[Molecular mechanism study of fetal nasal bone aplasia due to a frameshift variant of ARSL gene].

OBJECTIVE: To analyze the clinical phenotype and pathogenic mechanism of the ARSL gene variant in a fetus with nasal bone aplasia. METHODS: A 34-year-old pregnant woman who attended Quzhou Maternal and Child Health Care Hospital on January 3, 2023 was selected as the study subject. Whole exome sequencing (WES) was performed on the fetus. Bioinformatics analysis was carried out to identify and prioritize candidate gene variants, followed by Sanger sequencing for familial validation. A mutant plasmid expression vector was constructed and subsequently transfected into HEK293T cells to preliminarily investigate the pathogenetic mechanism of the identified variant. Additionally, a comprehensive review of literature was conducted to systematically summarize the associated clinical phenotypes. This study was approved by the Medical Ethics Committee of Quzhou Maternal and Child Health Care Hospital (Ethics No.: KY-2023-11). RESULTS: WES revealed that the fetus harbored a c.827del (p.L276Rfs*48) variant of the ARSL gene, for which its mother was heterozygous. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as pathogenic(PVS1+PM2_Supporting). In vitro cellular function studies demonstrated that this variant can result in a substantial decrease in the expression of mutant mRNA, thereby preventing the production of normal ARSL protein. Clinical phenotypes resulting from ARSL gene variants exhibited considerable diversity, with nasal hypoplasia being the most common manifestation. CONCLUSION: The c.827del (p.L276Rfs*48) variant of the ARSL gene can lead to degradation of mRNA via the nonsense-mediated mRNA decay pathway, resulting in reduced levels of ARSL protein. The pathogenetic mechanism underlying the ARSL gene variant may be associated with its haploinsufficiency effect.