Molecular cloning and regulation of mRNA expression of the thyrotropin beta and glycoprotein hormone alpha subunits in red drum, Sciaenops ocellatus

作者：Cohn William B^*; Jones Richard A; Valverde Roldan A; Leiner Kevin A; MacKenzie Duncan S

来源：Fish Physiology and Biochemistry, 2010, 36(4): 1277-1290.

DOI：10.1007/s10695-010-9408-5

• Thyrotropin
• Pituitary glycoprotein hormone subunits
• Red drum
• Thyroid

Full-length cDNAs for thyrotropin beta (TSH beta) and glycoprotem hormone a (GSU alpha) subunits were cloned and sequenced from the red drum (Sciaenops ocellatus) The cDNAs for TSH beta (877 bp) and GSU alpha (661 bp) yielded predicted coding regions of 126 and 94 amino acid proteins, respectively Both sequences contain all invariant cysteine and putative glycosylated asparagines characteristic of each as deduced by comparison with other GSUa and TSH beta sequences from representative vertebrate species Multiple protein sequence alignments show that each subunit shares highest identity (79% for the TSH beta and 86% for the GSU alpha) with perciform fish Furthermore, in a single Joint phylogenetic analysis, each subunit segregates most closely with corresponding GSU alpha and TSH beta subunit sequences from closely related fish Tissue-specific expression assays using RT-PCR showed expression of the TSH beta subunit limited to the pituitary GSU alpha mRNA was predominantly expressed in the pituitary but was also detected in the testis and ovary of adult animals Northern hybridization revealed the presence of a single transcript for both TSH beta and GSU alpha, each close in size to mRNA transcripts from other species Dot blot assays from total RNA Isolated from S ocellatus pituitaries showed that in vivo T(3) administration significantly diminished mRNA expression of both the TSH beta and GSU alpha subunits and that goitrogen treatment caused a significant induction of TSH beta mRNA only Both TSH beta and GSUa mRNA expression in the pituitary varied significantly in vivo over a 24-h period Maximal expression for both TSH beta and GSU alpha occurred during the early scotophase in relation to a peak in T(4) blood levels previously documented These results suggest the production of TSH in this species which may serve to drive daily cycles of thyroid activity Readily quantifiable, variable, and thyroid hormone-responsive pituitary TSH expression, coupled with previously described dynamic daily cycles of circulating T(4) and extensive background on the growth, nutrition, and laboratory culture of red drum, suggests that this species will serve as a useful model for experimental studies of the physiological regulation of TSH production

• 出版日期2010-12