bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 Language impairment with a partial duplication of DOCK8 2 Antonio Benítez-Burraco1, Maite Fernández-Urquiza2, Mª Salud Jiménez-Romero3 3 4 1. Department of Spanish, Linguistics, and Theory of Literature (Linguistics), 5 University of Seville, Seville, Spain 6 2. Department of Spanish Philology, University of Oviedo, Oviedo, Spain 7 3. Department of Education, University of Córdoba, Córdoba, Spain 8 9 Corresponding author: 10 Antonio Benítez-Burraco 11 Área de Lingüística General. Departamento de Lengua Española, Lingüística y Teoría 12 de la Literatura. Facultad de Filología. Universidad de Sevilla. C/ Palos de la Frontera 13 s/n. 41007-Sevilla (España) 14 e-mail: [email protected] 15 orcid.org/0000-0003-4574-5666 16 1 bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 17 ABSTRACT 18 Copy-number variations of the distal region of the short arm of chromosome 9 are 19 associated with learning disabilities and behavioral disturbances. Deletions of the 9p 20 are more frequent than duplications. We report in detail on the cognitive and language 21 features of a child with a duplication in the 9p24.3 region (arr[hg19] 9p24.3(266,045- 22 459,076)x3). He exhibits marked expressive and receptive problems, which affect to 23 both structural aspects of language (notably, inflectional morphology, complex syntax, 24 and sentence semantics), and to functional aspects (pragmatics). These problems might 25 result from a severe underlying deficit in working memory. Regarding the molecular 26 causes of the observed symptoms, they might result from the altered expression of 27 selected genes involved in procedural learning, particularly, some of components of the 28 SLIT/ROBO/FOXP2 network, strongly related to the development and evolution of 29 language. Dysregulation of specific components of this network can result in turn from 30 an altered interaction between DOCK8, affected by the microduplication in 9p24.3 31 borne by our proband, and CDC42, acting as the hub component of the network 32 encompassing language-related genes. Still, some genes found strongly upregulated in 33 the subject and not related to these genes, particularly NRCAM, can contribute to the 34 observed problems in the language domain, as well as to specific features of the 35 proband, particularly, his impulsivity. 36 37 Keywords: 9p24.3 duplication; DOCK8; cognitive delay; language deficits; working 38 memory 39 40 2 bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 41 INTRODUCTION 42 43 Copy number variants (CNVs) identified in subjects with language problems provide 44 important evidence of how changes in gene dosage affect the wiring and functioning of 45 brain areas involved in language processing, particularly, if they result in syndromic 46 features and encompass few genes. The terminal region of the short arm of chromosome 47 9 is prone to deletion, giving rise to a complex syndromic condition entailing mental 48 retardation, delayed psychomotor development, and speech delay (OMIM#158170). 49 Specifically, and according to the Unique database (https://www.rarechromo.org/), 50 deletions of the 9p24.3 region are associated with mild learning disabilities, that 51 commonly improve with appropriate early/supporting intervention, and with language 52 and speech delay, with a greater impact on the expressive domain. Although deletions 53 of the 9p are more frequent than duplications, an interstitial duplication at 9p24.3, 54 encompassing the genes DOCK8 and KANK1, has been recently associated with 55 multiple neurodevelopmental disorders, including schizophrenia (SZ), bipolar disease, 56 autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), and 57 depression, all of them conditions entailing problems with language (Glessner et al., 58 2017). 59 60 In this paper, we report on a boy with a partial duplication of DOCK8 resulting from a 61 de novo microduplication in 9p24.3 and provide a detailed characterization of his 62 language (dis)abilities. A growing body of evidence points to an association of DOCK8 63 deletions, duplications, and translocations interrupting its functionality, with 64 intellectual disability and developmental delay (Griggs et al., 2008; Krgovic et al., 65 2018). According to DECIPHER (https://decipher.sanger.ac.uk/), nearly 60% of the 3 bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 66 143 CNVs involving DOCK8 are losses and about 40% are gains. DOCK8 losses are 67 associated with intellectual disability, global developmental delay, abnormal facial 68 features, and microcephaly, whereas DOCK8 gains are mostly associated with 69 intellectual disability, global developmental delay, ASD, clinodactyly, and delayed 70 speech and language development. However, these CNVs usually involve other genes 71 besides DOCK8 and/or are found in patients with other chromosomal abnormalities. 