The Gene Encoding Ovine Follicle-Stimulating Hormone β: Isolation,Characterization,and Comparison to a Related Ovine Genomic Sequence

Abstract

Follicle-stimulating hormone (FSH), the primary stimulus for egg and sperm maturation in mammals, is an α/β heterodimer. Each subunit is encoded by a single-copy gene in the human, bovine, and rat genomes. Transcription of both subunits is inhibited by estradiol and progesterone in ovine pituitary cultures. We report the sequence of one ovine FSH-β gene (−1,527 to +3,664) that is expressed in vivo and the identification of a novel, second ovine FSH-β-like sequence. Digestion of ovine genomic DNA with Bgl II yielded two fragments of 10 kb and 15 kb that hybridized to a bovine FSH-β cDNA. The 10-kb fragment contained 6 kb of 5′-flanking region and all but about 200 bp of the 3′ terminus of the ovine FSH-β gene. This FSH-β gene encodes a protein that differs from the published ovine protein sequence only at the carboxy terminus (Arg109Glu-110[STOP codon] instead of Glu-109Arg-110[Glx-111]) and at positions 49 (Ala instead of Thr) and 88 (Arg instead of Ser). This gene is organized similarly to the human, bovine, porcine, and rat FSH-β genes, and its coding sequence is nearly identical (99.5%) to a reported ovine FSH-β cDNA. Expression of the FSH-β gene on the 10-kb fragment in vivo was determined by analysis of wether mRNA using the polymerase chain reaction. A 95-bp sequence of the 15-kb fragment was 87% homologous to the corresponding coding region of the 10-kb fragment. This comparison suggested that the 15-kb fragment contains either an FSH-β-like sequence or a pseudogene. Several potential steroid response elements were found by sequence analysis of the 5′-flanking region of the FSH-β gene on the 10-kb fragment. A mechanism by which these elements may act is suggested.