In: Biology
What basic lessons were learned in the classic experiments about gene regulation and regulation of the even-skipped gene by CRMs that determine stripe two formation in Drosophila embryos?
A number of CRMs have been recently been identified that support concurrent expression of individual genes in similar spatiotemporal profiles in early Drosophila embryos , as well as later in development. Moreover, in vertebrates genome it has been shown that many genes have multiple CRMs active concurrently, and that deletion of one cis-regulatory module can have no observable effect on the gene expression pattern.
By analysis of lacZ reporter transgenes, we found that both these CRMs supported expression in the ventral region of the early embryo in patterns that are spatiotemporally similar but not identical. In contrast to the broadened expression of the proximal CRM fragment, the distally located CRM fragment supports high level expression that is refined, sharp and similar to the endogenous sna expression pattern. It should be noted that our tested DNA fragment was defined by twist ChIP -seq analysis and was larger in size than the one recently tested by another group, a study in which no spatial distinctions between the patterns supported by the proximal and distal CRMs noted.
Our data show that expression of the drosophila snail gene in embryos is established through integrated activity of multiple CRMs that function concurrently and in part, through non-additive activity of CRMs, through sharing of repressors for example, is likely more commonplace than currently appreciated. It is possible concurrently acting CRMs function coordinately to regulate spatial domain and levels of expression in general, and may provide one explanation why genes in Drosophila and other animals often have multiple CRMs that support similar spatiotemporal patterns of expression.