B6.129-Gnmt^tm1Cwa/J

Stock number: 018066
Research areas: Cancer Research, Internal/Organ Research, Metabolism Research, Research Tools

Description

In this strain a NEO cassette replaces exon1 and the promoter region of the Gnmt gene. This strain is a model for Glycine N-Methyltransferase Deficiency and has applications in studies of methionine metabolism, methylation and molecular markers for hepatocellular carcinoma.

Detailed description

Glycine N-methyltransferase (GMNT) regulates the ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) and has a role in methionine metabolism and methylation of DNA and histones. GNMT is down-regulated in patients with liver cirrhosis and/or hepatocellular carcinoma. These mice carry a targeted mutation of the Gnmt gene. Mice that are homozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross behavioral abnormalities. No gene product (protein) is detected by Western blot or enzyme activity analysis of liver from homozygous mice. Homozygotes exhibit increased levels of free methionine and SAM (35 fold) in the liver, and decreased SAH levels in the liver, with the ratio of SAM/SAH elevated 100-fold. Serum levels of aminotransferases, methionine, and SAM are also elevated. Although heterozygotes have only approximately 50% of wildtype enzyme activity levels, hepatic methione, SAM and SAH levels are similar to wildtype control. At 3 months of age, homozygotes exhibit progressive liver steatosis and fibrosis. At 8 months of age, homozygotes exhibit hypermethlyation of DNA and develop multifocal hepatocellular carcinoma.

Development

A targeting vector containing a NEO cassette was used to disrupt exon 1 and promoter region of the gene. The construct was electroporated into 129/SvJ derived embryonic stem (ES) cells (IngenKo, Australia). Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting male chimeric animals were crossed to C57BL/6J females, and then backcrossed to for 6 generations using a marker assisted protocol. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.

Allele

Symbol: Gnmt^tm1Cwa
Name: targeted mutation 1, Conrad Wagner
MGI accession ID: MGI:3640328
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Gnmt
Marker name: glycine N-methyltransferase
Chromosome: 17
Strain of origin: 129
Molecular note: The first exon and promoter region were replaced with a neomycin resistance gene via homologous recombination. Western blot and enzyme activity assays did not detect any protein or activity in homozygous liver extracts.