C57BL/6-Epm2a^em1Cwor/J

Stock number: 036199
Product name: Laforin R240X

Strain synonyms: Epm2a R240X , Epm2a*R240X , Epm2a-R240X , Epm2a^R240X , Laforin*R240X , Laforin-R240X , Laforin^R240X
Research areas: Mouse/Human Gene Homologs, Neurobiology Research

Description

Laforin R240X knock-in mice express the R240X (arginine to termination codon) amino acid (aa) substitution in the Epm2a (epilepsy, progressive myoclonic epilepsy, type 2 gene alpha or laforin) locus. Mice homozygous for the mutation develop Lafora bodies upon aging. Loss of function mutations in EPM2A are associated with Lafora disease, a rare and severe form of progressive myoclonus epilepsy.

Detailed description

Epm2a (epilepsy, progressive myoclonic epilepsy, type 2 gene alpha or laforin) encodes a phosphatase involved in the regulation of glycogen metabolism. Specifically, laforin and the E3 ubiquitin ligase, malin (Nhlrc1), form a complex that prevents the formation of LaFora bodies. Loss of function mutations in laforin, such as R241X (corresponding to mouse R240X), are associated with Lafora disease, a rare and severe form of progressive myoclonus epilepsy. Lafora disease is characterized by epileptic seizures in late childhood or adolescence, difficulty walking, muscle spasms (myoclonus), dementia and death within 10 years of disease onset.

Laforin R240X knockin mice were created using CRISPR/cas9 genome editing to express the R240X (arginine to termination codon) amino acid (aa) substitution in the Epm2a locus. Homozygous mice are viable and fertile. Homozygotes develop Lafora bodies in the cerebellum, hippocampus, heart and skeletal muscle upon aging. In addition, glycogen is increased by approximately 2-fold in skeletal muscle and 3-fold in brain as compared to wild-type. Additional characterization of this strain will be included at a later date (March 2021).

Of note, mice carrying the D148N substitution in malin (Nhlrc1) are available as Stock No. 036238.

Development

CRISPR/cas9 endonuclease-mediated genome editing was used to create an amino acid substitution at position 240 (arginine to termination codon, R240X) in the Epm2a locus on chromosome 10. Single guide RNA and cas9 endonuclease were introduced into C57BL/6J-derived fertilized eggs by pronuclear injection. Embryos were transferred to pseudopregnant females, and correctly targeted pups were bred to C57BL/6J mice for germline transmission by the donating laboratory (see SNP results below). The colony was maintained on the C57BL/6 background. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

In 2021, a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 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 males sent to The Jackson Laboratory Repository. Of the 5 markers that determine C57BL/6J from C57BL/6N, the Chromosome 1 SNP (which includes the rd8 recessive mutation associated with retinal degeneration on Chromosome 1 within the Crb1 locus) was found to be segregating, while the other 4 markers agreed with C57BL/6J. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background.

Allele

Symbol: Epm2a^em1Cwor
Name: endonuclease-mediated mutation 1, Carolyn Worby
MGI accession ID: MGI:6828602
Generation method: Endonuclease-mediated
Attributes: Humanized sequence
Synonyms: Epm2a^R240X; Laforin R240X
Marker symbol: Epm2a
Marker name: epilepsy, progressive myoclonic epilepsy, type 2 gene alpha
Marker synonyms: EPM2; laforin; MELF; MELF2
Chromosome: 10
Strain of origin: C57BL/6J
Molecular note: CRISPR/cas9 endonuclease-mediated genome editing is used to create an amino acid substitution at position 240 (arginine to termination codon, R240X). Loss of function mutations in laforin, such as R241X (corresponding to mouse R240X), are associated with Lafora disease, a rare and severe form of progressive myoclonus epilepsy.