title: Genes within the serotonergic system are differentially expressed in human brain.
abstract: BACKGROUND
  Serotonin is an important neurotransmitter with wide-ranging functions throughout the central nervous system. There is strong evidence to suggest that regulation of serotonergic gene expression might be related to genetic variability, and several studies have focused on understanding the functional effects of specific polymorphisms within these genes on expression levels. However, the combination of genotype together with gender and brain region could have an overall effect on gene expression. In this study, we report expression patterns of five serotonergic genes (TPH1, TPH2, 5-HT2A, 5-HT2C, 5-HTT) in seven different human post-mortem brain regions (superior frontal gyrus, superior temporal gyrus, striatum, cerebellum, hippocampus, midbrain and thalamus) using TaqMan real-time quantitative PCR. In addition, the effect of genotype and gender on their expression levels was determined.
  
  
  RESULTS
  The data revealed that mRNA from the five genes investigated was detected in all brain regions and showed an overall significant difference in expression levels. Furthermore, the expression of 5-HT2C, 5-HT2A and TPH2 was found to be significantly different between the various brain regions. However, neither gender nor genotype showed significant effects on the expression levels of any of the genes assayed. Interestingly, TPH1 and TPH2 were expressed in all brain regions similarly except for within the striatum and cerebellum, where TPH1 was expressed at a significantly higher level than TPH2.
  
  
  CONCLUSIONS
  The effect of brain region has a greater influence on serotonergic gene expression than either genotype or gender. These data add to the growing body of evidence that effects of functional polymorphisms on gene expression in vitro are not observed ex vivo, and provide information that will aid in the design of expression studies of the serotonergic gene system within human post-mortem brain.
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, King's College London, UK. K.Sugden@iop.kcl.ac.uk
authors.forename: Karen
authors.initials: K
authors.lastname: Sugden
authors.forename: Ales
authors.initials: A
authors.lastname: Tichopad
authors.forename: Nadeem
authors.initials: N
authors.lastname: Khan
authors.forename: Ian W
authors.initials: IW
authors.lastname: Craig
authors.forename: Ursula M
authors.initials: UM
authors.lastname: D'Souza
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D015870:Gene Expression / Q000502:physiology*; D055106:Genome-Wide Association Study / Q000379:methods; D005838:Genotype; D006801:Humans; D008297:Male; D011180:Postmortem Changes; D044402:Receptor, Serotonin, 5-HT2A / Q000235:genetics / Q000378:metabolism; D044405:Receptor, Serotonin, 5-HT2C / Q000235:genetics / Q000378:metabolism; D012701:Serotonin / Q000235:genetics / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000235:genetics / Q000378:metabolism
chemical_list: D044402:Receptor, Serotonin, 5-HT2A; D044405:Receptor, Serotonin, 5-HT2C; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin; C497467:TPH1 protein, human; C494784:TPH2 protein, human; D014365:Tryptophan Hydroxylase