Genes required for functional glycosylation of dystroglycan are conserved in zebrafish

Mutations in human genes encoding proteins involved in alpha-dystroglycan glycosylation result in dystroglycanopathies: severe congenital muscular dystrophy phenotypes often accompanied by CNS abnormalities and ocular defects. We have identified the zebrafish orthologues of the seven known genes in this pathway and examined their expression during embryonic development. Zebrafish Large, POMT1, POMT2, POMGnT1, Fukutin, and FKRP show in situ hybridization patterns similar to those of dystroglycan, with broad expression throughout early development. By 30 h postfertilization (hpf), transcripts of all these genes are most prominent in the CNS, eye, and muscle, tissues that are predominantly affected in the dystroglycanopathies. In contrast, Large2 expression is more restricted and by 30 hpf is confined to the lens, cerebellum, and pronephric duct. We show that the monoclonal antibody IIH6, which recognizes a glycoform of dystroglycan, also detects the zebrafish protein. Injection of morpholino oligonucleotides against zebrafish Large2 resulted in loss of IIH6 immunostaining. These data indicate that the dystroglycan glycosylation pathway is conserved in zebrafish and suggest this organism is likely to be a useful model system for functional studies.