Cloning of the Elk TSH β-Subunit cDNA and Seasonal Expression of the Pituitary Glycoprotein Hormone Genes

Abstract

We report the elk (Cervus elaphus) thyroid stimulating hormone (TSH) β-subunit cDNA cloning, nucleotide and deduced amino acid sequences. The TSH β-subunit cDNA was obtained by RT-PCR of polyadenylated pituitary RNA. The deduced elk TSH β-subunit peptide chain shares between 93 to 99% sequence similarities with the reported TSH β-subunit of a sub-set of related species. The TSH β-subunit gene is expressed in the elk pituitary gland as a mature transcript of approximately 600 bases, which corresponds to the size of the mRNA expressed in the sheep pituitary gland. Seasonal expression of the pituitary gonadotropin genes was investigated by Northern blot analyses. Samples of elk pituitary glands collected during the breeding season showed elevated steady state levels of common α-subunit and FSH and LH β-subunit gene expression, consistent with the seasonal reproductive cycling of this species. Samples collected before the breeding season demonstrated decreased expression of the gonadotropin genes. TSH, which is not directly tied to reproduction, had similar levels of expression, regardless of the animal's reproductive status.