(The) roles of dTGIF and D-mef2 in the drosophila wing development

Abstract

Dpp(Decapentaplegic), a member of the $TGF-\beta$ superfamily, controls the growth and patterning in the Drosophila wing development. Recently, it was reported that TGIF(TG Interacting Factor) was specifically recruited to Smad target genes as a co-repressor by $TGF-\beta$ signaling in mammalian system. I examined whether Drosophila homolog of TGIF(dTGIF) was involved in Dpp signaling in vivo. Ectopic expression studies with dTGIF revealed that it regulated cell proliferation but not the expression of Dpp target genes at least in the developing Drosophila wing. These results imply that TGIF does not function as the co-repressor of Mad, a Drosophila homolog of Smad, in Drosophila wing patterning. It is still possible that dTGIF is involved in Dpp-dependent growth of the wing. In the meantime, I discovered a D-mef2 (myocyte-specific enhancer factor2) allele$(D-mef2^{ev})$ which gives ectopic cross vein phenotype. Previous studies with crossveinless 2 mutant suggest that cross vein formation probably requires a local morphogenic control by a $TGF-\beta$ superfamily member. The genetic complementation tests of $D-mef2^{ev}$ with previously known D-mef alleles showed that $D-mef^{ev}$ is a novel D-mef2 allele. D-mef2 was expressed in the presumptive intervein cells of pupal wing discs. Induction of D-mef2 null clones resulted in ectopic vein and marginal structure formation and notching. In conclusion, dTGIF has a growth inhibitory function and D-mef2 plays critical roles in vein patterning in the developing Drosophila wing.