Dedifferentiation‐derived neural stem cells exhibit perturbed temporal progression

Abstract

Dedifferentiation is the reversion of mature cells to a stem cell‐like fate, whereby gene expression programs are altered and genes associated with multipotency are (re)expressed. Misexpression of multipotency factors and pathways causes the formation of ectopic neural stem cells (NSCs). Whether dedifferentiated NSCs faithfully produce the correct number and types of progeny, or undergo timely terminal differentiation, has not been assessed. Here, we show that ectopic NSCs induced via bHLH transcription factor Deadpan (Dpn) expression fail to undergo appropriate temporal progression by constantly expressing mid‐temporal transcription factor(tTF), Sloppy‐paired 1/2 (Slp). Consequently, this resulted in impaired terminal differenation and generated an excess of Twin of eyeless (Toy)‐positive neurons at the expense of Reversed polarity (Repo)‐positive glial cells. Preference for a mid‐temporal fate in these ectopic NSCs is concordant with an enriched binding of Dpn at mid‐tTF loci and a depletion of Dpn binding at early‐ and late‐tTF loci. Retriggering the temporal series via manipulation of the temporal series or cell cycle is sufficient to reinstate neuronal diversity and timely termination.

Neuroepithelial depletion schedules cessation of neurogenesis in theDrosophilaoptic lobes

“…Immunostainings showed that EcR is expressed at very low levels in the medulla NBs at 12 hr APF (Supplementary Figure 1A). Additionally, when EcR was knocked down via RNAi in the medulla NBs with eyR16F10-GAL4, which is expressed in a subset of medulla NBs and their progeny (Veen et al , 2023), we could not detect any persistent NBs at 24 hr APF (Supplementary Figure 1B, C, E). A similar phenotype was observed using a dominant negative form of EcR (EcR DN ) (Supplementary Figure 1D, E).…”

“…Wildtype fly was w 1118 . eyR16F10-GAL4 (BL 48737) was used to induce expression of transgenes in a subset of medulla NBs and their progeny from larval development (Veen et al , 2023). Knockdown and overexpression clones were induced by flip-out system using hsFLP,act>CD2>GAL4;UAS-Dcr2,UAS-GFP (a gift from Lei Zhang).…”

Her6 and Prox1a are novel regulators of photoreceptor regeneration in the zebrafish retina

“…Dpn is expressed in NBs and necessary for the maintenance of NB 'stemness' (San-Jua ´n annbd Baonza 2011), and more recently, we have shown that Dpn overexpression is sufficient to induce neuron to NB dedifferentiation [24]. The zebrafish ortholog of dpn, her6, is expressed in developmental progenitors within the inner nuclear layer (INL) and is downregulated upon neurogenesis [27].…”

“…In future studies, it would be interesting to test whether the loss of Her6 can stimulate quiescent MG to re-enter cell cycle in the absence injury. Drosophila ortholog of her6, deadpan (dpn), is also a Notch target gene, however, it plays an opposite function within neurons, where the overexpression of Dpn triggers the transition of mature neurons to NSCs [24]. Together, this highlights the dynamic roles of Notch signalling in different cell types.…”