Identification and bioinformatics analysis of a novel variant in the HERC2 gene in a patient with intellectual developmental disorder.

HERC2-associated neurodevelopmental-disorders(NDD) encompass a cluster of medical conditions that arise from genetic mutations occurring within the HERC2 gene. These disorders can manifest a spectrum of symptoms that impact the brain and nervous system, including delayed psychomotor development, severe mental retardation, seizures and autistic features. Whole-Exome-Sequencing(WES) was performed on a ten-year-old male patient referred to the genetic center for genetic analysis. Blood samples were collected from the proband, his parents, and his sister to extract DNA. PCR-Sanger-sequencing was utilized to validate the findings obtained from WES. In order to obtain a more thorough understanding of the impact of the mutation, an extensive analysis was conducted using bioinformatics tools. WES data analysis identified a homozygous single nucleotide change(C > T) at position c14215 located in exon ninety-two of the HERC2 gene (NC_000015.10(NM_004667.6):c.14215C > T). The absence of this mutation among our cohort composed of four hundred normal healthy adults from the same ethnic group, and its absence in any other population database, confirms the pathogenicity of the mutation. This study revealed that the substitution of arginine with a stop codon within the Hect domain caused a premature stop codon at position 4739(p.Arg4739Ter). This mutation significantly results in the production of a truncated HERC2 protein with an incomplete HECT domain. In the final stage of ubiquitin attachment, HECT E3 ubiquitin ligases play a catalytic role by creating a thiolester intermediate using their conserved catalytic cysteine (Cys4762). This intermediate is formed before ubiquitin is transferred to a substrate protein. The truncation of the HERC2 protein is expected to disrupt its ability to perform this function, which could potentially hinder important regulatory processes related to the development and maintenance of synapses. The identification of a novel pathogenic variant, NC_000015.10(NM_004667.6):c.14215C > T, located within the ninety-two exon of the HERC2 gene, is notable for its association with an autosomal recessive inheritance pattern in cases of Intellectual Developmental Disorder(IDD). In the end, this variant could potentially play a part in the underlying mechanisms leading to the onset of intellectual developmental disorder.