Pluripotency of R1 was initially tested by tetraploid embryo <-> ES aggregates for completely ES derived development [PubMed: 8378314]. They were also tested by diploid embryo <-> ES aggregates and blastocyst injection for germline transmission in chimeras [PubMed: 8361547]. At early passages (up to passage #14), one third of the completely R1-derived newborns generated by tetraploid embryo <-> R1 aggregates survived. No live offspring were produced from cells older than passage #14.* .
However, about 20% of subclones derived from passage #14 had the original developmental potential of R1 when tested by tetraploid aggregates [PubMed: 8378314]]. R1-derived animals reached adulthood and were fertile. The genetically altered lines derived from R1 gave high efficiency of germline transmission either by injecting them into C57 blastocyst or aggregating them with CD-1 or ICR outbred 8-cell stage embryos. More than 90% of the individual K.O. clones went to germline (n>60) by aggregation chimeras.
*Current ATCC stocks of R1 cells are beyond passage 14. Current stocks of alternative subclone of R1 cells, designated R1/E (ATCC SCRC-1036), are below passage 14 and have been shown to be germline competent.
Matise M, et alProduction of targeted embryonic stem cell clonesIn: Matise M, et alGene Targeting: A Practical ApproachOxfordOxford University Press101-132, 1999
Nagy A, et al. Derivation of completely cell culture-derived mice from early-passage embryonic stem cells. Proc. Natl. Acad. Sci. USA : 8424-8428, 1993. PubMed: 8378314
Wood SA, et al. Non-injection methods for the production of embryonic stem cell-embryo chimaeras. Nature 365: 87-89, 1993. PubMed: 8361547
Nagy A, Rossant JProduction and analysis of ES-cell aggregation chimerasIn: Nagy A, Rossant JGene Targeting: A Practical ApproachOxfordOxford University Press177-206, 1999