C.129X1(B6N)-Cmah^tm1Avrk/J

Stock number: 028043
Research areas: Diabetes and Obesity Research, Endocrine Deficiency Research, Internal/Organ Research, Neurobiology Research

Description

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.

Detailed description

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-Dmd^mdx/J mice (Stock No. 001801), lack of CMAH accelerates the onset and severity of Duchenne muscular dystrophy (DMD) seen in the Dmd^mdx mice.

In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype of these Balb/c-congenic mice could vary from that originally described on a B6J genetic background. We may modify the strain description if necessary as published results become available.

Development

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/6N females. Resulting offspring were backcrossed to C57BL/6N mice for at least ten generations, and were brought into The Jackson Laboratory as Stock No. 017588. Subsequently, the donating investigator bred some of these mice to Balb/cAnHsd mice for at least 10 genrations. Upon arrival at The Jackson Laboratory Repository, males were used to cryopreserve sperm. To establish the living mouse colony, an aliquot of the frozen sperm was used to fertilize BALB/cByJ oocytes (Stock No. 001026).

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. Two of the 27 markers throughout the genome were segregating, one likely due to the mutation on Chromosome 13.

Allele

Symbol: Cmah^tm1Avrk
Name: targeted mutation 1, Ajit Varki
MGI accession ID: MGI:3715527
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Cmah
Marker name: cytidine monophospho-N-acetylneuraminic acid hydroxylase
Chromosome: 13
Strain of origin: 129X1/SvJ
Molecular note: Exon 6 and a floxed TK/neo were removed via transient cre mediated recombination.