Washington University School of Medicine Digital Commons@Becker Open Access Publications 2018 A high throughput, functional screen of human Body Mass Index GWAS loci using tissue-specific RNAi Drosophila melanogaster crosses Thomas J. Baranski Washington University School of Medicine in St. Louis Aldi T. Kraja Washington University School of Medicine in St. Louis Jill L. Fink Washington University School of Medicine in St. Louis Mary Feitosa Washington University School of Medicine in St. Louis Petra A. Lenzini Washington University School of Medicine in St. Louis See next page for additional authors Follow this and additional works at: https://digitalcommons.wustl.edu/open_access_pubs Recommended Citation Baranski, Thomas J.; Kraja, Aldi T.; Fink, Jill L.; Feitosa, Mary; Lenzini, Petra A.; Borecki, Ingrid B.; Liu, Ching-Ti; Cupples, L. Adrienne; North, Kari E.; and Province, Michael A., ,"A high throughput, functional screen of human Body Mass Index GWAS loci using tissue-specific RNAi Drosophila melanogaster crosses." PLoS Genetics.14,4. e1007222. (2018). https://digitalcommons.wustl.edu/open_access_pubs/6820 This Open Access Publication is brought to you for free and open access by Digital Commons@Becker. It has been accepted for inclusion in Open Access Publications by an authorized administrator of Digital Commons@Becker. For more information, please contact [email protected]. Authors Thomas J. Baranski, Aldi T. Kraja, Jill L. Fink, Mary Feitosa, Petra A. Lenzini, Ingrid B. Borecki, Ching-Ti Liu, L. Adrienne Cupples, Kari E. North, and Michael A. Province This open access publication is available at Digital Commons@Becker: https://digitalcommons.wustl.edu/open_access_pubs/6820 RESEARCH ARTICLE A high throughput, functional screen of human Body Mass Index GWAS loci using tissue-specific RNAi Drosophila melanogaster crosses Thomas J. Baranski1*, Aldi T. Kraja2, Jill L. Fink1, Mary Feitosa2, Petra A. Lenzini2, Ingrid B. Borecki3, Ching-Ti Liu4, L. Adrienne Cupples4, Kari E. North5, Michael A. Province2* a1111111111 1 Department of Internal Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri, United States of America, 2 Department of Genetics and a1111111111 Center for Genome Sciences and Systems Biology, Division of Statistical Genomics, Washington University a1111111111 School of Medicine, St. Louis, Missouri, United States of America, 3 Department of Biostatistics, University of a1111111111 Washington, Seattle, Washington, United States of America, 4 Department of Biostatistics, Boston University a1111111111 School of Public Health, Boston, Massachusetts, United States of America, 5 Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, United States of America * [email protected] (TJB); [email protected] (MAP) OPEN ACCESS Citation: Baranski TJ, Kraja AT, Fink JL, Feitosa M, Abstract Lenzini PA, Borecki IB, et al. (2018) A high Human GWAS of obesity have been successful in identifying loci associated with adiposity, throughput, functional screen of human Body Mass Index GWAS loci using tissue-specific RNAi but for the most part, these are non-coding SNPs whose function, or even whose gene of Drosophila melanogaster crosses. PLoS Genet 14 action, is unknown. To help identify the genes on which these human BMI loci may be oper- (4): e1007222. https://doi.org/10.1371/journal. ating, we conducted a high throughput screen in Drosophila melanogaster. Starting with 78 pgen.1007222 BMI loci from two recently published GWAS meta-analyses, we identified fly orthologs of all Editor: Giovanni Bosco, Geisel School of Medicine nearby genes (± 250KB). We crossed RNAi knockdown lines of each gene with flies contain- at Dartmouth, UNITED STATES ing tissue-specific drivers to knock down (KD) the expression of the genes only in the brain Received: September 22, 2017 and the fat body. We then raised the flies on a control diet and compared the amount of fat/ Accepted: January 25, 2018 triglyceride in the tissue-specific KD group compared to the driver-only control flies. 