Control of neural crest cell migration via signalling molecules (BMP-4, Noggin, eFGF, Wnts) in the Mexican axolotl (Ambystoma mexicanum)

神经嵴（NC）细胞的迁移是脊椎动物发育过程中的一个关键事件。野生型（黑暗）和白色突变胚胎的墨西哥蝾螈（Ambystoma mexicanum）提供了一个独特的实验系统，研究横向NC细胞迁移。在黑暗的胚胎NC衍生的色素细胞迁移横向表皮下。这种迁移在白色突变体中受到抑制。这种缺陷的分子性质尚不清楚。该建议的目的是研究TGF-β蛋白BMP-4、其拮抗剂Noggin、eFGF和Wnt-1样蛋白（8，3a）是否对NC细胞的侧向迁移发挥关键作用。当异位应用于其他脊椎动物如斑马鱼和鸡时，所有这些因子调节NC细胞的迁移和分化。我们将首先从美西螈中克隆这些因子的cDNA，并研究它们在胚胎中的表达模式。然后，我们将研究它们对侧向NC细胞迁移的影响。我们将植入蛋白包被的微珠以及表达BMP-4，头蛋白，eFGF和Wnt-1样蛋白的非洲爪蟾细胞在premigration蝾螈嵴附近。最后，将通过热休克诱导的BMP-4、头蛋白eFGF和Wnts表达构建体进行基因功能的时间分析。

The migration of neural crest (NC) cells is a key event during vertebrate development. Wild-type (dark) and white mutant embryos of the Mexican axolotl (Ambystoma mexicanum) provide a unique experimental system for studying lateral NC cell migration. In dark embryos NC-derived pigment cells migrate laterally under the epidermis. This migration is inhibited in the white mutant. The molecular nature of this defect is not known. The aim of this proposal is to investigate whether the TGF-ß protein BMP-4, its antagonist Noggin, eFGF and Wnt-1-like proteins (8, 3a) exert a crucial function on lateral NC cell migration. All of these factors modulate migration and differentiation of NC cells when applied ectopically in other vertebrates such as zebrafish and chicken. We will first clone the cDNAs of these factors from the axolotl and study their embryonic expression pattern. We will then investigate their effect on lateral NC cell migration. We will implant protein-coated microbeads as well as Xenopus cells expressing BMP-4, Noggin, eFGF and Wnt-1-like proteins in the vicinity of the premigratory axolotl crest. Finally, the temporal analysis of gene function will be performed by heat shock-inducible expression constructs for BMP-4, Noggin eFGF and Wnts.