A targeting vector was used to insert a loxP-flanked neomycin cassette, rat Trpv1 (transient receptor potential cation channel, subfamily V, member 1) cDNA, and IRES-ECFP sequence into the Gt(ROSA)26Sor gene. The mutation was created in 129P2/OlaHsd-derived E14 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. The resulting chimeric animals were backcrossed to C57BL/6 (see SNP notes below) three times by the donating laboratory, and then males were sent to The Jackson Laboratory Repository in 2008. Upon arrival, sperm was cryopreserved.
To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664). Then, the colony was backcrossed to C57BL/6J at least one more generation. C57BL/6-congenic mice from our colony were distributed from October 2009 through December 2011. From 2012 to present (December 2015), the strain has been available by rederivation from the stocks frozen in 2008.
In 2009, 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 rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 1 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a C57BL/6N genetic background.
