B6.129-Hpx^tm1Altr/J

Stock number: 029380
Product name: Hx KO
Research areas: Hematological Research, Immunology, Inflammation and Autoimmunity Research, Metabolism Research, Neurobiology Research, Research Tools

Description

This Hpx knockout strain is useful in studies of oxidative stress, iron metabolism, myelination, and intravascular hemolysis.

Detailed description

The targeted Hpx hemopexin gene encodes a plasma glycoprotein that has a high binding affinity to heme, scavenges and transports free heme, and is involved in heme/iron homeostasis. These knock-out mice carry an allele in which a lacZ-PGKneo cassette was inserted into the ATG start codon in exon 1. Mice that are homozygous for the targeted mutation are viable and fertile. No gene product (mRNA) is detected by Northern blot analysis of liver from homozygotes. β-galactosidase activity is detected in hepatocytes, ependymal cells and choroid plexi. Mutant homozygous mice recover more slowly from experimentally induced acute hemolysis, exhibiting protracted increased levels of plasma haptoglobin, renal iron, urine hemoglobin, and renal damage. Homozygotes have an earlier onset and more severe response to experimental autoimmune encephalomyelitis (EAE) due to increased production of Th17 cells. Iron levels in duodenal enterocytes are higher in homozygotes. Null mice on the 129Sv genetic background show an increase in the number of iron-loaded oligodendrocytes in the basal ganglia and thalamus, and exhibit impaired myelination of the cerebral cortex. The response to heme overload in homozygotes includes heme accumulation and oxidative stress in vascular endothelium and in macrophages compared to wildtype controls, increased vascular permeability as well as red blood cell congestion in liver sinusoids.

Development

A targeting vector containing a LacZ-PGKneo cassette was inserted into the ATG start codon to disrupt exon 1. 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 C57BL/6 blastocysts. The resulting chimeric male animals were crossed to C57BL/6 female mice, and then backcrossed to C57BL/6J for at least 8 generations by the donating lab (see SNP note below). Heterozygotes were then intercrossed to generate homozygotes. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

A 48 SNP (single nucleotide polymorphism) panel analysis, with 43 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. One the 43 markers throughout the genome was segregating with 129, and 3 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

Symbol: Hpx^tm1Altr
Name: targeted mutation 1, Fiorella Altruda
MGI accession ID: MGI:2447193
Generation method: Targeted
Attributes: Reporter; Null/Knockout
Marker symbol: Hpx
Marker name: hemopexin
Chromosome: 7
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Expressed genes: lacZ,beta-galactosidase,E. coli
Site of expression: Β-galactosidase is expressed in hepatocytes, ependymalcells and choroid plexi.
Molecular note: The gene was disrupted by insertion of a lacZ-neo cassette into the ATG start site of exon 1. Absence of gene expression in homozygous animals was confirmed by Northern blot analysis of total liver RNA. X-gal staining showed expression of lacZ in liver sections from mutant animals.