Tamori Y, Mita K, Katagiri C
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Dev Growth Differ. 2000 Oct;42(5):459-67. doi: 10.1046/j.1440-169x.2000.00528.x.
Ectoderm pieces explanted from embryos of Xenopus laevis were cultured and examined for differentiation of hatching gland cells, using immunoreactivity against anti-XHE (Xenopus hatching enzyme) as a marker. The anterio-dorsal ectoderm excised from stage 12-13 (mid-late gastrula) embryos developed hatching gland cells. Meanwhile, the posterio-, but not the anterio-dorsal ectoderm from stage 11 (early gastrula) embryos developed these cells, although it is not fated to do so during normogenesis. This hatching gland cell differentiation from stage 11 posterior ectoderm was not affected by conjugated sandwich culture with the mesoderm but was suppressed when explants contained an anterior portion of the ectoderm. Conjugated cultures of anterior and posterior portions of the ectoderm in various combinations indicated that differentiation of hatching gland cells from stage 11 posterior and stage 12 anterior portions was suppressed specifically by stage 11 anterior ectoderm. Northern blot analyses of cultured explants showed that XHE was expressed in association with XA-1, suggesting its dependence on the anteriorized state. These results indicate that the planar signal(s) emanating from stage 11 anterior ectoderm participates in suppression of the expression of the anteriorized phenotype so that an ordered differentiation along the anteroposterior axis of the surface ectoderm is accomplished.
从非洲爪蟾胚胎中取出外胚层组织块进行培养，以抗XHE（非洲爪蟾孵化酶）的免疫反应性作为标记，检测孵化腺细胞的分化情况。从第12 - 13期（中晚期原肠胚）胚胎切除的前背侧外胚层发育出了孵化腺细胞。同时，从第11期（早期原肠胚）胚胎切除的后背侧外胚层，而非前背侧外胚层，发育出了这些细胞，尽管在正常发育过程中它并无此分化命运。第11期后背侧外胚层的这种孵化腺细胞分化不受与中胚层共轭夹心培养的影响，但当外植体包含外胚层的前部时则受到抑制。外胚层前后部不同组合的共轭培养表明，第11期后背侧和第12期前背侧外胚层的孵化腺细胞分化被第11期前背侧外胚层特异性抑制。对培养的外植体进行Northern印迹分析表明，XHE与XA - 1共同表达，提示其依赖于前部化状态。这些结果表明，来自第11期前背侧外胚层的平面信号参与抑制前部化表型的表达，从而完成沿表面外胚层前后轴的有序分化。
