C57BL/6J-Tg(Nkx2-1-cre)2Sand/J

Stock number: 008661
Product name: Nkx2.1-Cre
Research areas: Neurobiology Research, Research Tools

Description

These Nkx2.1Cre (or BAC-Nkx2.1-Cre) transgenic mice express cre under the control of the Nkx2.1 promoter/enhancer regions and may be useful for generating conditional mutations for studying gain/loss of function or fate mapping in subgroups of brain progenitor cells (interneurons in telencephalon and hypothalamus cells), as well as developing lung, thyroid, and pituitary tissues.

Detailed description

Mice homozygous for the Nkx2.1Cre (or BAC-Nkx2.1-Cre) transgene are viable and fertile, with cre expression directed to major subgroups of brain interneuron progenitors, developing lung, thyroid, and pituitary by the Nkx2.1 promoter/enhancer regions within the BAC transgene. When bred with mice containing a loxP-flanked sequence of interest, Cre-mediated recombination will result in deletion of the floxed sequence(s) in the offspring. For example, when bred with beta-galactosidase reporter mice, the first detectable Cre recombinase expression in double mutant offspring is observed on embryonic day (E)10.5 in the basal telencephalon. These Nkx2.1Cre (or BAC-Nkx2.1-Cre) transgenic mice may be useful for generating conditional mutations for studying gain or loss of function and/or fate mapping in subgroups of brain progenitors (including future major interneurons in telencephalon and hypothalamus cells), as well as developing lung, thyroid, and pituitary.

View cre expression characterization.

If the recombinase activity pattern of this allele is further characterized by the Genetic Resource Science group at The Jackson Laboratory, such findings will be reported on the Mouse Genome Informatics (MGI) Allele Detail entry. This same information may also be found searching the MGI Recombinase Activity and MGI Gene Expression + Recombinase Activity Comparison Matrix.

Luo et al. 2020 Neuron 106:37 Table 1 shows germline recombination in offspring (F2) of Cre;floxed double mutant (F1) mice bred to floxed and/or wildtype mice. The authors also note that in general, the frequency of recombination in Cre;floxed double mutant germline cells appears to be considerably higher than in zygotes produced by breeding Cre mice to floxed mice.

This reports that both female and male BAC-Nkx2.1-Cre;floxed double mutants bred to floxed mice produced some offspring with germline deletion of the floxed allele [12.5% (24/192) and 5.4% (12/224) when using Cre female or Cre male, respectively, including some Cre negative offspring]. As such, for Cre-lox experiments and to reduce the frequency of germline deletion of the floxed allele, researchers may consider maintaining the BAC-Nkx2.1-Cre transgene as hemizygous rather than homozygous. Researchers are urged to monitor their Cre;floxed double mutant mice for any undesirable germline deletion of the floxed allele (e.g., genotyping tail/ear samples). Researchers may consider also maintaining a BAC-Nkx2.1-Cre colony separate from any floxed colonies.

Development

The 223 kb C57BL/6 mouse bacterial artificial chromosome (BAC) RP23-3H18 containing the entire Nkx2.1 (and Nkx2.9) gene, was modified by replacing the first 15 bp (including the ATG) of exon 2 of Nkx2.1 with a cre coding sequence and SV40 polyA signal. DNA from a cre modified BAC clone was used as the source for the BAC-Nkx2.1-Cre transgene, which was linearized to remove its original constructing vector backbone (pBACe3.6) and then microinjected into the pronucleus of C57BL/6 fertilized eggs. The resulting Nkx2.1Cre (or BAC-Nkx2.1-Cre) transgenic mice from founder line 2 were subsequently backcrossed to C57BL/6J for five generations prior to arrival at The Jackson Laboratory in 2008. Upon arrival, sperm was cryopreserved [generation N5]. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664). The live colony was maintained by breeding transgenic carrier mice together and/or to wildtype mice for ~40 generations. In 2022, the live colony will be refreshed by one generation of breeding with C57BL/6J [will be N7].

Allele

Symbol: Tg(Nkx2-1-cre)2Sand
Name: transgene insertion 2, Stewart Anderson
MGI accession ID: MGI:3773076
Generation method: Transgenic
Attributes: Recombinase-expressing
Marker symbol: Tg(Nkx2-1-cre)2Sand
Marker name: transgene insertion 2, Stewart Anderson
Chromosome: UN
Strain of origin: C57BL/6
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: Cre expression is directed to major subgroups of brain interneuron progenitors, developing lung, thyroid, and pituitary by the Nkx2.1 promoter/enhancer regions.
Molecular note: A mouse BAC clone containing the Nkx2-1 gene was engineered to express cre recombinase. Fifteen base pairs at the 5'end of exon 2 of the Nkx2-1 gene were replaced with a cre-poly(A) construct. The mutated BAC clone was then used to generate transgenic mice. This construct is expressed in brain, thyroid, pituitary, and lung, with telecephalic expression first detectable at E10.5.