Utility of trio-based exome sequencing in the elucidation of the genetic basis of isolated syndromic intellectual disability: illustrative cases

Author(s)

Carneiro, Thaise N. R. ^[1] ; Krepischi, Ana C. V. ^[1] ; Costa, Silvia S. ^[1] ; da Silva, Israel Tojal ^[2] ; Vianna-Morgante, Angela M. ^[1] ; Valieris, Renan ^[2] ; Ezquina, Suzana A. M. ^[1] ; Bertola, Debora R. ^[3] ; Otto, Paulo A. ^[1] ; Rosenberg, Carla ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Biosci, Dept Genet & Evolutionary Biol, Human Genome & Stem Cell Res Ctr, Sao Paulo - Brazil

^[2] AC Camargo Canc Ctr, Int Res Ctr, Lab Computat Biol & Bioinformat, Sao Paulo - Brazil

^[3] Univ Sao Paulo, Hosp Clin, Med Sch, Genet Unit, Inst Crianca, Sao Paulo - Brazil

• Document type: Journal article
• Source: APPLICATION OF CLINICAL GENETICS; v. 11, p. 93-98, 2018.
• Web of Science Citations: 9

Abstract

Introduction: Exome sequencing is recognized as a powerful tool for identifying the genetic cause of intellectual disability (ID). It is uncertain, however, whether only the exome of the proband should be sequenced or if the sequencing of parental genomes is also required, and the resulting increase in diagnostic yield justifies the increase in costs. Patients and methods: We sequenced the exomes of eight individuals with sporadic syndromic ID and their parents. Results and discussion: Likely pathogenic variants were detected in eight candidate genes, namely homozygous or compound heterozygous variants in three autosomal genes (ADAMTSL2, NALCN, VPS13B), one in an X-linked gene (MID1), and de novo heterozygous variants in four autosomal genes (RYR2, GABBR2, CDK13, DDX3X). Two patients harbored rare variants in two or more candidate genes, while in three other patients no candidate was identified. In five probands (62%), the detected variants explained their clinical findings. The causative recessive variants would have led to diagnosis even without parental exome sequencing, but for the heterozygous dominant ones, the exome trio-based approach was fundamental in the identification of the de novo likely pathogenic variants. (AU)

• FAPESP's process: 12/50981-5 - High resolution genomic arrays and next generation sequencing in mental deficiency and congenital anomalies diagnosis
• Grantee: Francine Campagnari Guilhem
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• FAPESP's process: 13/08028-1 - CEGH-CEL - Human Genome and Stem Cell Research Center
• Grantee: Mayana Zatz
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC