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Cell. 1991 Apr 19;65(2):229-39.

Positive autoregulation of sex-lethal by alternative splicing maintains the female determined state in Drosophila.

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Department of Biology, Princeton University, New Jersey 08544.


Sex-lethal is a binary switch gene that controls all aspects of Drosophila sexual dimorphism. It must be active in females and inactive in males. The on/off regulation reflects alternative RNA splicing in which full-length proteins are produced only in females. Here we investigate the role of Sxl in maintaining sexual pathway commitments. By ectopic expression of a female Sxl cDNA in transgenic male flies, we show that Sxl protein induces a rapid switch from male- to female-specific splicing. The ectopically expressed Sxl protein wil trans-activate an endogenous wild-type Sxl gene. This establishes a feedback loop in which Sxl proteins induce their own synthesis by directing the female-specific splicing of Sxl transcripts. We conclude that the female determined state is maintained by Sxl through positive autoregulation, while the male determined state is maintained by default.

[Indexed for MEDLINE]

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