CHARACTERIZATION AND RELATIVE ABUNDANCE OF ALTERNATIVELY SPLICED LUTEINIZING-HORMONE RECEPTOR MESSENGER-RIBONUCLEIC-ACID IN THE OVINE OVARY

Complementary DNA (cDNA) clones encoding the LH receptor (LHR) were re cently isolated from pig, rat, mouse, and human testes or ovaries. Man y of the LHR cDNAs isolated from these species encoded incomplete and, therefore, possibly inactive forms of the LHR. The four major incompl ete cDNAs, designated B, C, D, and E, were due to alternative splicing of the full-length cDNA, designated the A form. Northern analyses of messenger RNA (mRNA) encoding LHR in these species and in sheep reveal ed multiple mRNA species in ovarian tissue, but were unable to disting uish between the full-length (functional) form and the splice variants . We have used reverse transcription of mRNA, amplification via the po lymerase chain reaction, and cDNA sequencing to determine which altern atively spliced mRNA species were present in ovine ovarian follicles a nd corpora lutes, and ribonuclease protection assays to confirm these results and determine the relative abundance of these splice variants. Ovine LHR cDNAs of the full-length A form, B form, and two novel spli ce forms, designated F and G, were isolated and sequenced. By using LH R cDNAs that spanned the regions of the gene in which the majority of splicing variation occurred, ribonuclease-protected fragments of diffe rent sizes were generated depending on which mRNA species (A-G) were p resent. It is estimated that the ratios of the steady state mRNA level s of the splice variant B form/full-length A form/G form/F form were 5 -3.5:1:1:0.3. The E, C, and D forms were not detected, even when using the sensitive method of reverse transcription-polymerase chain reacti on for the latter two forms. The overall level of expression of LHR mR NA was greater in corpora lutea than follicles, but the relative abund ance of the splice variants was similar in follicles and corpora lutea .