Mouse Mif cDNA isolated from C57BL/6-derived Lewis lung carcinoma (LLC) cells was inserted into an expression cassette consisting of seven tetO repeats, a cytomegalovirus minimal promoter, and a bovine growth hormone polyadenylation sequence. The transgenic vector was introduced to B6SJL hybrid embryos. The donating investigator reported the mice were backcrossed to C57BL/6 mice for at least seven generations (see SNP results below) prior to sending males to The Jackson Laboratory Repository in 2013. Upon arrival, males were used to cryopreserve sperm. To establish the living mouse colony, an aliquot of the frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
In 2013, a 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the first generation rederived living colony at The Jackson Laboratory Repository. While 26 of 27 markers were fixed for C57BL/6 allele-type, one marker on chromosome 1 was not C57BL/6 allele-type in some mice tested (e.g., still segregating for SJL allele-type). In addition, 4 of 5 markers that determine C57BL/6J from C57BL/6N were also found to be segregating on chromosomes 8, 13, 15 and 19 (note that these markers are the same for C57BL/6N and SJL). These data suggest the mice sent to The Jackson Laboratory Repository were on a C57BL/6N or a mixed C57BL/6N;C57BL/6J genetic background.
