Transcription factor that can both stimulate and repress transcription. Binds to the consensus DNA sequence 5'-A/GCAGGTG-3'. Regulates cell motility and adhesion during tracheal morphogenesis by stimulating transcription of the DE-cadherin gene shg at branch tips, thereby promoting tracheal tube fusion. Maintains diploidy in imaginal cells by inhibiting the transcription of genes required for endoreplication. Required for development of the genital disk and acts as an intrinsic determinant of wing cell fate. The somatic protein is required for maintenance of male germ cells. Acts with other members of the snail protein family to control embryonic central nervous system development. Expression is complex and dynamic. In early embryogenesis, expression begins on the dorsal side of the embryo. Expressed in a pattern of longitudinal stripes early in germband elongation. Later in embryogenesis, expression is in cells that correspond to the wing, haltere, leg and genital imaginal disks and the abdominal histoblasts. In the embryonic leg disk, expression is restricted to imaginal cells. Also expressed in the central nervous system (CNS), tracheae and head of stage 14 embryos. CNS and tracheal expression decays during later stages, though head expression persists until late in embryogenesis. In third instar larvae, expression is seen in the brain and in regions of many imaginal tissues including the eye-antennal, wing, leg and haltere disks. Expressed in embryonic, larval and adult male germline stem cells and in the somatic cells of the embryonic gonads. Belongs to the snail C2H2-type zinc-finger protein family.