26 and disease are associated. To capture the multitude of biological entities underlying pathogenesis, we
27 constructed a heterogeneous network, containing multiple node and edge types. We built on a technique
28 developed for social network analysis, which embraces disparate sources of data to make predictions from
29 heterogeneous networks. Using the compendium of associations from genome-wide studies, we learned
30 the influential mechanisms underlying pathogenesis. Our findings provide a novel perspective about
31 the existence of pervasive pleiotropy across complex diseases. Furthermore, we suggest transcriptional
32 signatures of perturbations are an underutilized resource amongst prioritization approaches. For multiple
33 sclerosis, we demonstrated our ability to prioritize future studies and discover novel susceptibility genes.
34 Researchers can use these predictions to increase the statistical power of their studies, to suggest the
35 causal genes from a set of candidates, or to generate evidence-based experimental hypothesis. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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36 Introduction
37 In the last decade, genome-wide association studies (GWAS) have been established as the main strategy
38 to map genetic susceptibility in dozens of complex diseases and phenotypes. Despite the undeniable
39 success of this approach, researchers are now confronted with the challenge of maximizing the scientific
40 contribution of existing GWAS datasets, whose undertakings represented a substantial investment of
41 human and monetary resources from the community at large.
42 A central assumption in GWAS is that every region in the genome (and hence every gene) is a-
43 priori equally likely to be associated with the phenotype in question. As a result, small effect sizes and
44 multiple comparisons limit the pace of discovery. However, rational prioritization approaches may afford
45 an increase in study power while avoiding the constraints and expense related to expanded sampling. One
46 such a way forward is the current trend on analyzing the combined contribution of susceptibility variants
47 in the context of biological pathways, rather than single SNPs [1, 2]. A less explored but potentially
48 revealing strategy is the integration of diverse sources of data to build more accurate and comprehensive
49 models of disease susceptibility.
50 Several strategies have been attempted to identify the mechanisms underlying pathogenesis and use
51 these insights to prioritize genes for genetic association analyses. Gene-set enrichment analyses iden-
52 tify prevalent biological functions amongst genes contained in disease-associated loci [3]. Gene network
53 approaches search for neighborhoods of genes where disease-associated loci aggregate [4]. Literature min-
54 ing techniques aim to chronicle the relatedness of genes to identify a subset of highly-related associated
55 genes [5]. These strategies generally rely on user-provided loci as the sole input and do not incorporate
56 broader disease-specific knowledge. Typically, the proportion of genome-wide significant discoveries in a
57 given GWAS is low, thus leaving little high-confidence signal for seed-based approaches to build from.
58 To overcome this limitation, here we aimed at characterizing the ability of various information domains
59 to identify pathogenic variants across the entire compendium of complex disease associations. Using this
60 multiscale approach, we developed a framework to prioritize both existing and future GWAS analyses
61 and highlight candidate genes for further analysis.
62 To approach this problem, we resorted to a method that integrated diverse information domains
63 naturally. Heterogeneous networks are a class of networks which contain multiple types of entities (nodes)
64 and relationships (edges), and provide a data structure capable of expressing diversity in an intuitive and
65 scalable fashion. However, current techniques available for network analysis have been developed for
66 homogeneous networks and are not directly extensible to heterogenous networks. Furthermore, research
67 into heterogeneous network analysis is in its early stages [6]. One of the few existing methods for
68 predicting edges on heterogeneous networks was developed by researchers studying social sciences to
69 predict future coauthorship [7]. In this work, we extended this methodology to predict the probability
70 that an association between a gene and disease exists. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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71 Results
72 Constructing a heterogeneous network to integrate diverse information do-
73 mains
74 Using publicly-available databases and standardized vocabularies, we constructed a heterogeneous net-
75 work with 40,343 nodes and 1,608,168 edges (Figure 1). Databases were selected based on quality,
76 reusability, and throughput. The network was designed to encode entities and relationships relevant
77 to pathogenesis. The network contained 18 node types (metanodes) and 19 edge types (metaedges),
78 displayed in Figure S2A. Entities represented by metanodes consisted of diseases, genes, tissues, patho-
79 physiologies, and gene sets for 14 MSigDB collections including pathways, perturbation signatures, motifs,
80 and Gene Ontology domains (Table 1). Relationships represented by metaedges consisted of gene-disease
81 association, disease pathophysiology, disease localization, tissue-specific gene expression, protein interac-
82 tion, and gene-set membership for each MSigDB collection (Table 2).
Pathophysiologies Diseases Tissues
Genomic Positions Immunologic Genes Perturbations Oncogenic
BioCarta GO: CC
KEGG GO: MF
Reactome GO: BP Cancer miRNA Modules Targets TF Cancer Targets Hoods
Figure 1. Heterogeneous network integrates diverse information domains. We constructed a heterogeneous network with 18 metanodes (denoted with labels) and 19 metaedges (denoted by color). For each metanode, nodes are laid out circularly. Incorporating type information adds structure to a network which would otherwise appear as an undecipherable agglomeration of 40,343 nodes and 1,608,168 edges.
83 Gene-disease associations were extracted from the GWAS Catalog [8] by overlapping associations into
84 disease-specific loci. Loci were classified as low or high-confidence based on p-value and sample size of
85 the corresponding GWAS. When possible, for each loci, the most-commonly reported gene across studies
86 was designated as primary and subsequently considered responsible for the association. Additional genes bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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87 reported for the loci were considered secondary. Only high-confidence primary associations were included
88 in the network yielding 938 associations between 99 diseases and 711 genes (Figure S1 visualizes a subset
89 of these associations).
90 Features quantify the network topology between a gene and disease
91 To describe the network topology connecting a specific gene and disease, we computed 24 features, each
92 describing a different aspect of connectivity. Each feature corresponds to a type of path (metapath)
93 originating in a given source gene and terminating in a given target disease. The biological interpretation
94 of a feature derives from its metapath (Table S1), and features simply quantify the prevalence of a specific
95 metapath between any gene-disease pair. To quantify metapath prevalence, we adapted an existing
96 method originally developed for social network analysis (PathPredict) [7], and developed a new metric
97 called degree-weighted path count (DWPC, Figure S2D), which we employed in all but two features.
98 The DWPC downweights paths through high-degree nodes when computing metapath prevalence. The
99 strength of downweighting depends on a single parameter (w), which we optimized to w = 0.4 and that
100 outperformed the top metric resulting from PathPredict (Figure S3A) [7]. Two non-DWPC features were
101 included to assess the pleiotropy of the source gene and the polygenicity of the target disease. Referred
102 to as ‘path count’ features, they respectively equal the number of diseases associated with the source
103 gene and the number of genes associated with the target disease. For all features, paths with duplicate
104 nodes were excluded, and, if present, the association edge between the source gene and target disease was
105 masked.
106 Machine learning approach to predict the probability of association of gene-
107 disease pairs
108 Further analysis focused on the 29 diseases with at least ten associated genes (Table 3). The 698 high-
109 confidence primary associations of these 29 diseases were considered positives—gene-disease pairs with
110 positive experimental relationships (as defined in Methods, Figure S1). The remaining 551,823 (i.e.
111 unassociated) gene-disease pairs were considered negatives. Low-confidence or secondary associations
112 were excluded from either set. We partitioned gene-disease pairs into training (75%) and testing (25%)
113 sets and created a training network with the testing associations removed.
114 To learn the importance of each feature and model the probability of association of a given gene-disease
115 pair, we used regularized logistic regression which is designed to prevent overfitting and accurately es-
116 timate regression coefficients when models include many features. Elastic net regression is a regression
117 method that balances two regularization techniques: ridge (which performs coefficient shrinkage) and
118 lasso (which performs coefficient shrinkage and variable selection) [9]. On the training set, we optimized
119 the elastic net mixing parameter, a single parameter behind the DWPC metric, and two edge-inclusion
120 thresholds (Figure S3). While cross-validated performance was similar across elastic net mixing parame-
121 ters, ridge demonstrated the greatest consistency (Figure S3A), and thus we proceeded with logistic ridge
122 regression as the primary model for predictions. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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123 Method prioritizes associations withheld for testing
124 We extracted network-based features for gene-disease pairs from the training network and modeled the
125 training set. We next evaluated performance on the 25% of gene-disease pairs (175 positives, 137,956
126 negatives) withheld for testing. Our predictions achieved an area under the ROC curve (AUROC) of 0.83
127 (Figure 2A) demonstrating an excellent performance in retrieving hidden associations. Importantly, we
128 did not observe any significant degradation of performance from training to testing (Figure 2A), indicating
129 that our disciplined regularization approach avoided overfitting and that predictions for associations
130 included in the network were not biased by their presence in the network. Furthermore, we observed that
131 at 10% recall (the classification threshold where 10% of true positives were predicted as positives), our
132 predictions achieved 16.7% precision (the proportion of predicted positives that were correct). Since the
133 prevalence of positives in our dataset was 0.13%, the observed precision represents a 132-fold enrichment
134 over the expected probability under a uniform distribution of priors (as in GWAS).
