Expression of achaete and scute genes in Drosophila imaginal discs and their function in sensory organ development.

Abstract

Several kinds of sensory organs (SOs) appear in stereotyped positions on the adult Drosophila cuticle. The generation of these SOs requires the activity of the achaete (ac) and scute (sc) genes. To investigate whether ac and sc also provide spatial information for the positioning of SOs, we have analyzed the patterns of expression of these genes in the wing imaginal disc around the time that SO precursors are being specified. We find that expression coincides with and is restricted to areas of the disc where these precursors are known to be located. In the loss-of-function sc 6 mutant, sc RNA is depleted in a single area located in the region where the precursor for the supressed macrochaeta should be found. Moreover, some, and probably all, SOs require expression of these genes to reach the earliest detectable differentiated state. These and other results presented here, together with the finding that expansion of the areas of ac and/or sc expression causes the development of ectopic SOs, indicate that ac and sc promote the determination of SO precursors and delimit the regions of the imaginal discs where they can develop.

Transgenic Wnt/TCF pathway reporters: all you need is Lef?

“…TOPGAL, TOPdGFP and p-Lef 7 -fos-GFP use a promoter taken from the c-fos gene, which is a transcriptional target of Wnt/b-catenin signaling (Staal et al, 2004) Imaginal discs and embryos in (a-c) were fixed and stained with X-gal as described by Romani et al (1989). 4 Â TCF-lacZ was constructed in the H-Pelican vector (Barolo et al, 2000); additional details are provided in Table 1.…”

Emc, a negative HLH regulator with multiple functions in Drosophila development

“…ac and sc are expressed at the right place and time to promote SMC determination, as anticipated by the genetic analyses. Both genes are coexpressed in the wing imaginal discs, the anlagen of most of the thorax and the wings, in clusters of cells located at precisely determined positions (Cubas et al, 1991;Romani et al, 1989;Skeath and Carroll, 1991) (Figure 1a). SMCs are born within these clusters of ac ± sc expressing cells (Cubas et al, 1991;Skeath and Carroll, 1991) (Figure 1a).…”

“…SMCs are born within these clusters of ac ± sc expressing cells (Cubas et al, 1991;Skeath and Carroll, 1991) (Figure 1a). Moreover, removal of speci®c proneural clusters in ac or sc mutants removes the corresponding SMCs and SOs (Cubas et al, 1991;Romani et al, 1989;Skeath and Carroll, 1991) and a generalized distribution of Ac ± Sc products (in Hairy wing mutants) promotes development of extra SOs in ectopic positions (Balcells et al, 1988;Skeath and Carroll, 1991). Since AS-C proteins confer on cells the ability to become neural (Only the prospective wing region is shown).…”

Opposing inputs by Hedgehog and Brinker define a stripe ofhairyexpression in theDrosophilaleg imaginal disc

“…The bHLH transcription factors, Ac and Sc, are expressed in proneural clusters, groups of cells that roughly define the positions of future sensory structures in the adult (Cubas et al, 1991;Romani et al, 1989;Skeath and Carroll, 1991). Then, through local regulatory events controlled by the neurogenic genes, a cell(s) is selected from each proneural cluster to become a sensory organ precursor, which undergoes a few differential cell divisions (Calleja et al, 2002;Modolell, 1997).…”