Mapping a new locus for non-syndromic strabismus with high-throughput genome analysis

Eye misalignment, called strabismus, occurs in up to 5% of individuals. While misalignment is frequently observed in rare complex syndromes, the majority of strabismus cases are non-syndromic. Over the past decade, genes and pathways associated with syndromic forms of strabismus have emerged, but the genes contributing to non-syndromic strabismus remain elusive. Non-syndromic strabismus is highly heterogeneous, and different loci have been inferred from previous genetics studies. Only a single strabismus locus, STBMS1, on chromosome 7 has been confirmed in more than one family, but the reported inheritance patterns of this locus with disease conflict and no specific variant has been proposed. Here, I analyzed a large non-consanguineous family with multiple individuals affected by strabismus across seven generations. The hypothesis is that a single variant is responsible for the non-syndromic strabismus in this particular family displaying dominant patterns of inheritance. Whole exome sequencing (WES) was performed to uncover large- blocks of variations within protein-coding regions of the genome shared by two affected distant relatives. In parallel, chromosome regions segregating with the strabismus phenotype in the family were identified using linkage analysis on 12 individuals. Linkage analysis identified one specific risk locus of high confidence. Based on the lack of protein-coding alterations in the locus, whole genome sequencing (WGS) was performed to find additional shared candidate causal variants. Combining the available information, a 10 Mb region on chromosome 14 was identified with high confidence that it was associated with strabismus, within which a set of potential regulatory sequence alterations have been highlighted for further study. This study represents the first identified locus for autosomal dominant, non- syndromic, strabismus. The project utilizes next-generation sequencing (NGS), linkage analysis, and bioinformatic analyses to prioritize and select both coding and non-coding variants, demonstrating the effectiveness of combining NGS and classical genetic approaches. The research findings improve our understanding of strabismus genetics and defines multiple paths for future research, family-specific genetic testing for early diagnosis, and consequent preventive therapy.Medicine, Faculty ofMedical Genetics, Department ofGraduat