1.0 1.0 = A B AUPRC 0.062 Prediction Threshold 0.8 0.8 0.6
0.6 0.6 Ridge 0.4 0.2 Recall 0.4 0.4 Partition (AUROC) Precision 0.2 Testing (0.829) 0.2 Training (0.810) 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 False Positive Rate Recall
Figure 2. Predicting associations withheld for testing. Performance was evaluated on 25% of gene-disease pairs withheld for testing. A) Testing and training ROC curves. At top prediction thresholds, associated gene-disease pairs are recalled at a much higher rate than unassociated pairs are incorrectly classified as positives. The testing area under the curve (AUROC) is slightly greater than the training AUROC, demonstrating the method’s lack of overfitting. Performance greatly exceeds random denoted by gray line. B) The precision-recall curve showing performance in the context of the low prevalence of associated gene-disease pairs (0.13%). Nevertheless, at top prediction thresholds, a high percentage of pairs classified as positives are truly associated. Prediction thresholds, shown as points and colored by value, align with the observed precision at that threshold.
135 Predicting associations on the complete network
136 As a next step in our analysis, we recomputed features on the complete network, which now included the
137 previously withheld testing associations. On all positives and negatives, we fit a ridge model (the primary
138 model for predictions) and a lasso model (for comparison). Standardized coefficients (Figure 3) indicate
139 the effect attributed to each feature by the models. The lasso highlighted features that captured pleiotropy bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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140 (4 features), pathways (2), transcriptional signatures of perturbations (1) and protein interactions (1).
141 Despite the parsimony of the lasso, performance was similar between models with training AUROCs of
142 0.83 (ridge) and 0.82 (lasso). However, since multiple features from a correlated group may be causal,
143 the lasso model risks oversimplifying. Ridge regression disperses an effect across a correlated group of
144 features, providing users greater flexibility when interpreting predictions. From the ridge model, we
145 predicted the probability that each protein-coding gene was associated with each analyzed disease and
146 built a webapp to display the predictions (http://het.io/disease-genes/browse).
GaDaGaD GaDlTlD
GaD (anyGaDmPmD disease) {Perturbation} {Reactome}
{Immunologic}{KEGG} GiGaD
{GO GiGiGaDProcess}
{Cancer Module} GaD {TF(any Target} gene) {Oncogenic} {BioCarta}
{miRNA Target} Method (AUROC) {GO Component}GeTlD {GO Function} ridge (0.829) GiGeTlD lasso (0.823) GeTeGaD {Positional} 2024 {Cancer Hood} Standardized Coecient
Figure 3. Feature selection identifies a parsimonious yet predictive model. Ridge and lasso models were fit from the complete network. The resulting standardized coefficients (x-axis) are plotted for each feature (y-axis). Brackets indicate features from MSigDB-traversing metapaths (Gm{}mGaD). The ridge model disperses effects amongst features whereas the lasso concentrates effects. The lasso identifies an 8-feature model with minimal performance loss compared to the ridge model. Besides KEGG, gene-set based features were largely captured by Perturbations. The lasso retains several measures of pleiotropy as well as the one-step interactome feature (GiGaD). bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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147 Degree-preserving network permutations highlight the importance of edge-
148 specificity for top predictions and ten features
149 Using Markov chain randomized edge-swaps, we created 5 permuted networks. Since metaedge-specific
150 node degree is preserved, features extracted from the permuted network retain unspecific effects. These
151 effects include general measures a disease’s polygenicity and a gene’s pleiotropy, multifunctionality, and
152 tissue-specificity. On the first permuted network, we partitioned associations into training and testing
153 sets. Testing associations were masked from the network, features were computed, and a ridge model was
154 fit on the training gene-disease pairs.
155 Compared to the unpermuted-network model, testing performance was noticeably inferior: the AU-
156 ROC declined from 0.83 (Figure 2A) to 0.79 (Figure S4A) and the AUPRC (area under the precision-recall
157 curve) declined from 0.06 (Figure 2B) to 0.02 (Figure S4B). We interpret the modest decline in AUROC
158 but marked reduction in AUPRC as a direct consequence of the permutation’s particularly detrimental
159 effect on top predictions (Figure S4C–D). In other words, edge-specificity was crucial for top predictions,
160 while general effects gleaned from node degree performed reasonably well when ranking the entire spec-
161 trum of protein-coding genes for association. A commonly-overlooked finding is that the discriminatory
162 ability of gene networks largely relies on node-degree rather than the edge-specificity [10]. However, we
163 found that for top predictions—which are the only predictions considered by many applications—edge-
164 specificity was critical.
165 Interestingly, predictions from the permuted-network model displayed a reduced dynamic range with
166 none exceeding 4%, while predictions from the unpermuted-network model exceeded 75% (Figure S4D).
167 Therefore, even though they achieve reasonable AUROC, the permuted-network predictions would have
168 little utility as prior probabilities in a bayesian analysis where dynamic range is crucial. Furthermore,
169 the signal present in permuted-network features was greatly diminished: few features survived the lasso’s
170 selection resulting in an average lasso AUROC of 0.70 versus 0.80 for ridge (Figure S5). Permuting
171 the network significantly reduced the predictiveness of features based on pleiotropy (2 features), protein
172 interactions (2), transcriptional signatures of perturbations (1), tissue-specificity (1), pathways (3), and
173 immunologic signatures (1) (Table S2). Six of the eight features selected by the lasso and eight of the
174 top ten ridge features (ranked by standardized coefficients) were negatively affected by the permutation.
175 Since our modeling technique preferentially selected/weighted features affected by permutation, we can
176 infer that network components where edge-specificity matters underlie a large portion of predictions.
177 Feature importance identifies the mechanisms underlying associations
178 We assessed the informativeness of each feature by calculating feature-specific AUROCs. Feature-specific
179 AUROCs universally exceeded 0.5, indicating that network connectivity, regardless of type, positively dis-
180 criminates associations. However, performance varied widely by feature and within feature from disease to
181 disease (Figure 4). Top performing domains consisted of transcriptional signatures of perturbations (AU-
182 ROC = 0.74), immunologic signatures (0.70), and pleiotropy (0.68, 0.67, 0.64, 0.63). Notably, the models
183 greatly outperformed any individual feature, highlighting the importance of an integrative approach.
184 Features whose metapaths originate with an association (GaD) metaedge measure pleiotropy (Ta- bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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A Gene—{MSigDB Collection}—Gene—Disease DWPC Model 1.0
0.8 — —— — — —— — AUROC 0.6 — —— — —— —— — —— —— — — —— —— —— —— —
0.4
KEGG Lasso Ridge BioCarta Positional ReactomeOncogenicTF Target GO Function GO Process ImmunologicPerturbation Cancer Hood miRNA Target GO Component Cancer Module B Degree-Weighted Path Count Path Count Model 1.0
Pathophysiology 0.8 — —— degenerative immunologic — —— — metabolic — neoplastic
AUROC — — 0.6 —— —— — —— — —— — psychiatric — — — unspecic
0.4
GiGaD GeTlD Lasso Ridge GiGeTlD GiGiGaD GaDlTlD GeTeGaD GaDaGaD GaDmPmD GaD (any gene) GaD (any disease)
Figure 4. Decomposing performance shows the superiority of the integrative model and compares individual features. Disease, feature, and model-specific performance on the complete network. The AUROC (y-axis) was calculated for each classifier (x-axis). In addition to the ridge and lasso models (rightmost panels), each feature was considered as a classifier. Line segments show the classifier’s global performance (average performance across permuted networks shown in violet as opposed to dark grey). Points indicate disease-specific performance and are colored by the disease’s pathophysiology. Grey rectangles show the 95% confidence interval for mean disease-specific performance. A) Features from metapaths that traverse an MSigDB collection. B) Features from non-MSigDB-traversing metapaths. Metapaths are abbreviated using first letters of metanodes (uppercase, Table 1) and metaedges (lowercase, Table 2). Feature descriptions are provided in Table S1. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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185 ble S1). The four pleiotropic features were among the top performing features that did not rely on
186 set-based gene categorization (Figure 4). Of the four features, GaD (any disease) had the highest AU-
187 ROC despite its lack of disease-specificity, reflecting both the sparsity of disease-specific features and
188 the existence of genetic overlap between seemingly disparate diseases. GaDmPmD and GaDaGaD per-
189 formed best for immunologic diseases and were affected by permutation, indicating that genetic overlap
190 was greatest between immunologic diseases. On the other hand, the performance of GaDlTlD did not
191 decrease after permutation indicating disease colocalization was not a primary driver of genetic overlap.
