Mthfr KO mice have a neo cassette disrupting exon 3 of the 5,10-methylenetetrahydrofolate reductase (Mthfr) gene, abolishing gene expression. MTHFR is the rate-limiting enzyme in the methyl cycle. It is involved in the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, which is a cosubstrate for homocysteine remethylation to methionine. Homozygous KO of MTHFR causes an abnormally high level of homocysteine in blood and urine, called homocysteinemia. Patients with this disorder exhibit developmental delay, thrombosis, motor and gait dysfunction, seizures, and other neurological symptoms. Mild MTHFR deficiency due to polymorphic variation causes a more modest elevation of plasma homocysteine (mild hyperhomocysteinemia) which is associated with increased risk for some common multifactorial disorders. Homozygous Mthfr KO mice low viability, with 25% surviving at 5 weeks of age. They have a 10 fold increase in plasma homocysteine levels. They are smaller and show developmental retardation with cerebellar pathology, abnormal lipid deposition in the proximal portion of the aorta, kinked tail, kyphosis, facial anomalies, and liver steatosis. Heterozygotes are normal in size and survival, and have a 1.6 fold increase in plasma homocysteine levels over wildtype. Heterozygotes are often studied as a model for mild MTHFR deficiency. These mice on a BALB/cJ background have a more deleterious phenotype than on a C57BL/6NJ background (Stock No. 024316).
A targeting vector was designed to insert a neomycin resistance (neo) cassette, in reverse orientation, into exon 3 of the 5,10-methylenetetrahydrofolate reductase (Mthfr) gene. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl+-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into BALB/c blastocysts and the resulting chimeric males were bred to BALB/cAnCrlBR females. These mice were backcrossed to BALB/cAnCrlBR mice for at least 10 generations. Upon arrival at The Jackson Laboratory, mice were bred to BALB/cByJ (Stock No. 001026) for at least one generation to establish the colony.
|Allele Name||targeted mutation 1, Rima Rozen|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Mthfr, methylenetetrahydrofolate reductase|
|Strain of Origin||(129X1/SvJ x 129S1/Sv)F1-Kitl+|
|Molecular Note||Exon 3 was disrupted by the insertion of a neomycin selection cassette. Transcript was undetected by RT-PCR analysis of brain tissue obtained from homozygous mutant mice. Enzymatic activity assays showed a lack of activity in homozygous mutant mice and levels reduced to 60 to 70% of wild-type in heterozygotes.|
When maintaining a live colony, heterozygous mice may be bred together. The donating investigator reports that only 25% of homozygotes survive to 5 weeks of age.
When using the C.129-Mthfrtm1Rzn/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #024503 in your Materials and Methods section.