Ovine follistatin: characterization of cDNA and expression in sheep ovary during the luteal phase of the oestrous cycle.

We have isolated ovine follistatin cDNA from an ovarian follicle cDNA library and determined its sequence. The deduced amino acid sequence of the ovine follistatin precursor is highly homologous (greater than 97%) to the porcine, human and rat follistatins. Northern analysis was used to characterize follistatin gene expression in ovaries of adult ewes, collected from days 11 to 13 of the oestrous cycle. Two major (about 2.7 kb and 1.5 kb) and one minor (about 0.5 kb) transcripts were detected in polyadenylated RNA extracted from ovarian follicles and corpora lutea. The degree of expression of the transcripts varied in the two ovarian compartments, with the 2.7 kb species predominating in the follicles and the 1.5 kb species being more abundant in the corpora lutea. No transcripts were detected in stromal tissue containing preantral follicles of less than 1 mm.