B6.129-Cck^tm1Lcs/J

Stock number: 017710
Research areas: Diabetes and Obesity Research, Metabolism Research, Reproductive Biology Research, Research Tools

Description

The cholecystokinin gene is disrupted by the insertion of a β-geo fusion cassette in these knockin/knockout mice. LacZ is detected in the gut and brain, and homozygotes exhibit a range of metabolic and behavioral defects.

Detailed description

A β-geo fusion cassette was inserted into exon 2 of the cholecystokinin (Cck) gene, abolishing gene function. Cholecystokinin is a gastrointestinal satiety hormone secreted by enteroendocrine intestinal I cells in response to fat and protein. Its release stimulates pancreatic enzyme secretion, modulates intestinal motility, and regulates meal size in the central nervous system. CCK is also a neurotransmitter released by subpopulations of neurons in the central nervous system, where it influences both memory and exploratory behaviors. Homozygous CCK^-/- mice are viable, fertile, and normal in size, with lacZ staining visible in the gut and brain. Specifically, lacZ expression is evident in the neural tube, neural crest, mid- and hindbrain, and heart (E8.5-9.5), from the proximal stomach into the colon (E10.5-15.5), and persists in scattered endocrine cells in the upper intestine in adults. Expression is also evident in the cortex, hippocampus, and thalamus of adult mice. On a high fat diet, these mice gain less weight, have less fat mass, and absorb less total fat than wildtype mice. They have higher energy expenditure, enhanced insulin sensitivity, and decreased glucose tolerance than control mice, with no change to triglyceride, cholesterol, glucose and insulin levels. These CCK^-/- mice exhibit impaired glucose-stimulated insulin secretion with no change in islet size, number, or morphology. Pancreatic amylase levels are 60% higher in these mice and they have a higher frequency of gall stones than wildtype mice. They also display spatial learning and memory defects, with reduced exploratory and increased anxiety-related behaviors.

Development

A targeting vector was designed to insert a neomycin-β-galactosidase fusion protein (β-geo) into exon 2 of the cholecystokinin (Cck) gene. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl⁺-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts and the resulting chimeric males were bred to 129/SvJ females. These mice were then backcrossed at least 10 generations to C57BL/6J background. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.

Allele

Symbol: Cck^tm1Lcs
Name: targeted mutation 1, Linda C Samuelson
MGI accession ID: MGI:2180568
Generation method: Targeted
Attributes: Reporter; Null/Knockout
Marker symbol: Cck
Marker name: cholecystokinin
Chromosome: 9
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Expressed genes: lacZ,beta-galactosidase,E. coli
Site of expression: lacZ expression is evident in the neural tube, neural crest, mid- and hindbrain, and heart (E8.5-9.5), from the proximal stomach into the colon (E10.5-15.5), and persists in scattered endocrine cells in the upper intestine in adults. Expression is also evident in the cortex, hippocampus, and thalamus of adult mice.
Molecular note: A cassette containing a lacZ-neo fusiong gene was inserted into exon 2 to delete 168 nucleotides encoding the amino-terminal signal sequence in exon 2. Radioimmunoassays of brain and duodenum tissue from homozygous mutant mice showed an absence of bioactive protein product.