Pluripotent embryonic stem cells from the rat are capable of producing chimeras.

Embryonic stem cells have been enormously important in the production of targeted mutations in mice used in the study of gene function and biological aspects of disease states. The use of these cells for mouse studies is now wide-spread but the production of animals from similar cell lines derived from other species has not been previously reported. We demonstrate here the derivation of diploid rat embryonic stem cells (RESC-01). RESC-01 cells are SSEA-1 and alkaline phosphatase positive, grow best on primary rat embryonic fibroblasts, and can differentiate extensively in vivo. RESC-01 cells form cystic embryoid bodies capable of rhythmic contractions. Rat blastocysts injected with RESC-01 cells form chimeras. The results indicate that the successful in vitro propagation and chimera production with embryonic stem cells is not limited to the mouse. The long-term culture of rat ES cells will provide an important resource for the study of normal physiology and disease models where rat is the species of choice.