title: Primary Sex Determination in Drosophila melanogaster Does Not Rely on the Male-Specific Lethal Complex.
abstract: It has been proposed that the Male Specific Lethal (MSL) complex is active in Drosophila melanogaster embryos of both sexes prior to the maternal-to-zygotic transition. Elevated gene expression from the two X chromosomes of female embryos is proposed to facilitate the stable establishment of Sex-lethal (Sxl) expression, which determines sex and represses further activity of the MSL complex, leaving it active only in males. Important supporting data included female-lethal genetic interactions between the seven msl genes and either Sxl or scute and sisterlessA, two of the X-signal elements (XSE) that regulate early Sxl expression. Here I report contrary findings that there are no female-lethal genetic interactions between the msl genes and Sxl or its XSE regulators. Fly stocks containing the msl3(1) allele were found to exhibit a maternal-effect interaction with Sxl, scute, and sisterlessA mutations, but genetic complementation experiments showed that msl3 is neither necessary nor sufficient for the female-lethal interactions, which appear to be due to an unidentified maternal regulator of Sxl. Published data cited as evidence for an early function of the MSL complex in females, including a maternal effect of msl2, have been reevaluated and found not to support a maternal, or other effect, of the MSL complex in sex determination. These findings suggest that the MSL complex is not involved in primary sex determination or in X chromosome dosage compensation prior to the maternal-to-zygotic transition.
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas 77843.
authors.forename: James W
authors.identifier: http://orcid.org/0000-0002-4378-9449
authors.initials: JW
authors.lastname: Erickson
mesh_terms: D000818:Animals; D004303:Dosage Compensation, Genetic; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics*; D005260:Female; D005804:Genes, Lethal; D005838:Genotype; D008297:Male; D009154:Mutation; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012730:Sex Chromosomes; D019849:Sex Determination Processes / Q000235:genetics*
chemical_list: D029721:Drosophila Proteins; D016601:RNA-Binding Proteins; C067777:Sxl protein, Drosophila
keywords: Genetics of Sex; Sxl; X-signal element; dosage compensation; maternal-to-zygotic transition; sex chromosomes