Engrailed: a gene controlling compartment and segment formation in Drosophila.

A total of 58 mutations at the engrailed locus were isolated. Analysis suggests that this genetic locus is necessary for survival but required only in the cells of the posterior compartments. Inactivation of the engrailed locus renders the animal incapable of maintaining the separation between the groups of cells that constitute either the compartments that subdivide each segment or the individual segments themselves.