Requirements for GSK3 in development of cranial and trunk neural crest

Abstract

Neural crest (NC) cells are embryonic stem cells that arise from the border between the neural plate and non-neural ectoderm. These cells will go through epithelial-to-mesenchymal transition (EMT) to delaminate and migrate throughout the embryo, where they differentiate into many cell types. In the head, the cranial NC forms most of the craniofacial skeleton and is implicated in several congenital anomalies that present facial phenotypes. In the trunk, NC cells can give rise to the adrenal medullary cells, and are thought to be the cells of origin of neuroblastoma, a childhood cancer. Previous data from our group showed that loss of Glycogen Synthase Kinase 3 (GSK3) in NC cells of mouse embryos impairs migration of the cranial subpopulation, but has no effect in the trunk. Conversely, high-risk cases of neuroblastoma, which only arises from trunk NC, are associated with gain-of-function mutations in Anaplastic Lymphoma Kinase (ALK). Here, we investigate divergences in cranial and trunk neural crest cell development in mouse embryos. SOX proteins are transcription factors with highly dynamic expression patterns. Particularly, Sox9 and Sox10 have been implicated in regulation of NC potential, migration and differentiation. We observed that, in wildtype animals, Sox9 expression is seen in premigratory cranial NC and persists during early migration. While trunk NC cells are predominantly Sox10+ when migrating. When we examined GSK3 mutant mice, we saw a partial loss of Sox9 and Sox10 expression in both subpopulations. Cranial and trunk neural crest face different microenvironments, thus they must come up with distinct migration strategies. To analyse morphological differences between the two subpopulations, we cultured primary neural plate border explants of cranial and trunk regions of mouse embryos. We noticed that cranial NC cells present a wider cell shape than trunk cells and still maintain cell-to-cell contact at the leading edge of migration, while the trunk NC cells are more elongated, exhibit longer cell protrusions and are more detached from one another at the migrating front. These data indicates that trunk NC cells are possibly more progressed in a mesenchymal state once migrating from the neural plate border. One key EMT event is the cadherin switch, from (E- to N-cadherin) that occurs as cells progress for a mesenchymal signature. Cranial NC explants showed predominantly E-cadherin at their cell membrane and trunk neural crest explants had more N-cadherin, consistent with a more progressed EMT state. Strikingly, upon GSK3 inhibition, both cranial and trunk NC explants had an accumulation of E-cadherin, although more critical in the cranial cells. This phenotype was also reproduced, though less severe, upon ALK inhibition. These data corroborate the hypothesis that the cranial and trunk NC subpopulations are autonomously distinct cells that might transition differently upon migration.

Date of Award	1 May 2024
Original language	English
Awarding Institution	King's College London
Supervisor	Karen Liu (Supervisor)