B6N.129(C)-Mthfr^tm1Rzn/J

Stock number: 024316
Research areas: Cell Biology Research, Metabolism Research, Neurobiology Research

Description

Mthfr KO mice may be useful for studying DNA methylation control.

Detailed description

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 hyperhomocysteinemia. 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 exhibit motor and behavioral anomalies, memory impairment, and liver steatosis. Homozygous KO males have normal fertility and relatively normal viability (~80%). These mice on a C57BL/6 background have a milder phenotype than on a BALB/cJ background (Stock No. 024503), although mice on both backgrounds exhibit a 10 fold increase in plasma homocysteine levels.

Development

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, and subsequently they were bred to C57BL/6NCrl mice for at least 10 generations. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6NJ (Stock No. 005304) for at least one generation to establish the colony.

Allele

Symbol: Mthfr^tm1Rzn
Name: targeted mutation 1, Rima Rozen
MGI accession ID: MGI:2385823
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Mthfr
Marker name: methylenetetrahydrofolate reductase
Chromosome: 4
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.