STOCK Tg(ACTA1-cre/Esr1*)2Kesr/J

Stock number: 025750
Product name: HSA-MCM
Strain synonyms: HSA-MerCreMer
Research areas: Neurobiology Research, Research Tools

Description

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HSA-MCM mice express tamoxifen-inducible cre in both limb and craniofacial skeletal muscles.

Similar strains include:
Stock No. 031934 which contains the same promoter driving expression of a MerCreMer tamoxifen inducible Cre recombinase on a congenic C57BL/6J genetic background.
Stock No. 039097 which contains the same promoter driving expression of a Cre-ERT2 fusion protein consisting of Cre recombinase fused to a triple mutant form of the human estrogen receptor.

Detailed description

HSA-MCM mice express MerCreMer double fusion protein under the control of the human ACTA1 (actin, alpha 1, skeletal muscle) promoter. Heterozygous mice are viable and fertile. Homozygotes are also viable but exhibit significanly reduced fertility. Of note, the MerCreMer double fusion protein has substantially greater Cre recombinase activity with less promiscuity compared with the CreMer single fusion protein. When HSA-MCM mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination is expected to result in deletion of the floxed sequences in skeletal muscles of the limbs, face/tongue, and diaphragm of the offspring.

When cre mice are treated with tamoxifen and then fed a high fat diet, glucose tolerance and circulating insulin levels are significantly improved. [Batran et al. Diabetologia June 2018].

The MerCreMer double fusion protein consists of Cre recombinase flanked on each end with a mutated murine estrogen receptor (mer) ligand binding domain (amino acids 281-599, G525R); 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, MerCreMer 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.

 

Development

A transgenic construct was designed to contain a MerCreMer sequence under the control of the human ACTA1 (actin, alpha 1, skeletal muscle) promoter. The MerCreMer double fusion protein has a Cre recombinase cDNA sequence flanked on each end with a mutated murine estrogen receptor (mer) ligand binding domain (amino acids 281-599, G525R); thus rendering cre expression tamoxifen-inducible yet estrogen-insensitive. A β-globin intron II sequence, followed by a polyadenylation sequence, was inserted downstream of the promoter to ensure proper splicing. This HSA-MCM transgene was introduced into (C57BL/6 X C3H)F2 donor oocytes. The donating investigator reports that the resulting offspring from founder line 2 were bred to C57BL/6J mice 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.

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. Two of the 27 markers throughout the genome were segregating suggesting an incomplete backcross. Also, 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 mixed genetic background.

 

Allele

Symbol: Tg(ACTA1-cre/Esr1*)2Kesr
Name: transgene insertion 2, Karyn A Esser
MGI accession ID: MGI:5435875
Generation method: Transgenic
Attributes: Recombinase-expressing; Inducible
Synonyms: HSA-Cre; HSA-MCM; HSA-MerCreMer
Marker symbol: Tg(ACTA1-cre/Esr1*)2Kesr
Marker name: transgene insertion 2, Karyn A Esser
Chromosome: UN
Strain of origin: (C57BL/6 x C3H)F2
Expressed genes: cre/Esr1,Cre recombinase and estrogen receptor 1 fusion gene,
Site of expression: When mice carrying this transgne are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination is expected to result in deletion of the floxed sequences in skeletal muscles of the limbs, face/tongue, and diaphragm of the offspring.
Molecular note: The human alpha-skeletal actin gene promoter (ACTA1; HSA) was cloned into a vector upstream the cre recombinase gene fused at the N- and C-termini to mutated estrogen receptor ligand-binding domains (MerCreMer). A beta-globin intron II sequence followed by a polyadenylation sequence was inserted downstream of the promoter to ensure proper splicing. The construct was injected into B6C3F2 embryos. Five founders were generated and crossed to Rosa-lacz reporter mice to assess germline transmission and inducible muscle-specific recombinase activity. Line 2 was established.