B6.129S-Sftpc^{tm1(cre/ERT2)Blh}/J

Stock number: 028054
Product name: Sftpc-CreER^T2
Research areas: Cancer Research, Research Tools

Description

These knock-in Sftpc-CreER^T2 mice express a tamoxifen-inducible Cre recombinase from the endogenous promoter/enhancer elements of the Sftpc locus. When induced, Cre activity is observed in Type II alveolar cells.

Detailed description

The Sftpc gene encodes pulmonary-associated surfactant protein C which is produced at high levels by type II alveolar epithelial cells in the lung. These Sftpc-CreER^T2 knock-in mice carry IRES-cre/ERT2 in the 3' UTR of the Sftpc gene. When crossed with a strain containing a loxP site flanked sequence of interest, the offspring are useful for generating tamoxifen-induced, Cre-mediated targeted deletions of the floxed sequences specifically in Type II alveolar cells of the lung. In adult mice after tamoxifen treatment, Cre recombinase activity is detected in approximately 85% of Sftpc expressing alveolar epithelial cells. No significant Cre recombinase activity is detected in the airway epithelium except in a few cells at the bronchioalveolar duct junction. There may also be low levels of Sftpc expression in tissues secreting lubricating fluids. Mice homozygous for this knock-in allele are viable and fertile.

Importantly, the donating investigator reports some spontaneous recombination is detected in the lung in the absence of tamoxifen. The level of spontaneous recombination at the time of donation from Dr. Rock (UCSF) was 5-10% - the same level as first reported. Dr. Hogan (Duke) reports that when continually maintained on the C57BL/6NCr genetic background, they observed spontaneous recombination levels up to 25%.

Development

A targeting vector was used to insert a FRT site flanked PGK-NEO cassette and an IRES- CreER^T2 into the 3' UTR of the Sftpc gene. The construct was electroporated into unspecified 129S6/SvEvTac derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric animals were tested for germline transmission. Heterozygotes were bred to FLP recombinase expressing mice (Stock No. 007844), on the 129S4/SvJae background, to remove the PGK-NEO selection cassette. The mice were then backcrossed to C57BL/6NCr (National Cancer Institute) for several generations. Next, the mice were sent to Dr. Jason Rock (University of California, San Francisco), where they were reported to have been backcrossed onto C57BL/6J for more than eight generations (see SNP results below). In 2016, Dr. Rock sent one Sftpc-CreER^T2 male to The Jackson Laboratory. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304).



In 2016, a 35 SNP (single nucleotide polymorphism) panel analysis, with 30 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 a cohort of first generation rederived living colony at The Jackson Laboratory Repository. The 30 markers throughout the genome all show C57BL/6 genetic background. For the 5 markers that determine C57BL/6J from C57BL/6N, half of the mice were homozygous C57BL/6N for all 5 marker, while the other half were homozygous C57BL/6N for 4 markers and heterozygous B6N;B6J for the other marker. These data suggest that the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background (predominantly C57BL/6N).

Subsequent SNP testing was performed yearly from 2017-2020 on cohorts from the live colony using a 48 SNP panel, 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. The 43 markers throughout the genome all show C57BL/6 genetic background, and the C57BL/6 substrain markers all show homozygous C57BL/6N.

Allele

Symbol: Sftpc^{tm1(cre/ERT2)Blh}
Name: targeted mutation 1, Brigid L Hogan
MGI accession ID: MGI:5305340
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Marker symbol: Sftpc
Marker name: surfactant associated protein C
Chromosome: 14
Strain of origin: 129S6/SvEvTac
Expressed genes: cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,
Site of expression: Tamoxifen-induced Cre-mediated deletions in alveolar epithelial cells can be achieved when bred with mice containing floxed sequences of a target gene.
Molecular note: An IRES-creERT cassette, together with an FRT flanked PGK-neo cassette, were inserted into the 3' UTR. The neo selection cassette was subsequently excised by crossing to mice expressing flp recombinase.