EXPRESSION OF EXOGENOUS DNA IN THE GONADS OF CHIMERIC CHICKEN EMBRYOSPRODUCED BY TRANSFER OF PRIMORDIAL GERM-CELLS TRANSFECTED IN-VITRO AND SUBSEQUENT FATE OF THE INTRODUCED DNA

The expression and fate of exogenous DNA (lacZ gene), introduced into the gonads of chimaeric embryos and chickens that had been produced by transfer of primordial germ cells (PGCs) transfected in vitro, were e xamined. PGCs obtained from embryonic blood were transfected in vitro by lipofection and transferred to the partially sterilized recipient e mbryos. Expression of the lacZ, gene was observed in the gonads of chi maeric embryos incubated for 3 days after the PGC injection (71.2%, 37 /52). Introduction of the lacZ gene into the gonads of chimaeric embry os was confirmed by PCR analysis. The percentage of embryos with gonad s positive for the lacZ gene was 95% (38/40) after 3 days of incubatio n after the PGC injection. The lacZ gene, however, appeared to persist episomally but was gradually lost during embryonic development. After 17 days of incubation after the PGC injection, the lacZ gene was dete cted in only 14.3% (3/21) of the embryos examined. Although the lacZ g ene was detected in the gonads of two hatched chicks (11.1%), it was n ot detected in the gonads of chimaeric chickens at sexual maturity. Of fspring derived from the lipofected PGCs were obtained from the chimae ric chickens at frequencies of 12.1-69.9% in males and 71.6-97.6% in f emales. The technique developed in the present work could be used to t est the expression of exogenous DNA in the gonads of early chicken emb ryos and should facilitate the production of transgenic chickens.