Functional validation using a zebrafish model reclassifies the rare COL1A2 p.Gly418Ala variant as a cause of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a genetically heterogeneous skeletal dysplasia mainly caused by mutations in the COL1A1 and COL1A2 genes, which encode type I collagen. Here, using whole-exome sequencing(WES), we identified a rare heterozygous missense mutation (c.1253G > C, p.Gly418Ala) in COL1A2 in a Chinese family with recurrent prenatal skeletal dysplasia. This variant is located within the highly conserved Gly-X-Y repeat of the collagen triple-helical domain and predicted to be deleterious by bioinformatics programs. However, according to the American College of Medical Genetics and Genomics (ACMG) guidelines, it was initially classified as a variant of uncertain significance (VUS). To validate its pathogenicity, we overexpressed the mutant in a zebrafish model. The results revealed that mutant mRNA induced significant phenotypic abnormalities in zebrafish larvae, including shortened body length, axial curvature, fin malformations, and reduced vertebral mineralization—recapitulating key features of human OI. Our findings confirm the pathogenic role of the p.Gly418Ala mutation and highlight the zebrafish model as a powerful tool for rapid functional validation of VUS, facilitating clinical variant interpretation and precision medicine.