Abdominal-B and caudal inhibit the formation of specific neuroblasts in the Drosophila tail region

Abstract

The central nervous system of Drosophila melanogaster consists of fused segmental units (neuromeres), each generated by a characteristic number of neural stem cells (neuroblasts). In the embryo, thoracic and anterior abdominal neuromeres are almost equally sized and formed by repetitive sets of neuroblasts, whereas the terminal abdominal neuromeres are generated by significantly smaller populations of progenitor cells. Here we investigated the role of the Hox gene Abdominal-B in shaping the terminal neuromeres. We show that the regulatory isoform of Abdominal-B (Abd-B.r) not only confers abdominal fate to specific neuroblasts (e.g. NB6-4) and regulates programmed cell death of several progeny cells within certain neuroblast lineages (e.g. NB3-3) in parasegment 14, but also inhibits the formation of a specific set of neuroblasts in parasegment 15 (including NB7-3). We further show that Abd-B.r requires cooperation of the ParaHox gene caudal to unfold its full competence concerning neuroblast inhibition and specification. Thus, our findings demonstrate that combined action of Abdominal-B and caudal contributes to the size and composition of the terminal neuromeres by regulating both the number and lineages of specific neuroblasts.

Neural stem cell progeny regulate stem cell death in a Notch and Hox dependent manner

“…The homeobox genes of the Antennapedia and bithorax complexes specify the anterior/posterior segmental identity of the Drosophila embryo. 11,34,37,[39][40][41] A role for a pulse of abdA expression to activate the death of postembryonic NBs has been previously demonstrated, 11 as has the involvement of abdA in embryonic NB fate. 35 Here, we show that AbdA regulates NB death in the embryo, acting upstream of Enh1 to turn on rpr and grim transcription specifically in abdominal NBs.…”

Novel Genes Involved in Controlling Specification of Drosophila FMRFamide Neuropeptide Cells

“…The VNC is formed from the ventral part of the neuroectoderm by highly conserved anterior-posterior and dorsal-ventral patterning of the embryo (Skeath 1999;Skeath and Thor 2003). The VNC can be subdivided into three thoracic and 10 abdominal segments (Birkholz et al 2013). During early embryogenesis 30 progenitors, denoted neuroblasts (NBs), are born in each hemi-segment (Bossing et al 1996;Schmidt et al 1997;Schmid et al 1999).…”

Roles ofHoxgenes in the patterning of the central nervous system ofDrosophila

“…In addition to their early role in shaping large cellular territories, Hox genes influence the activities of individual cells, controlling processes in the CNS such as programmed cell death, [12][13][14][15] proliferation, 9,16,17 and cell specification. 13,15,[17][18][19][20][21] (Table 1) …”

“…For example, Birkholz et al 15 have shown that Abd-B inhibits the formation of a specific set of NBs in the most posterior abdominal segments. Specifically, they found that there were more neuroblasts in parasegment 15 (i.e., the posterior half of abdominal segment 9 and anterior half of abdominal segment 10) in Abd-B mutant embryos than in the wild-type, 1 of these extra progenitors being NB7-3 and its lineage.…”

“…Since lethal of scute was found to be a putative Abd-B targets, 30 Birkholz et al 15 speculated that it prevented the formation of these neuroblasts in the more posterior segments of the VNC by repressing the formation of neural equivalence groups. However, overexpression of Abd-B in more anterior segments was unable to produce complete transformations toward the number of NBs present in PS15.…”