192 We also observed that the lasso regression model discarded the majority of features with a minimal
193 performance deficit, suggesting redundancy among features. Indeed, pairwise feature correlations showed
194 moderate collinearity among features (Figure S6). Collinearity was especially pervasive with respect
195 to the Perturbations feature, explaining its threefold increase in standardized coefficient in the lasso
196 versus ridge model. The disappearance of all but one other MSigDB-based feature in the lasso model
197 indicated that Perturbations—the feature traversing chemical and genetic transcriptional signatures of
198 perturbations—exhausted meaningful gene-set characterization. In other words, the faulty molecular
199 processes behind pathogenesis align with and are encapsulated by the processes perturbed by chemical
200 and genetic modifications. The Immunologic signatures feature—traversing gene-sets characterizing “cell
201 types, states, and perturbations within the immune system”—was highly predictive and correlated with
202 Perturbations. As expected this feature performed best for diseases with an immune pathophysiology.
203 The one well-performing neoplastic disease (Figure 4) was chronic lymphocytic leukemia, a hematologic
204 cancer with a strong immune component [11]. Additionally, the performance of both the Perturbation
205 and Immunologic features was affected by permutation indicating information beyond the extent of a
206 gene’s multifunctionality was encoded.
207 Existing network-based gene-prioritization methods, frequently rely solely on protein-protein inter-
208 actions. Our results supported incorporating protein interactions as the two interactome-based features
209 were discriminatory (AUROCs = 0.65, 0.56) and affected by permutation. However, when compared
210 to the integrative models or other top-performing features, performance of features that relied solely on
211 the interactome was severely limited. Pathways, another founding resource for many approaches, proved
212 important with KEGG selected by the lasso and all three pathway resources (AUROCs = 0.61 for KEGG,
213 0.60 for Reactome, 0.55 for BioCarta) affected by permutation. The GeTlD feature—measuring to what
214 extent a gene is expressed in tissues affected by the disease in question—peaked in performance around
215 AUROC = 0.58 (Figure S3B), was affected by permutation, and required no preexisting knowledge of
216 associated genes. In other words, while approaches based on tissue-specificity may have limited predictive
217 ability on their own, they are broadly applicable (i.e. less susceptible to knowledge bias) and provide
218 orthogonal information that could enhance the overall performance of a model.
219 Case study: prioritizing multiple sclerosis associations
220 The WTCCC2 multiple sclerosis (MS) GWAS tested 465,434 SNPs for 9,772 cases and 17,376 controls
221 and identified over 50 independently associated loci [12]. Since the GWAS Catalog excludes targeted
222 arrays (such as ImmunoChip), this study remains the largest MS GWAS in the Catalog. To evaluate our bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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223 method’s ability to prioritize associations identified in a future study, we masked the WTCCC2 MS study
224 from the GWAS Catalog and created a pre-WTCCC2 network. The number of high-confidence primary
225 MS associations was thus reduced from 50 to 13, with the 37 novel genes identified by WTCCC2 available
226 to evaluate performance. On the pre-WTCCC2 network, we extracted features, fit a ridge model, and
227 predicted each gene’s probability of association with MS. Amongst all 18,993 potentially novel genes, the
228 37 WTCCC2 genes were ranked highly (AUROC = 0.79, Figure 5).
1.0 IL12B = A B CD40 AUPRC 0.05 Prediction IL7R MAPK1 Threshold 0.8 0.4 BACH2 TNFSF14 ZFP36L1 NFKBIZ 0.25 CLEC16A MALT1 right aligned 0.20 ZMIZ1 IL22RA2 0.6 GPR65 left aligned MERTK 0.15 SP140 BATF TAGAP CYP27B1 0.10 MYC AHI1 Recall 0.4 0.2 C1orf106 SLC30A7 0.05
Precision CD86 EVI5 RGS1 CYP24A1 PLEK TIMMDC1 DKKL1 0.2 HHEX DSC1 ZNF767 PTPRK OLIG3 ODF3B AUROC = 0.789 MPV17L2 CLECL1 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 False Positive Rate Recall
Figure 5. Prioritizing multiple sclerosis associations identified by a masked GWAS. From a network with the WTCCC2 MS associations omitted, we predicted probabilities of association for all potentially novel genes. The 37 novel genes identified by the WTCCC2 GWAS were considered positives, and the resulting performance was plotted. The ROC (A) and precision-recall (B) curves show performance, with AUCs in line with the testing performance across all diseases (Figure 2). A prediction threshold (black cross) that resulted in high performance was selected as the discovery threshold for further analysis. As the classification threshold decreases along the precision-recall curve, the advent of each true positive is denoted by its gene symbol.
229 Prioritizing statistical candidates with network-based predictions identifies
230 novel multiple sclerosis genes
231 Finally, we designed a framework for discovering and validating novel MS genes that incorporates our
232 network-based predictions. Meta2.5 is a meta-analysis of all MS GWAS prior to the WTCCC2 study [13].
233 We calculated genewise p-values for Meta2.5 using VEGAS [14] and observed a large enrichment in nom-
234 inally significant (p < 0.05) genes, suggesting multiple potential associations (Figure S8). We combined
235 this set of experimental candidates with the top predictions from the pre-WTCCC2 network to discover
236 genes with both strong statistical and biological evidence of association. To ensure novelty, we excluded
237 genes from GWAS-established MS loci and the extended MHC region. We chose a threshold (Table S3) for
238 network-based predictions that performed well in prioritizing the genes identified by WTCCC2 (Figure 5).
239 This strategy discovered four genes, three of which—JAK2, REL, RUNX3 —achieved Bonferroni
240 validation on VEGAS-converted WTCCC2 p-values (Table 4). The probability of the observed validation
241 rate occurring under random prioritization is 0.01 (Table S3), demonstrating that incorporating our bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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242 network-based predictions as a prior increased study power. JAK2 displays overexpression in MS-affected
243 Th17 cells [15] and was implicated in an interactome-based prioritization of GWAS [2]. RUNX3, a
244 transcription factor influencing T lymphocyte development, has been associated with celiac disease [16]
245 and ankylosing spondylitis [17] and was hypermethylated in systemic lupus erythematosus patients [18].
246 The region containing REL was uncovered in a recent MS ImmunoChip-based study with 14,498 cases [19,
247 p. S40]. For the gene-dense region containing REL, the ImmunoChip study reported a long non-coding
248 RNA, LINC01185, overlapping the lead-SNP, rs842639. However, since greater than 80% of the genome
249 shows evidence of transcription [20], the probability of incidental overlap with long non-coding RNA is
250 high. REL, however, is an essential transcription factor for lymphocyte development [21] and plays a
251 critical role in autoimmune inflammation [22]. Hence, gene prioritization through integrative analyses
252 offers not only to streamline loci discovery but also subsequent causal gene identification.
253 Discussion
254 In this work, we developed a framework to predict the probability that each protein-coding gene is asso-
255 ciated with each of 29 complex diseases. Our predictions draw on a diverse set of pathogenically-relevant
256 relationships encoded in a heterogeneous network. The predictions successfully prioritized associations
257 hidden from the network. Using MS as a representative example, we were able to combine our predic-
258 tions with statistical evidence of association to increase study power and identify three novel susceptibility
259 genes in this disease. The disease-specific performance (measured by the AUROC) for MS was exceeded
260 by twelve other diseases suggesting that our predictions have broad applicability for prioritizing genetic
261 association analyses. Prioritization can range from a genome-wide scale to a single loci where this ap-
262 proach can highlight the causal gene from several candidates within the same association block. For
263 researchers focused on a specific disease, these predictions can be used to propose genes for experimental
264 investigation. Inversely, researchers focused on a specific gene can use this resource to find suggestions
265 for relevant complex disease phenotypes.
266 Most previous explorations of the factors underlying pathogenicity have focused on a single domain
267 such as tissue-specificity [23], protein interactions [24], pathways [1], or disease similarity [25]. The method
268 presented here integrates disparate data sources, learns their importance, and unifies them under a com-
269 mon framework enabling comparison. Therefore, we can conclude that perturbation gene sets—the core of
270 our top-performing feature—are an underutilized resource for disease-associated gene prioritization. Not
271 only did perturbations encompass other set-based gene categorizations, but they greatly outperformed
272 features based on protein interactions, pathways, and tissue-specificity, which form the basis of several
273 prominent prioritization techniques. In addition to characterizing the overall importance of each feature,
274 our online prediction browser visually decomposes an individual prediction into its components.
275 We observed a prominent influence of pleiotropy, consistent with previous studies that identified perva-
276 sive overlap of susceptibility loci across complex diseases [26], especially those of autoimmune nature [27].
277 Since many existing prioritization techniques are agnostic to the compendia of GWAS associations, they
278 fail to adequately leverage pleiotropy. Unlike approaches initiated from a user-provided gene list, our
279 study only provides predictions for 29 diseases. By not relying on user-provided input, our predictions bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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280 can serve as independent priors for future analyses. By predicting probabilities, we provide an extensi-
281 ble and interpretable assessment of association that circumvents the limitations inherent to frequentist
282 analyses [28]. Many approaches return no assessment for the majority of genes which fall outside of their
283 set of predicted positives. Here, we overcome this issue and provide a comprehensive and genome-wide
284 output by returning a probability of association for each protein-coding gene.
285 High-throughput biological data is frequently noisy and incomplete [29]. Combining orthogonal re-
286 sources can help overcome these issues. Accordingly, we found that our integrative model outperformed
287 any individual domain. While this method has shown encouraging performance, some limitations are
288 worth noticing. For example, many biological networks preferentially cover well-studied vicinities [30].
