Gene expression studies on human primordial germ cells and preimplantationembryos

Research on the regulation of gene expression in human germ cells and preim plantation embryos is restricted due to the scarcity of samples and the req uirement for highly sensitive molecular techniques to investigate the few c ells available. To overcome these difficulties, we have developed a reliabl e procedure capable of generating amplified cDNA preparations from single c ells. Using this procedure, we prepared cDNA from primordial germ cells (PG Cs) isolated from the gonads of fetuses at 10 weeks gestation and from prei mplantation embryos at the 1-cell, 4-cell, 8-cell and blastocyst stages. Ou r cDNA preparations allow us to investigate the expression profile of an al most unlimited number of different genes in the same sample preparation. Th is is of great advantage for studies of a panel of genes in a particular fa mily or functional group, or with related mechanisms of regulation, e.g., d evelopmental genes, oncogenes, cell cycle-control genes and imprinted genes . We have used these cDNA preparations in conjunction with differential dis play to identify genes specifically expressed in PGCs and preimplantation e mbryos in a sex- and developmental stage-specific manner. Genes specificall y expressed in PGCs, oocytes and embryos were further analysed for their ex pression in embryonal carcinoma cells and in their differentiated derivativ es following treatment by retinoic acid. Our strategy will disclose genes e ssential for gametogenesis and embryonic development which may only be expr essed at certain stages of their development. The germ cell- and embryo-spe cific cDNA molecules, cDNA libraries and microarrays are a valuable resourc e for other researchers in this field.