B6;129S1-Atp7b^tm1Tcg/LtsnkJ

Stock number: 032624
Product name: Atp7b-
Research areas: Developmental Biology Research, Internal/Organ Research

Description

Atp7b^-/- mice contain a neo cassette replacing part of exon 2, of the ATPase, Cu++ transporting, beta polypeptide (Atp7b) gene, abolishing protein expression. These mice may be useful when studying hepatic copper accumulation.

Detailed description

Atp7b^-/- mice contain a neo cassette replacing part of exon 2, of the ATPase, Cu++ transporting, beta polypeptide (Atp7b) gene, abolishing protein expression. Atp7b encodes a copper-transporting enzyme expressed predominantly in the liver, with lower levels in the brain, intestine, mammary gland, placenta and other tissues. Mutations in this gene are associated with the onset of Wilson disease, a copper misbalance disorder characterized by a build-up of intracellular copper in the liver leading to hepatitis and/or cirrhosis. ~40% of cases also manifest neurological and/or psychiatric disorders. Hematological, renal and endocrine forms of the disease are much less common. The insertion of the neo cassette results in alternative spicing which produces a truncated ATP7B mRNA that lacks 1270bp and a frame shift mutation resulting in multiple stop codons. Heterozygous animals are viable and fertile and do not develop disease. Homozygous mice are viable and fertile with shortened life expectancy. They display copper overload with metabolic changes in the liver and altered lipid metabolism by 6 weeks. By 10-12 weeks of age these mice develop liver inflammation and other pathologic changes. The life expectancy of homozygous mice varies from 20 weeks to one year of age.

Homozygous mice display a gradual accumulation of hepatic copper that increases to a level 60-fold greater than normal by 5 months of age. An increase in copper concentration was also observed in the kidney, brain, placenta and lactating mammary glands of homozygous mutants, although milk from the mutant glands was copper deficient. Morphological abnormalities resembling cirrhosis developed in the majority of the livers from homozygous mutants older than 7 months of age. Progeny of the homozygous mutant females demonstrated neurological abnormalities and growth retardation characteristic of copper deficiency.

Development

The Atp7b^- targeting vector was designed to replace part of exon 2 of the ATPase, Cu++ transporting, beta polypeptide (Atp7b) gene with a neomycin resistance (neo) cassette in reverse orientation to the gene. The construct was electroporated into 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺-derived W9.5 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric mice were bred to C57BL/6 mice to generate a colony of Atp7b^-/- mice. These mice were maintained on a mixed genetic background. Upon arrival at The Jackson Laboratory Repository, sperm was cryopreserved. To generate our live colony, an aliquot of the frozen sperm was used to fertilize oocytes from C57BL/6J mice (Stock No. 000664).

Allele

Symbol: Atp7b^tm1Tcg
Name: targeted mutation 1, T Conrad Gilliam
MGI accession ID: MGI:2158253
Generation method: Targeted
Attributes: Null/Knockout
Synonyms: Atp7b-; ATPB7-
Marker symbol: Atp7b
Marker name: ATPase, Cu++ transporting, beta polypeptide
Marker synonyms: Atp7a; Hts; PINA; PWD; WC1; WD; Wilson protein; WND
Chromosome: 8
Strain of origin: 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺
Molecular note: A genomic fragment containing part of exon 2 was replaced with a neomycin selection cassette. RT-PCR analysis indicated that an abnormal transcript is made from this allele that splices exon 1 to exon 3. This abnormal splicing pattern is predicted to result in a frameshift mutation. Western blot analysis on brain extracts derived from homozygous mice demostrated that no stable full length protein is produced from this allele.