Hereditary peroneal muscular atrophy in the mouse: an experimental model for congenital contractures (arthrogryposis).

A new mutant, peroneal muscular atrophy (pma) mouse in CF#1 strain has an autosomal recessively inherited equinovarus (club foot deformity) of the hind legs because of the absence of the common peroneal nerve branch of the sciatic nerve. We found the peroneal muscles were hypoplastic with histochemical and electron microscopic characteristics of fetal muscle. The anterior horn cells in the spinal cord were not reduced in number and they appeared to be normal. The density and size of the myelinated fibers in the anterior spinal roots of L3, L4, and L5 and the sciatic nerve in the affected side were not different from those in the unaffected. Therefore, the absence of the common peroneal nerve in the pma mouse is thought to result from the misdirection of these nerve bundles into other peripheral nerves. As the anomalous condition was present at birth with no progression, the pma mouse may be an experimental model for the study of arthrogryposis multiplex congenita or club foot deformity, and may lead to the understanding of the muscle and nerve interaction during development.