The construction of different types of aggregates and chimaeric aggregates from individual blastomeres of mouse 8-cell embryos.

Different types of aggregates and chimaeric aggregates were constructed from individual 1/8-blastomeres of C57BL/6J and 129/Sv 8-cell embryos. Addition of phytohaemagglutinin into manipulation medium allowed us to construct large numbers of 4/8 to 9/8 aggregates and chimaeric aggregates exactly according to the design of the experiment. The developmental potential of reconstructed embryos was high. Over 93% of 4/8 to 8/8 aggregates and 90% of different types of 7/8 to 9/8 chimaeric aggregates formed blastocysts during 30 to 34 h of in vitro culture. All types of 4/8 to 8/8 aggregates and 7/8 to 9/8 chimaeric aggregates, in vitro cultured for 24 h, were able to undergo normal implantation after transfer into day-3 recipients. Live young were born after the transfer of morulae and blastocysts developed from 8/8 aggregates, and chimaeric morulae and blastocysts formed from different types of 7/8 to 9/8 chimaeric aggregates. All young born after the transfer of chimaeric embryos were overt C57BL/6J in equilibrium 129/Sv chimaeras.