Fig. 1. Characterization of by. (A) Genomic structure of by and the corresponding protein domain structure with the amino acid number presented underneath. The P-element insertion site of the by² mutant allele is noted. (B) Drosophila tensin (Dtensin) exhibits highly homologous C-terminal SH2 and PTB domain structures to its human orthologs. (C) by mRNA was expressed throughout all the developmental stages, and its level was highest in the adult male (upper panel). 18S rRNA was used as a loading control (lower panel). E, Embryo; L1, first instar larva; L2, second instar larva; L3, third instar larva; P, pupa; F, female; M, male. (D) In RNA in situ hybridization analyses, by was abundantly expressed in the wing pouch of wild-type flies (left), while significantly reduced signal was detected in the wing imaginal disc of by² mutant (right).