Drosophila small ovary encodes a zinc-finger repressor required for ovarian differentiation

Repression is essential for coordinated cell type-specific gene regulation and controlling the expression of transposons. In the Drosophila ovary, stem cell regeneration and differentiation requires controlled gene expression, with derepression leading to tissue degeneration and ovarian tumors. Likewise, the ovary is acutely sensitive to deleterious consequences of transposon derepression. The small ovary (sov) locus was identified in a female sterile screen, and mutants show dramatic ovarian morphogenesis defects. We mapped the locus to the uncharacterized gene CG14438, which encodes a zinc-finger protein that colocalizes with the essential Heterochromatin Protein 1 (HP1a). We demonstrate that Sov functions to repress inappropriate cell signaling, silence transposons, and suppress position-effect variegation in the eye, suggesting a central role in heterochromatin stabilization.