Structural and expression analyses of gonadotropin I beta subunit genes ingoldfish (Carassius auratus)

Gonadotropin (GTH) is a pituitary glycoprotein hormone that regulates gonad al development in vertebrates. In teleosts, it is considered that two types of GTH, GTH I (follicle-stimulating hormone-like GTH) and GTH II (luteiniz ing hormone-like GTH), are produced in the pituitary, and their molecules a re comprised of common alpha and distinct beta subunits, In this study, we describe the complete structure and 5'-flanking regulatory region of two di stinct genes encoding GTH I beta in goldfish, Carassius auratus. The two go ldfish GTH I beta genes, gfGTHI beta-1 and gfGTHI beta-2, span 1719 and 154 5 base pairs (bp) nucleotides, respectively, and there is a high sequence i dentity (92.1%) between the coding regions. Both genes consist of three exo ns separated by two introns as in mammalian FSH beta genes. The locations o f the first intron and second intron showed a well-conserved pattern simila r to those of mammalian FSH beta genes. Inspection of the 5'-flanking regio n of the gfGTH1 beta-1 and gfGTHI beta-2 (approximately 1.4 and 1.1 kb, res pectively) revealed the presence of several putative cis-acting elements, i ncluding the gonadotrope-specific element, gonadotropin-releasing hormone r esponsive element, and half steroid hormone responsive elements. Interestin gly, some of their elements were located contiguously between -187 and -124 bp upstream from a TATAA sequence. Reverse transcription polymerase chain reaction confirmed that these two genes are expressed in the pituitary of i ndividual fish. These results, taken together, demonstrate that there are a t least two functional genes encoding GTH I beta, probably due to the tetra ploidy of goldfish. The unique locations of the cis-acting elements in the GTH I beta genes suggest they may be involved in the expression of the gold fish GTH I beta gene. (C) 1998 Elsevier Science B.V. All rights reserved.