129-Cckar^tm1Kpn Cckbr^tm1Kpn/J

Stock number: 006365
Product name: ABKO
Research areas: Endocrine Deficiency Research, Internal/Organ Research, Metabolism Research

Description

These double Cckar^tm1Kpn, Cckbr^tm1Kpn knock-out mice have the combined phenotype of the individual knock-outs (Stock No. 006367 and Stock No. 006369 respectively), and may be useful in applications relating to gastrointestinal studies.

Detailed description

Mice that are homozygous for both of the targeted mutations are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. The donating investigator reports that the double mutants have a combined phenotype.
No CCKBR receptor function was detected in competition binding assay of brain (cerebral plasma) membranes. When compared to wildtype, gastric pH in homozygotes is higher, pH 5.2, after overnight fast. Histological analysis reveals diminished parietal cell, enterochromaffin-like cell and antral comatostatin-producing D cell densities. An increase in the number of gastrin-producing G cells is observed. There is an increased number of H+, K+ -ATPase immunoreactive negative cells and abnormal distribution of parietal cells in oxyntic glands. Circulating gastrin levels are 10-fold higher in homozygotes.
No CCKAR receptor function was detected in competition binding assay of pancreatic membranes. Homozygotes do not exhibit decreased food intake due to peritoneal injection of cholecystokinin. Baseline food and water intake and body weight is normal in mutant mice. These mutant mice have larger gallbladder volumes and are more likely to develop spontaneous gallstones than wildtype controls. Gastric function is impaired due to diminished intestinal lipid feedback response. Small-intestine transit time is increased in mutant mice. When fed a lithogenic diet, mutant mice have an increase in biliary cholesterol secretion rates, when compared to the wildtype. Although the total number of olfactory-gonadotropin-releasing hormone-1 neuroendocrine (GnRH-1)neurons is the same in embryonic day 14.5 aged mutant and wildtype mice, more GnRH-1 neurons are found in the forebrain of the mutant than in the wildtype. This mutant mouse strain may be useful in studies of the neuroendocrine and gastrointestinal systems, lipid metabolism, gastric differentiation, hypochlorhydria and hypergastinemia.

Development

For the Cckar targeted mutation, a targeting vector containing neomycin resistance and herpes simplex virus thymidine kinase genes was used to disrupt exon 3. The construct was electroporated into 129-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric male animals were crossed to 129/SvEv mice.
For the Cckbr targeted mutation, a targeting vector containing neomycin resistance and herpes simplex virus thymidine kinase genes was used to disrupt exon 3. The construct was electroporated into 129S2/SvPas-derived D3 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts.
The two single targeted mutation strains, 129-Cckar^tm1Kpn/J (Stock No. 6367) and 129-Cckbr^tm1Kpn/J (Stock No. 6369), were then crossed to generate the double targeted mutation line.

Allele

Symbol: Cckbr^tm1Kpn
Name: targeted mutation 1, Alan S Kopin
MGI accession ID: MGI:2180591
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Cckbr
Marker name: cholecystokinin B receptor
Chromosome: 7
Strain of origin: 129S2/SvPas
Molecular note: The insertion of a neomycin selection cassette deleted sequence encoding transmembrane domains V through VII, which are essential for structure. Radiolabeled binding experiments of cerbral plasma membranes isolated from homozygous mutant mice confirmed a lack of functional protein.

Allele

Symbol: Cckar^tm1Kpn
Name: targeted mutation 1, Alan S Kopin
MGI accession ID: MGI:3051882
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Cckar
Marker name: cholecystokinin A receptor
Chromosome: 5
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Molecular note: A PGK-neo replaced exon 3, which encodes a portion of the third transmembrane domain and the second intracellular loop including the "ERY" motif. Southern blot of mutant mice indicated successful recombination. Testing for 125I-CCK-8 binding in pancreatic membranes mutant mice indicated showed no displaceable binding and therefore a lack a Cckar receptors.