Analysis of serotonin receptor 2A gene (HTR2A): Association study with autism spectrum disorder in the Indian population and investigation of the gene expression in peripheral blood leukocytes Subhrangshu Guhathakurta a , Asem Surindro Singh a , Swagata Sinha b , Anindita Chatterjee b , Shabina Ahmed c , Saurabh Ghosh d , Rajamma Usha a, * a Manovikas Biomedical Research and Diagnostic Centre, Manovikas Kendra, Rehabilitation and Research Institute for the Handicapped, 482 Madudah, Plot I-24, Sector-J, EM Bypass, Kolkata 700107, India b Out Patients Department, Manovikas Kendra Rehabilitation and Research, Institute for the Handicapped, 482 Madudah, Plot I-24, Sector-J, EM Bypass, Kolkata 700107, India c Assam Autism Foundation, Amarwati Path, Christian Basti, Guwahati 781005, India d Human Genetics Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata 700108, India 1. Introduction Autism is a childhood neurodevelopmental disorder character- ized by impairments in social interaction and communication with the occurrence of stereotyped behaviors (Diagnostic and Statistical Manual of Mental Disorders—4th edition, APA, 1994; Kanner, 1943). Various family studies demonstrated high heritability and multigenic complex mode of inheritance for autism (Folstein and Rosen-Sheidley, 2001). Genome-wide scans identified several autism risk regions in different chromosomes and chromosome 13q region shows maximum multipoint heterogeneity LOD score of 3 (Badner and Gershon, 2002; Barrett et al., 1999; IMGSAC, 1998; Philippe et al., 1999; Risch et al., 1999). Serotonin receptor 2A (5-HT 2A ) gene (HTR2A) resides at 13q14-q21 with three exons and two introns spanning approximately 63 kb (Serretti et al., 2007; Sparkes et al., 1991). The platelet hyperserotoninemia in autistic probands indicates abnormalities of serotoninergic neu- rotransmission in the etiology of autism (Cook and Leventhal, 1996). The receptor binding studies also supported this hypothesis. McBride et al. (1989) has reported decreased ‘‘serotonergic responsivity’’, reduced mean number of platelet 5-HT 2 receptor sites and platelet 5-HT 2 receptor-mediated platelet aggregation in autistic individuals. Furthermore, 3 H-lysergic acid diethylamide (3H-LSD), a partial serotonin receptor 2A agonist exhibited decreased 5-HT 2A receptor binding in first-degree relatives of Neurochemistry International 55 (2009) 754–759 ARTICLE INFO Article history: Received 30 April 2009 Received in revised form 15 July 2009 Accepted 21 July 2009 Available online 30 July 2009 Keywords: Serotonin receptor 2A Autism spectrum disorder Genetic association Gene expression Peripheral blood leukocytes ABSTRACT Several studies suggest involvement of serotoninergic system in the pathophysiology of Autism Spectrum Disorder (ASD). The 5-HT receptor binding studies using 3 H-lysergic acid diethylamide ( 3 H- LSD) and linkage analysis provided evidences to consider HTR2A as a potential candidate gene for ASD. The three SNPs, 1438A/G (rs6311), 102T/C (rs6313) and 1354C/T (rs6314) of HTR2A have been well studied in the etiology of various neuropsychiatric disorders. But studies on association of this gene with ASD are limited to two reports from American and Korean populations. Additionally there are reports, which demonstrated paternal imprinting of HTR2A with expression from only one allele. So far no reports are available on HTR2A and its association with any neuropsychiatric disorders from Indian population. Therefore, the present study investigates association of the above mentioned three markers of HTR2A with ASD in Indian population using population and family-based approaches. The study also deals with allelic expression pattern of HTR2A in Peripheral Blood Leukocytes (PBLs) to understand the parental imprinting status. The genotyping analyses were carried out for probands, parents and controls. The subsequent association analyses did not show association of these markers with ASD. So, HTR2A is unlikely to be a genetic marker for ASD in Indian population. The expression analyses showed absence of monoallelic expression, suggesting lack of parental imprinting of HTR2A gene. However, we noticed methylation of the CpG sites at 1438A/G and 102T/C loci of HTR2A gene. Further bioinformatics analysis revealed absence of CpG islands in the promoter of the gene supporting biallelic expression pattern of HTR2A in PBLs. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author at: Manovikas Biomedical Research and Diagnostic Centre, Manovikas Kendra Rehabilitation and Research Institute for the, Handi- capped, 482 Madudah, Plot I-24, Sector-J, EM Bypass, Kolkata 700107, India. Tel.: +91 33 40012732x238; fax: +91 33 2442 8275. E-mail address: ushamvk@yahoo.co.in (R. Usha). Contents lists available at ScienceDirect Neurochemistry International journal homepage: www.elsevier.com/locate/neuint 0197-0186/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuint.2009.07.008