Mice that are homozygous for the Hcn4 (hyperpolarization-activated, cyclic nucleotide-gated K+ 4) targeted mutation, HCN4R699Q, have an embryonic lethal phenotype with defective heart development. This mutant mouse strain may be useful in studies of cardiovascular development and physiology and ion channel function in the heart.
U Benjamin Kaupp, Center of Advanced European Studies
These mice carry the HCN4R699Q mutation which results in an amino acid substitution in the cyclic nucleotide (cAMP)-binding domain of the protein. Mice that are heterozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Homozygous mice have an embryonic lethal phenotype, developing normally until embryonic day 11 but then failing to develop past embryonic day 12. Western blot analysis of embryonic hearts indicates that the mutation does not alter the level of gene product (protein) expression. Isolated embryonic hearts from homozygous and heterozygous animals younger than embryonic day 11.5 have decreased heart rates when compared to wild-type. Homozygous embryonic hearts do not respond with increased heart rate to adrenergic stimulation. Cardiomyocytes isolated from homozygous embryos beat more slowly, and have slower current activation and faster current deactivation when compared to controls. Isolated homozygous embryonic cardiomyocytes also do not react to exogenous cAMP treatment. Adult heterozygote heart rates are similar to wild-type controls. This mutant mouse strain may be useful in studies of cardiovascular development and physiology and ion channel function in the heart.
A targeting vector containing a loxP site flanked neo cassette and the single amino acid mutation R669Q (CG to AG) in exon 7 was inserted into the endogenous locus. The construct was electroporated into (C57BL/6 x 129S4/SvJae)F1 derived v6.5 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric animals were crossed to transgenic mice, on the C57BL/6 background, carrying the Tg(CMV-cre)1Cgn transgene to remove the selection cassette. The mice were then backcrossed to C57BL/6J for 10 generations.
|Allele Name||targeted mutation 1, Reinhart Seifert|
|Allele Type||Targeted (Null/Knockout, Inserted expressed sequence)|
|Gene Symbol and Name||Hcn4, hyperpolarization-activated, cyclic nucleotide-gated K+ 4|
|Promoter||Hcn4, hyperpolarization-activated, cyclic nucleotide-gated K+ 4, mouse, laboratory|
|Strain of Origin||(C57BL/6 x 129S4/SvJae)F1|
|Molecular Note||A floxed neo cassette and an exon 7 containing a nucleotide substitution that resulted in a glutamine for arginine amino acid substitution at position 669 (R669Q) was knocked into the open reading frame. The neo cassette was removed by subsequent germ-line cre-mediated recombination.|
|Mutations Made By|| |
Dagmar Harzheim, Babraham Institute
When maintaining a live colony, these mice can be bred as heterozygotes. Homozygotes are not viable and die by embryonic day 12.
When using the B6.Cg-Hcn4tm1Rsei/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #008780 in your Materials and Methods section.