A novel de novo frameshift variant in the CHD2 gene related to intellectual and developmental disability, seizures and speech problems

Abstract

Background: The chromodomain helicase DNA-binding protein 2 (CHD2) is a member of the ATP-dependent chromatin remodelling family of proteins, which are critical for the assembly and regulation of chromatin. De novo variants and deletions in the CHD2 gene have been associated with childhood-onset developmental and epileptic encephalopathies type 94 (DEE 94). This study reports a novel deleterious de novo heterozygous frameshift insertion variant in the CHD2 gene.

Methods: The causative variant was diagnosed using whole-exome sequencing. Sanger sequencing and cosegregation analysis were applied to confirm the candidate variant. Multiple in silico analysis tools were employed to interpret the variant using the American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines.

Results: A de novo deleterious variant, NM_001271.4:c.1570dup (NP_001262.3:p.Ser524PhefsTer30), in the CHD2 gene, was identified in a 16-year-old boy with an intellectual and developmental disability, seizures and speech problems. The de novo occurrence of the variant was confirmed by segregation analysis in the family.

Conclusion: The findings of this study expand the existing knowledge of variants of the CHD2 gene and provide a detailed phenotype associated with this gene. These data could have implications for genetic diagnosis and counselling in similar conditions. Moreover, this information could be useful for therapeutic purposes, including the proper administration of medication to control epilepsy.

Keywords: CHD2; DEE; Iran; developmental delay; duplication; epilepsy; intellectual disability.