289 Knowledge biases that span multiple presumably-orthogonal resources could diminish the benefits of
290 integration. Here, several of the literature-derived domains were removed by the lasso suggesting redun-
291 dancy. Biases in network completeness can also lead to high-quality predictions for well-studied vicinities
292 and low-quality predictions for poorly-studied vicinities. The permutation analysis provided evidence
293 of this disparity: edge-specificity was critical for top predictions yet only moderately beneficial for the
294 remainder of predictions. Subsequently, we caution users to avoid overinterpreting predictions for poorly-
295 characterized genes. To help place predictions in context, the online browser provides a gene’s mean
296 prediction across all diseases and a disease’s mean prediction across all genes. As more systematic and
297 unbiased resources become available [29], high-quality predictions will be possible for a higher percentage
298 of network vicinities.
299 We reason that the desirable qualities of our predictions are the consequence of the heterogenous
300 network edge prediction methodology. The approach is versatile (most biological phenomena are decom-
301 posable into entities connected by relationships), scalable (no theoretical limit to metagraph complexity
302 or graph size), and efficient (low marginal cost to including an additional network component). We have
303 extended the previous metapath-based framework set forth by PathPredict [7], by: 1) incorporating reg-
304 ularization allowing coefficient estimation for more features without overfitting; 2) designing a framework
305 for predicting a metaedge that is included in the network; 3) developing an improved metric for assessing
306 path specificity; and 4) implementing a degree-preserving permutation. Metapath-based heterogeneous
307 network edge prediction provides a powerful new platform for bioinformatic discovery.
308 Methods
309 Heterogeneous networks
310 We created a general framework and open source software package for representing heterogeneous net-
311 works. Like traditional graphs, heterogeneous networks consist of nodes connected by edges, except that
312 an additional meta layer defines type. Node type signifies the kind of entity encoded, whereas edge type
313 signifies the kind of relationship encoded. Edge types are comprised of a source node type, target node
314 type, kind (to differentiate between multiple edge types connecting the same node types), and direction
315 (allowing for both directed and undirected edge types). The user defines these types and annotates each
316 node and edge, upon creation, with its corresponding type. The meta layer itself can be represented as bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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317 a graph consisting of node types connected by edge types. When referring to this graph of types, we use
318 the prefix ‘meta’. Metagraphs—called schemas in previous work [6, 7]—consist of metanodes connected
319 by metaedges. In a heterogeneous network, each path, a series of edges with common intermediary nodes,
320 corresponds to a metapath representing the type of path. A path’s metapath is the series of metaedges
321 corresponding to that path’s edges. The possible metapaths within a heterogeneous network can be
322 enumerated by traversing the metagraph. We implemented this framework as an object-oriented data
323 structure in python and named the resulting package hetio. Users are free to browse, use, or contribute
324 to the software, through the online repository (http://github.com/dhimmel/hetio).
325 Network construction
326 Protein-coding genes were extracted from the HGNC database [31]. Resources were mapped to HGNC
327 terms via gene symbol (ambiguous symbols were resolved in the order: approved, previous, synonyms)
328 or Entrez identifiers. Disease nodes were taken from the Disease Ontology (DO) [32]. Due to the limited
329 number of diseases with GWAS, relevant disease references were manually mapped to the DO. Tissues
330 were taken from the BRENDA Tissue Ontology (BTO) [33]. Only tissues with profiled expression were
331 included enabling manual mapping. Nodes for the 14 MSigDB metanodes were directly imported from the
332 Molecular Signature Database version 4.0 [34]. MSigDB collections that were supersets of other collections
333 were excluded. Diseases were classified manually into 10 categories according to pathophysiology. The
334 ‘idiopathic’ and ‘unspecific’ categories were not included as pathophysiology nodes, since they do not
335 signify meaningful similarities between member diseases.
336 Association processing
337 Disease-gene associations were extracted from the GWAS Catalog [8], a compilation of GWAS associa- 5 338 tions where p < 10− . First, associations were segregated by disease. GWAS Catalog phenotypes were
339 converted to Experimental Factor Ontology (EFO) terms using mappings produced by the European
340 Bioinformatics Institute. Associations mapping to multiple EFO terms were excluded to eliminate cross-
341 phenotype studies. We manually mapped EFO to DO terms (now included in the DO as cross-references)
342 and annotated each DO term with its associations.
343 Associations were classified as either high or low-confidence, where exceeding two thresholds granted 8 344 high-confidence status. First, p ≤ 5 × 10− corresponding to p ≤ 0.05 after Bonferroni adjustment for
345 one million comparisons (an approximate upper bound for the number of independent SNPs evaluated by
346 most GWAS). Second, a minimum sample size (counting both cases and controls) of 1,000 was required,
347 since studies below this size are underpowered [35]—i.e. any discovered associations are more likely than
348 not to be false—for the majority of true effect size distributions commonly assumed to underlie complex
349 disease etiology [28].
350 Lead-SNP were assigned windows—regions wherein the causal SNPs are assumed to lie—retrieved
351 from the DAPPLE server [4]. Windows were calculated for each lead-SNP by finding the furthest upstream 2 352 and downstream SNPs where r > 0.5 and extending outwards to the next recombination hotspot.
353 Associations were ordered by confidence, sorting on following criteria: high/low confidence, p-value (low bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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354 to high), and recency. In order of confidence, associations were overlapped by their windows into disease-
355 specific loci. By organizing associations into loci, associations from multiple studies tagging the same
356 underlying signal were condensed. A locus was classified as high-confidence if any of its composite
357 associations were high-confidence and low-confidence otherwise.
358 For each disease-specific loci, we attempted to identify a primary gene. The primary gene was resolved
359 in the following order: 1) the mode author-reported gene; 2) the containing gene for an intragenic lead-
360 SNP; 3) the mode author-reported gene for an intragenic lead-SNP (in the case of overlapping genes); 4)
361 the mode author-reported gene of the most proximal up and downstream genes. Steps 2–4 were repeated
362 on each association composing the loci, in order of confidence, until a single gene resolved as primary.
363 Loci where ambiguity was unresolvable or where no genes were returned did not receive a primary gene.
364 All non-primary genes—genes that were author-reported, overlapping the lead-SNP, or immediately up
365 or downstream from the lead-SNP—were considered secondary.
366 Accordingly, four categories of processed associations were created: high-confidence primary, high-
367 confidence secondary, low-confidence primary, and low-confidence secondary. We assume that our pri-
368 mary gene annotation for each loci represents the single causal gene responsible for the association. To
369 investigate the validity of this assumption, we evaluated the performance of our predictions separately
370 using each category of association as positives (Figure S7). For both confidence levels, primary associa-
371 tions outperformed secondary associations suggesting our method succeeded at categorizing causal genes
372 as primary. However, for high-confidence secondary associations, the AUROC equaled 0.74, which could
373 result from multiple causal genes per loci or categorizing sole causal genes as secondary. The perfor-
374 mance decline from high to low confidence associations was severe, pointing to a preponderance of falsely 8 375 identified loci in the GWAS Catalog when p > 5 × 10− or sample size drops below 1000.
376 Protein interactions
377 Physical protein-protein interactions were extracted from iRefIndex 12.0, a compilation of 15 primary
378 interaction databases [36]. The iRefIndex was processed with ppiTrim to convert proteins to genes,
379 remove protein complexes, and condense duplicated entries [37].
380 Tissue-specific gene expression
381 Tissue-specific gene expression levels were extracted from the GNF Gene Expression Atlas [38]. Starting
382 with the GCRMA-normalized and multisample-averaged expression values, 44,775 probes were converted
383 to 16,466 HGNC genes and 84 tissues were manually mapped and converted to 77 BTO terms. For both
384 conversions, the geometric mean was used to average expression values. The log base 10 of expression
385 value was used as the threshold criteria for GeT edge inclusion.
386 Disease localization
387 Disease localization was calculated for the 77 tissues with expression profiles. Literature co-occurrence
388 was used to assess whether a tissue is affected by a disease. We used CoPub 5.0 to extract R-scaled
389 scores between tissues and diseases measuring whether two terms occurred together in Medline abstracts bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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390 more than would be expected by chance [39]. DO terms for diseases with GWAS and BTO tissues with
391 expression profiles were manually mapped to the ‘biological identifier’ terminology used by CoPub. The
392 R-scaled score was used as the threshold criteria for TlD edge inclusion.
393 Feature computation metrics
394 The simplest metapath-based metric is path count (PC ): the number of paths, of a specified metapath,
395 between a source and target node. However, PC does not adjust for the extent of graph connectivity
396 along the path. Paths traversing high-degree nodes will account for a large portion of the PC, despite
397 high-degree nodes frequently representing a biologically broad or vague entity with little informativeness.
