Zebrafish pigment cells develop directly from persistent highly multipotent progenitors

Abstract

Neural crest cells are highly multipotent stem cells, but it remains unclear how their fate restriction to specific fates occurs. The direct fate restriction model hypothesises that migrating cells maintain full multipotency, whilst progressive fate restriction envisages fully multipotent cells transitioning to partially-restricted intermediates before committing to individual fates. Using zebrafish pigment cell development as a model, we show applying NanoString hybridization single cell transcriptional profiling and RNAscope in situ hybridization that neural crest cells retain broad multipotency throughout migration and even in post-migratory cells in vivo, with no evidence for partially-restricted intermediates. We find that leukocyte tyrosine kinase early expression marks a multipotent stage, with signalling driving iridophore differentiation through repression of fate-specific transcription factors for other fates. We reconcile the direct and progressive fate restriction models by proposing that pigment cell development occurs directly, but dynamically, from a highly multipotent state, consistent with our recently-proposed Cyclical Fate Restriction model.

Leukocyte Tyrosine Kinase (Ltk) Is the Mendelian Determinant of the Axolotl Melanoid Color Variant

“…Our results suggest a broader role for Ltk in specifying axolotl pigment cell fates, showing that Ltk knockdown affects iridophore, melanophore, and, presumably, xanthophore populations, as is observed in melanoid . A lesion that simultaneously affects the fate of multiple cell types supports the idea of a multipotent progenitor and direct fate specification ( Figure 7 C), as has been recently proposed for zebrafish pigment cell differentiation [ 10 , 16 ] and as was proposed in the single-origin hypothesis for pigment cells [ 8 ]. Additional studies are needed to determine if there are fundamental differences within amphibia in terms of how key genes function to regulate pigment cell fates.…”

“…( B ) In zebrafish shady , Ltk knockout only affects the specification of iridophores and does not affect melanophore or xanthophore abundances, consistent with progressive fate specification of iridophores and xanthophores [ 31 ]. ( C ) A cyclical fate restriction model recently proposed for zebrafish [ 15 , 16 ] posits dynamic, direct fate specification from highly multipotent progenitor cells. Yellow circles denote xanthophore lineage cells, white circles denote iridophore lineage cells, and black circles denote melanophore lineage cells.…”

“…A cyclical fate restriction hypothesis was recently advanced to reconcile patterns of gene expression within pigment cell progenitor populations that are unexpected under a strict model of progressive fate specification [ 15 ]. A more recent analysis using techniques to accurately measure lowly expressed genes during zebrafish neural crest and pigment cell differentiation provide support for the hypothesis and direct fate specification of at least some pigment cell types [ 16 ].…”

Keratinocytes Drive the Epithelial Hyperplasia Key to Sea Lice Resistance in Coho Salmon

“…Neural crest cells were characterized by multiple pigment cell genes (Table 1) including ltk , which directs multipotent neural crest cell development into pigment cells in zebrafish [56], suggesting these cells are pigment cell progenitors. The detection of neural crest cells, red blood cells, and muscle cells predominately in trunk skin samples (Fig.1 e,f), is consistent with expectations of greater abundance of these cell types in the trunk skin than in the fins [30] given the potential to cut deeper into the dermal layer.…”

Pigment cell progenitor heterogeneity and reiteration of developmental signaling underlie melanocyte regeneration in zebrafish

“…Firstly, these cells arose in response to specific ablation of melanocytes. Secondly, this subpopulation expresses markers that are associated with multipotent pigment progenitors cells found during development ( Brombin et al, 2022 ; Brunsdon et al, 2022 ; Budi et al, 2011 ; Johansson et al, 2020 ; Saunders et al, 2019 ; Subkhankulova et al, 2023 ). Thirdly, although this subpopulation expresses aox5 and some other markers associated with xanthophores, we showed that differentiated xanthophores are not ablated by the melanocyte-ablating drug neocuproine and this mitfa + aox5 hi subpopulation does not make new pigmented xanthophores following neocuproine treatment.…”