Alternatively spliced mRNA transcripts encoding the extracellular domain of the FSH receptor gene: Expression in the mouse ovary during the ovulatory cycle

OBJECTIVE: To evaluate regulation of follicle-stimulating hormone (FSH) receptor expression in the mouse ovary during different stages of an artificially induced ovulatory cycle. STUDY DESIGN: Follicular maturation was achieved in pubertal female mice by pregnant mares' serum gonadotropin (PMSG). Ovulation was induced 48 hours later by human chorionic gonadotropin (hCG). Ovaries were harvested before treatment, at 24 and 48 hours after PMSG and at 3, 9 and 12 hours after hCG. RNA was extracted using a single-step isolation method and used for reverse transcription. The cDNA was amplified by polymerase chain reaction (PCR) using primers designed to amplify a 512- basepair product corresponding to the extracellular fragment of the FSH receptor. RESULTS: PCR products, resolved by electrophoresis on agarose gels, showed four bands corresponding to four discrete, alternatively spliced forms of the FSH receptor. Expression of the various transcripts varied at different stages of the ovulatory cycle such that the larger transcripts increased up to 48 hours following PMSG and began to decrease thereafter, reaching a trough 12 hours following hCG administration. Conversely, a smaller transcript reached a peak 9 hours following hCG administration and decreased thereafter. CONCLUSION: The various transcripts represent different FSH receptor mRNA splicing and may mediate changes in receptor function. Since these alternative spliced forms encode different portions of the extracellular domain, it is possible that they have altered hormone-binding affinity serving a regulatory purpose, such as decreasing hormone binding affinity.