TISSUE-SPECIFIC VARIATION IN THE LENGTH OF THE 5' UNTRANSLATED REGIONOF THE BETA-A-INHIBIN MESSENGER-RNA IN SHEEP

The 5' untranslated region (UTR) of beta A inhibin mRNA was compared i n a variety of sheep tissues, using primer extension. Considerable var iation in the length and number of 5' extended products were noted bet ween tissues. Specific bands were noted in ovarian follicular RNA, whi ch were also present in samples from corpora lutea, stroma, and placen tal cotyledon RNA. Other extended products were observed in RNA from c orpora lutea, stroma, cotyledon, pituitary, bone marrow, frontal corte x, medial basal hypothalamus, adrenal, liver, and kidney, which were n ot present or weakly represented in follicular RNA. Additional tissue- specific bands were noted in testis and bone marrow RNA. No specific d ifferences in the lengths of the 5' UTR of the beta A inhibin mRNA wer e observed in sheep homozygous for the Booroola fecundity gene Fec(B), in any tissue studied. The coding region of ovine beta A inhibin cDNA was sequenced and a genetic polymorphism confirmed within or close to the ovine beta A inhibin gene. We conclude that the beta A inhibin ge ne is expressed widely in the sheep. Furthermore there is variation in the length of the 5' UTR of beta A inhibin mRNA between male and fema le gonads and other tissues, implying that expression of this gene is differentially controlled. However, the Fec(B) mutation does not affec t mRNA splicing events or the initiation site used in ovarian transcri ption. The mechanism by which the Fec(B) mutation influences the amoun ts of beta A inhibin mRNA, follicle-stimulating hormone (FSH) secretio n and ovulation rate has still to be elucidated. (C) 1995 Wiley-Liss, Inc.