Androgen receptor polymorphism and platelet reactivity in healthy men

Whole exome sequencing in the Framingham Heart Study identifies rare variation in HYAL2 that influences platelet aggregation

Inhibition of platelet reactivity is a common therapeutic strategy in secondary prevention of cardiovascular disease. Genetic and environmental factors influence inter-individual variation in platelet reactivity. Identifying genes that contribute to platelet reactivity can reveal new biological mechanisms and possible therapeutic targets. Here, we examined rare coding variation to identify genes associated with platelet reactivity in a population-based cohort. To do so, we performed whole exome sequencing in the Framingham Heart Study and conducted single variant and gene-based association tests against platelet reactivity to collagen, adenosine diphosphate (ADP), and epinephrine agonists in up to 1,211 individuals. Single variant tests revealed no significant associations (p<1.44×10^-7), though we observed a suggestive association with previously implicated MRVI1 (rs11042902, p = 1.95×10^-7). Using gene-based association tests of rare and low-frequency variants, we found significant associations of HYAL2 with increased ADP-induced aggregation (p = 1.07×10^-7) and GSTZ1 with increased epinephrine-induced aggregation (p = 1.62×10^-6). HYAL2 also showed suggestive associations with epinephrine-induced aggregation (p = 2.64×10^-5). The rare variants in the HYAL2 gene-based association included a missense variant (N357S) at a known N-glycosylation site and a nonsense variant (Q406*) that removes a glycophosphatidylinositol (GPI) anchor from the resulting protein. These variants suggest that improper membrane trafficking of HYAL2 influences platelet reactivity. We also observed suggestive associations of AR (p = 7.39×10^-6) and MAPRE1 (p = 7.26×10^-6) with ADP-induced reactivity. Our study demonstrates that gene-based tests and other grouping strategies of rare variants are powerful approaches to detect associations in population-based analyses of complex traits not detected by single variant tests and possible new genetic influences on platelet reactivity.

Androgen receptor (CAG)n polymorphism and androgen levels in women with systemic lupus erythematosus and healthy controls

Systemic lupus erythematosus (SLE) is an autoimmune disorder that affects mainly females. Therefore, interrelations between the reproductive and immune system have been assumed. Considering the complex influence of hormones and receptors, we aimed to investigate the influence of androgens and androgen receptor (AR) polymorphism in women with SLE. One hundred and sixteen patients and 44 healthy women were investigated. Testosterone, sex hormone-binding globulin (SHBG), dehydroepiandrosterone-sulphate (DHEAS) concentrations and AR (CAG)n polymorphism were determined. SLE patients had significantly lower levels of total and free testosterone and DHEAS in comparison with the controls. No differences in the CAG repeat length between the groups were established. Women with two alleles carrying more than 22 CAG repeats had significantly higher levels of SHBG (101.51 ± 61.81 vs. 69.22 ± 45.93 nmol/l, p = 0.015) and DHEAS (3.11 ± 2.65 vs. 2.11 ± 3.06 μmol/l, p = 0.007) and a tendency to higher testosterone concentrations (2.35 ± 2.10 vs. 1.71 ± 1.70 nmol/l, p = 0.056) in comparison with other women. The CAG repeat length in the relatively longer (CAG)n allele was inversely related to the Systemic Lupus International Collaborating Clinics/ACR index (r = -0.258, p = 0.009). In conclusion, the androgen receptor (CAG)n polymorphism is not related to the development of SLE, but it could modulate the severity of the lupus chronic damages as well as the androgen levels in women.