Three different turkey luteinizing hormone receptor (tLH-R) isoforms I: Characterization of alternatively spliced tLH-R isoforms and their regulated expression in diverse tissues

Using combinations of reverse transcription-polymerase chain reaction (RT-P CR) and 5'- and 3'-rapid amplification of cDNA ends, three different, alter natively spliced, partial turkey LH receptor (tLH-R) cDNA isoforms were cha racterized from ovarian mRNA. The first cDNA (tLH-R-intact) showed 98% and 72-75% similarity with chicken and mammalian LH-R sequences, respectively. The second cloned cDNA isoform (tLH-R-insert) contained an in-frame TCA sto p codon within an 86-base pair insertion that was located in the extracellu lar domain of the seven-transmembrane region. The tLH-R-insert isoform coul d encode a truncated soluble protein isoform that tacked the transmembrane region. The third cDNA isoform truncated the transmembrane region (tLH-R-tr unc) and was derived by the deletion of the last exon by incomplete splicin g. Generation of multiple transcripts by alternative splicing was elucidate d by partial characterization of tLH-R genomic sequences. The differentially regulated expression of the tLH-R mRNA isoforms in nongo nadal tissues and ovarian stromal tissues during various reproductive stage s was quantified and analyzed by Northern blot and/or RT-PCR Alternatively spliced tLH-R isoforms were differentially expressed in a tissue-specific m anner in most of the tissues examined. The steady-state levels of tLH-R mRN A isoforms were relatively high in the hypothalamus and optic nerve and rel atively low in the cortex, pituitary, and cerebellum when compared to level s in ovarian follicles. In nongonadal reproductive tissues, the steady-stat e levels of tLH-R mRNA isoforms were relatively high in the uterus and infu ndibulum and relatively low in the isthmus, oviduct, and magnum. In additio n, in the nongonadal peripheral tissues, the steady-state levels of tLH-R i soforms were relatively high in the thyroid gland and relatively low in the spleen, adrenal grand, kidney, skin, bursa, and muscle. The present study suggests that the alternative splicing of LH-R transcript s occurs in a tissue-specific manner and has been evolutionarily conserved (similar results were obtained in chicken and swine). These results raise f undamental questions as to the function of LH-R isoforms in nongonadal tiss ues.