title: Seven up acts as a temporal factor during two different stages of neuroblast 5-6 development.
abstract: Drosophila embryonic neuroblasts generate different cell types at different time points. This is controlled by a temporal cascade of Hb→Kr→Pdm→Cas→Grh, which acts to dictate distinct competence windows sequentially. In addition, Seven up (Svp), a member of the nuclear hormone receptor family, acts early in the temporal cascade, to ensure the transition from Hb to Kr, and has been referred to as a 'switching factor'. However, Svp is also expressed in a second wave within the developing CNS, but here, the possible role of Svp has not been previously addressed. In a genetic screen for mutants affecting the last-born cell in the embryonic NB5-6T lineage, the Ap4/FMRFamide neuron, we have isolated a novel allele of svp. Expression analysis shows that Svp is expressed in two distinct pulses in NB5-6T, and mutant analysis reveals that svp plays two distinct roles. In the first pulse, svp acts to ensure proper downregulation of Hb. In the second pulse, which occurs in a Cas/Grh double-positive window, svp acts to ensure proper sub-division of this window. These studies show that a temporal factor may play dual roles, acting at two different stages during the development of one neural lineage.
authors: Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.
authors: Jonathan
authors: J
authors: Benito-Sipos
authors: Carina
authors: C
authors: Ulvklo
authors: Hugo
authors: H
authors: Gabilondo
authors: Magnus
authors: M
authors: Baumgardt
authors: Anna
authors: A
authors: Angel
authors: Laura
authors: L
authors: Torroja
authors: Stefan
authors: S
authors: Thor
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D019835:FMRFamide / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005820:Genetic Testing; D009154:Mutation; D055495:Neurogenesis / Q000235:genetics*; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D011987:Receptors, Steroid; C094295:svp protein, Drosophila; D019835:FMRFamide