Molecular cloning of cDNA for equine follistatin and its gene expression in the reproductive tissues of the mare

A cDNA clone encoding equine follistatin was isolated from an equine ovaria n cDNA library. Out of 1.2 x 10(5) independent clones screened, one positiv e clone was isolated and its cDNA sequence determined. The isolated clone, named EQ-FS-1, contained a complete open reading frame encoding 344 amino a cid residues. The similarity of its deduced amino acid sequence to these of other mammalian species was greater than 95%. Although its expression leve l varied among the tissues examined, follistatin mRNA was detected in the e quine uteroplacental tissues, follicles and corpora lutea by Northern blot analysis. In situ hybridization revealed that the expression of follistatin mRNA in the equine follicle was restricted exclusively to granulosa cells. When the expression pattern of follistatin mRNA in the equine uteroplacent al tissues from mid- to late-pregnancy was examined, it was shown that its expression level tended to decrease after mid-pregnancy. These results sugg est that follistatin acts in the reproductive tissues of the mare in mainta ining pregnancy.