398 The previous work evaluated several metrics that include a PC denominator to adjust for connectivity and
399 reported that normalized path count (NPC ) performed best [7]. The denominator for NPC equals the
400 number of paths from the source to any target plus the number of paths from any target to the source. We
401 adopt the any source/target concept to compute the two GaD features. However, dividing the PC by a
402 denominator is flawed because each path composing the PC deserves a distinct degree adjustment. If two
403 paths—one traversing only high-degree nodes and one traversing only low-degree nodes—compose the PC,
404 the network surrounding the high-degree path will monopolize the NPC denominator and overwhelm the
405 contribution of the low-degree path despite its specificity. Therefore, we developed the degree-weighted
406 path count (DWPC ) which individually downweights each path between a source and target node. Each
407 path receives a path-degree product (PDP) calculated by: 1) extracting all metaedge-specific degrees
408 along the path (each edge composing the path contributes two degrees); 2) raising each degree to the
409 −w power, where w ≥ 0 and is called the damping exponent; 3) multiplying all exponentiated degrees
410 to yield the PDP. The DWPC equals the sum of PDPs. See Figure S2C–D for a visual and algebraic
411 description of the DWPC.
412 Machine learning approach
413 Regularized logistic regression requires a parameter, λ, setting the strength of regularization. We op-
414 timized λ separately for each model fit. Using 10-fold cross-validation and the “one-standard-error”
415 rule to choose the optimal λ from deviance, we adopted a conservative approach designed to prevent
416 overfitting [40].
417 On the training set of gene-disease pairs, we optimized the elastic net mixing parameter (α), the
418 DWPC damping exponent (w), and two edge inclusion thresholds. First, we optimized α and w on the
419 20 features whose metapaths did not include threshold-dependent metaedges. For each combination of α
420 and w, we calculated average testing AUROC using 20-fold cross-validation repeated for 10 randomized
421 partitionings. After setting α and w (Figure S3A), we jointly optimized the two edge-inclusion thresholds
422 using the AUROC for the GeTlD feature, whose metapath is composed from the two edges requiring
423 thresholds (Figure S3B). bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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424 Degree-preserving permutation
425 Starting from the complete network, a permuted network was created by swapping edges separately for
426 each metaedge. Edge swaps were performed by switching the target nodes for two randomly selecting
427 edges [41]. For each metaedge, the number of attempted swaps was ten times the corresponding edge
428 count. We adopted a Markov Chain strategy where additional rounds of permutation were initiated from
429 the most-recently permuted network [41]. A training network was generated from the first permuted
430 network by masking 25% of the associations for testing. Testing performance for the permuted training
431 network model is shown by Figure S4. When contrasting this performance with the unpermuted-network
432 model, we employed the Condensed-ROC curve to magnify the importance of top predictions [42]. Using
433 the exponential transformation with a magnification factor of 460—the value which maps a FPR of 0.01 to
434 0.99—we concentrated on the top 1% of predictions (Figure S4C). A one-sided unpaired DeLong test [43]
435 was used to assess whether feature-specific AUROCs from the complete network exceeded those from the
436 first permuted network (Table S2).
437 Multiple sclerosis gene discovery
438 We excluded 588 genes from the discovery phase of the multiple sclerosis analysis. First we excluded
439 genes in the extended MHC region (spanning from SCGN to SYNGAP1 on chromosome 6 [44]) due
440 to the complex pattern of linkage characterizing this region containing several highly-penetrant MS-risk
441 alleles [12]. Second, we excluded putative MS genes: high-confidence primary genes from the GWAS
442 Catalog and reported genes for the WTCCC2-replicated loci. We omitted genes in linkage disequilibrium
443 with the putative genes by excluding: 1) consecutive sequences of nominally significant genes (using the
444 WTCCC2-VEGAS p-values) that included a putative gene; and 2) high-confidence secondary genes from
445 the GWAS catalog. Post exclusion, 1211 genes were nominally significant in Meta2.5, four of which
446 exceeded the network-based discovery threshold. Using a hypergeometric test for overrepresentation, we
447 calculated the probability of randomly selecting 4 of the 1211 genes and Bonferroni validating at least 3
448 of the 4 on WTCCC2 (Table S3).
449 Data availability
450 See Datasets S1–10 for the supporting data. The website provides additional resources (http://het.io/disease-
451 genes/downloads/) as well as an interface for browsing results (http://het.io/disease-genes/browse/).
452 Project related code is available from the github repository (http://github.com/dhimmel/hetio).
453 Ethics Statement
454 This study was approved by the UCSF institutional review board on human subjects under protocol
455 #10-00104. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Supporting Figure Legends
Gene—{MSigDB Collection}—Gene—Disease DWPC Model
CLNK CHRNA3 DDX6 1.0 BPTF TP63 HLA-A MPC2 TCF4 UBASH3A TOB2 MIPEP TYR TRAF1 PADI4 BAG6 ANXA3 CSMD1 TSPAN18 CASP7 KIF21B XXYLT1 ANO6 LMAN2L CCDC68 RERE CD44 MICA PPM1M IL13 NFKBIE CCL21 ZSWIM6 PRSS16 PSMG1 ANK3 VTI1A SLA EDIL3 MAD1L1 RBPJ NT5C2 GZMB C5orf30 Gene—{MSigDB Collection}—Gene—Disease DWPC Model NOS2 B3GNT2 CD83 AIRE BTNL2 PDE2A PALB2 NKAPL REL ERAP1 DPYD RUNX3 HLA-G NCAN lung carcinoma ARHGAP31 AFF3 1.0 vitiligo SPRED2 FBXL19 IL23A TRIM26 FCRL3 CCR1 bipolar disorder CACNA1C NRGN schizophrenia — PLD4 0.8 CSF2 — FLG TG LPP rheumatoid C6orf15 NFKBIA ankylosing TRANK1 — CARD11 RNASET2 arthritis LSM1 spondylitis CCR4 GLB1 OVOL1 RBM45 LCE3D IL18RAP ACTL9 TSHR BLK PTGFR TRAF3IP2 SLAMF6 ARID5B DRAM1 GPSM3 HLA-DQA1 TNFAIP3 DGKH KIF3A SLC15A4 — KIAA1109 MTMR3 TENM4 MUC22 psoriasis TNIP1 MMEL1 LAMP3 IFIH1 UBE2E3 SH2B3 ITGAM — — CCDC80 MST1 ETS1 AFF1 WDFY4 — Graves' disease SLC43A3 ICOS ANKRD55 LMO7 —— ITPR3 0.8 EFR3B — CTLA4 atopic dermatitis SLC22A23 VPS53 celiac disease CTSH — MUC19 PTPN22 TNXB AUROC MSMB FADS1 RBX1 COBL TNFSF4 —— PICALM KLK3 C1QTNF6 CD69 systemic lupus 0.6 —— CR1 — MLPH — CCR6 PTPN2 — erythematosus — CPEB4 ERBB3 BIK — KCNN3 SLAIN2 SBSPON TNFSF18 IL2RA UBE2L3 FOSL2 — CD2AP IKZF1 APOE ABCA7 CLU SLC22A3 RASGRP3 — — — EBF2 LMTK2 FUT2 IL2 — — — C11orf30 — PDLIM5 RAD23B NOD2 TYK2 BACH2 CD40 — HLA-DQA2 — TNFSF11 CAPSL — MMP7 LILRA3 TERT SLCO6A1 C5orf56 — SORL1 RGS17 DNMT3A UHRF1BP1 — PHRF1 MS4A6A — EPHA1 HLA-DRB1 SIRPG — —— RFX6 PRDX5 — — IKZF4 IL23R ORMDL3 HLA-B IL27 — EHBP1 type 1 diabetes AFM UBE2D1 VAMP3 mellitus HIP1 ZBTB38 NOTCH4 ZGPAT PTPRK RNLS PRKCQ
