| Research Abstract |
BarH1 and BarH2 are two closely related homeo box genes that form a small complex at the Bar locus on the X chromosome of Drosophila. These genes encode polypeptides similar in size and sequence and share a common homeodomain that is identical in sequence except for the putative trans-activator-binding sites. They are strictly coexpressed in various types of neural cells, functionally redundant to each other, and are required for development for some neural tissues. As a first step to clarify how the strict coexpression of Bar homeobox genes are regulated, about 80kb region spanning between BarH1 and BarH2 were molecularly dissected and their enhancer activity was assayd at the level of individuals using P-mediated transformation and a lac-Z reporter system. We identified and localized almost all Bar-specific enhancers (15 enhnacers) in the region, an observation supporting the notion that BarH1 and BarH2 genes are regulated by a series of common enhancer elements. During the course of experiments, we also isolated related genes and examined their propertiss. They include two FGF receptor genes, hedgehog segment polarity gene, forked gene, eagle neuroblast-specific hormon receptor gene and NAD (P) H-flavin oxidoreductase genes. In addition, we examined possible interactions between Bar homeobox genes and hedgehog, and foundthat, in a particular case, the spatial and temporal expression of Bar homeobox genes are strictly controlled by the positional information formed by hesgehog and wingless, another key segment polarity gene.
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