B6;129-Cdk5r1^tm2.1Lht/J

Stock number: 022401
Product name: Δp35KI
Research areas: Neurobiology Research

Description

These Δp35 knock in mice express a mutant Cdk5r1 gene product that results in a calpain cleavage-resistant p35 protein. They are suitable for use in applications related to the study of cyclin-dependent kinase 5 activity and neurodegenerative diseases such as Alzheimer's Disease.

Detailed description

The Cdk5r1, cyclin-dependent kinase 5, regulatory subunit 1 (p35) gene encodes the p35 protein, which when cleaved by calpain results in a truncated p25 protein. The p25 protein is an activator of cyclin-dependent kinase 5, and as a complex with CDK5 causes hyperphosphorylation of tau and neurofilament proteins, as well as neuronal cell death. These Δp35 KI mice express a mutant calpain cleavage-resistant p35 protein in which six amino acid residues adjacent to the calpain-cleavage site (Δ93 -98) were deleted with a leucine replacing the alanine. In mice homozygous for the mutation, expression levels for the mutant protein are similar to wildtype levels. Calpain cleavage of p35 and formation of the p25 truncated protein is abolished in homozygotes while other native CDK5R1 protein activity is unaltered. Homozygotes are viable and fertile, and exhibit impaired memory extinction. While hippocampal long-term potentiation (LTP) is the same as wildtype controls, hippocampal N-methyl-D-aspartate receptor (NMDAR)-dependent long-term depression (LTD) is compromised.



When crossed with the 5XFAD mouse model of Alzheimer's Disease, Β-amyloid accumulation, synaptic dysfunction and memory impairment is improved in the compound mutant mice when compared with the 5XFAD mice.

Development

The Δp35-3xHA knock-in cassette, encoding for deletion of six amino acid residues adjacent to the calpain-cleavage site (Δ93-98) and leucine replacement of the alanine residue in the cleavage site, was generated via two sequential recombination reactions. The targeting vector contained this Δp35-3xHA knock-in cassette and a loxP site-flanked NEO cassette. The construct was electroporated into unspecified 129-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. Heterozygous males were crossed to Meox2-Cre females (on the B6.129S4 background) to remove the floxed NEO cassette. The donating investigator reported that the mice that no longer carried the floxed NEO cassette were then backcrossed to C57BL/6 for at least 8 generations (see SNP note). Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once 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, 2 of 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 C57BL/6J ; C57BL/6N genetic background.

Allele

Symbol: Cdk5r1^tm2.1Lht
Name: targeted mutation 2.1, Li-Huei Tsai
MGI accession ID: MGI:5560495
Generation method: Targeted
Marker symbol: Cdk5r1
Marker name: cyclin-dependent kinase 5, regulatory subunit 1 (p35)
Chromosome: 11
Strain of origin: 129
Molecular note: The deltap35-3xHA knock-in cassette encodes for deletion of the six amino acid residues adjacent to the calpain-cleavage site (delta93-98) and replaces the alanine residue in the cleavage site for leucine., The cassette was generated via two sequential recombination reactions. The final targeting vector contains this deltap35-3xHA knock-in cassette and a loxP site-flanked NEO cassette. Mutant mice were bred with Meox2-cre mice to remove the neo selection cassette.