Effect of genetic background on establishment of mouse embryonic stem cells

We established 13 embryonic stem (ES) cell lines from 542 embryos crossed between various strains of mice: 10 lines from 129/Sv-ter embryos (10/48, 20.8%) and 3 lines out of other 9 combinations of intra- or inter-strain matings (1 from intracross of C57BL/6CrSlc, 1 from B6D2F1 x C57BL/6CrSlc, 1 from Yok:ddY x Slc:ICR). No ES cell line from 129/Sv-ter x Slc:ICR embryos suggests that ICR strain might have inhibitory genetic factor(s) for the ES cell formation. Some ES cell lines could be obtained from hybrids even if none or few lines from their parental strains, suggesting a heterosis effect can be expected for establishing ES cell lines in mice.