Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2005
Publication Date: 5/1/2005
Citation: Connor, E.E., Laiakis, E.C., Fernandes, V.M., Williams, J.L., Capuco, A.V. 2005. Molecular cloning, expression and radiation hybrid mapping of the bovine deiodinase type II (DI02) and deiodinase type III (DI03) genes. Animal Genetics. 36(3):240-243. Interpretive Summary: Thyroid hormones are essential for normal mammalian development and metabolism. Activity of the thyroid hormones is regulated in a very complex manner partly by three types of deiodinases. These enzymes are responsible for the conversion of thyroid hormones into their active and inactive forms and are expressed in different tissues where local thyroid hormone activity must be closely regulated. The goal of this study was to determine the nucleotide sequence of the type II and type III deiodinase enzymes of cattle, characterize the mRNA expression of the type I, type II and type III deiodinases in various bovine tissues, and map the deiodinase type II and type III genes to the bovine genome. Results of this work will aid in the study of deiodinase gene expression and thyroid hormone metabolism in cattle. Our results suggest that deiodinases of cattle are similar in nucleotide sequence and expression to those of human and that cattle may serve as a useful model to study deiodinases in humans.
Technical Abstract: Thyroid hormones play a critical role in mammalian development and metabolism and their activity is regulated in a highly complex, tissue-specific manner by three isoforms of deiodinases. The goal of this study was to sequence the full-length bovine type II deiodinase (DIO2) and type III deiodinase (DIO3) cDNAs and characterize mRNA expression levels of each of the three deiodinase isoforms in various bovine tissues. Sequencing of bovine DIO2 and DIO3 cDNAs revealed a high degree of predicted amino acid sequence identity to their orthologs in other mammalian species and demonstrated the conservation of selenocysteine residues within the catalytic domains of both bovine proteins. In addition, three putative single nucleotide polymorphisms and one insertion/deletion were identified in the bovine DIO2 transcript. Bovine DIO2 and DIO3 were positioned on chromosomes 10 and 21, respectively, by radiation hybrid mapping. Expression patterns of the three deiodinase isoforms in bovine tissues were similar for deiodinase type I (DIO1) and DIO2 to those observed in other species. Expression level of DIO3 transcripts was greatest in bovine mammary gland and kidney, although expression was detected in all tissues sampled. Results of this work will aid in the study of deiodinase gene expression and thyroid hormone deiodination in cattle and suggest that cattle may serve as a useful model to study deiodinases in humans.