BACKGROUND: Two polymorphic regions of serotonin transporter (5-HTT) gene: a 44 base pair (bp) insertion/deletion in the promoter region (5-HTTLPR) and a 17 bp variable number of tandem repeats in second intron (VNTR-2), seem to modulate the gene's transcription in allele-dependent manner. METHODS: We have earlier demonstrated association with 5-HTT gene in families multiply affected by schizophrenia. Here, we investigated separate and combined effects of VNTR-2 and 5-HTTLPR on the rate of peripheral 5-HTT transcription in a sample of offspring from those families. Relative 5-HTT mRNA levels were determined in 53 permanent lymphoblast cell lines by semiquantitative real-time polymerase chain reaction using beta-actin as reference. RESULTS: Since the low-expressing alleles (short [S], 10) appeared to act dominantly, genotypes were grouped as "high-expressing" (long [L]/L, 12/12) versus "low-expressing" (S, 10). At both loci, nonsignificant differences in 5-HTT mRNA levels ( approximately 30%) were observed between "high"- and "low-expressing" genotypes. In order to search for the potential combined effect of 5-HTTLPR and VNTR-2, levels of 5-HTT mRNA were compared among three groups of samples having "low-expressing" genotype at none, one, or both loci. Increase in number of "low-expressing" genotypes significantly reduced relative 5-HTT gene expression (p <.02). CONCLUSIONS: Our results indicate weak individual influence, but possible combined effect, of 5-HTTLPR and VNTR-2 polymorphisms on 5-HTT gene expression.
BACKGROUND: Two polymorphic regions of serotonin transporter (5-HTT) gene: a 44 base pair (bp) insertion/deletion in the promoter region (5-HTTLPR) and a 17 bp variable number of tandem repeats in second intron (VNTR-2), seem to modulate the gene's transcription in allele-dependent manner. METHODS: We have earlier demonstrated association with 5-HTT gene in families multiply affected by schizophrenia. Here, we investigated separate and combined effects of VNTR-2 and 5-HTTLPR on the rate of peripheral 5-HTT transcription in a sample of offspring from those families. Relative 5-HTT mRNA levels were determined in 53 permanent lymphoblast cell lines by semiquantitative real-time polymerase chain reaction using beta-actin as reference. RESULTS: Since the low-expressing alleles (short [S], 10) appeared to act dominantly, genotypes were grouped as "high-expressing" (long [L]/L, 12/12) versus "low-expressing" (S, 10). At both loci, nonsignificant differences in 5-HTT mRNA levels ( approximately 30%) were observed between "high"- and "low-expressing" genotypes. In order to search for the potential combined effect of 5-HTTLPR and VNTR-2, levels of 5-HTT mRNA were compared among three groups of samples having "low-expressing" genotype at none, one, or both loci. Increase in number of "low-expressing" genotypes significantly reduced relative 5-HTT gene expression (p <.02). CONCLUSIONS: Our results indicate weak individual influence, but possible combined effect, of 5-HTTLPR and VNTR-2 polymorphisms on 5-HTT gene expression.
Authors: Songfa Zhong; Salomon Israel; Hong Xue; Pak C Sham; Richard P Ebstein; Soo Hong Chew Journal: Proc Biol Sci Date: 2009-09-02 Impact factor: 5.349
Authors: Robert A Philibert; Harinder Sandhu; Nancy Hollenbeck; Tracy Gunter; William Adams; Anup Madan Journal: Am J Med Genet B Neuropsychiatr Genet Date: 2008-07-05 Impact factor: 3.568