THE ACQUISITION OF DEVELOPMENTAL CAPACITY OF 16 CELL STAGE ANIMAL BLASTOMERES IN XENOPUS EMBRYO
XIONG Hao DING Xiao Yan (Shanghai Institute of Cell Biology, Shanghai 200031)
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.