Porcine follistatin gene structure supports two forms of mature follistatin produced by alternative splicing

Follistatin (FS), a novel gonadal protein which inhibits specifically the secretion of pituitary follicle stimulating hormone(FSH), has recently been isolated from porcine follicular fluid, cDNA cloning of the porcine ovarian FS precursor revealed two populations of cDNAs which differed at the 3′-region of the open reading frames; one population encodes a precursor of 317 amino acids while the other encodes another precursor having the same 317 amino acids, but with an additional 27 amino acids at the carboxy-terminal. Herein, we report the cloning of the porcine FS gene whose DNA structure reveals that the two populations of mRNA are generated by alternative splicing. In addition, restriction endonuclease mapping and DNA sequencing show that the FS gene is approximately 6 Kb long and consists of six exons separated by five introns. The first exon encodes the putative signal sequence, followed by four exons which encode the four domains of FS, three of which are highly homologous to each other. The last exon encodes the extra 27-amino acid carboxy-terminal domain of the 344-residued precursor.