Context: Polymorphisms of the FSHR gene are associated with variable ovarian response to FSH stimulation in subjects undergoing in vitro fertilization (IVF) treatment. The type of ovarian response is correlated with the level of FSH receptor (FSHR) expression on granulosa cells.
Objective: We investigated whether the polymorphism at position -29 in the promoter of the FSHR gene may contribute in altered receptor expression.
Design and patients: FSHR polymorphism at position -29 was studied in 100 subjects undergoing IVF treatment. Association of this polymorphism with level of FSHR expression was retrospectively analyzed.
Setting: The study was conducted at an academic research institute and private IVF clinic.
Methods: The genotype at position -29 of the FSHR gene was studied in IVF subjects by PCR-restriction fragment length polymorphism. Total RNA and protein was extracted from granulosa cells. The relative FSHR mRNA expression was carried out by real-time PCR. The receptor protein expression was evaluated by Western blot and confocal microscopy.
Results: The clinical and endocrinological parameters revealed that almost 72% of subjects with the AA genotype at position -29 of FSHR gene were poor ovarian responders (odds ratio 8.63, 95% confidential interval 1.84-45.79; P = 0.001). The lower cleavage intensity predicted by in silico analysis for A allele as compared with the G allele suggest the difference in the DNA-protein binding affinity. The relative expression of FSHR at mRNA and protein level was significantly reduced in subjects with AA genotype as compared with the GG genotype.
Conclusion: Poor ovarian response observed in subjects with the AA genotype at position -29 of the FSHR gene is due to reduced receptor expression.