Functional inhibition of deep brain non-visual opsins facilitates acute long day induction of reproductive recrudescence in male Japanese quail.

For nearly a century, we have known that brain photoreceptors regulate avian seasonal biology. Two photopigments, vertebrate ancient opsin (VA) and neuropsin (OPN5), provide possible molecular substrates for these photoreceptor pathways. VA fulfills many criteria for providing light input to the reproductive response, but a functional link has yet to be demonstrated. This study examined the role of VA and OPN5 in the avian photoperiodic response of Japanese quail (Coturnix japonica). Non-breeding male quail were housed under short days (6L:18D) and received an intracerebroventricular infusion of adeno-associated viral vectors with shRNAi that selectively inhibited either VA or OPN5. An empty viral vector acted as a control. Quail were then photostimulated (16L:8D) to stimulate gonadal growth. Two long days significantly increased pituitary thyrotrophin-stimulating hormone ß-subunit (TSHß) and luteinizing hormone ß-subunit (LHß) mRNA of VA shRNAi treated quail compared to controls. Furthermore, at one week there was a significant increase, compared to controls, in both hypothalamic gonadotrophin releasing hormone-I (GnRH-I) mRNA and paired testicular mass in VA shRNAi birds. Opn5 shRNAi facilitated the photoinduced increase in TSHß mRNA at 2 days, but no other differences were identified compared to controls. Contrary to our expectations, the silencing of deep brain photoreceptors enhanced the response of the reproductive axis to photostimulation rather than preventing it. In addition, we show that VA opsin plays a dominant role in the light-dependent neuroendocrine control of seasonal reproduction in birds. Together our findings suggest the photoperiodic response involves at least two photoreceptor types and populations working together with VA opsin playing a dominant role.

Diagnosis and Management of Central Congenital Hypothyroidism.

Central congenital hypothyroidism (CH) is defined as thyroid hormone (TH) deficiency at birth due to insufficient stimulation by the pituitary of the thyroid gland. The incidence of central CH is currently estimated at around 1:13,000. Central CH may occur in isolation, but in the majority of cases (60%) it is part of combined pituitary hormone deficiencies (CPHD). In recent years several novel genetic causes of isolated central CH have been discovered (IGSF1, TBL1X, IRS4), and up to 90% of isolated central CH cases can be genetically explained. For CPHD the etiology usually remains unknown, although pituitary stalk interruption syndrome does seem to be the most common anatomic pituitary malformation associated with CPHD. Recent studies have shown that central CH is a more severe condition than previously thought, and that early detection and treatment leads to good neurodevelopmental outcome. However, in the neonatal period the clinical diagnosis is often missed despite hospital admission because of feeding problems, hypoglycemia and prolonged jaundice. This review provides an update on the etiology and prognosis of central CH, and a practical approach to diagnosis and management of this intriguing condition.

Impairment of the Hypothalamus-Pituitary-Thyroid Axis Caused by Naturally Occurring GATA2 Mutations In Vitro.

The transcription factor GATA2 regulates gene expression in several cells and tissues, including hematopoietic tissues and the central nervous system. Recent studies revealed that loss-of-function mutations in GATA2 are associated with hematological disorders. Our earlier in vitro studies showed that GATA2 plays an essential role in the hypothalamus-pituitary-thyroid axis (HPT axis) by regulating the genes encoding prepro-thyrotropin-releasing hormone (preproTRH) and thyroid-stimulating hormone ß (TSHß). However, the effect of GATA2 mutants on the transcriptional activity of their promoters remains unelucidated. In this study, we created five human GATA2 mutations (R308P, T354M, R396Q, R398W, and S447R) that were reported to be associated with hematological disorders and analyzed their functional properties, including transactivation potential and DNA-binding capacity toward the preproTRH and the TSHß promoters. Three mutations (T354M, R396Q, and R398W) within the C-terminal zinc-finger domain reduced the basal GATA2 transcriptional activity on both the preproTRH and the TSHß promoters with a significant loss of DNA binding affinity. Interestingly, only the R398W mutation reduced the GATA2 protein expression. Subsequent analysis demonstrated that the R398W mutation possibly facilitated the GATA2 degradation process. R308P and S447R mutants exhibited decreased transcriptional activity under protein kinase C compared to the wild-type protein. In conclusion, we demonstrated that naturally occurring GATA2 mutations impair the HPT axis through differential functional mechanisms in vitro.

