Notch signalling and the cell cycle regulate Trunk Neural Crest collective migration

Abstract

Neural crest cells are a multipotent population that migrate extensively during development and differentiate into a plethora of derivatives. Trunk neural crest (TNC) migrate collectively forming single cell chains, in which the leader cell directs movement and is trailed by followers. We have previously shown that leader and follower identities are established before migration initiation, but how migratory identities are acquired is not understood. In this work, we investigated the mechanisms of migratory identity acquisition and how these affect TNC differentiation capacities. First, we asked if leader and follower cells arise from a common progenitor. We found that a single progenitor divides asymmetrically giving rise to one leader and one follower cell, while all other TNC progenitors give rise to two follower cells. Next, we investigated the mechanisms by which TNC identities are defined. Interestingly, we found that communications via Notch regulate migratory identity acquisition. Our data show that leader cells are defined upon high Notch levels, while followers present low Notch activity. Alteration of Notch activity in TNC leads to the establishment of a more homogeneous population unable to migrate coherently. Concurrently, we observed that leaders are larger than follower cells, and sought to investigate the role of cell cycle dynamics in this difference. We found that leaders and followers exhibit different division patterns and cell cycle dynamics. Although the total duration of the cell cycle is similar, the durations of G1 and S-phases are inversely proportional. Leaders spend the majority of the cell cycle in S-phase, while followers present a longer G1-phase. Our data show that differences in cell cycle patterns are under the regulation of Notch signalling. Finally, we investigated whether leader and follower cells present differences in their long-term fate. We found that unlike followers, leaders divide asymmetrically giving rise to a new leader and a follower cell. This division asymmetry translates into a long term fate asymmetry. The sibling that retains the leader’s identity gives rise to the sympathetic chain ganglia, while its follower sibling differentiates into a Schwann cell. On the other hand, followers divide symmetrically, giving rise to the dorsal root ganglia or Schwann cells. In this work, we have shown that coordination between Notch signalling and the cell cycle pathway regulate TNC migratory identity and fate.

Date of Award	1 Mar 2022
Original language	English
Awarding Institution	King's College London
Supervisor	Claudia Linker (Supervisor) & Jon Clarke (Supervisor)