ESTABLISHMENT OF AN EMBRYONIC STEM-CELL LINE FROM 8-CELL STAGE MOUSE EMBRYOS

The aim of this study was to try establishing mouse ES cell lines from the early developmental stage. Fifty-two uncompacted 8-cell stage emb ryos were dissociated and single blastomeres were seeded on primary em bryonic fibroblasts in DMEM/F12 completed with 10% foetal calf serum, 10% new born calf serum, 10(-4) M beta-mercaptoethanol. After approxim ately 5 days of culture, multiple cell clones exhibiting stern cell mo rphology grew our and were dissociated. One cell line was established (MSB1) and characterised. The karyotype and the G-banding revealed a m ale diploid cell line. MSB1 cells were injected into syngenic mice and produced teratocarcinomas. Derailed histological examination of the r umours showed a great variety of cell types including representatives of all three primary germ layers. Several nests of undifferentiated st em cells were also present. Microinjections of MSB1 cells into 52 blas tocysts produced 2 chimeras, 1 male and 1 female. These results demons trate that a highly pluripotent ES cell line can be derived from 8-cel l stage mouse embryos. However, the male chimera appeared sterile. Mor e experiments would thus be necessary to prove that the cell line obta ined is capable to colonise the germ line.