The Ets protein pointed prevents both premature differentiation and dedifferentiation of Drosophila intermediate neural progenitors

Abstract

Intermediate neural progenitors (INPs) need to avoid both dedifferentiation and differentiation during neurogenesis, but the underlying mechanisms are not well understood. In Drosophila, the Ets protein Pointed P1 (PntP1) is required to generate INPs from type II neuroblasts. Here, we investigated how PntP1 promotes INP generation. By generating pntP1-specific mutants and using RNAi knockdown, we show that the loss of PntP1 leads to both an increase in type II neuroblast number and the elimination of INPs. The elimination of INPs results from the premature differentiation of INPs due to ectopic Prospero expression in newly generated immature INPs (imINPs), whereas the increase in type II neuroblasts results from the dedifferentiation of imINPs due to loss of Earmuff at later stages of imINP development. Furthermore, reducing Buttonhead enhances the loss of INPs in pntP1 mutants, suggesting that PntP1 and Buttonhead act cooperatively to prevent premature INP differentiation. Our results demonstrate that PntP1 prevents both the premature differentiation and the dedifferentiation of INPs by regulating the expression of distinct target genes at different stages of imINP development.

An Hdac1/Rpd3-Poised Circuit Balances Continual Self-Renewal and Rapid Restriction of Developmental Potential during Asymmetric Stem Cell Division

“…First, PntP1 is specifically expressed in type II neuroblasts and in Ase − immature INPs (Figure 1A). Second, loss of pntP1 function leads to reduced Erm expression in immature INPs as well as supernumerary type II neuroblast formation (Komori et al, 2014a; Xie et al, 2016). Indeed, we found that knocking down pntP1 function reduced the expression of 9D11 2-5 -GFP in vivo , and the ETS-domain of PntP1 bound five of the seven putative PntP1-binding sites in the 9D11 2-5 enhancer in vitro (Figure 3J; Supplementary Figures 3H-I).…”

bHLH-O proteins balance the self-renewal and differentiation of Drosophila neural stem cells by regulating Earmuff expression

“…PntP1 is expressed in type II NBs and imINPs to specify type II NBs and promote the generation of INPs by preventing both the dedifferentiation and premature differentiation of INPs (Xie et al, 2016; Zhu et al, 2011). Erm is normally activated by PntP1 only in imINPs, in which Notch is turned off (Koe et al, 2014; Xie et al, 2016). In the absence of Notch or its downstream E(spl) proteins, PntP1 activates erm in type II NBs.…”

Lessons from Drosophila Pointed, an ETS family transcription factor and key nuclear effector of the RTK signaling pathway

“…The other possibility is that PntP1 functions in concert with another transcription factor leading to repression of Ase expression in type II NBs. In support of the latter, PntP1 was shown to genetically interact with the transcription factor Buttonhead (Btd), as halving the dosage of btd in pnt mutant background led to an increase in the number of Ase expressing type II NBs (Xie et al, , ). This suggests that PntP1 and Btd function together to inhibit Ase expression in type II NBs.…”

“…Intestinal stem cell proliferation P1, P2 Yes (Jin et al, 2015;Ren et al, 2013) Renal and nephric stem cells P1 Yes (Li, Liu, & Cai, 2015) Female germline stem cell niche (Liu, Lim, & Cai, 2010) Neural stem cell (Xie et al, 2014(Xie et al, , 2016Zhu, Barshow, Wildonger, Jan, & Jan, 2011) Tracheal branching Patterning the ventral ectoderm P1 Yes (Gabay et al, 1996;Golembo, Yarnitzky, Volk, & Shilo, 1999) Wing development P2 Yes (Paul et al, 2013) to directly regulate the expression of loco, which codes for an RGS domain containing protein that is required for ensheathment of longitudinal connectives and maintaining the integrity of the blood-brain barrier Granderath et al, 2000;Yuasa et al, 2003). As mutations in pnt affect glial cell differentiation, migration and ensheathment of commissural and longitudinal axons, considerable effort should be placed on identifying the downstream transcriptional targets genes that they activate in order to gain insight into how these processes are regulated.…”