Catechol-O-methyltransferase, COMT, metabolizes endogenous catechol substrates, and thus is important in a variety of processes, including neurotransmission. Dysregulation of catechol levels is implicated in neurobehavioral disorders. Numerous genetic association studies suggest the involvement of COMT in brain diseases like schizophrenia and panic disorder. Many of these allelic associations involve a functional COMT DNA that alters enzymatic activity. These association results are often contradictory and implicate another variant or variants at or near the COMT locus. Additionally, allele-specific mRNA expression using this functional COMT variant has been observed. This proposal outlines a feasibility study to characterize the DNA sequence and expression variation in individuals in an effort to understand the potential impact of sequence variation on COMT expression in a disease population. We hypothesize that DNA variation in the catechol-O-methlytransferase gene region contributes to variability in COMT mRNA expression. In order to test this hypothesis, we will use lymphoblastoid cell lines from 30 Caucasian CEPH trios from Utah, a population that has been genotyped by the HapMap Consortium in order to characterize genetic diversity in the human population. With this population, we will characterize cell line COMT mRNA expression using quantitative reverse transcription-polymerase chain reaction. For subjects heterozygous for DNA variants present in transcripts, we will measure allele-specific mRNA expression using a single base extension method. We will then test the correlation between genotype and mRNA expression variation in COMT. We will genotype our sample for common single nucleotide polymorphisms (SNPs) within the COMT locus and across a region approximately 340kb upstream of COMT, as well as use genotypes from ~100 SNPs already genotyped in this same sample in this same region during the HapMap project. Single markers and multiple-marker haplotypes will be used to test for correlation with variation in mRNA expression. Finally, we will exploit observations of the regulatory role that estrogen plays in COMT activity by assessing COMT expression after treating cell lines with estrogen, and then measuring association to SNP genotypes, including variants in predicted estrogen response elements. Genetic polymorphisms correlated with differences in COMT expression can be used to identify cis- acting regulatory elements for predicting COMT functional differences. This in vitro work may be useful for the understanding of the genetic contribution of COMT to disease susceptibility, particularly with regard to the cis regulation of the COMT locus. ? ? ?
