Effect of the unreported COL5A2 variant c.2499 + 4_2499 + 5insTAA on RNA splicing: Insights from minigene assays.

BACKGROUND: Classical Ehlers-Danlos syndrome (cEDS), caused by pathogenic variants in COL5A2, is characterized by skin hyperextensibility, joint hypermobility and atrophic scarring. This study aimed to identify and validate the pathogenicity of an unreported COL5A2 intronic variant in a Chinese family with cEDS. METHODS: Trio-based whole exome sequencing (Trio-WES) was performed to screen for pathogenic variants, and the candidate variant was confirmed by Sanger sequencing. Minigene assays were then conducted to evaluate the functional consequences of key variants. RESULTS: A de novo COL5A2 (NM_000393.3) c.2499 + 4_2499 + 5insTAA variant was identified. Minigene assays demonstrated that this variant induced exon 37 skipping, resulting in an in-frame deletion. Based on ACMG guidelines, the variant was classified as pathogenic and considered the likely underlying etiology of cEDS in this family. CONCLUSION: These findings expand the variant spectrum of COL5A2, improving molecular diagnosis of cEDS.