Altered FRG1 levels during Xenopus laevis development leads to muscular and vascular phenotypes supporting a role for the misregulation of FRG1 in FSHD

The genetic lesion diagnostic for facioscapulohumeral muscular dystrophy (FSHD) results in an epigenetic misregulation of gene expression, which in turn is what ultimately leads to the disease pathology. FRG1 (FSHD region gene 1) is a leading candidate gene whose misexpression may lead to FSHD. As FSHD pathology is most prominent in the musculature, most research and therapy efforts have focused on muscle cells. However, between 50-75% of FSHD patients also exhibit retinal vasculopathy and FSHD muscle has increased levels of vascular-endothelial related transcripts, suggesting an underappreciated vascular component to the disease. Using Xenopus laevis as a model, we have shown a previously unsuspected role for FRG1 in the development of both muscular and vascular structures. Furthermore, overexpression of frg1 displays disrupted muscle and dilated and tortuous vessels, phenocopying the symptoms of FSHD patients. Thus, our work strongly supports a role for FRG1 in FSHD disease pathology.