Obsessive-compulsive disorder has a reported association with a low-activity allele of the enzyme catechol-O-methyltransferase; however, the low-activity genotype is also seen in a significant proportion of unaffected individuals.
Therefore, this case-control study assessed whether genetics variations in catechol-O-methyltransferase gene (COMT) could influence susceptibility to OCD and OCD features in a Brazilian sample.
This polymorphism (valine to methionine at codon 158) has been previously reported to influence the activity of COMT by three to four-fold and has recently been reported to be associated with OCD.1 We tested for linkage using an autosomal dominant model with reduced penetrance and non-parametric methods.
As several other uncommon, less well quantitated genetic variations occur with an OCD phenotype, including chromosomal anomalies and some other rare gene variants (SGCE, GCH1 and SLITRK1), a tentative conclusion is that OCD resembles other complex disorders in being etiologically heterogeneous and in having both highly penetrant familial subtypes associated with rare alleles or chromosomal anomalies, as well as having a more common, polygenetic form that may involve polymorphisms in such genes as BDNF, COMT, GRIN2beta, TPH2, HTR2A and SLC1A1.
The COMT M158 allele was associated with reduced plasma 3-OMD levels in a co-dominant manner, both in OCD probands and their relatives, but not in controls.
A polymorphism in the coding region of catechol-O-methyltransferase gene (COMT) was previously reported to be associated with obsessive-compulsive disorder (OCD), particularly in male probands.
In the main meta-analysis, OCD was associated with serotonin-related polymorphisms (5-HTTLPR and HTR2A) and, in males only, with polymorphisms involved in catecholamine modulation (COMT and MAOA).
The Met allele load of the COMT receptor gene was associated with response to 10 weeks of treatment with citalopram in drug-free or drug-naïve OCD patients.
The present case-control/pharmacogenetic study did not provide clear evidence that the COMTVal158Met polymorphism is a predictor of OCD or of OCD patients' clinical responses.
Transmission disequilibrium analyses were performed after genotyping 13 single-nucleotide polymorphisms (eight in COMT and five in MAO-A) in 783 OCD trios (probands and their parents).
In subjects of Afrikaner descent, the L/L genotype of the COMTVal158Met polymorphism was significantly more common in the OCD hoarding group, with a preponderance of low activity alleles, compared with nonhoarding patients and controls.
A haplotype composed of three SNPs [rs2097603; rs4680 (158Val/Met); rs165599] representing the major linkage disequilibrium blocks in COMT and previously implicated in functional variation, was found to be associated with ADHD and OCD in 22q11.2DS individuals.
Although these findings do not replicate the previous reports, they do provide limited support to demonstrate a trend for homozygosity at the COMT locus in the OCD patients and, in turn, further implicate a potential role for COMT in the genetic etiology of OCD.Am.J. Med.Genet.(Neuropsychiatr.Genet.)96:721-724, 2000.
Family and twin studies have indicated a genetic component in the etiology of OCD, and the catechol-O-methyl transferase (COMT) gene is an important candidate gene for OCD.