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. The gene discussed is FKTN; the disease is neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan.