Myf5/Fktn KO mice were selected for this study because (1) Fktn-deficiency is the most common form of congenital dystroglycanopathy; (2) this conditional knockout model bypasses embryonic lethality associated with total Fktn loss; and (3) Fktn excision is initiated during muscle development causing moderate to severe dystroglycanopathy, similar to the phenotypic spectrum observed in human patients. Here, MYF5 is linked to neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan.