体节中胚层细胞等级决定的基因调控研究

Cell decision mechanisms specify cellar developmental fates and differentiation directions in embryogenesis process. Somatic mesoderm cell decisions associate with correct development of somites and body axises, which is one of the most important events in the current field of Developmental Biology. Some studies suggested that somite cells are initially specified in stage of presomite mesoderm, and continue their final development under actions of inducers secreted from notochord and floor plate or neurotubules. Recently, we have set up a method of dispersed cell transplantation and used it to analyse cell fate of avian somatic mesoderm. The results show that the first cell decision of presomite occurred in Hensen's node and the decided cells were one kind of lonely-potential cells; the second decision in segmentation plates endowed cells with multiple potency. However some questions remains to be investigated, such as what or if more and other factors are further required for the subsequent development, and how the gene regulation and expression are involved in determination of somite fate, so which this program has studied on. Main research contents focus on: 1 gene cloning and expression pattern that related to the cell decision of presomite mesoderm in chick embryo; 2 the correlation between the genes and cell differentiation or determination by utilizing marker genes, dispersed cell transplantation and embryo cutting operations; 3 systems analysis and cloning genes related to presomite cell determination using RDA and modified Subtraction Hybridization. Major results, key data and science implications are as following: 1. Sonic hedgehog (Shh) and Paraxis whole cDNA, which are two genes of important correlation with axis and somites conformation, have been cloned. The sequence homologies of Shh and Paraxis to GenBank are 99.5%and 98% respectively; 2. The fate of presomite cells had initially been determined in Henson's node by dispersed cell transplantation and embryo cutting operations. The cell, losing inducing signals in order, only became a kind of primary epithelia-like somite. No advanced development and cell migration were discovered. 3. Results of in situ Hybridization show that b-Catenin gene has high expression in novo-somites；gene Shh expression prefers in tissues from ectoderm, and Paraxis rather in mesoderm, their transcription don't only limited within body axis. These results illustrate that the genes have basic and embryonic layer-specific expression properties. 4. Experiments of embryo cutting operations suggested that Shh' function acted in diffusing manner from notochord, floor plate, and neurotubules to presomites；but Paraxis'action is expressing directly in segmentation plate and somites, then disappeared in elder somites than 36th ones. .So, taken together, presomite cells determined firstly in Henson's node, and continue to be differentiated under induction of inducers from notochord, floorplate, and neurotubules till to reach to mature somites. Shh factor is an important one for directing differentiation and decision of presomite cell, but presomite cell don't transcribe Shh gene. We suggest firstly that inducer Shh and somite marker genes are following embryonic layer-specific expression property. b-Catenin, another developmental regulator expressed highly in nero-somites.

细胞的决定规定了细胞发育的命运和分化的方向,它是当前发育生物学前沿最重要的问题之?本工作在原有工作基础上深入研究体节细胞第二次决定相关基因的表达和功能,以便从根旧喜髋咛バ翁⑸姆肿踊?同时探索体壁肌肉细胞决定的时间,地点和潜能的变化,及体壁肌肉闭合基因的表达和功能,为以后研究closure gene基因的进化打基础......