Isolation and characterization of testis-specific cDNAs for luteinizing hormone beta-subunit in the rat

To study further the unexpected expression of the luteinizing hormone (LH) beta-subunit in the rat testis, we identified in a rat testicular cDNA library three LH beta clones with lengths of 3.2, 2.4 and 0.86 kb (TLH beta 1, TLH beta 2 and TLH beta 3). The clones were identified using a 32P-labeled cDNA probe complimentary to the known rat pituitary LH beta mRNA. Clone TLH beta 2 corresponds in size to the main LH beta mRNA species (2.7 kb) detected by Northern hybridization in the rat testis. Sequence analysis indicated that the different sizes of the three clones are due to alternative RNA splicing and differences at the 5' ends of transcripts. The sequence of one open reading frame deduced from TLH beta 1 is almost identical with the pituitary LH beta peptide, differing only in three amino acids in the putative signal peptide. It might encode a functional testis-specific LH beta peptide. Shorter transcripts from clones TLH beta 2 and TLH beta 3 may correspond to short testicular LH beta peptides. The present findings provide further evidence in the rat for expression of testis-specific mRNA variants of the LH beta gene. Their translation products may form a novel class of testicular para/autocrine factors.