AUROC BIN1 Alzheimer's prostate KSR1 IL12B SKAP2 TAGAP — —— ITGA6 INS 0.6 — disease SIDT1 — carcinoma HLA-C Crohn's disease IRF5 CD226 — TBX5 ADAM30 — CENPW — ZNF365 ATG16L1 CD80 — — ZFP36L1 CD33 ITLN1 MDM4 ICOSLG CD86 0.4 — — GRHL1 PUS10 RGS1 — — AHI1 — TRIM8 — CLN3 IL12A EVI5 OLIG3 STAT4 — — ARMC2 IRGM STAT3 — MKL1 ELL IFNGR2 TBC1D1 PLEK CBLB IL10 — COX11 LACC1 — — MAP3K1 — SLC22A1 ZNF767 — PAX9 NKX2-3 NKX3-1 CCHCR1 ZMIZ1 CLEC16A CLECL1 GPR65 DENND1B TMEM18 CDYL2 ERAP2 TNFSF14 POC5 TAB2 OLFM4 MTHFD1L ITPR1 ABO LPIN2 TMEM17 CARD9 PTGER4 TET2 EBF1 SMAD3 ADCY9 multiple CD6 TNFRSF1A CCDC88C TNFSF15 SLC30A7 IL2RB JAK2 DKKL1 SP140 TIMMDC1 sclerosis TFAP2B GPRC5B KCNN4 PDE4D SCAMP3 GNAT2 MC4R TRIM66 MALT1 ESR1 SLC4A7 DSC1 IL22RA2 Lasso Ridge LSP1 MPV17L2 0.4 PTHLH DAP THADA IRF8 KEGG PRKD2 NCAM2 RPTOR FGFR2 ETV5 BABAM1 MAPK1 ELMO1 BioCarta breast carcinoma ulcerative colitis EOMES RALY ARHGEF5 CDKAL1 IL7R Positional TF Target FARP2 C1orf106 ODF3B ReactomeOncogenic MAP2K5 HNF4A GLIS3 ZZZ3 HS6ST3 HNF4G asthma primary biliary CXCR5 GO Process Perturbation HNF1B IL26 GO Function Immunologic NRIP1 ADAM29 MERTK CD58 TAB1 Cancer Hood obesity FAM46A GSDMB GNA12 cirrhosis miRNA Target LRRC32 FANCL HLA-DRB5 CCNY Cancer ModuleSH2B1 SEC16B PSRC1 IL17REL GO Component NTN4 CDCA7 CYP24A1 SPIB TGFBR2 CHST9 CCND1 IL33 GPR35 ITGAL PEX14 NFKB1 NFKBIZ PEMT IL1RL1 MYC IKZF3 GUCY1A3 FCGR2A ADCY3 HLA-DOA MAML2 HHEX DLD LYPLAL1Lasso Ridge PYHIN1 PROCR CYP27B1 KEGG LGR6 MRPS30 BATF TOX3 CRB1 GCKR GNPDA2 MRPS6 DNAJC1 NXPE1 MLANA PLCL2 Degree-Weighted Path Count Path Count Model HHIPL1 IL6R SFMBT1 RPS6KA4 HLA-DQB1 BioCarta NRXN3 TSLP IL1R2 PLCL1 C5orf66 Positional TF Target HOXB5 SLC30A8 ReactomeOncogenic BDNF ERBB4 USP12 PPAP2B TCF7L2 NEGR1 C6orf10 ARAP1 ZFP90 IL12RB2 1.0 BCAP29 coronary artery OTUD3 TNFAIP2 GO Process Perturbation KCNK16 Cancer Hood GO Function Immunologic PAX4 NR5A2 disease SHISA6 miRNA Target IRS1 ANKS1A PTPRD RASGRF1 Cancer Module FTO RAD51B GO Component MMP16 BMP2 ATP2B1 C2CD4B KCNJ2 chronic lymphocytic PRSS56 migraine PDGFD TP53INP1 ZFAND6 type 2 diabetes leukemia LEF1 GJD2 LAMA2 ZBED3 TCF21 MIA3 mellitus CDKN2B CYP26A1 PRDM16 ZC3HC1 Degree-Weighted Path Count Path Count Model RASGRP1 ZFAND3 TSPAN2 PHACTR1 CXCL12 MRAS PPARG PMAIP1 PSMD6 CASP8 TOX PathophysiologyCNNM2 OAS1 KIAA1462 RDH5 LIPA LAMA1 CPQ ALDH2 1.0 AJAP1 SRR RND3 C6orf57 PCCA LRP1 RPLP1 refractive error UBE2Z FAS GRAMD1B KCNQ5 PRC1 HMGA2 TRPM8 LPA ZNF259 ACOXL — KCNQ1 CDC123 0.8 FHL5 degenerativeADAMTS7 TJP2 —MEF2D BCL11A FAM47E MYL2 NXN IRF4 — ANK1 JAZF1 TSPAN32 BCL2 SUGCT HMG20A KCNJ11 CACNA1D ASTN2 AP3S2 PEPD MYO1D ZMAT4 immunologic metabolic SPRY2 SLC16A8 GRK5 HNF1A LRRK2 HLA-DRA syndrome X MTNR1B age related macular PTPRR GRB14 GRIA4 RBFOX1 BICC1 TOMM40 IGF2BP2 degeneration Pathophysiology KLF14 APOC1 — metabolic RBMS1 RORB Parkinson's GCK SLC41A1 — HECTD4 COL10A1 — — disease — G6PC2 MICB — GAK 0.8 degenerative neoplastic CFI — TIMP3 IER3 AUROC — — — EDC4 — — ABCA1 SMEK2 CETP VEGFA —— — WNT3 0.6 MAPT — GALNT2 CFB REST — COL8A1 ARMS2 immunologic psychiatric MCCC1 APOB LPL LIPC NR1H3 ADAMTS9 BST1 CFH SNCA — — TNFRSF10A RIT2 — C3 — DGKQ — — —— —— — metabolic unspecic — neoplastic
AUROC — — 0.6 —— —— — —— Figure S1. Bipartite network of gene-disease associations. Gene-disease associations were ——0.4— psychiatric — — — extractedunspeci fromc the GWAS Catalog. Here we show the 698 high-confidence primary associations for the — 29 diseases with at least 10 associations. Diseases (large nodes) and their incident edges are colored according to disease pathophysiology. The network highlights pervasive pleiotropy as well as the overlap 0.4 GiGaD GeTlD Lasso Ridge GiGeTlD GiGiGaD GaDlTlD of susceptibility genes among autoimmune diseases. GeTeGaD GaDaGaD GaDmPmD GaD (any gene) GaD (any disease) GiGaD GeTlD Lasso Ridge GiGeTlD GiGiGaD GaDlTlD GeTeGaD GaDaGaD GaDmPmD GaD (any gene) GaD (any disease) bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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A MetaGraph C Graph Subset
Tissue STAT3 Lung localization Leukocyte association
tio association rac n e xpression t e n i Crohn’s association Gene Disease Disease
localization
m Multiple
embership expression Sclerosis
association
MSigDB embership Collection m IRF1 interaction association Patho- physiology CXCR4 IRF8 IL2RA B SUMO1 ITCH interaction G a D D MetaPaths metapath paths path degree degree weighted G e T l D D product path count l
G i G a D 2 1 1 1 Multiple
T 0.707 IRF1 Leukocyte Sclerosis 0.707
G i G i G a D e metaedge-specific degrees G G a D a G a D 4 1 1 4 IRF1 IL2RA Multiple 0.25 G a D m P m D D Sclerosis a G a D l T l D 4 1 1 4 Multiple G IRF1 IRF8 Sclerosis 0.25 0.677
G e T e G a D i 4 2 1 4 G Multiple IRF1 CXCR4 Sclerosis 0.177 G m M m G a D G m M m G a D G m M m G a D G m M m G a D G m M m G a D PDP(path)= DWPC(metapath)= G m M m G a D G m M m G a D w G m M m G a D d PDP(path)
d Dpath path Paths 2Y X2 Figure S2. Heterogeneous network edge prediction methodology. A) We constructed the network according to a schema, called a metagraph, which is composed of metanodes (node types) and metaedges (edge types). B) The network topology connecting a gene and disease node is measured along metapaths (types of paths). Starting on Gene and ending on Disease, all metapaths length three or less are computed by traversing the metagraph. C) A hypothetical graph subset showing select nodes and edges surrounding IRF1 and multiple sclerosis. To characterize this relationship, features are computed that measure the prevalence of a specific metapath between IRF1 and multiple sclerosis. D) Two features (for the GeTlD and GiGaD metapaths) are calculated to describe the relationship between IRF1 and multiple sclerosis. The metric underlying the features is degree-weighted path count (DWPC ). First, for the specified metapath, all paths are extracted from the network. Next, each path receives a path-degree product measuring its specificity (calculated from node-degrees along the path, Dpath). This step requires a damping exponent (here w = 0.5), which adjusts how severely high-degree paths are downweighted. Finally, the path-degree products are summed to produce the DWPC. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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A α = 0 (ridge) α = 0.2 (elastic net) α = 0.4 (elastic net) B ● ● ● ● AUROC ● ● ● ● ● ● ● C ● ● ● ● 40 0.80 ● ● ● ● ● ● ● O 0.58 ● ●
R 0.78 ● U ● 0.54 A 0.76 ● 30 V
C 0.50 α = 0.6 (elastic net) α = 0.8 (elastic net) α = 1 (lasso) d l ● ● ● ● ● ● ● o ● ● ● ● ● ● f ● ●
0.80 ● ● ● ● ● ● 20
20 0.78 ● ● ● ×
0.76 Localization Threshold ● ● 10 ● 10 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 0.1 0.3 0.5 0.7 1 2 3 4 DWPC Exponent Expression Threshold
