The multitype zinc-finger protein U-shaped functions in heart cell specification in the Drosophila embryo

Multitype zinc-finger proteins of the Friend of GATA/U-shaped (Ush) class f unction as transcriptional regulators of gene expression through their modu lation of GATA factor activity. To better understand intrinsic properties o f these proteins, we investigated the expression and function of the ush ge ne during Drosophila embryogenesis. ush is dynamically expressed in the emb ryo, including several cell types present within the mesoderm, The gene is active in the cardiogenic mesoderm. and a loss of function results in an ov erproduction of both cardial and pericardial cells, indicating a requiremen t for the gene in the formation of these distinct cardiac cell types. Conve rsely, ectopic expression of lah results in a decrease in the number of car dioblasts in the heart and the inhibition of a cardial cell enhancer normal ly regulated by the synergistic activity of the Pannier and Tinman cardioge nic factors. These findings suggest that, similar to its known function in thoracic bristle patterning, Ush functions in the control of heart cell spe cification through its modulation of Pannier transcriptional activity. ush is also required for mesodermal cell migration early in embryogenesis. wher e it shows a genetic interaction with the Heartless fibroblast growth facto r receptor gene. Taken together, these results demonstrate a critical role for the Ush transcriptional regulator in several diverse processes of mesod erm differentiation and heart formation.