These CMAH knock-out mice may be useful for studying the hydroxylation of sialic acids required for protein/lipid synthesis and pancreatic beta cell function. In combination with other alleles, they may also have applications in studies related to Duchenne muscular dystrophy.
Ajit Varki, University of California, San Diego
These Cmah KO mice lack exon 6 of the cytidine monophospho-N-acetylneuraminic acid hydroxylase gene (Cmah or CMP-Neu5Ac hydroxylase). CMAH catalyses the biosynthesis of the sialic acid N-glycolylneuraminic acid (Neu5Gc). Sialic acids (Sias) mediate cell-cell interactions and signaling. They also function as receptors for some pathogens. Humans lack functional CMAH and these mice exhibit a human-like inactivation of CMAH function. KO mice have elevated levels of N-acetylneuraminic acid (Neu5Ac) and sialic acid O acetylation. They exhibit a 65% decrease in pancreatic islet size and area, a 50% decrease in islet number, and a 40% reduction in response to insulin leading to fasting hyperglycemia and glucose intolerance on a high-fat diet. They also display diminished startle response, age-related hearing loss, and a delay in skin wound healing.
When bred to C57BL/10ScSn-Dmdmdx/J mice (Stock No. 001801), lack of CMAH accelerates the onset and severity of Duchenne muscular dystrophy (DMD) seen in the Dmdmdx mice.
A targeting vector was designed to insert a loxP site upstream of exon 6, and a loxP-flanked neomycin resistance (neo) cassette downstream of exon 6 of the cytidine monophospho-N-acetylneuraminic acid hydroxylase (Cmah) gene. The construct was electroporated into 129/SvJ-derived embryonic stem (ES) cells. Correctly targeted ES cells were transiently transfected with a Cre-expressing plasmid to delete the neo cassette. Resulting ES cells contained multiple gene rearrangments; intact floxed-exon 6, intact floxed-neo cassette, or excision of both exon 6 and the neo cassette. Correctly targeted ES cells, lacking both exon 6 and the neo cassette, were injected into blastocysts and resulting chimeric males were bred with C57BL/6 females. Resulting offspring were backcrossed to C57BL/6 mice for at least ten generations (see SNP results below) prior to sending males to The Jackson Laboratory Repository. Upon arrival, males were used to cryopreserve sperm. To establish the living mouse colony, an aliquot of the frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
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 first generation rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, all 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 C57BL/6N genetic background.
|Allele Name||targeted mutation 1, Ajit Varki|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Cmah, cytidine monophospho-N-acetylneuraminic acid hydroxylase|
|Strain of Origin||129X1/SvJ|
|Molecular Note||Exon 6 and a floxed TK/neo were removed via transient cre mediated recombination.|
|Mutations Made By|| |
Ajit Varki, University of California, San Diego
When maintaining a live colony, homozygous mice may be bred together.
When using the Cmah- mouse strain in a publication, please cite the originating article(s) and include JAX stock #017588 in your Materials and Methods section.
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