Mrp1-/- KO mice lack the second putative ATP-binding domain of the Abcc1 gene. These mice may be useful for studying the role of ATP-dependent transporters on cardiotoxicity causes by cancer chemotherapeutic agents.
Mary Vore, University of Kentucky
Mrp1-/- mice have a neo cassette replacing exon 3 and part of exon 2 of the ATP-binding cassette, sub-family C (CFTR/MRP), member 1 (Abcc1) gene, abolishing gene expression.
Chemotherapeutic drugs, such as doxorubicin (DOX), epipodophyllotoxins and Vinca alkaloids, cause irreversible and often fatal drug-induced congestive heart failure due to the overproduction of reactive oxygen species and oxidative stress. One toxic product of oxidative stress, 4-hydroxy-2-nonenal (HNE), interacts with glutathione (GSH) to produce a less toxic metabolite (GS-HNE) which can still cause toxicity due to accumulation with in the cell.
ABCC1, also known as MRP1 (multidrug resistance-associated protein), is an ATP-dependent transporter that provides the energy for the movement of GSH, glucuronide, and sulfate conjugates, across membranes. As such, MRP1 mediates the efflux of GS-HNE across cell membranes and away from sites of toxicity. Mrp1-/- mice lack part of the second putative ATP-binding domain of the gene, in particular, the B motif, which is one of the characteristic signatures of the ATP-binding domain. This domain is required for the recognition, binding, and hydrolysis of ATP. Homozygous mice are viable and fertile. They have higher levels of GSH, since MRP is not present to mediate its removal. Mrp1-/- mice have tissue concentrations of DOX similar to controls, yet they are more sensitive to the drug. When treated with DOX, Mrp1-/- mice show significantly greater cardiac injury in terms of increased apoptosis in the heart and decreased cardiac function. GS-HNE was only modestly increased after DOX treatment.
A targeting vector was designed to replace a 0.7-kb fragment, including exon 3 and part of exon 2, of the ATP-binding cassette, sub-family C (CFTR/MRP), member 1 (Abcc1) 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 C57BL/6 blastocysts and the resulting chimeric males were bred to C57BL/6 females, before being intercrossed. The donating investigator reported that Mrp1-/- mice were backcrossed for at least 15 generations to C57BL/6J background (see SNP note below). Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation 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. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 4 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 Name||targeted mutation 1, Alan C Sartorelli|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Abcc1, ATP-binding cassette, sub-family C (CFTR/MRP), member 1|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|Molecular Note||A 0.7 kb genomic fragment was replaced with a neomycin selection cassette inserted by homologous recombination. The deleted region included sequence encoding a portion of the B motif of the putative ATP-binding domain. Protein was undetected by Western blot analysis of homozygous mutant mice.|
When maintaining a live colony, homozygous mice may be bred together.
When using the Mrp- mouse strain in a publication, please cite the originating article(s) and include JAX stock #028129 in your Materials and Methods section.