Xenopus hairy2 functions in neural crest formation by maintaining cells in a mitotic and undifferentiated state

Abstract

The neural crest is a population of mitotically active, multipotent progenitor cells that arise at the neural plate border. Neural crest progenitors must be maintained in a multipotent state until after neural tube closure. However, the molecular underpinnings of this process have yet to be fully elucidated. Here we show that the basic helix-loop-helix (bHLH) transcriptional repressor gene, Xenopus hairy2 (Xhairy2), is an essential early regulator of neural crest formation in Xenopus. During gastrulation, Xhairy2 is localized at the presumptive neural crest prior to the expression of such neural crest markers as Slug and FoxD3. Morpholino-mediated knockdown of Xhairy2 results in the repression of neural crest marker gene expression while inducing the ectopic expression of the cell cycle inhibitor p27 xic1 in the presumptive neural crest. We also found that ectopic p27 xic1 disturbs neural crest formation. Furthermore, the depletion of Xhairy2 leads to the apoptosis of mitotic cells. Our results suggest that Xhairy2 functions in neural crest specification by maintaining cells in the mitotic and undifferentiated state.

Mechanisms driving neural crest induction and migration in the zebrafish andXenopus laevis

“…135 Migration begins with the disassembly of the cell-cell adherence junction complex, and the acquisition of a mobile phenotype; cells are maintained in an undifferentiated state in part through the action of the transcription factor Hairy2. 136,137 Within the embryo, neural crest cells migrate through spaces between the basal laminae that define the basal surface of the epidermis and the developing dermomyotome. 138,139 These spaces are occupied by extracellular matrix rich in laminin and fibronectin.…”

Xhairy2 functions in Xenopus lens development by regulating p27xic1 expression

“…5;Nagatomo and Hashimoto 2007). As the double inhibition of Xhairy2 and p27 xic1 rescued the phenotype of neurogenic marker up-regulation as well as the loss of LF expression of pax6 (Fig.…”

“…In other words, Xhairy2 may keep lens lineage cells competent to incoming inducing signal(s) by maintaining undifferentiated, or pluripotent, states of those cells via regulation of p27 xic1 expression. Interestingly, our previous report showed that Xhairy2 in the anterior prechordal plate mesoderm and the neural crest, which are thought to be a group of pluripotent cells, is necessary to maintain tissue identity or the undifferentiated state of such cells (Yamaguti et al, 2005;Nagatomo and Hashimoto, 2007). Maintenance of these states of cells in the presence of Xhairy2 might be in part related to the still-unknown molecular nature of lens competence, which is conceptually the basal state of ectoderm leading to lens formation (Henry and Grainger, 1987).…”

“…Our previous functional analyses suggested that Xhairy2 functions in the maintenance of tissue identity and of the proliferative as well as the undifferentiated state (Yamaguti et al, 2005;Nagatomo and Hashimoto, 2007). Xhairy2 is also expressed in the PPE region from gastrula stage, but its possible contribution to cranial sensory organ formation was not elucidated.…”

Two alloalleles of Xenopus laevis hairy2 gene—evolution of duplicated gene function from a developmental perspective

“…Red arrowheads indicate repression of foxd3 expression on the injected side. The dose of morpholinos was as follows: co mo, 3.4 ng; h2A mo, 3.4 ng; h2B mo, 3.5 ng Specificity of the morpholinos was examined elsewhere with rescue experiments (Nagatomo and Hashimoto 2007).…”