β-catenin mediates the specification of endoderm cells in ascidian embryos

Abstract

In the present study, we addressed the role of (beta)-catenin in the specification of embryonic cells of the ascidians Ciona intestinalis and C. savignyi and obtained the following results: (1) During cleavages, (beta)-catenin accumulated in the nuclei of vegetal blastomeres, suggesting that it plays a role in the specification of endoderm. (2) Mis- and/or overexpression of (beta)-catenin induced the development of an endoderm-specific alkaline phosphatase (AP) in presumptive notochord cells and epidermis cells without affecting differentiation of primary lineage muscle cells. (3) Downregulation of (beta)-catenin induced by the overexpression of cadherin resulted in the suppression of endoderm cell differentiation. This suppression was compensated for by the differentiation of extra epidermis cells. (4) Specification of notochord cells did not take place in the absence of endoderm differentiation. Both the overexpression of (beta)-catenin in presumptive notochord cells and the downregulation of (beta)-catenin in presumptive endoderm cells led to the suppression of Brachyury gene expression, resulting in the failure of notochord specification. These results suggest that the accumulation of (beta)-catenin in the nuclei of endoderm progenitor cells is the first step in the process of ascidian endoderm specification.

Animal regeneration: ancestral character or evolutionary novelty?

“…Space precludes consideration of most of these data, but some results are particularly relevant to the issue of ancestral versus adaptive regeneration. Perhaps the main theme that has emerged is a consensus that the establishment of all bilaterian body plans is controlled during development by gradients of Wnt (anteroposterior, AP) and bone morphogenetic protein (BMP) (dorsal-ventral, DV) [23] ( Vegetal in embryo [85] Vegetal in embryo (Ciona) [89] No clear role in buds (Botryllus) [90] Posterior in embryo, controls AP pattern [91] Controls AP polarity of blastema [25] Controls AP polarity of blastema [25] Expressed in hypostome and controls polarity of blastema [101] Posterior in larva (C. elegans) [93] Posterior and segmental in embryo, needed for abdomen formation (Tribolium) [94] Posterior and segmental in trochophore (Platynereis) [98] Posterovegetal in Saccoglossus embryo [87] Whole body regeneration…”

Evolution of embryonic cis-regulatory landscapes between divergent Phallusia and Ciona ascidians

“…The Ciona dataset was also extended with mid-gastrula and mid-neurula stage samples. In addition, to estimate the impact of tissue specification on chromatin accessibility landscapes, we collected in both species ATAC-seq data from early gastrula embryos in which the GSK3 kinase was inhibited from the 8-cell stage, a treatment known to activate the canonical Wnt/ß-catenin signalling pathway, thereby converting most embryonic cells into endoderm (Imai et al, 2000).…”

Wnt signaling pathway and the Evo-Devo of deuterostome axis

“…Cys 区域, 但缺少跨膜区, 因此能在细胞外结合 Wnt 配体, 抑制 Wnt 信号传导 [17] ; Dickkopf-like 蛋白 (Micromeres)表达, 并且一直持续到 60 细胞期, 揭示 植物极的 wnt8 调控中、内胚层原肠的形成和分化 [43] 。 外胚层是从海胆的动物极方向产生的, 内胚层和中 胚层从植物极方向产生的, 若 Wnt 信号被抑制将阻 止中、内胚层的形成。此外, 研究揭示 β-catenin 同 样控制海胆动-植物极轴向的极性 [44] , 并在植物极发 挥作用 [45] , 而 β-catenin 的过表达将导致植物极化的 胚胎 [44][45][46] 。实际上, β-catenin 蛋白在早期动、植物极 轴向极化方面的作用在其它很多动物中均有报道, 例如在水螅和海葵中, β-catenin 蛋白主要定位在动 物极, 而在大多数两侧对称动物中则发生了颠倒, β-catenin 蛋白主要位于植物极 [12,47,48] 。…”