These IT/IT mice contain a I4895T mutation in the ryanodine receptor 1 gene, similar to that found in patients with severe central core disease. They may be useful in studies of Ca2+ release channels and muscle contractility.
David H. MacLennan, University of Toronto
The mutant mice express a knockin (KI) amino acid mutation Ile4895Thr (IT) in the skeletal muscle type 1 ryanodine receptor /Ca2+ release channel (RyR1). The IT mutation corresponds to the human I4898T RyR1 mutation, which causes a severe form of central core disease (CCD) in heterozygous carriers. RyR1 plays a key role in excitation-contraction (EC) coupling in skeletal muscle by releasing Ca2+ from the sarcoplasmic reticulum (SR) and triggering muscle contraction. Mutations in RYR1 have been associated with central core disease (CCD), multiminicore disease, nemaline rod myopathy, and malignant hyperthermia.
The IT mutation affects a highly conserved GGIG4899 motif in the selectivity filter of the Ca2+ release channel. The mutation disrupts Ca2+ release channel conductance without altering the integrity of the RyR1 protein complex. The homozygous IT/IT mice are born paralyzed in all skeletal muscles, are unable to breathe and die perinatally. IT/IT embryos show a generalized developmental delay including growth retardation, marked delay in ossification, myogenesis, dermatogenesis, and cardiovascular development. Heterozygous IT/+ mice are viable and fertile. They exhibit a slowly progressive congenital myopathy with spatiotemporal development of minicores, cores, and rods in their skeletal muscle.
A targeting construct was designed to insert a loxP-flanked neomycin (neo) resistance cassette, in reverse orientation to the gene, downstream of exon 101 of the ryanodine receptor 1 (Ryr1) gene. A point mutation (T14693C) was introduced to change amino acid 4895, in exon 102, from an isoleucine to a threonine (I4895T), corresponding to human amino acid 4898. The I4898T mutation is commonly found in patients with a severe form of central core disease. This targeting construct was electroporated into 129S6/SvEv-derived TC-1 embryonic stem (ES) cells and correctly targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric males were bred to 129S2/SvPasCrl females, and the colony was maintained by breeding to 129S2/SvPasCrl mice for at least 20 generations. Resulting IT/IT mice were bred to 129S/Sv-Tg(Prm-cre)58Og/J mice (Stock No. 003328) to remove the floxed neo cassette. Mice were crossed to remove the Cre-expressing transgene, and subsequently were bred 129S2/SvPasCrl mice. Upon arrival at The Jackson Laboratory, mutant mice were bred to 129S1/SvImJ inbred mice (Stock No. 002448) for at least one generation to establish the colony.
|Allele Name||targeted mutation 1.1, David H MacLennan|
|Allele Type||Targeted (Humanized sequence)|
|Allele Synonym(s)||Ryr1I4895T; Ryr1IT|
|Gene Symbol and Name||Ryr1, ryanodine receptor 1, skeletal muscle|
|Strain of Origin||129S6/SvEvTac|
|Molecular Note||A targeting vector was designed to insert a t14693c mutation into exon 102 that results in the amino acid substitution of threonine for isoleucine at position 4895 (I4895T). An additional silent substitution (g14697t) was introduced to aid in genotyping and allele expression studies. A neomycin selection cassette originally inserted in intron 101 was removed by cre mediated recombination.|
When maintaining a live colony, heterozygous mice may be bred to wildtype mice from the colony or to 129S1/SvImJ inbred mice (Stock No. 002448). Homozygous mice die shortly after birth likely due to asphyxia.
When using the Ryr1IT mouse strain in a publication, please cite the originating article(s) and include JAX stock #025199 in your Materials and Methods section.