OBJECTIVE:To investigate the clinical and genetic characteristics of a Chinese pedigree affected with Neurodevelopmental disorder with absent language and variable seizures (NEDALVS) due to variant of WASF1 gene, and to review the literature on NEDALVS associated with WASF1 gene variants.
METHODS:A 4-year-and-8-month-old boy with NEDALVS diagnosed at Linyi People's Hospital in July 2024 due to "discovering language development delay for more than 2 years" and his family members were selected as the study subjects. Clinical data of the family members were collected. Peripheral venous blood samples were collected from family members. Whole-exome sequencing (WES) was performed, and candidate variants were verified, by Sanger sequencing. Pathogenicity of candidate variant was classified according to the Standards and Guidelines for the Interpretation of Sequence Variants established by the American College of Medical Genetics and Genomics (ACMG). Using the MUpro website, SWISS-MODEL, PyMOL, Clustal X, PolyPhen-2, and Mutation Taster software, bioinformatics analysis of protein three-dimensional structure modeling for gene mutations, cross-species conservation of mutant amino acids, and pathogenicity prediction of mutation sites. Relevant literature was retrieved from databases such as CNKI, Wanfang Data Knowledge Service Platform, and PubMed, and the clinical phenotypes and genotypes of patients with WASF1 gene mutations reported in the literature were summarized and analyzed. This study was approved by the Medical Ethics Committee of Linyi People's Hospital (Ethics No.: YX200303).
RESULTS:The proband, a 4-year and 8-month-old male, mainly presented with delayed language and motor development, accompanied by autistic behaviors; the proband's younger brother was 2 years and 7 months old at the time of consultation, mainly presented with delayed language and motor development, accompanied by short stature; the proband's mother mainly presents with limited language expression and poor interpersonal interaction; the proband's maternal grandmother mainly presents with soliloquizing?behavior. The results of WES showed that the proband carried a heterozygous mutation c.214C>T (p.Arg72Cys) in the WASF1 gene, and this site has not been recorded in the database. Sanger sequencing confirmed that the proband's younger brother, mother, and maternal grandmother had harbored the same variant. Based on the guidelines from the ACMG, this variant was rated as likely pathogenic (PM2_Supporting+PP1+PP3+PP4). Through SWISS-MODEL homology modeling and PyMOL structure visualization analysis, it was further confirmed that this variant can lead to a decrease in protein stability. Amino acid sequence conservation analysis of the WASF1 protein using Clustal X software suggested that the c.214C>T (p.Arg72Cys) variant has caused replacement of a highly conserved amino acid. According to the results of PolyPhen-2 and Mutation Taster, the p.Arg72Cys variant was predicted to be a hazardous. By following the retrieval strategy set in this study, a total of 5 research articles regarding to patients with NEDALVS caused by WASF1 gene mutations were retrieved, which involved 15 patients. Combining the proband and their family members discovered in this study, there were a total of 19 NEDALVS patients. The main clinical features included: motor developmental delay (100%, 17/17), language/intellectual developmental delay (100%, 17/17), epilepsy (64.7%, 11/17), autistic behavior (76.5%, 13/17), hypotonia (70.6%, 12/17), abnormal electroencephalogram (64.7%, 11/17), and short stature (17.6%, 3/17). All 19 patients had heterozygous mutations, with 8 mutation sites. Missense mutations were the most common, accounting for 84.2% (16/19).
CONCLUSION:A pathogenic variant of the WASF1 gene was identified in a pedigree affected with NEDALVS. Discovery of the novel variant has, expanded the mutational spectrum of the WASF1 gene.