P1.04 Some of disease-causing missense fukutin mutants mislocalize to endoplasmic reticulum

Abstract

ases fukutin and fukutin-related protein (FKRP), cause forms of muscular dystrophy (MD) associated with defective glycosylation of a-dystroglycan. The ‘‘vascular hypothesis” of MD predicts that the muscle necrosis associated with MD is caused by chronic muscle ischaemia. Since dystroglycan is known to be essential in vascular development, transgenic zebrafish expressing EGFP in the blood vessel endothelium, driven by the fli-1 promoter were treated with translational blocking morpholinos. The morpholinos were directed against the FKRP and Fukutin transcripts. At 1 day post fertilisation (dpf) the eye vasculature in both knock downs was distorted and correlated with severity of phenotype. In the embryos with the most severe phenotypes at 3 dpf the eye areas were significantly smaller than controls. In the more mildly affected morphant embryos there is a failure of the somitic intersegmental vessels to reach the dorsal longitudinal anastomosis. As the phenotype became more severe the intersegmental vessels retracted further and in some cases were found to be missing. Fukutin knock downs had a more severe vascular phenotype than FKRP knockdowns. Downregulation of FKRP and Fukutin in TG(fli1:EGFP) zebrafish may therefore provide a good model system to investigate how these deficiencies relate to vascular development.