ISOLATION OF A PRIMATE EMBRYONIC STEM-CELL LINE

Embryonic stem cells have the ability to remain undifferentiated and p roliferate indefinitely in vitro while maintaining the potential to di fferentiate into derivatives of all three embryonic germ layers. Here we report the derivation of a cloned cell line (R278.5) from a rhesus monkey blastocyst that remains undifferentiated in continuous passage for >1 year, maintains a normal XY karyotype, and expresses the cell s urface markers (alkaline phosphatase, stage-specific embryonic antigen 3, stage-specific embryonic antigen 4, TRA-1-60 and TRA-1-(81) that a re characteristic of human embryonal carcinoma cells. R278.5 cells rem ain undifferentiated when grown on mouse embryonic fibroblast feeder l ayers but differentiate or die in the absence of fibroblasts, despite the presence of recombinant human leukemia inhibitory factor. R278.5 c ells allowed to differentiate in vitro secrete bioactive chorionic gon adotropin into the medium, express chorionic gonadotropin alpha- and b eta-subunit mRNAs, and express alpha-fetoprotein mRNA, indicating trop hoblast and endoderm differentiation. When injected into severe combin ed immunodeficient mice, R278.5 cells consistently differentiate into derivatives of all three embryonic germ layers. These results define R 278.5 cells as an embryonic stem cell line, to our knowledge, the firs t to be derived from any primate species.