1. ¹Department of Pharmacology, College of Medicine and Public Health, The Ohio State University, Columbus, OH, USA
2. ²Department of Psychiatry, College of Medicine and Public Health, The Ohio State University, Columbus, OH, USA
3. ³Program in Pharmacogenomics, College of Medicine and Public Health, The Ohio State University, Columbus, OH, USA
4. ⁴The Neuroscience Graduate Studies Program, College of Medicine and Public Health, The Ohio State University, Columbus, OH, USA

Correspondence: Professor W Sadée or Professor D Saffen, Department of Pharmacology and Psychiatry, College of Medicine and Public Health, The Ohio State University, 5072 Graves Hall, 333 West 10th Ave., Columbus, OH 43210, USA. E-mails: sadee.1@osu.edu or saffen.1@osu.edu

Received 7 September 2005; Revised 7 November 2005; Accepted 12 December 2005; Published online 24 January 2006.

Abstract

An insertion/deletion polymorphism in the SERT linked promoter region (SERTLPR), previously reported to regulate mRNA expression in vitro, has been associated with mental disorders and response to psychotropic drugs. Contradictory evidence, however, has raised questions about the role of SERTLPR in regulating mRNA expression in vivo. We have used analysis of allelic expression imbalance (AEI) of SERT mRNA to assess quantitatively the contribution of SERTLPR to mRNA expression in human post-mortem pons tissue sections containing serotonergic neurons of the dorsal and median raphe nuclei. Any difference in the expression of one allele over the other indicates the presence of cis-acting elements that differentially affect transcription and/or mRNA processing and turnover. Using a marker SNP in the 3' untranslated region of SERT mRNA, statistically significant differences in allelic mRNA levels were detected in nine out of 29 samples heterozygous for the marker SNP. While the allelic expression differences were relatively small (15–25%), they could nevertheless be physiologically relevant. Although previous results had suggested that the long form of SERTLPR yields higher mRNA levels than the short form, we did not observe a correlation between SERTLPR and allelic expression ratios. Also in contrast to previous results, we found no correlation between SERTLPR and allelic expression ratios or SERT mRNA levels in B-lymphocytes. This study demonstrates that regulation of SERT mRNA is independent of SERTLPR, but could be associated with polymorphisms in partial linkage disequilibrium with SERTLPR.