Specific muscle identities are regulated by Krüppel during Drosophila embryogenesis.

During Drosophila embryogenesis, mesodermal cells are recruited to form a complex pattern of larval muscles. The formation of the pattern is initiated by the segregation of a special class of founder myoblasts. Single founders fuse with neighbouring nonfounder myoblasts to form the precursors of individual muscles. Founders and the muscles that they give rise to have specific patterns of gene expression and it has been suggested that it is the expression of these founder cell genes that determines individual muscle attributes such as size, shape, insertion sites and innervation. We find that the segmentation gene Krüppel is expressed in a subset of founders and muscles, regulates specific patterns of gene expression in these cells and is required for the acquisition of proper muscle identity. We show that gain and loss of Krüppel expression in sibling founder cells is sufficient to switch these cells, and the muscles that they give rise to, between alternative cell fates.