5-Hydroxytryptamine (serotonin) 2A receptor gene polymorphism is associated with schizophrenia.

Background & objectives: Schizophrenia, the debilitating neuropsychiatric disorder, is known to be heritable, involving complex genetic mechanisms. Several chromosomal regions associated with schizophrenia have been identified during the past; putative gene (s) in question, to be called the global signature for the pathophysiology of the disease, however, seems to evade us. The results obtained from the several population-wise association-non association studies have been diverse. we therefore, undertook the present study on Tamil speaking population in south India to examine the association between the single nucleotide polymorphisms (SNPs) at the serotonin receptor gene (5HT2A) and the occurrence of the disease. Methods: Blood samples collected from 266 cases and 272 controls were subjected to genotyping (PCR amplification of candidate SNPs, RFLP and sequencing). The data on the SNPs were subjected to statistical analysis for assessing the gene frequencies in both the cases and the controls. Results: The study revealed significant association between the genotypic frequencies of the serotonin receptor polymorphism and schizophrenia. SNP analysis revealed that the frequencies of GG (30%, rs6311) and CC genotypes (32%, rs6313), were higher in patients (P<0.05) than in controls. The study also showed presence of G and C alleles in patients. significant levels of linkage disequilibrium (LD) were found to exist between the genotype frequencies of rs6311 and rs6313. Interpretation & conclusions: This study indicated an association between the SNPs (rs6311 and rs6313) of the serotonin receptor 5HT2A and schizophrenia. HapMap analysis revealed that in its genotype distribution, the Tamil speaking population was different from several other populations across the world, signifying the importance of such ethnicity-based studies to improve our understanding of this complex disease.

The Genetic Studies of Obsessive-Compulsive Disorder and Its Future Directions

Obsessive-compulsive disorder (OCD) is characterized by recurrent and persistent thoughts (obsessions), and repetitive behaviors or mental acts (compulsions). In Korea, an epidemiological study reported that the lifetime prevalence of OCD in the population was greater than two percent. The exact cause of OCD is still unknown. Evidence from familial, twin and segregation studies supports the role of a genetic component in the etiology of OCD. In addition, there is growing evidence that OCD has a specific neurochemical and neuroanatomical basis. According to this evidence, researchers have selected various candidate genes which have been implicated in the neurophysiology of OCD, and differences of allelic variants in OCD patients and controls have been analyzed. In this review we will introduce the results of previous genetic studies of OCD which have been performed in other populations, including twin studies, family studies, segregation analyses, linkage analyses, and association studies. In addition to these studies, we will present the results of our genetic studies of OCD performed in Korea.

Serotonin Transporter Gene Polymorphism in Healthy Adults and Patients with Irritable Bowel Syndrome / 대한소화기학회지

BACKGROUND/AIMS: Serotonin is thought to be an important neurotransmitter in the pathogenesis of irritable bowel syndrome (IBS). It is reported that functional polymorphism in the promotor region of the serotonin transporter gene is related with the subtypes of IBS and shows racial difference. However, a functional relation between polymorphism and IBS is not clear. The aim of this study was to investigate 5-hydroxytryptamine transporter (5-HTT) gene polymorphism in patients with IBS. METHODS: For fifty-six healthy controls and 33 patients with IBS fulfilling Rome II criteria, 5'-flank promotor region of 5-HTT gene was analyzed by polymerase chain reaction. RESULTS: The genotypes of healthy controls were S/S (57.1%), S/L (37.5%), and L/L (5.4%). Those of IBS patients were S/S (54.5%), S/L (36.4%), and L/L (9.1%). IBS patients were divided into three groups: diarrhea predominant (n=15; S/S, 40%; S/L, 53.3%; L/L, 6.7%), constipation predominant (n=12; S/S, 75.0%; S/L, 8.3%; L/L, 16.7%), diarrhea-constipation alternating type (n=6; S/S, 50%; S/L, 50%). There was no statistical difference in the 5-HTT gene polymorphism between patients and controls, and according to the subtypes of IBS patients (p=0.135). CONCLUSIONS: There was no relationship between serotonin transporter gene polymorphism and IBS. However, allele S/S genotype was most prominent genotype in both controls and patients.