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Analysis of variation in mouse TPMT genotype, expression and activity
James W Watters1, Wanghai Zhang, Melissa A Meucci
1Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO 63110, USA.
Pharmacogenetics
|April 15, 2004
Summary
Mouse strain variation in thiopurine methyltransferase (TPMT) activity is linked to mRNA expression, not genetic sequence. This low genetic diversity makes mice valuable for pharmacogenomic drug response studies.
Area of Science:
- Pharmacogenomics
- Genetics
- Biochemistry
Background:
- Inbred mouse strains offer potential for pharmacogenomic discovery.
- Limited knowledge exists regarding drug response variation and genetic differences in pharmacologically relevant genes among mouse strains.
Purpose of the Study:
- To investigate variations in gene sequence, mRNA expression, and protein activity of thiopurine methyltransferase (TPMT) across different inbred mouse strains.
- To determine the genetic and molecular basis for differential TPMT activity in mice.
Main Methods:
- TPMT activity was quantified using high-performance liquid chromatography (HPLC) to measure 6-MMP production from 6-MP.
- Genetic variation was assessed through gene resequencing and SNP genotyping via pyrosequencing.
- mRNA expression levels were determined using real-time polymerase chain reaction (PCR).
Main Results:
- A nearly five-fold variation in TPMT activity was observed, with strains categorized into distinct low and high activity groups.
- TPMT activity strongly correlated with TPMT mRNA expression levels.
- Genotyping of 30 polymorphisms revealed only two haplotypes, corresponding to the low and high activity groups, indicating low haplotype diversity.
Conclusions:
- Differential TPMT activity in mice is primarily attributed to variations in mRNA expression.
- The observed low haplotype diversity in the mouse TPMT gene suggests its utility for pharmacogenomic studies associating genetic variations with drug response phenotypes in inbred strains.