1. Analysis of the composite 5-HTTLPR/rs25531 polymorphism in premenstrual dysphoric disorder
Conclusion
These data do not support a major role for rs25531or 5-HTTLPR in contributing to susceptibility to PMDD, whether considered separately or as a combined functional marker. However, they do illustrate the possible modifying effect of multiple closely-linked functional markers on the overall function of SERT.
Data analysis
Genotype frequencies were recorded separately for each marker. Data were then combined to produce a composite functional classification (S = S(A or G)):
:S/S, LG/LG and LG/S = S’/S’ (Low)
LA/S and LA/LG = L’/S’ (Intermediate)
LA/LA = L’/L’ (High)
Results
Controls
PMDD
105 women were recruited; 53 were diagnosed with PMDD (mean age 26.6 years) and 52 as healthy controls (mean age 27.7 years). Fig 1 shows the genotype categorisation for each group. We did not detect any G/G or composite LG/LG genotypes in any of our samples. Nor did we detect any SG haplotypes.
χ2 analysis showed no significant association of any genotype with PMDD, whether viewed as separate polymorphisms or as the composite 5-HTTLPR/rs25531 marker. Interestingly, genotypic differences between the PMDD and control groups were eliminated when the 2 polymorphisms were combined into a composite functional marker which showed virtually identical frequencies in both study cohorts (fig 1)
Introduction
The aim of this study was to investigate whether 2 closely-linked funtional promoter polymorphisms in the serotonin transporter (SERT) gene are risk factors for premenstrual dysphoric disorder (PMDD). 5-HTTLPR comprises a 43 base pair insertion/deletion that produces L (long) and S (short) alleles. rs25531 is an A/G single nucleotide polymorphism that is located 19 nucleotides upstream of 5-HTTLPR. The S and G variants are associated with lower SERT expression compared to L and A. Considered together, the allelic composites LG and S(AorG) are associated with low, nearly equivalent expression of SERT protein compared to LA.
A/G insertion/deletion
Deletion = S; Insertion = L
Methods
Women aged were recruited from the local population, according to the following criteria:
Ethnic group: white European
Regular menstrual cycles (28±4 days)
Not taking hormonal therapy
No history of mood disorder
Women were prospectively diagnosed over 2 menstrual cycles by daily symptom rating scores, using DSM-IV criteria.
DNA was extracted from leukocytes. A genomic region of SERT containing both 5-HTTLPR and rs25531 was amplified by polymerase chain reaction (PCR). To genotype 5-HTTLPR, amplicons were electrophoresed on 2% agarose. To genotype rs25531, PCR products were first digested with Msp1.