Amplification of neural stem cell proliferation by intermediate progenitor cells in Drosophila brain development

Abstract

Background: In the mammalian brain, neural stem cells divide asymmetrically and often amplify the number of progeny they generate via symmetrically dividing intermediate progenitors. Here we investigate whether specific neural stem cell-like neuroblasts in the brain of Drosophila might also amplify neuronal proliferation by generating symmetrically dividing intermediate progenitors.

Gcm protein degradation suppresses proliferation of glial progenitors

“…2C). While embryos homozygous for the null allele slimb P1493 or ago 3 (19,21) exhibited normal glial patterns (Fig. S2), the double slimb ago mutant showed a distinct glial pattern to that of wild-type animals (compare Fig.…”

Opportunities lost and gained: Changes in progenitor competence during nervous system development

“…2c). 13,14,15 In this section, we will discuss how (a) embryonic type I neuroblasts lose competence to respond to early temporal transcription factors due to changes in subnuclear gene position, (b) larval type I neuroblasts lose competence to respond to oncogenic mutations, (c) larval INPs lose competence to respond to Notch signaling, (d) larval type II neuroblasts use Trithorax to maintain competence to generate INPs, and (e) sensory neuron progenitors change competence to respond to Notch signaling.…”

“…13,14,15,32 Type II neuroblasts divide asymmetrically to generate a series of INPs that produce an average of 10 neurons each, whereas larval type I neuroblasts make GMCs that only produce a pair of neurons. 13,14,15 How do type II neuroblasts generate INPs rather than GMCs?…”

“…13,14,15,32 Type II neuroblasts divide asymmetrically to generate a series of INPs that produce an average of 10 neurons each, whereas larval type I neuroblasts make GMCs that only produce a pair of neurons. 13,14,15 How do type II neuroblasts generate INPs rather than GMCs? Recent work demonstrated that type II neuroblasts require the Buttonhead (Btd) transcription factor to maintain INP production, and that Trithorax (member of the SET1/MLL histone methyltransferase complex) is required to maintain the btd locus in a permissive chromatin state, allowing its expression in type II neuroblasts.…”

Stem cells in multiple time zones

“…In addition to the type I lineages, in which daughter cells usually divide once, a second subclass of larval neuroblasts designated type II has been identified [16][17][18] . Intriguingly, type II neuroblasts generate daughter cells that divide multiple times.…”