B6.129X1-Ppargc1a^tm1Dpk/J

Stock number: 009662
Research areas: Cardiovascular Research, Cell Biology Research, Metabolism Research, Research Tools

Description

Mice that are homozygous for this targeted mutation of Ppargc1a (peroxisome proliferative activated receptor, gamma, coactivator 1 alpha) have fewer and smaller mitochondria in heart and soleus muscle and exhibit hypoactivity, reduced exercise capacity, increase sensitivity to cold temperatures and in adults, heavier body weights and increased percent body fat. This mutant mouse strain may be useful in studies of mitochondrial respiration and physiology, muscle physiology, and energy metabolism.

Detailed description

Mice that are homozygous for the targeted mutation are viable and fertile. During the generation of this allele, a 3' homologous recombination and insertion occurred with a duplication of exon 3 between exons 5 and 6. The exon 3 insertion, which was confirmed by RT-PCR, results in a mutant transcript that encodes a truncated protein due to a stop codon at amino acid 255. Normal gene product (mRNA) containing an exon 5?6 border is not detected. If the truncated protein gene product is stable, it could theoretically have some activity, given that it would contain nuclear receptor-interacting domains and the amino-terminal activation domain. Total body weights for homozygotes are reduced 15-20% for the first week after birth, but become normal by 3 weeks of age. By 18 weeks of age, homozygotes have heavier body weights and increased percent body fat than wildtype controls. Heart and slow twitch skeletal muscle (gastrocnemius, soleus) weights are lower in homozygotes than controls. Electron microscopy analysis reveals lower density and smaller mitochondria in soleus muscle. The state 3 (ADP-stimulated) mitochondrial respiration rate is diminished. Overall activity is decreased and thigmotaxis behavior is increased. Mutant mice exhibit reduced strength, activity endurance capacity, muscle fatigue and reduced cardiac output. Homozygotes are more sensitive to cold temperatures. 24 hour fasting results in hepatic steatosis. 4.5 month old homozygous females exhibit increased body weight, but normal glucose tolerance and insulin sensitivity on standard chow diet. Female homozygotes on high fat chow exhibit mildly increased glucose tolerance and insulin sensitivity. Histological examination of the parietal cerebral cortex, hippocampus, brainstem and basal ganglia reveals microvacuolation. This mutant mouse strain may be useful in studies of mitochondrial respiration and physiology, muscle physiology, and energy metabolism.

Development

A targeting vector containing neomycin resistance and herpes simplex virus thymidine kinase genes was used to disrupt exons 4 and 5. The construct was electroporated into 129X1/SvJ derived RW-4 embryonic stem (ES) cells. A 3' homologous recombination and insertion occurred with a duplication of exon 3 between exons 5 and 6. The exon 3 insertion, which was confirmed by RT-PCR, results in a mutant transcript that encodes a truncated protein due to a stop codon at amino acid 255. Correctly targeted ES cells were injected into C57BL/6J blastocysts. The resulting chimeric animals were crossed to C57BL/6J mice, and then backcrossed to C57BL/6J for 9 generations using a marker assisted (speed congenic) protocol. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J once to establish the colony.

Allele

Symbol: Ppargc1a^tm1Dpk
Name: targeted mutation 1, Daniel P Kelly
MGI accession ID: MGI:3522468
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Ppargc1a
Marker name: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha
Chromosome: 5
Strain of origin: 129X1/SvJ
Molecular note: The targeting event for this knock-out resulted in a 3 prime end recombination and an insertion on the 5 prime end causing an additional exon 3 in the allele downstream of exon 5. This additional exon 3 causes a premature stop codon at amino acid 255 and an unstable transcript (no smaller proteins were identified by Western blot analysis). RT-PCR, Northern and Western blot analysis confirmed the absence of a stable transcript and no detectable protein.