Mahowald A P, Wei G
Department of Molecular Genetics and Cell Biology, University of Chicago, IL 60637.
Ciba Found Symp. 1994;182:193-202; discussion 202-9. doi: 10.1002/9780470514573.ch11.
Many lines of evidence indicate that in Drosophila the mechanism for establishing the sex of the female germline is different from that acting in somatic cells. In the soma Sxl has an embryonic determinative role and is required throughout the life of female flies; in germ cells its expression begins only in the larval ovary. Both the mechanism for activating Sxl and the genes controlled by Sxl are different in the germline. A number of genes have been identified that are essential either for survival (e.g. ovo, otu) or differentiation (snf, Sxl, fl(2)d, bgcn) of female germ cells. ovo is required during embryogenesis for survival of pole cells. Genetic interactions with dominant alleles of ovo and/or Sxl indicate that otu, Sxl, snf and fl(2)d act in the same pathway as does ovo. bgcn differs in that neither ovo nor SxlD mutations affect the bgcn phenotype even though XX bgcn germ cells enter the male pathway. bgcn causes sterility in both sexes. Although the germline defect is cell autonomous in mosaic gonads, bgcn is also required in the somatic tissue for maintaining oogenesis of wild-type germ cells. Several dominant suppressors of bgcn have been identified and some have properties similar to Suppressors of variegation, suggesting that chromatin structure is critical for proper germ cell sex determination.
许多证据表明，在果蝇中，雌性生殖系性别确定机制与体细胞中的不同。在体细胞中，Sxl具有胚胎决定性作用，雌性果蝇一生都需要它；在生殖细胞中，其表达仅在幼虫卵巢中开始。生殖系中激活Sxl的机制和受Sxl控制的基因都不同。已经鉴定出许多对雌性生殖细胞的存活（如ovo、otu）或分化（snf、Sxl、fl(2)d、bgcn）至关重要的基因。ovo在胚胎发育期间是极细胞存活所必需的。与ovo和/或Sxl的显性等位基因的遗传相互作用表明，otu、Sxl、snf和fl(2)d与ovo在同一途径中起作用。bgcn的不同之处在于，即使XX bgcn生殖细胞进入雄性途径，ovo和SxlD突变也不会影响bgcn表型。bgcn导致两性不育。尽管在嵌合性腺中生殖系缺陷是细胞自主的，但在体细胞组织中维持野生型生殖细胞的卵子发生也需要bgcn。已经鉴定出几种bgcn的显性抑制因子，其中一些具有类似于斑驳抑制因子的特性，这表明染色质结构对于正确的生殖细胞性别确定至关重要。