Figure S3. Parameter optimization. Using the training network, optimal parameter values (yellow dashed lines) were chosen. A) Using average cross-validated AUROC to assess performance, six elastic net mixing parameters were evaluated. For each mixing parameter value α, 10 feature metrics were evaluated: the DWPC for 9 weighting exponents (w, magenta with a 99.99% loess confidence band) and the NPC (violet with a 99.99% confidence interval). The DWPC with w = 0.4 outperformed the NPC, the best metric from previous work, as well as the path count which equals the DWPC when w = 0. Performance variability was minimized when α = 0. B) Edge-inclusion thresholds for two metaedges were jointly optimized. Expression threshold refers to the minimum microarray intensity required for a tissue-specific expression (GeT ) edge. Localization threshold refers to the minimum literature co-occurrence score required for a disease localization (TlD) edge. Treating the DWPC (w = 0.4) for the GeTlD metapath as a classifier, the AUROC was calculated at each pairwise threshold combination. The optimal thresholds were chosen as the center of a stable, high-performing, and computationally-feasible section of the solution space. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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1.0 1.0 = A B AUPRC 0.019 Prediction Threshold 0.8 0.8 0.04 Permuted Ridge 0.03 0.6 0.6 0.02
Recall 0.4 0.4 0.01 Partition (AUROC) Precision 0.2 Testing (0.787) 0.2 Training (0.779) 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 False Positive Rate Recall
0.5 Permuted Ridge Ridge C Method (AUCROC) D 3.0 Ridge (0.153) 0.4 Perm. Ridge (0.087) 0.15
0.3 0.10
Recall 0.2 0.05 1.2 Percent Positive Percent 2.2 1.6 0.1 1.2 1.2 1.4 1.2 0.00 0.6 1.1
0.0 0.102–0.110.11–0.117 0.638–3.62 0.143–0.160.16–0.233 0.847–3.083.08–75.2 0.0 0.2 0.4 0.6 0.8 1.0 0.117–0.1270.127–0.1360.136–0.1440.144–0.1670.167–0.2480.248–0.4240.424–0.6380.0892–0.1020.102–0.1110.111–0.1260.126–0.143 0.233–0.3430.343–0.847 Transformed FPR Prediction (%) Quantile
Figure S4. Performance of the degree-preserving permutation. Testing performance is contrasted between ridge models for the permuted-network and unpermuted-network. A) Testing and training ROC curves for the permuted-network model. B) Testing precision-recall curve for the permuted-network model. C) Testing CROC curves for the permuted-network and unpermuted-network models. The FPR has been scaled to focus on the first 1% placing greater emphasis on top predictions. While both models vastly outperform random (grey line), the unpermuted-network model provides far superior top predictions. D) For both networks, gene-disease pairs were stratified by deciles of the predicted probabilities for positives. For each strata, the percent of positive pairs (precision) is plotted. The fold change over permuted is denoted for the unpermuted deciles. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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A Gene—{MSigDB Collection}—Gene—Disease DWPC Model 1.0
0.8 — — AUROC — — 0.6 — — — — — — — — — — — —
KEGG Lasso Ridge BioCarta Positional Reactome OncogenicTF Target GO Function GO Process ImmunologicPerturbation Cancer Hood miRNA Target GO Component Cancer Module B Degree-Weighted Path Count Path Count Model 1.0
Pathophysiology degenerative 0.8 — immunologic metabolic — neoplastic
AUROC — — psychiatric 0.6 — — — — unspecic — — — —
GiGaD GeTlD Lasso Ridge GiGeTlDGiGiGaD GaDlTlD GeTeGaDGaDaGaD GaDmPmD GaD (any gene) GaD (any disease)
Figure S5. Disease, feature, and model-specific performance across permuted-network models. Disease, feature, and model-specific AUROCs were calculated separately for each of 5 permuted networks and averaged. The figure is analogous to Figure 4, except all measures refer to permuted-network performance. Disease-specific performance tends towards the mean, as disease-specific information has been altered by permutation. For features ending with an association (GaD) metaedge, global performance exceeds disease-specific performance. These features capture disease polygenicity, which improves the ranking of gene-disease pairs only if multiple diseases are included. Performance of the lasso model is affected, since the signals become too weak and few features survive regularization. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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GaDmPmD 45 GaD (any disease) 44 50 GaDlTlD 42 58 65 GeTlD 02 01 01 02 GeTeGaD 01 00 01 01 79 GaD (any gene) 04 01 00 00 01 19 {TF Target} 03 03 05 04 08 14 25 {miRNA Target} 02 01 03 02 09 14 18 34 {Perturbation} 09 08 10 09 22 32 33 33 25 {Immunologic} 09 07 08 07 26 34 36 25 20 57 {Cancer Module} 05 05 07 06 10 13 11 14 07 35 27 {Oncogenic} 04 03 05 04 03 07 14 15 09 32 25 20 {BioCarta} 08 07 08 07 03 03 03 05 02 14 11 10 05 {KEGG} 10 10 10 10 04 05 06 09 03 21 15 18 09 32 {Reactome} 06 06 05 05 05 06 07 08 04 18 14 16 07 23 37 GiGaD 03 03 03 03 04 05 03 05 03 09 07 07 03 14 13 15 GiGeTlD 03 03 04 04 21 19 01 11 09 19 17 10 05 11 13 13 15 GiGiGaD 06 06 07 06 15 20 16 17 14 29 25 16 10 23 23 25 25 40 {GO Component} 02 02 03 03 06 08 09 11 06 21 16 19 12 06 12 11 05 10 13 {GO Process} 06 05 07 06 08 11 16 18 11 28 23 19 13 16 20 19 09 18 24 29 {GO Function} 03 03 04 04 04 06 08 12 07 18 14 16 09 10 17 15 07 09 17 22 32 {Positional} 01 01 01 01 01 02 08 04 03 06 05 02 02 01 02 02 01 01 03 02 02 02 {Cancer Hood} 02 02 02 02 08 10 05 06 05 13 11 11 05 03 06 07 02 06 08 07 08 05 01
GeTlD GiGaD {KEGG} GaDlTlD GiGeTlD GiGiGaD GaDaGaD GeTeGaD {BioCarta} GaDmPmD {TF Target} {Reactome} {Positional} {Oncogenic} {Perturbation}{Immunologic} {GO Process}{GO Function} {miRNA Target} GaD (any gene) {Cancer Module} {GO Component} GaD (any disease)
Figure S6. Pairwise feature correlation. Pearson’s correlation coefficients (shown by color and as a percent) were calculated for all pairwise feature combinations. Features were ordered using Ward’s hierarchical clustering. Moderate collinearity is pervasive across features. The four pleiotropy-focused features form a tight cluster (top left). Perturbations and Immunologic signatures are correlated with many other features, including several other MSigDB features. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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1.0
0.8
0.6
Recall 0.4 Positive Set (AUROC) HC Primary (0.83) 0.2 HC Secondary (0.74) LC Primary (0.68) LC Secondary (0.59) 0.0 0.0 0.2 0.4 0.6 0.8 1.0 False Positive Rate
Figure S7. Performance of the predictions on the four categories of associations. Keeping unassociated gene-disease pairs as negatives, ROC curves were calculated separately for each category of association as positives. Predictions from the complete-network ridge model were used as the classifier. For both high and low-confidence associations, primary gene annotations received higher predictions than secondary gene annotations. High-confidence associations received considerably higher predictions than low-confidence associations suggesting a high frequency of false positives amongst low-confidence associations.
