msl-2 open reading frame from nucleotides 255-2978, lacking the internal 52 nucleotide intron and the putative Sxl binding sites in the 5' and 3' UTR of the transcripts, is expressed under the control of the Hsp83 promoter.
Expression of msl-2Hsp83.PK in a Iswi2 background (but not in a wild-type background) results in the X chromosome having a bloated morphology in salivary gland polytene chromosome preparations from female larvae. In approximately 30% of the salivary gland nuclei, the phenotype is so severe that the X chromosome is almost completely dispersed and detaches from the chromocenter.
Addition of msl-2Hsp83.PK leads to partial suppression of the abdominal etching phenotype seen in SxlM12/Y males. For SxlM12/Y males with msl-2Hsp83.PK, 72% of their fifth and sixth hemitergites were completely feminized. In contrast none of their forelegs were fully female and 77% were entirely male. The addition of msl-2Hsp83.PK to SxlMf1/Y flies leads to males with completely female genitalia and forelegs, yet nearly normal abdomens.