B6.129S-Lum^tm1Chak/J

Stock number: 019749

Description

In this strain a PGK-neo cassette replaces sequence including exon 2 of the Lum (lumican) gene. These mice exhibit corneal opacity, poor wound healing, are hyporesponsive to LPS-induced sepsis and may be useful in studies of corneal dystrophy, extracellular matrix and neutrophil migration during the immune response.

Detailed description

The protein encoded by the Lum (lumican) gene, lumican, is a member of the small leucine-rich proteoglycan family, the predominant corneal keratan sulfate proteoglycan, is also found in interstitial extracellular matrices. Lumican regulates collagen fibril structure and is involved with the innate immune response, wound healing and neutrophil migration. These mice carry a targeted mutation for the Lum gene in which exon 2 is replaced by a NEO cassette. Mice that are homozygous for the targeted mutation are viable and fertile, but homozygous female mice on the C57BL/6 background are not good breeders. Homozygotes on the C57BL/6J background have loose skin around the neck, and older mice develop spontaneous lesion and tears of the skin. No gene product (protein) is detected by Western blot analysis of eye tissue, bone marrow extracts and peritoneal lavage from homozygotes. Homozygotes exhibit hyperextensible (8-fold reduced tensile strength) skin with abnormal collagen fibril structure and develop corneal opacity. Histological analysis of homozygotes reveals disorganized disorganized collagen fibrils with increased diameter in connective tissues of the skin, tendon, and cornea. Polymorphonuclear neutrophils from homozygotes exhibit poor chemotactic migration. In cell culture assays peritoneal macrophages (from homozygotes) exhibit defective phagocytosis of gram-negative bacteria. In response to LPS challenge, peritoneal macrophages and polymorphonuclear neutrophils (from homozygotes) exhibit a sub-normal production of proinflammatory cytokine (TNFalpha and IL6) production. Mutant mice are hyporesponsive to LPS-induced septic shock compared to wildtype controls and clearance of Gram-negative bacterial infections is impaired. During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background.

Development

A targeting vector designed by Dr. Shukti Chakravarti, while at Case Western Reserve University, containing a PGK-neo cassette was used to disrupt 3kb of sequence, including exon 2. The construct was electroporated into 129S/Sv (129/Sv) derived CT129#25 embryonic stem (ES) cells. Correctly targeted ES cells were injected into CD-1 blastocysts. The resulting chimeric animals were tested for germline transmission by intercrossing. The donating investigator reported that these mice were backcrossed to C57BL/6J for 10 generations (see SNP note below). During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once 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

Symbol: Lum^tm1Chak
Name: targeted mutation 1, Shukti Chakravarti
MGI accession ID: MGI:2153008
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Lum
Marker name: lumican
Chromosome: 10
Strain of origin: 129S/Sv
Molecular note: A neomycin resistance cassette replaced 3kb of sequence containing exon 2.
General note: ES cell line = CT 129#25.