1.8
1.4 Meta2.5
1.0
Density 0.6
0.2
0.0 0.2 0.4 0.6 0.8 1.0 P-value
Figure S8. Excess of nominally significant genewise p-values in Meta2.5. The histogram of genewise p-values from Meta2.5, a meta-analysis of multiple sclerosis GWAS preceding the WTCCC2 study. If no associations are present, uniformly distributed p-values (grey line) would be expected. Instead, we observed an excess of nominally significant genes (p ≤ 0.05, red) indicating a set of genes likely enriched for true associations. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Tables
MetaNode Count Source Disease 99 Disease Ontology Gene 19,116 HGNC (coding) Tissue 77 BRENDA (BTO) Pathophysiology 8 manual Positional 326 MSigDB (C1) Perturbation 3,402 MSigDB (C2) BioCarta 217 MSigDB (C2) KEGG 186 MSigDB (C2) Reactome 674 MSigDB (C2) miRNA Target 221 MSigDB (C3) TF Target 615 MSigDB (C3) Cancer Hood 427 MSigDB (C4) Cancer Module 431 MSigDB (C4) GO Process 825 MSigDB (C5) GO Component 233 MSigDB (C5) GO Function 396 MSigDB (C5) Oncogenic 189 MSigDB (C6) Immunologic 1,910 MSigDB (C7)
Table 1. Metanodes. The kind, number of corresponding nodes, and data source for each type of node. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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MetaEdge Count Source Disease - association - Gene 938 GWAS Catalog Disease - membership - Pathophysiology 90 manual Disease - localization - Tissue 1,086 CoPub 5.0 Gene - expression - Tissue 251,366 GNF BodyMap Gene - interaction - Gene 97,938 iRefIndex Gene - membership - Positional 18,343 MSigDB (C1) Gene - membership - Perturbation 366,211 MSigDB (C2) Gene - membership - BioCarta 4,456 MSigDB (C2) Gene - membership - KEGG 12,656 MSigDB (C2) Gene - membership - Reactome 35,597 MSigDB (C2) Gene - membership - miRNA Target 33,455 MSigDB (C3) Gene - membership - TF Target 161,258 MSigDB (C3) Gene - membership - Cancer Hood 41,913 MSigDB (C4) Gene - membership - Cancer Module 48,220 MSigDB (C4) Gene - membership - GO Process 75,155 MSigDB (C5) Gene - membership - GO Component 34,880 MSigDB (C5) Gene - membership - GO Function 23,578 MSigDB (C5) Gene - membership - Oncogenic 30,166 MSigDB (C6) Gene - membership - Immunologic 370,862 MSigDB (C7)
Table 2. Metaedges. The kind, number of corresponding edges, and data source for each type of edge. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Disease Pathophysiology HC-P HC-S LC-P LC-S Crohn’s disease immunologic 67 179 4 2 multiple sclerosis immunologic 50 43 38 29 type 2 diabetes mellitus immunologic 49 49 20 15 breast carcinoma neoplastic 43 65 2 6 ulcerative colitis immunologic 40 96 2 3 prostate carcinoma neoplastic 34 202 3 4 type 1 diabetes mellitus immunologic 33 56 9 6 rheumatoid arthritis immunologic 30 27 20 11 coronary artery disease metabolic 29 43 15 9 obesity metabolic 28 22 34 18 celiac disease immunologic 24 32 9 8 systemic lupus erythematosus immunologic 22 35 14 8 refractive error degenerative 21 11 2 1 primary biliary cirrhosis immunologic 20 16 2 0 vitiligo immunologic 20 27 4 0 age related macular degeneration degenerative 18 30 11 18 metabolic syndrome X metabolic 17 11 1 0 asthma immunologic 17 23 13 4 psoriasis immunologic 16 14 5 5 schizophrenia psychiatric 15 27 20 13 chronic lymphocytic leukemia neoplastic 14 16 3 4 migraine unspecific 13 15 38 58 Alzheimer’s disease degenerative 12 11 27 18 Graves’ disease immunologic 12 15 1 1 Parkinson’s disease degenerative 12 21 8 13 atopic dermatitis immunologic 11 15 5 1 bipolar disorder psychiatric 11 34 26 74 lung carcinoma neoplastic 10 14 6 6 ankylosing spondylitis immunologic 10 5 6 6
Table 3. Diseases. Associations were predicted for 29 diseases with at least 10 positives. For these diseases, the number of high-confidence primary (HC-P), high-confidence secondary (HC-S), low-confidence primary (LC-P), and low-confidence secondary associations (LC-S) that were extracted from the GWAS Catalog is indicated.
Gene Meta2.5 HNLP WTCCC2 JAK2 0.047 0.102 0.0015 REL 0.001 0.040 0.0003 SH2B3 0.012 0.034 0.0130 RUNX3 0.016 0.025 0.0073
Table 4. Multiple sclerosis gene discovery. Four genes showed nominal statistical evidence of association (Meta2.5 column) and exceeded the network prediction threshold (HNLP column). Three genes achieved Bonferroni validation (bold) in an independent GWAS (WTCCC2 column). bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Path Count Measures the number of . . . GaD (any disease) diseases that the source gene is associated with, ignoring the association with the target disease if present. GaD (any gene) genes that the target disease is associated with, ignoring the association with the source gene if present. DWPC Measures the extent that . . . GeTlD the source gene is expressed in tissues affected by target disease. GiGaD genes associated with the target disease interact with the source gene. GiGiGaD genes associated with the target disease interact with genes that interact with the source gene. GaDaGaD genes associated with the same diseases as the source gene are associated with the target disease. GaDmPmD diseases with the same pathophysiology as the target disease are associated with the source gene. GaDlTlD diseases affecting the same tissues as the target disease are associated with the source gene. GeTeGaD genes expressed in the same tissues as the source gene are associated with the target disease. GiGeTlD genes interacting with the source gene are expressed in tissues that are affected by the target disease. {Positional} genes located in the same cytogenetic band as the source gene are associated with the target disease. {Perturbation} genes belonging to the same perterbation signatures as the source gene are associated with the target disease. {BioCarta} genes involved in the same BioCarta pathways as the source gene are asso- ciated with the target disease. {KEGG} genes involved in the same KEGG pathways as the source gene are associ- ated with the target disease. {Reactome} genes involved in the same Reactome pathways as the source gene are as- sociated with the target disease. {miRNA Target} genes sharing 3’-UTR microRNA binding motifs with the source gene are associated with the target disease. {TF Target} genes sharing transcription factor binding sites with the source gene are associated with the target disease. {Cancer Hood} genes present in the same expression neighborhoods of cancer-related genes as the source gene are associated with the target disease. {Cancer Module} genes belonging to the same cancer modules as the source gene are associ- ated with the target disease. {GO Process} genes participating in the same GO Biological Processes as the source gene are associated with the target disease. {GO Component} genes belonging to the same GO Cellular Components as the source gene are associated with the target disease. {GO Function} genes contributing to the same GO Molecular Functions as the source gene are associated with the target disease. {Oncogenic} genes belonging to the same cancer-dysregulated cellular pathways as the source gene are associated with the target disease. {Immunologic} genes belonging to the same immunologic signatures as the source gene are associated with the target disease.
Table S1. Features. The 24 features computed for each gene-disease pair and the aspect of network topology described. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Feature AUROC p-AUROC p-value 20 GaDmPmD 0.643 0.547 1.6 × 10− 9 GiGaD 0.558 0.514 2.1 × 10− 7 {Perturbation} 0.740 0.667 2.3 × 10− 5 GeTlD 0.573 0.518 1.8 × 10− 5 {KEGG} 0.613 0.566 5.6 × 10− 4 GaDaGaD 0.633 0.592 1.5 × 10− {BioCarta} 0.548 0.526 0.001 {Reactome} 0.599 0.562 0.002 {Immunologic} 0.703 0.665 0.006 GiGiGaD 0.646 0.621 0.05 {Cancer Module} 0.629 0.612 0.11 GeTeGaD 0.570 0.554 0.14 {TF Target} 0.612 0.596 0.16 {GO Component} 0.560 0.547 0.17 {Positional} 0.529 0.520 0.19 GiGeTlD 0.628 0.616 0.20 {GO Process} 0.626 0.617 0.26 GaD (any disease) 0.683 0.676 0.30 {GO Function} 0.577 0.571 0.31 {Cancer Hood} 0.533 0.532 0.45 GaD (any gene) 0.620 0.620 0.49 GaDlTlD 0.674 0.674 0.49 {Oncogenic} 0.601 0.604 0.60 {miRNA Target} 0.562 0.569 0.72
Table S2. Feature-specific performance before and after network permutation. Ten features (bold) showed a significant (p < 0.05, one-sided DeLong test) decrease in performance.
Value Prediction Threshold 0.024 False Positive Rate 0.001 Recall 0.108 Precision 0.133 Lift 68.4 Novel & Meta2.5-nominal Total 1211 Discovered 4 Bonferroni Cutoff 0.0125 Discovered < Bonferroni 3 Total < Bonferroni 199 Replication p-value 0.015
Table S3. Multiple sclerosis gene discovery statistics. The upper section details the high-performing network prediction threshold. The lower section details the hypergeometric test for overrepresentation of validating genes. bioRxiv preprint doi: https://doi.org/10.1101/011569; this version posted December 11, 2014. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license.
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Supporting Data
Dataset S1. Predictions. Predicted probabilities of association between all genes (rows) and diseases (columns).
Dataset S2. Features. The features (columns) computed for each gene-disease pair (rows). Column names with beginning with ‘XB’ refer to standardized features.
Dataset S3. Serialized network. A JSON formatted text file storing the complete network. The top level is an JSON object with four pairs (metanodes, metaedges, nodes, edges). The value for each pair is a JSON array containing the corresponding items.
Dataset S4. Processed GWAS Catalog Loci. Loci-disease associations. The file includes the gene resolution information for each loci including the studies and SNPs underlying the association.
Dataset S5. Gene-Disease Associations. All gene-disease associations extracted from the GWAS catalog for the four categories of association.
Dataset S6. Disease Ontology Modifications. Ten DO terms that appeared in the GWAS Catalog were redundant with other terms. Seven were removed. Three were merged with recipient terms by removing the term and transferring the associations.
Dataset S7. Tissue-specific gene expression. A processed version of the GNF BodyMap providing a gene’s (row, HGNC symbols) expression value for each of 77 tissues (columns, BRENDA Tissue Ontology IDs).
Dataset S8. Disease localization. Literature co-occurrence scores between diseases and tissues com- puted using CoPub 5.0.
Dataset S9. Terminology Mappings. All mappings that were manually performed. Specifically, tissue and disease mappings to CoPub ’Biologic Identifiers’, tissue mappings to GNF BodyMap samples, disease mappings to the EFO terms appearing in the GWAS Catalog, and disease pathophysiologies.
Dataset S10. Multiple Sclerosis Analysis. For each gene (row), the genewise Meta2.5 and WTCCC2 p-values and network-based predictions are reported.
Dataset S11. Vector Images. PDF formatted versions of the figures.