B6.129S4(Cg)-Myl2^tm1(cre)Krc/AchakJ

Stock number: 029465
Product name: Mlc2v-Cre on C57BL/6J
Research areas: Cardiovascular Research, Research Tools

Description

The Mlc2v-cre knock-in/knock-out allele has a Cre recombinase gene which replaced part of exon 1 and all of exon 2 of the Myl2 gene; both abolishing endogenous Myl2 gene function and placing cre expression under the control of the endogenous Myl2 promoter/enhancer elements. Cre recombinase expression is directed at the cardiac ventricular muscle starting at approximately E8. These mice may be useful for Cre-lox studies of cardiogenesis.

Detailed description

Ventricular myosin light chain 2, encoded by the Myl2 gene, is essential in vertebrate smooth muscle contraction and has a regulatory role in striated slow twitch muscle contraction. Mutations in this gene have been associated with hypertrophic cardiomyopathy. This strain expresses Cre recombinase from the endogenous Myl2 locus. Cre recombinase activity is detected in cardiac ventricular muscle starting at day E8.75. Myl2 expression initiates at E7.5 in the ventricular cardiac primordia. Heterozygous knock-in/knock-out mice are viable and fertile. Mice that are homozygous for the knock-in mutation have an embryonic lethal phenotype, dying at approximately E12.5. No gene product (protein) is detected by Western blot analysis of embryonic heart ventricles. Homozygous embryos exhibit enlarged hearts with thin walls, dilated chambers and pleural effusion, indicating congestive heart failure. Ultrastructural analysis reveals abnormal sarcomere assembly with myofibrillar disorganization, narrowed fiber width and larger distance between Z-bands.

In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.

The Mlc2v-Cre knock-in mice are also available on a FVB/NJ congenic background (Stock No. 029466).

Development

A targeting vector designed by Dr. Kenneth Chien (while at the University of California at San Diego) containing cre recombinase coding sequence, IRES-GFP and a floxed PGK-neo-tk cassette was used to disrupt part of exon 1 and all of exon 2 of the Myl2 gene. The construct was electroporated into 129S4/SvJae derived J1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric animals were crossed to Black Swiss female mice to test for germline transmission. The mice were then backcrossed to C57BL/6J for 5 generations using a marker assisted protocol, then backcrossed to C57BL/6J for an additional 2 generations. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Myl2^tm1(cre)Krc
Name: targeted mutation 1, Kenneth R Chien
MGI accession ID: MGI:2385922
Generation method: Targeted
Attributes: Recombinase-expressing
Synonyms: MLC-2v -; Mlc2v-cre; MLC2vcreKI
Marker symbol: Myl2
Marker name: myosin, light polypeptide 2, regulatory, cardiac, slow
Marker synonyms: CMH10; Gm32672; MFM12; Mlc2; MLC-2; MLC-2s/v; Mlc2v; MLC-2v; Mylpc
Chromosome: 5
Strain of origin: 129S4/SvJae
Expressed genes: cre,cre recombinase,bacteriophage P1
Molecular note: Part of exon 1 and all of exon 2 were replaced with a cre gene and a floxed PGK-neo-tk cassette via homologous recombination. Western blot analysis showed that homozygous embryos did not express Myl2 protein product. The knocked in cre gene is expressed by the Myl2 promoter in ventricular tissue starting at day E7.5.