Cell autonomy of expression of neurogenic genes of Drosophila melanogaster

In embryos of Drosophila melanogaster the development of a pluripotent cell in the neurogenic ectoderm as a member of either a neural or an epidermal lineage depends on its interactions with neighboring cells. Certain genes, designated neurogenic, participate in this process in that there is a deficiency of epidermal histotypes in mutant embryos lacking neurogenic gene functions. To test the cell autonomy of expression of the neurogenic phenotype, individual cells were transplanted from the neurogenic ectoderm of mutant donor embryos into wild-type host embryos. Cells transplanted from donors homozygous for any of several mutant alleles of the neurogenic genes amx, N, bib, mam, neu, and Dl were found to give rise to clones exhibiting a distribution of neural and epidermal histotypes similar to that of the wild type. By contrast, cells transplanted from donors homozygous for loss of the neurogenic E(spl) gene gave rise exclusively to clones of neural histotypes. Thus, only the expression of E(spl) is autonomous, with that of all of the other tested neurogenic genes being nonautonomous. These results are consistent with the inference that the nonautonomous genes provide a source and the autonomous gene provides a receptor of a hypothetical intercellular regulatory signal that is necessary for cell commitment to an epidermal rather than neural fate.