Mice homozygous for the knock-out allele exhibit abnormal macrophage physiology, decreased sensitivity to cigarette smoke, reduced IL-13 induced tissue inflammation, and decreased littler size. This mutant mouse strain may be useful in studies of wound repair and extracellular matrix remodeling.
Steven D Shapiro, University of Pittsburgh
Mice that are homozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Homozygous females have reduced litter sizes (~60% of wildtype). No gene product (mRNA or protein) is detected by Northern or Western blot analysis of peritoneal macrophages and fluid. Casein substrate gel zymographic analysis of thioglycollate-stimulated cultured macrophages and peritoneal fluid reveals there is no lytic activity. In whole lung extracts, no elastase activity was detected by zymography. Immunohistochemistry of lung tissue does not detect macrophage elastase. Macrophages from homozygous mice are unable to penetrate artificial basement membrane matrix. Addition of plasminogen to cultured macrophages does not increase elastase activity. When challenged with chronic exposure to cigarette smoke, mutant mice do not develop emphysema. IL-13 induced tissue inflammation is reduced in homozygotes. This mutant mouse strain may be useful in studies of wound repair and extracellular matrix remodeling.
A targeting vector containing a neomycin resistance gene driven by the mouse phosphoglycerate kinase promoter was used to disrupt most of exon 2 of the targeted gene. The construct was electroporated into 129X1/SvJ derived RW4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric animals were crossed to C57BL/6J mice to establish the colony. The donating investigator reported to have backcrossed the colony to C57BL/6J for ten generations (see SNP note below), and then bred homozygous mice together for several generations prior to sending to The Jackson Laboratory Repository in 2004. In 2007, a single nucleotide panel (SNP) analysis of the living colony revealed the mice may not have been completely backcrossed onto the C57BL/6J genetic background. The colony was then backcrossed onto C57BL/6J for at least three additional generations. In 2010, a 32 SNP panel analysis covering all chromosomes showed all markers were C57BL/6 allele-type.
|Allele Name||targeted mutation 1, Steven D Shapiro|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||MME-; MMP-12-; Mmp12-|
|Gene Symbol and Name||Mmp12, matrix metallopeptidase 12|
|Strain of Origin||129X1/SvJ|
|Molecular Note||The gene was disrupted by replacement of the majority of exon 2 with a PGK-neo cassette via homologous recombination. Gene transcription and protein production was absent in homozygous mutant animals as demonstrated by Northern and Western blot analysis of peritoneal macrophages and peritoneal fluid.|
|Mutations Made By|| |
Emily Heiss, Brigham and Women's Hospital
When maintaining a live colony, homozygous mice may be bred together. Homozygous females have reduced litter sizes (~60% of wildtype).
When using the MME KO mouse strain in a publication, please cite the originating article(s) and include JAX stock #004855 in your Materials and Methods section.