A novel cold‐sensitive mutant of ntla reveals temporal roles of brachyury in zebrafish

Abstract

Background With the exception of the head, the vertebrate embryonic body is formed progressively in an anterior-posterior direction, originating from a posteriorly located bipotential neural-mesodermal progenitor population. The T-box transcription factor Brachyury is expressed within the progenitors, and is essential for the formation of the posterior mesoderm. A novel cold-sensitive mutant of zebrafish Brachyury (ntlacs) is described that allows exploration of the temporal role of this key factor. Results The ntlacs mutant is used to show that Ntla has an essential role during early gastrulation, but as gastrulation proceeds the importance of Ntla declines as Ntlb acquires a capacity to form the posterior mesoderm. Remarkably, ntlacs embryos held at the non-permissive temperature just during the gastrula stages show recovery of normal levels of mesodermal gene expression, demonstrating the plasticity of the posterior progenitors. Conclusion ntlacs is a valuable tool for exploring the processes forming the posterior body since it allows temporally specific activation and inactivation of Brachyury function. It is used here to show the changing roles of Ntla during early development, and the dynamics of the neuromesdermal progenitors.

Targeted degradation of transcription factors by TRAFTACs: TRAnscription Factor TArgeting Chimeras

“…Brachyury is an essential protein expressed during early embryonic stages and plays a central role in the formation of the embryonic framework of vertebrates (Herrmann, 1991;Wilson et al, 1995). Zebrafish no tail a (ntla) protein is a mutant ll Article form of brachyury associated with truncated or completely abolished notochord and tail somites, highlighting the essential function of brachyury in many aspects of embryonic development including cell movements and tail outgrowth (Halpern et al, 1993;Kimelman, 2016). Therefore, we chose zebrafish as a model system to evaluate the effect of brachyury-TRAFTACs in tail formation.…”

Identification of in vivo Hox13-binding sites reveals an essential locus controlling zebrafish brachyury expression

“…This might be because of partial compensation by Hox element 2, given that we observed tbxta expression in the tailbud of the mutants lacking Hox element 1 until fairly late in somitogenesis. However, previous experiments with a temperature-sensitive Tbxta demonstrated that a strong reduction in Tbxta activity from the start of gastrulation onward causes severe phenotypic changes in posterior body formation, whereas the same reduction in Tbxta activity beginning at the end of gastrulation produced only mild phenotypic changes restricted to the most posterior somites (Kimelman, 2016a). This surprising minor requirement for Tbxta function during somitogenesis stages in zebrafish is potentially explained by a study that showed that, although most of the neural and mesodermal cells in the posterior body are allocated from a NMp pool during the gastrula stages, a second NMp population remains resident in the tailbud and contributes only to the most caudal somites (Attardi et al, 2018).…”

Regulation of stem cell identity by miR-200a during spinal cord regeneration

“…It is still not clear whether brachyury directly regulates Sox2 levels in the regenerating axolotl spinal cord or whether it is via an indirect mechanism. Work from other labs in other research organisms has indicated that brachyury and Sox2 can have a mutually repressive relationship ( Kimelman, 2016; Koch et al, 2017 ; Martin, 2016 ). We have shown that miR-200a directly regulates brachyury and ctnnb1 via seed sequences in the 3′ UTR of these genes.…”