Loss-of-function mutations reveal that the Drosophila nautilus gene is not essential for embryonic myogenesis or viability

nautilus (nau), the single Drosophila member of the bHLH-containing myogenic regulatory family of genes, is expressed in a subset of muscle precursors and differentiated fibers. It is capable of inducing muscle-specific transcription as well as myogenic transformation, and plays a role in the differentiation of a subset of muscle precursors into mature muscle fibers. In previous studies, the nau zygotic loss-of-function phenotype was determined using genetic deficiencies in which the gene is deleted. We note that this genetic loss-of-function phenotype differs from the loss-of-function phenotype determined using RNA interference (L. Misquitta and B. M. Paterson, 1999, Proc. Natl. Acad. Sci. USA 96, 1451-1456). The present study re-examines this loss of-function phenotype using EMS-induced mutations that specifically alter the nan gene, and extends the genetic analysis to include the loss of both maternal and zygotic nau function. In brief, embryos lacking nau both maternally and zygotically are missing a distinct subset of muscle fibers, consistent with its apparent expression in a subset of muscle fibers. The muscle loss is tolerated, however, such that the loss of nau both maternally and zygotically does not result in lethality at any stage of development. (C) 2001 Academic Press.