16细胞期爪蟾胚胎背方与腹方裂球的发育能力

THE ACQUISITION OF DEVELOPMENTAL CAPACITY OF 16 CELL STAGE ANIMAL BLASTOMERES IN XENOPUS EMBRYO

在两栖类爪蟾胚胎发育中,由受精引起的皮层转动造成了受精卵的背腹极性。为了研究受精卵细胞质的不均一分布对胚胎体轴形成的影响,我们进行了16细胞期动物极背、腹方裂球的外植和异位移植实验。16细胞期的动物极背方裂球在外植和移植到腹方位置后都表现出背方特征,如外植块培养到原肠中期时伸长,背方裂球在移植到腹方后引发第二体轴等;而16细胞期动物极腹方裂球移植到背方后其发育命运则遵循背方裂球的命运,参与背方结构的形成。我们认为在16细胞期,动物极背、腹方的裂球由于包含着不同的卵质,因而在发育能力上已经具有背、腹的差异。

The establishment of the body axis in vertebrate embryogenesis is the central problem in developmental biology. In Xenopus embryos , fertilization causes the cortical rotation and initiates the cytoplasmic rearrangement, resulting in the establishment of the dorsal-ventral polarity of the body. To understand the rule involved in this process, the developmental capacity of 16-cell stage animal dorsal and ventral blastomeres was investigated by explantation and transplantation. The ex-planted animal dorsal blastomeres elongated at a time when the control embryos start gastru-lation but have no distinct mesodermal differentiation when checked at tail bud stage. The animal dorsal blastomeres gave rise to a secondary axis when transplanted to the animal ventral side of a recipient embryo and composed the major dorsal structure of the secondary axis. The animal ventral blastomeres showed no morphological features in explantation but they followed the developmental fate of dorsal blastomeres when transplanted to the dorsal side of a recipient embryo. Data shown here indicate that in 16 cell stage, the animal dorsal and ventral blastomeres already have different developmental capacity, which may be due to the acquisition of different cytoplasm component of the fertilized egg.