A loxP site flanked targeting vector containing a FRT site flanked PGK-Neo selection cassette was utilized in the construction of this mutant. This selection cassette was inserted downstream of exon 4 of the targeted gene, and another loxP site was inserted upstream of exon 4. This construct was electroporated into C57BL/6NTac derived B6-3 embryonic stem (ES) cells which were transiently transfected with a FLP1 recombinase vector to remove the selection cassette. ES cells that had successfully undergone FLP1 recombination and no longer retained the cassette but did retain the loxP-flanked exon 4 were injected into albino C57BL/6 (C57BL/6J-Tyr^c-2J/J) blastocysts. The resulting chimeric male animals were backcrossed to C57BL/6J by the donating lab (see SNP note below). The strain was then cryopreserved as sperm, and recovered on C57BL/6J (Stock No. 000664) at least once to establish the colony.

In 2019 a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 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 43 markers throughout the genome suggested a C57BL/6 genetic background, 3 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 mixed C57BL/6J ; C57BL/6N genetic background.

In 2020, PCR and Sanger sequencing analysis performed by The Jackson Laboratory shows intact loxP sites flanking exon 4 where expected.

Approximate Controls

• 000664 C57BL/6J

Additional Information

• Considerations for Choosing Controls

• Hernandez CM; Cortez I; Gu Z; Colon-Saez JO; Lamb PW; Wakamiya M; Yakel JL; Dineley KT. 2014. Research tool: Validation of floxed alpha7 nicotinic acetylcholine receptor conditional knockout mice using in vitro and in vivo approaches. J Physiol 592(Pt 15):3201-14PubMed: 24879866MGI: J:219327