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Symbol: {Links} Flybase ID: {Flybase_ID}
Synonyms: {Name} {GadFly}
Function: {Short_Function} {LocusLink}
Keywords: {Keywords} {Interactive_Fly}

  • Sex-lethal (Sxl) is the sex determination master switch and it controls somatic sexual development.
  • Sxl is a splicing and translational regulator.
  • "Sxl is activated in females where the X chromosome to autosome (X:A) ratio is 1. It remains ‘off’ in males where the X:A ratio is 0.5. Once set, these two modes of Sxl expression are maintained through the rest of the life cycle (Sanchez and Nothiger, 1983; Cline, 1984). In females, a positive autoregulatory feedback loop that functions through alternative splicing maintains the on state (Bell et al., 1991). The male mode of splicing is maintained by default. Sxl directs somatic sexual development by controlling the dosage compensation system (Lucchesi, 1978) and the somatic sexual differentiation pathway (reviewed by Cline and Meyer, 1996). The dose compensation system is turned off by Sxl, through both splicing regulation and translational repression (Bashaw and Baker, 1997; Kelley et al., 1997). In somatic sexual development, Sxl promotes female differentiation by controlling the female specific splicing of the transformer gene (Boggs et al., 1987; McKeown et al., 1987). The final requirement of Sxl is in oogenesis. Pole cell transplantation experiments have demonstrated that female germ cells require Sxl for regulating mitosis. Germ cells that lack Sxl develop as tumorous cysts of many small undifferentiated cells (Schupbach, 1985), a phenotype that is shared by the female sterile alleles of Sxl. Additionally, Sxl regulates the splicing of its own transcripts (Hager and Cline,1997), as well as the female-specific process of meiotic recombination (Schütt et al., 1998; Bopp et al., 1999). The germline targets of Sxl are not known, but they are not the somatic ones (Marsh and Wieschaus, 1978; Schupbach, 1985)" (Vied, 2001)
  • Vied, 2001 propose that g-tubulin together with Cos2, tether Sxl to microtubules maintaining Sxl in the cytoplasm until Hh, or an effector of the Hh signal, releases Sxl from the complex.
Genetic interactions
  • Ptc and Fu in the germarium undergo changes in expression that are coincident with Sxl (Vied, 2001)
Physical interactions
  • Immunoprecipitations from ovarian extracts show that Sxl is in a complex with Fu and Cos2, along with b- and g-tubulin (Vied, 2001)
Transcriptional Regulation
Location (protein and transcript)
Protein Modifications and Regulation
Related to
{Related to}
Overexpression / Ectopic expression


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