Cardiac enhancer activity of the homeobox gene tinman depends on CREB consensus binding sites in Drosophila

Abstract

The Drosophila homeobox gene tinman plays a critical role in subdividing the early mesoderm. In particular, tinman is absolutely required for formation of the heart and visceral mesoderm. tinman expression is initiated throughout the mesoderm of the trunk region under the control of the bHLH transcription factor encoded by the twist gene, a determinant of all mesoderm. Later, tinman expression is restricted to the dorsal portion of the mesoderm, a process that is directed by decapentaplegic (dpp) whose product (a TGF-beta-related protein) is secreted by the overlaying ectoderm. Further restriction of tinman expression to the cardiac progenitors, in which it will persist throughout development, involves the secreted segmentation gene product encoded by wingless (wg, a Drosophila Wnt gene). Here, we show that strong early expression depends on the synergistic action of an enhancer element at the 5' end of the gene in conjunction with an element in the first intron. Moreover, two distinct enhancer regions are responsible for tinman expression in the heart: one region confers expression in the heart-tube-associated pericardial cells, the other element drives expression in the contractile, myocardial cells. The latter element contains two CREB consensus binding sites that are essential for cardiac-specific expression. genesis 26:55-66, 2000.

Cardioblast-intrinsic Tinman activity controls proper diversification and differentiation of myocardial cells inDrosophila

“…The early expression of Tinman is necessary and sufficient to specify all dorsal mesoderm derivatives Embryonic tin expression can be separated into the three major phases (Azpiazu and Frasch, 1993;Bodmer, 1993), each regulated by a separable enhancer module that is subject to distinct regulatory inputs (Yin et al, 1997;Venkatesh et al, 2000). The earliest tin expression, which is observed in the entire trunk mesoderm during gastrulation, is recapitulated by constructs containing the enhancer element tinB (Fig.…”

Dystrophin deficiency in Drosophila reduces lifespan and causes a dilated cardiomyopathy phenotype

“…dys RNAi transgenic Drosophila against all isoforms was generously provided by Uri Nudel (Weizmann Institute of Science, Rehovot, Israel; Shcherbata et al, 2007). The heartspecific driver GMH5-Gal4 is a 900 bp heart enhancer fragment 73 from the tinman gene (Bodmer, 1993;Venkatesh et al, 2000) that was cloned into the P{GaWB} vector upstream of the Gal4 sequences. This driver was enhanced with multiple copies of a UAS-Gal4 element allowing stronger myocardial expression when activated in late embryonic or during adult stages (detailed description in .…”

TheDrosophilahomolog of vertebrateIslet1is a key component in early cardiogenesis

“…Embryos from double immunostainings were analyzed using a Leica TCS SP confocal microscope. Primary antibodies were used at the following dilutions: mouse anti-chicken Isl1 (Tup), 1:50 with TSA [Developmental Studies Hybridoma Bank (DSHB)]; rabbit anti-Dmef2, 1:2000 (Lilly et al, 1995); rabbit anti-Tin, 1:50 (Venkatesh et al, 2000); mouse anti-Pericardin (EC11), 1:10 with TSA (DSHB); rabbit anti-Eve, 1:3000 (Frasch et al, 1987); rabbit anti-Odd, 1:100 (Ward and Skeath, 2000); and mouse anti-Pnr, 1:400 with TSA (Herranz and Morata, 2001). Fluorescent in situ hybridization for dpp was performed essentially as described (Klinedinst and Bodmer, 2003).…”