B6.FVB-Tg(Myh11-icre/ERT2)1Soff/J

Stock number: 019079
Product name: SMMHC-iCreER^T2
Research areas: Research Tools

Description

SMMHC-CreER^T2 transgenic mice allow sufficient Myh11-driven tamoxifen-inducible Cre expression in smooth muscle cells (SMCs).

In 2021, expanded quality control screening at The Jackson Laboratory determined the cre/ERT2 sequence to be that of a codon-improved variant icre/ERT2.

Of note, Stock No. 019079 has the SMMHC-CreER^T2 BAC transgene inserted on the Y chromosome, whereas Stock No. 036935 contains the same transgene inserted on the X chromosome. Additionally, Stock No. 037658 has a similar transgene (Myh11-CreER^T2-RAD) integrated into mouse Chromosome 2 in a region devoid of other genes.

Detailed description

Male SMMHC-CreER^T2 transgenic mice are viable and fertile, with expression of iCreER^T2 under control of the mouse smooth muscle myosin, heavy polypeptide 11, smooth muscle (Myh11) promoter/enhancer regions on the BAC transgene. The donating investigator reports that the BAC transgene inserted on the Y Chromosome. Myh11, also known as SMMHC, is a contractile protein expressed only in smooth muscle cells. When SMMHC-CreER^T2 males are bred with females containing loxP-flanked sequence, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the floxed sequences in the smooth muscle cells of the offspring.

The iCre-ERT2 fusion protein consists of a codon improved Cre recombinase fused to a triple mutant form of the human estrogen receptor which does not bind its natural ligand (17β-estradiol) at physiological concentrations but will bind the synthetic estrogen receptor ligands 4-hydroxytamoxifen (OHT or tamoxifen) and, with lesser sensitivity, ICI 182780. Restricted to the cytoplasm, Cre-ERT2 can only gain access to the nuclear compartment after exposure to tamoxifen. To counteract the mixed estrogen agonist effects of tamoxifen injections, which can result in late fetal abortions in pregnant mice, progesterone may be coadministered.

In 2021, expanded quality control screening at The Jackson Laboratory determined the cre/ERT2 sequence to be that of a codon-improved variant icre/ERT2.

Of note, Stock No. 036935 and Stock No. 037658 each contain a similar transgene inserted on the Y chromosome and Chromosome 2, respectively.

Development

A bacterial artificial chromosome (BAC) containing the mouse smooth muscle myosin, heavy polypeptide 11, smooth muscle (Myh11) gene was obtained. A CreER^T2 sequence (a mutated human estrogen receptor ligand binding domain fused to Cre), a polyadenylation signal, and a frt-flanked beta-lactamase cassette were inserted into the initiation codon of Myh11. After Flp-mediated removal of the beta-lactamase cassette, the modified 180 kb BAC transgene was microinjected into the pronuclei of fertilized FVB/N oocytes. Transgenic mice, in which the transgene integrated on the Y Chromosome, were identified and bred to C57BL/6 mice to establish a colony. The donating investigator reported that male SMMHC-CreER^T2 mice were bred to C57BL/6 females for at least 8 generations (see SNP note below). Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the colony.

In 2021, expanded quality control screening at The Jackson Laboratory determined the cre/ERT2 sequence to be that of a codon-improved variant icre/ERT2.

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 25 of the the 27 markers throughout the genome suggested a C57BL/6 genetic background, all 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.

Allele

Symbol: Tg(Myh11-icre/ERT2)1Soff
Name: transgene insertion 1, Stefan Offermanns
MGI accession ID: MGI:3819270
Generation method: Transgenic
Attributes: Recombinase-expressing; Inducible
Marker symbol: Tg(Myh11-icre/ERT2)1Soff
Marker name: transgene insertion 1, Stefan Offermanns
Chromosome: Y
Strain of origin: FVB/N
Expressed genes: cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,
Site of expression: inducible cre is expressed in smooth muscle cells.
Molecular note: The mouse promoter from BAC clone 26630 was used to drive inducible icre expression in smooth muscle cells. An frt-flanked beta-lactamase gene contained within the cre/ESR1 cassette was removed by flp mediated recombination prior to micro-injection into fertilized oocytes. No line information was given.