爪蟾胚胎原肠中期背方中胚层的组织分化

原肠中期内卷的背方中胚层出现了分别控制脊索和肌肉发育的专一分子的区域化表达。为了研究这个时期的背方中胚层是否已经能够在脱离体内信号的情况下向预定命运分化,我们进行了预定脊索和预定肌肉组织的体外培养,以及两者的共培养,并检测了细胞表达组织专一性分子的情况。原肠中期的预定脊索区域和预定体节区域都能在体外分化成相应的组织——空泡化的脊索和肌细胞,但脊索只能微弱表达其功能分子Shh,肌细胞不能形成肌节。预定脊索区域和预定肌肉区域的共培养也无法增强脊索表达Shh和促进肌细胞形成肌节。我们的结论是,原肠中期内卷的中胚层细胞已经具有了朝预定命运独立分化的能力,但进一步形成功能和结构都完整的相应组织可能还需要周围组织的作用。

TISSUE SPECIFIC DIFFERENTIATION OF DORSAL MESODERM IN XENOPUS MID-GASTRULA EMBRYOS

Genes involved in differentiation of notochord or muscle are expressed in specific regions of the involuted dorsal mesoderm in mid-gastrula Xenopus embryo. The presumptive notochord or the presomitic mesoderm have been cultured either in isolation or recombination to investigate whether these tissues have been determined. Cell differentiation was checked by specific markers of notochord ( Shh ) or muscle cell ( desmin, myosin). The results show that the pre:5umptive notochord can differentiate into vacuolated noto- chord with a weak expression of Shh, while the presomitic mesoderm differentiate into muscle cells with a normal expression of desmin and myosin in vitro. The same result was obtained when the two tissues have been cocultured. These data suggest that the cell fate of the involuted dorsal mesoderm in mid-gastrula has been determined, cells can differentiate according to their fates without further signals from the adjacent tissues, but no functional structures can be formed by these tissues in vitro.