Evaluating variants of uncertain significance in adult zebrafish via prime editing: a proof of concept with a COL1A2 variant.

Genomic variants of uncertain significance (VUS) impede clinical decision-making. In this study, we employ a knock-in strategy in zebrafish to evaluate the COL1A2 c.2123G>A VUS, identified in a 78-year-old female with atypical femoral fractures. Using prime editing, we generated different col1a2 zebrafish lines respectively harboring the VUS, a known pathogenic variant, and a known benign variant. Comprehensive skeletal phenotyping revealed no significant abnormalities in zebrafish harboring the VUS. In contrast, zebrafish with the pathogenic variant showed an increased eye diameter, scoliosis, vertebral fusions, vertebral compressions, fractures, and increased mineralization of the notochord and intervertebral ligament compared to wild type controls. Our findings represent the first demonstration that COL1A2 variant modeling via prime editing in zebrafish not only aids in functional validation, but also holds promise for uncovering the underlying pathogenic mechanisms. This approach can be applied to investigate VUS in other genes as well.