Whole-Exome Sequencing for Identifying Genetic Causes of Intellectual Developmental Disorders

Yu-Xiong Guo,1,2,* Hong-Xia Ma,1– 3,* Yu-Xin Zhang,2 Zhi-Hong Chen,2 Qiong-Xiang Zhai1,2 1The Second School of Clinical Medicine, Southern Medical University, Guangzhou, 510280, People’s Republic of China; 2Department of Pediatrics, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, 510080, People’s Republic of China; 3Department of Pediatrics, Affiliated Hospital of Guangdong Medical University, Zhanjiang, 524000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Qiong-Xiang ZhaiDepartment of Pediatrics, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, 106 Zhongshan Second Road, Yuexiu District, Guangzhou, 510080, People’s Republic of ChinaTel +86-2083827812-76222Fax +86-20-8328480Email zhaiqx_241@163.comBackground: Intellectual developmental disorders (IDD) generally refers to the persistent impairment of cognitive activities and mental retardation caused by physical damage to the brain or incomplete brain development. We aimed to explore its genetic causes.Methods: In this study, 21 IDD patients were recruited. The Gesell developmental scales (GDS) and Wechsler intelligence scale for children (WISC) were used to assess the impaired level of intellectual development for all probands. A superconducting MRI scanner (Philips AcsNT 3.0 T Philips, Best, The Netherlands) was used to perform a plain MRI scan of the skull on the probands. The whole-exome sequencing was carried out using next-generation sequencing in all probands and their families.Results: Eight had seizures and four had typical characteristics of autism. Pregnancy and delivery were uneventful except for three patients. Moderate IDD (52.4%) accounted for the majority. The abnormal MRI results included ventriculomegaly, pachygyria, broadening external cerebral space, abnormal signal change and agenesis of corpus callosum. Eleven variants were identified, including the variant in CREBBP, MECP2, HCFC1, ATRX, RAB39B, CLCN4, DYRK1A and CASKgenes. The function areas result of gene-positive group were compared to that of gene-negative group. Not significant (p> 0.05) items were revealed after this analysis.Conclusion: Eleven variants were identified, including the variant in CREBBP, MECP2, HCFC1, ATRX, RAB39B, CLCN4, DYRK1A and CASK genes. The function areas result of gene-positive group were not significantly different from the gene-negative group.Keywords: intellectual developmental disorders, gene variant, whole-exome sequencing