The kyphoscoliosis (ky) mouse is deficient in hypertrophic responses and is caused by a mutation in a novel muscle-specific protein

The ky mouse mutant exhibits a primary degenerative myopathy preceding chro nic thoraco-lumbar kyphoscoliosis. The histopathology of the ky mutant sugg ests that Ky protein activity is crucial for normal muscle growth and funct ion as well as the maturation and stabilization of the neuromuscular juncti on. Muscle hypertrophy in response to increasing demand is deficient in the ky mutant, whereas adaptive fibre type shifts take place. The ky locus has previously been localized to a small region of mouse chromosome 9 and we h ave now identified the gene and the mutation underlying the kyphoscoliotic mouse. The ky transcript encodes a novel protein that is detected only in s keletal muscle and heart. The identification of the ky gene will allow deta iled analysis of the impact of primary myopathy on idiopathic scoliosis in mice and man.