Establishment of New Embryonic Stem (ES) Cell Lines from C57BL/6 Strain Mice by Whole Blastocyst Culture Method

Two embryonic stem (ES) cell lines (OKB6-I and -II) derived from C57BL/6 strain mice were established by the whole blastocyst culture method, and the net isolation ratio was 3.9% (2/51). They had pluripotency and normal karyotype, and were positive for alkaline phosphatase activity. It was indicated that OKB6-I was a female cell line, and OKB6-II was a male, judged by the size and morphology of their chromosomes. By coculture with ICR embryos, a chimeric mouse and a hermaphrodite were generated from OKB6-II, but no chimera was generated from OKB6-I. OKB6-II⇔ICR chimera generated 3 albino type viable offspring, when mated with ICR strain mouse. OKB6-II⇔ICR hermaphrodite was sterile, and had a contralateral ovary and testis-like structure.