Expression of follicle-stimulating hormone-receptor mRNA alternate transcripts in bovine granulosa cells during luteinization in vivo and in vitro.

In cattle, as in many other species, formation of the corpus luteum is associated with loss of sensitivity to FSH. To determine whether this is associated with changes in FSH-receptor mRNA levels or alternate splicing of the primary transcript, reverse transcription and the polymerase chain reaction (RT-PCR) were used to examine transcripts during granulosa cell luteinization in vivo and in vitro. Using RT-PCR and Southern blotting, three alternate transcripts of the FSH-receptor were found consistently in bovine granulosa cells. The largest transcript encoded the full-length receptor while the other transcripts lacked either exon 9 or exons 4, 5 and 9. One day after luteinization in vivo, full-length FSH-receptor mRNA was detectable at low levels in the newly-formed corpus luteum. By day 3, however, no full-length transcripts were detectable in the corpus luteum. In contrast, when primers were used which amplify only the extracellular domain, FSH-receptor transcripts were detectable in all corpora lutea tested up to mid-cycle. In granulosa cells, luteinized in vitro, there was a similar loss of full-length FSH-receptor transcripts after day 1 but continued expression of transcripts encoding the extracellular domain. Results show that granulosa cell luteinization in cattle is associated with a change in splicing of the FSH-receptor primary transcript such that after luteinization only shortened transcripts coding for the extracellular domain are detectable. This process resembles, in reverse, changes in FSH-receptor transcript splicing during development of the gonads.