Different allelic distribution of a single SNP between sexes in humans

Sex-Related Differences in Allelic Frequency of the Human Beta T Cell Receptor SNP rs1800907: A Retrospective Analysis from Milan Metropolitan Area

This paper aims at retrospectively re-analyzing the different distribution, between males and females, in the allelic frequency of the human β T cell receptor (TCR β) single nucleotide polymorphism (SNPs) rs1800907 in Caucasian patients in the Milan metropolitan area. The allelic frequency significantly differed between sexes. Females showed higher frequency of C/C genotype than males, but lower T/C genotype (p < 0.0001). Heterozygous (T/C) versus homozygous (T/T + C/C) genotypes resulted in a different distribution of frequencies in males than in females, the latter possessing higher homozygosis (p < 0.0001). Within the limitations of this work (small number of included studies that concerned just a specific geographical area), allelic distribution according to sex might account the role of TCRβ-related SNPs in autoimmune diseases and further investigations are required to explain better this genetic background, in the perspective of a sex-related T cell immune responsiveness and auto-immunity.

T-cell receptor beta polymorphism is not associated with endometriosis

AIM

We carried out an association study between T-cell receptor beta polymorphism (TCRB) and endometriosis to investigate the difference in allelic frequency. Polymorphisms in T-cell receptor genes can provide important information for the study of the immune response and autoimmune diseases; indeed, rs1800907, a very common single nucleotide polymorphism (SNP) of the TCRB, has been extensively studied in autoimmune diseases in the 1990s using Southern blot analysis and more recently polymerase chain reaction (PCR) and sequencing. An autoimmune etiology for endometriosis has been strongly suggested for the presence of antibodies against endometrium, high rates of autoimmune disorders and associated atopic diseases.

MATERIAL AND METHODS

We investigated 70 patients with endometriosis and 120 controls. DNA of patients and controls was studied by PCR followed by restriction digestion and sequencing to determine genotype and presence of linkage disequilibrium (LD). Statistical analysis was carried out using STATA Routine GENHW (StataCorp, College Station, TX, USA) for estimation of Hardy-Weinberg equilibrium and test power calculation. The difference of allele distribution between patients and controls was calculated according to Pearson's and Fisher's tests. Test power for the estimation of linkage disequilibrium is low (0.16).

RESULTS

We performed an association study of the SNP rs1800907 of TCRB between 70 patients with endometriosis and 120 controls, and did not find any significant difference (χ(2) = 0.27 and P = 0.87). Fisher's test confirmed a P-value of 0.872.

CONCLUSION

Our study does not suggest an evidential and major involvement of TCRB in the pathogenesis of endometriosis in an Italian population in a small case control study.