72 Accordingly, we expect that smaller CNVs affecting to DOCK8 only, like the one found 73 in our patient, help to achieve more robust genotype-to-phenotype correlations. 74 75 DOCK8 plays an important role in modulating the immune response and mutations in 76 the gene are known to cause immunodeficiency disease (Biggs et al., 2017; Broides et 77 al., 2017; Kearney et al., 2017). Because the gene is also expressed in the fetal and adult 78 brains (Griggs et al., 2008), it is expected to play a key role as well in brain development 79 and function. Accordingly, in mice the Dock8 protein contributes to Schwann cell 80 precursor migration during embryonic development of the peripheral nervous system 81 (Miyamoto et al., 2016). DOCK8 is upregulated in neuronally differentiated cells after 82 the over-expression of MECP2_e1, which is the etiologically relevant variant of the 83 MECP2 protein for Rett syndrome (Orlic-Milacic et al., 2014). DOCK8 is a candidate 84 for ASD too. Two de novo loss-of-function variants of DOCK8 have been found in 85 probands from the Autism Sequencing Consortium and the Autism Clinical and Genetic 86 Resources in China (ACGC) cohort (De Rubeis et al., 2014; Wang et al., 2016). The 87 9p24.3 region overlaps with linkage regions found in large ASD extended pedigrees 88 (Allen-Brady et al., 2009; Coon et al., 2010). Nonetheless, little is known about the 89 causes of the neuropsychiatric features and neurodevelopmental anomalies associated 90 to mutations of DOCK8 or to CNVs encompassing the gene. This is particularly true of 4 bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 91 the language deficits that are commonly observed in patients, among other reasons, 92 because we still lack a detailed account of the language problems caused by DOCK8 93 mutations or dosage alterations. In this paper, we build on our current knowledge of the 94 genetic aspects of language development and language evolution, as well as on the 95 expression pattern of selected genes in the blood of our proband, for advancing a 96 hypothesis of the molecular causes of language dysfunction associated to DOCK8 97 alterations. 98 99 MATERIAL AND METHODS 100 101 Linguistic, cognitive, and behavioral assessment 102 The global developmental profile of the proband was defined with the Spanish versions 103 of the Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V) (Hernández et 104 al., 2015) and the Inventory for Client and Agency Planning (ICAP) (Montero, 1996). 105 106 Wechsler Intelligence Scale for Children (WISC-V) 107 The WISC-V was used for testing multiple cognitive abilities of the child. It consists of 108 10 primary subtests and 5 secondary subtests, which are combined to generate different 109 composite score indices. The five primary composite score indices are: Verbal 110 Comprehension (VCI), Visual Spatial Index (VSI), Fluid Reasoning Index (FRI), 111 Working Memory Index (WMI), and Processing Speed Index (PSI). The VCI measures 112 verbal reasoning, understanding, concept formation, and crystallized intelligence. The 113 VSI measures nonverbal reasoning and concept formation, visual perception and 114 organization, visual-motor coordination, and the child’s ability to analyze and 115 synthesize abstract information, and to distinguish figure-ground in visual stimuli. The 5 bioRxiv preprint doi: https://doi.org/10.1101/2020.06.16.155523; this version posted June 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 116 FRI evaluates quantitative reasoning, classification and spatial abilities, knowledge of 117 part to whole relationships, as well as fluid reasoning abilities. The WMI assesses the 118 child’s ability to sustain auditory attention, concentrate, and exert mental control. 119 Lastly, the PSI determines the speed and accuracy of the child when processing 120 information. 121 122 The Inventory for Client and Agency Planning (ICAP) 123 The ICAP was used for evaluating the subject’s functional abilities and maladaptive 124 behaviors in the following general areas: motor skills, social and communication skills, 125 personal living skills, and community living skills.