16 of Published: April 2, 2018 the 78 BMI GWAS loci could not be screened with this approach, as no gene in the 500-kb region had a fly ortholog. Of the remaining 62 GWAS loci testable in the fly, we found a signifi- Copyright: © 2018 Baranski et al. This is an open access article distributed under the terms of the cant fat phenotype in the KD flies for at least one gene for 26 loci (42%) even after correcting Creative Commons Attribution License, which for multiple comparisons. By contrast, the rate of significant fat phenotypes in RNAi KD found permits unrestricted use, distribution, and in a recent genome-wide Drosophila screen (Pospisilik et al. (2010) is ~5%. More interest- reproduction in any medium, provided the original author and source are credited. ingly, for 10 of the 26 positive regions, we found that the nearest gene was not the one that showed a significant phenotype in the fly. Specifically, our screen suggests that for the 10 Data Availability Statement: All relevant data are within the paper and its Supporting Information human BMI SNPs rs11057405, rs205262, rs9925964, rs9914578, rs2287019, rs11688816, files. rs13107325, rs7164727, rs17724992, and rs299412, the functional genes may NOT be the Funding: This work was supported in part by nearest ones (CLIP1, C6orf106, KAT8, SMG6, QPCTL, EHBP1, SLC39A8, ADPGK National Institute of Diabetes and Digestive and /ADPGK-AS1, PGPEP1, KCTD15, respectively), but instead, the specific nearby cis genes Kidney Diseases (NIDDK) grant DK089256 are the functional target (namely: ZCCHC8, VPS33A, RSRC2; SPDEF, NUDT3; PAGR1; (Multiple PIs MAP, TJB, CTL, LAC, KEN and IBB). SETD1, VKORC1; SGSM2, SRR; VASP, SIX5; OTX1; BANK1; ARIH1; ELL; CHST8, The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. PLOS Genetics | https://doi.org/10.1371/journal.pgen.1007222 April 2, 2018 1 / 18 Fly functional RNAi screen for BMI Competing interests: The authors have declared respectively). The study also suggests further functional experiments to elucidate mecha- that no competing interests exist. nism of action for genes evolutionarily conserved for fat storage. Author summary Human Genome Wide Association Studies have successfully found thousands of novel genetic variants associated with many diseases. While these undoubtedly point to new biology, the field has been slowed in exploiting these new findings to reach a better under- standing of exactly how they confer increased risk. Many, if not most, appear to be regula- tory not coding variants, so their immediate consequence is not obvious. A real rate limiting step is even identifying which gene these variants might be regulating, and in what tissues they are operating to increase disease risk. In the absence of any other infor- mation, a first order assumption is that they may be more likely to be regulating a nearby gene, and such variants are often initially annotated by the ªnearestº gene until their func- tion is more definitively validated. Exploiting the idea that many genes may have con- served function across species, we conducted a high-throughput screen of fruit-fly orthologs of human genes nearby 78 well validated GWAS variants for human obesity, in order to more precisely identify the gene(s) of action. We systematically knocked down the function of each of these nearby genes in the brain and fat-body of the flies, raised them on a standard diet, and compared their percent body fat with control flies, in order to validate which genes showed a fat response. 43% of the time when fly orthologs existed in the region, we were able to identify the causal gene. Interestingly, nearly half the time (46%), it was not the nearest gene but another nearby one that regulated fat. Introduction Human Genome-Wide Association Scans (GWAS) have been successful in discovering many genetic loci that are significantly associated with Body Mass Index (BMI). These associations have been replicated across consortia consisting of many large and independent studies, some- times numbering into hundreds of thousands of subjects. From a statistical point of view, the evidence that single nucleotide polymorphisms (SNPs) are tagging something real is over- whelming. However, progress has been slowed in moving beyond the discovery phase to a deeper understanding the biological significance of these findings, due to difficulties isolating the driving causal variants or even identifying the acting genes tagged by these GWAS variants. Most of the findings are not in gene coding regions. Indeed, many are intergenic, suggesting that much of the underlying modes of action of these loci may be regulatory. Unfortunately, our limited biological understanding of the regulome has hampered further progress. While the field has begun serious annotation of the regulatory regions of the genome with ini- tiatives and resources such as ENCODE, RoadMap and GTEx, the annotation is still far from complete and the answers that are emerging are complex. As a result, many publications anno- tate the statistically significant SNPs simply with the ªclosestº gene, even though trans-acting reg- ulatory sequences certainly exist[1], and some enhancers have been shown to regulate multiple genes[2]. Recently, it was reported that rs1421085 T-to-C intron of the well-known obesity-asso- ciated FTO gene, disrupts a conserved motif for the ARID5B repressor,