Cited by 376Thyroid Disorders and TreatmentsSelenium in Biological SystemsGrowth Hormone and Insulin-like Growth Factors

Targeted Disruption of the Type 2 Selenodeiodinase Gene (DIO 2) Results in a Phenotype of Pituitary Resistance to T4

Schneider, Mark J., Fiering, Steven N., Pallud, Sophie E., Parlow, Albert F., St. Germain, Donald L., Galton, Valerie Anne·2001·Molecular Endocrinology

Abstract

The type 2 deiodinase (D2), a selenoenzyme that catalyzes the conversion of T4 to T3 via 5'-deiodination, is expressed in the pituitary, brain, brown adipose tissue (BAT), and the reproductive tract. To examine the physiological role of this enzyme, a mouse strain lacking D2 activity was developed using homologous recombination. The targeting vector contained the Neo gene in place of a 2.6-kb segment of the Dio2 gene. This segment comprises 72% of the coding region and includes the TGA codon that codes for the selenocysteine located at the active site of the enzyme. Mice homologous for the targeted deletion [D2 knockout (D2KO)] had no gross phenotypic abnormalities, and development and reproductive function appeared normal, except for mild growth retardation (9%) in males. No D2 activity was observed in any tissue in D2KO mice under basal conditions, or under those that normally induce this enzyme such as cold-exposure (BAT) or hypothyroidism (brain, BAT, and pituitary gland). Furthermore, no D2 activity was present in cultured astrocytes, nor could it be induced by treatment of the cells with forskolin. Although D2 mRNA transcripts were detected in BAT RNA obtained from cold-exposed wild-type (WT) mice, none was detected in BAT RNA from comparably-treated D2KO mice. Levels of D1 in the liver, thyroid, and pituitary were the same in WT and D2KO animals, whereas D3 activity in D2KO cerebrum was twice that in WT cerebrum. Serum T3 levels were comparable in adult WT and D2KO mice. However, serum T4 and TSH levels were both elevated significantly (40% and 100%, respectively) in the D2KO mice, suggesting that the pituitary gland of the D2KO mouse is resistant to the feedback effect of plasma T4. This view was substantiated by the finding that serum TSH levels in hypothyroid WT mice were suppressed by administration of either T4 or T3, but only T3 was effective in the D2KO mouse. The data also suggest that the clearance of T4 from plasma was reduced in the D2KO mouse. In summary, targeted inactivation of the selenodeiodinase Dio2 gene results in the complete loss of D2 activity in all tissues examined. The increased serum levels of T4 and TSH observed in D2KO animals demonstrate that the D2 is of critical importance in the feedback regulation of TSH secretion.

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Crossref · 10.1210/mend.15.12.0740

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Authors
Schneider, M. J., Fiering, S. N., Pallud, S. E., Parlow, A. F., St. Germain, D. L., & Galton, V. A.
Affiliations
University of California, Los Angeles (US)
Corresponding author
Galton, Valerie Anne
Venue
Molecular Endocrinology
Published
2001-12
Volume
15
Issue
12
Pages
2137-2148
ISSN
  • 0888-8809 (ISSN-L)
  • 1944-9917
OpenAlex
W2142718693
Cited by
376
References
43
Citations by year
2026: 5 · 2025: 6 · 2024: 7 · 2023: 7 · 2022: 16 · 2021: 14 · 2020: 13 · 2019: 14 · 2018: 9 · 2017: 13 · 2016: 21 · 2015: 20 · 2014: 21 · 2013: 17 · 2012: 13
FWCI
8.63
Type
journal article
Language
en
Open access
closed
Locations
  • Molecular Endocrinology (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Dartmouth College
  • National Cancer Institute (P30CA023108)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Nursing › Nutrition and Dietetics › Selenium in Biological Systems
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Growth Hormone and Insulin-like Growth Factors
Keywords
type 2 deiodinase, selenoenzymes, T4 to T3 conversion, TSH secretion, thyroid hormone feedback, selenocysteine, type I deiodinase, type 3 deiodinase, brown adipose tissue, hypothyroidism
MeSH terms
Iodothyronine Deiodinase Type II, Animals, Astrocytes, Adipose Tissue, Brown, Female, Colforsin, Hypothyroidism, Iodide Peroxidase, Male, Mice, Inbred C57BL, Pituitary Gland, Tetradecanoylphorbol Acetate, Thyrotropin, Thyroxine, Triiodothyronine, Blotting, Northern, Mice, Knockout, Thyroid Hormone Resistance Syndrome, Mice

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