The crooked neck dwarf muscular dysgenesis in fowl is due to a selective alteration of the somitic myogenic cell line.

Muscular dysgenesis in trunk and limb regions of the crooked neck dwarf (cn/cn) fowl is characterized by a complete disorganization of the muscles, starting at 7.5 days of incubation and resulting, at the end of the incubation period, in a profound muscular atrophy. It has previously been attributed to progressively extending defects of the myotubes. In this paper, embryonic cn/cn head and neck muscles were subjected to histological and ultrastructural analysis. The mononucleated myoblasts of the skeletal muscles are not diseased. Pathology is only expressed in the multinucleated cells, mainly by impaired sarcomerogenesis and distension of the sarcoplasmic reticulum. In the non-skeletal (cardiac or smooth) muscles, the connective tissue scaffolding and the ultrastructural features are similar to those of normal muscles at the same age. The present report confirms that the cn defect is confined to the skeletal muscle cells. All of them belong to the same lineage, which is contained in the somitic mesoderm, whether the latter becomes segmented or not during embryogenesis.