| Summary: | 碩士 === 國立陽明大學 === 神經科學研究所 === 87 === The Drosophila peripheral nervous system (PNS) comprises three types of sensory elements: external sense (es) organs, chordotonal (ch) organs, and multiple dendritic (md) neurons. At the beginning of the PNS development, the proneural genes are expressed in patches of ectodermal cells and endow these cells with competence to become sense organ precursors (SOPs). The proneural gene achaete (ac) and scute (sc) are required for formation of the es organs and es organ-related md neurons while atonal (ato) is required for chordotonal organs and ch organ-related md neurons. ac, sc, and ato encode basic-helix-loop-helix (bHLH) domain-containing proteins. Our lab has identified a novel bHLH gene asolo (aso) that may be responsible for the formation of solo-md neuron. During embryonic development, the aso gene mRNA appears expressed transiently in a typical proneural gene pattern, from a cluster of cells to two SOP's. One SOP will develop into the bipolar dendritic neuron (dbp), while the other SOP may develop into one of the dmd6 neurons.
We have shown that Aso forms heterodimer with Daughterless binding to two different E boxes in vitro. Genetic interaction also suggests the in vivo interaction of both genes. When ectopically expressed, aso can promote the formation of ectopic md neurons, as well as ch and es organs.
We have also compared the differential abilities of the three types of the proneural genes and found that (1) aso has the unique ability to promote md neuron formation; (2) ato and aso are equally competent to promote ch organ formation; (3) sc is more capable in promoting es organs. These results suggest that the basic domain is the determinant for ch organs and an unidentified domain outside the basic domain determines the md neuron specificity.
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