NCBI Summary:
The protein encoded by this gene belongs to the iodothyronine deiodinase family. It catalyzes the conversion of prohormone thyroxine (3,5,3',5'-tetraiodothyronine, T4) to the bioactive thyroid hormone (3,5,3'-triiodothyronine, T3) by outer ring 5'-deiodination. This gene is widely expressed, including in thyroid, placenta, pituitary and brain. It is thought to be responsible for the 'local' production of T3, and thus important in influencing thyroid hormone action in these tissues. It has also been reported to be highly expressed in thyroids of patients with Graves disease, and in follicular adenomas. The intrathyroidal T4 to T3 conversion by this enzyme may contribute significantly to the relative increase in thyroidal T3 production in these patients. This protein is a selenoprotein containing the rare selenocysteine (Sec) amino acid at its active site, and may contain additional Sec residues. Sec is encoded by the UGA codon, which normally signals translation termination. The 3' UTRs of selenoprotein mRNAs contain a conserved stem-loop structure, designated the Sec insertion sequence (SECIS) element, that is necessary for the recognition of UGA as a Sec codon, rather than as a stop signal. Alternatively spliced transcript variants have been described for this gene. [provided by RefSeq, May 2016]
General function
Enzyme
Comment
Cellular localization
Cytoplasmic
Comment
Ovarian function
Initiation of primordial follicle growth
Comment
Prolonged hypothyroidism severely reduces ovarian follicular reserve in adult rats. Meng L et al. (2017) There is substantial evidence both in humans and in animals that a prolonged reduction in plasma thyroid hormone concentration leads to reproductive problems, including disturbed folliculogenesis, impaired ovulation and fertilization rates, miscarriage and pregnancy complications. The objective of the present study is to examine the consequences of chronic hypothyroidism, induced in adulthood, for the size of the ovarian follicle pool. In order to investigate this, adult female rats were provided either a control or an iodide deficient diet in combination with perchlorate supplementation to inhibit iodide uptake by the thyroid. Sixteen weeks later animals were sacrificed. Blood was collected for hormone analyses and ovaries were evaluated histologically. At the time of sacrifice, plasma thyroid-stimulating hormone concentrations were 20- to 40-fold increased, thyroxine concentrations were negligible while tri-iothyronin concentrations were decreased by 40% in the hypothyroid group, confirming that the animals were hypothyroid. Primordial, primary and preantral follicle numbers were significantly lower in the hypothyroid ovaries compared to the euthyroid controls, while a downward trend in antral follicle and corpora lutea numbers was observed. Surprisingly the percentage of atretic follicles was not significantly different between the two groups, suggesting that the reduced preantral and antral follicle numbers were presumably not the consequence of increased degeneration of these follicle types in the hypothyroid group. Plasma anti-Müllerian hormone (AMH) levels showed a significant correlation with the growing follicle population represented by the total ovarian number of primary, preantral and antral follicles, suggesting that also under hypothyroid conditions AMH can serve as a surrogate marker to assess the growing ovarian follicle population. The induction of a chronic hypothyroid condition in adult female rats negatively affects the ovarian follicular reserve and the size of the growing follicle population, which may impact fertility.//////////////////
Expression regulated by
Comment
GATA Depletion Impacts Insulin-like Growth Factor 1 mRNA and Protein Levels in Luteinizing Porcine Granulosa Cells. Lavoie HA et al. GATA4 and GATA6 are zinc finger transcription factors that regulate specific genes involved in steroidogenesis. Using RNAi-mediated reduction of GATA4 and/or GATA6 with microarray analysis we aimed to identify novel GATA target genes in luteinizing porcine granulosa cells under vehicle- and cyclic AMP-treated conditions. Microarray identified IGF1 mRNA to be cAMP- and GATA-responsive and real-time PCR demonstrated that the cAMP-induced increase in IGF1 mRNA was reduced under conditions of GATA6 and GATA4+GATA6 depletion, but not by GATA4 depletion. Insulin-like growth factor 1 protein levels in media were also decreased by GATA6 or GATA4+GATA6 reduction. IGFBP2 and IGFBP4 mRNAs were increased and IGFBP5 mRNA decreased with vehicle and cAMP treatment under GATA4+GATA6 RNAi conditions. GATA6 reduction alone increased basal IGFBP4, decreased IGFBP5 with both vehicle and cAMP, and GATA4 reduction alone lowered cAMP IGFBP5 levels with cAMP. No changes in IGFBP3 mRNA were observed with GATA reduction relative to the Control RNAi condition. IGFBP2-5 protein levels in media as assessed by Western ligand blotting were not altered by GATA reduction. Electromobility gel shift assays with two GATA-containing oligonucleotides of the IGF1 5'-regulatory region showed GATA4 and GATA6 could bind the more proximal GATA-B site. These studies indicate that although GATA4 and GATA6 can bind the porcine IGF1 5'-region, that GATA6 is functionally most important for cAMP-stimulated mRNA levels. Using microarray, we identified other mRNAs that were altered by GATA-reduced conditions including ALDH1, DIO2, and EDNRB. Our findings further support GATA as a coordinator of endocrine/paracrine/autocrine signals in the ovary.
Ovarian localization
Granulosa
Comment
Receptors for thyroid-stimulating hormone and thyroid hormones in human ovarian tissue. Aghajanova L et al. Dysfunction in thyroid regulation can cause menstrual and ovulatory disturbances, the mechanism of which is not clear. The distribution and activity of the thyroid-stimulating hormone (TSHR), and the thyroid hormone receptors (TR) alpha1, alpha2 and beta1 in human ovarian tissue and in granulosa cells was studied using immunohistochemistry, reverse-transcriptase polymerase chain reaction (RT-PCR), quantitative PCR and immunoassays. Strong immunostaining of TSHR, TRalpha1 and TRbeta1 was observed in ovarian surface epithelium and in oocytes of primordial, primary and secondary follicles, with minimal staining in granulosa cells of secondary follicles. Granulosa cells of antral follicles expressed TSHR, TRalpha1 and TRbeta1 proteins. Messenger RNA for all receptors was present in ovarian tissue. Mature human granulosa cells expressed transcripts for 5' deiodinases types 2 and 3, but not type 1, indicating the possibility of conversion of peripheral thyroid hormone thyroxin (T(4)). Granulosa cells stimulated with TSH showed a significant increase in cAMP concentrations after 2 h of culture (P = 0.047), indicating activation through TSHR. Stimulation with T(4) resulted in increased extracellular signal-regulated kinase 1 and 2 activation after 10, 30, 60 min and 24 h. These data demonstrate that TSH and thyroid hormone receptors may participate in the regulation of ovarian function.