Functions of the Thyroid-Stimulating Hormone on Key Developmental Features Revealed in a Series of Zebrafish Dyshormonogenesis Models.

The hypothalamic-pituitary-thyroid (HPT) axis regulates many critical features in vertebrates. Utilizing TALENs and CRISPR/Cas9 techniques, thyroid-stimulating hormone subunit beta a (tshba), thyroglobulin (tg), and solute carrier family 16 member 2 (slc16a2) mutant zebrafish lines were generated. Among the three mutants, the earliest time point for the significantly altered T3 contents was observed in tshba mutants, which resulted in the most severe defects, including typical defects such as the retardation of inflated anterior swimming bladder (aSB), proper formation of fin ray and posterior squamation (SP), the larval-to-juvenile transition (LTJT) process, juvenile growth retardation, and mating failure. In tg mutants, which are actually compensated with an alternative splicing form, growth retardation was observed in the juvenile stage without LTJT and reproductive defects. The evident goiter phenotype was only observed in tg- and slc16a2 mutants, but not in tshba mutants. Other than goiters being observed, no other significant developmental defects were found in the slc16a2 mutants. Regarding the reproductive defects observed in tshba mutants, the defective formation of the secondary sex characteristics (SSCs) was observed, while no obvious alterations during gonad development were found. Based on our analyses, zebrafish at the 6-12 mm standard length or 16-35 days post-fertilization (dpf) should be considered to be in their LTJT phase. Using a series of zebrafish dyshormonogenesis models, this study demonstrated that the TSH function is critical for the proper promotion of zebrafish LTJT and SSC formation. In addition, the elevation of TSH levels appears to be essential for goiter appearance in zebrafish.

Functional differences between TSHR alleles associate with variation in spawning season in Atlantic herring.

The underlying molecular mechanisms that determine long day versus short day breeders remain unknown in any organism. Atlantic herring provides a unique opportunity to examine the molecular mechanisms involved in reproduction timing, because both spring and autumn spawners exist within the same species. Although our previous whole genome comparisons revealed a strong association of TSHR alleles with spawning seasons, the functional consequences of these variants remain unknown. Here we examined the functional significance of six candidate TSHR mutations strongly associated with herring reproductive seasonality. We show that the L471M missense mutation in the spring-allele causes enhanced cAMP signaling. The best candidate non-coding mutation is a 5.2 kb retrotransposon insertion upstream of the TSHR transcription start site, near an open chromatin region, which is likely to affect TSHR expression. The insertion occurred prior to the split between Pacific and Atlantic herring and was lost in the autumn-allele. Our study shows that strongly associated coding and non-coding variants at the TSHR locus may both contribute to the regulation of seasonal reproduction in herring.

Pituitary Tumors and Immortalized Cell Lines Generated by Cre-Inducible Expression of SV40 T Antigen.

Targeted oncogenesis is the process of driving tumor formation by engineering transgenic mice that express an oncogene under the control of a cell-type specific promoter. Such tumors can be adapted to cell culture, providing immortalized cell lines. To make it feasible to follow the process of tumorigenesis and increase the opportunity for generating cell lines, we developed a mouse strain that expresses SV40 T antigens in response to Cre-recombinase. Using CRISPR/Cas9 we inserted a cassette with coding sequences for SV40 T antigens and an internal ribosome entry site with green fluorescent protein cassette (IRES-GFP) into the Rosa26 locus, downstream from a stop sequence flanked by loxP sites: Rosa26LSL-SV40-GFP. These mice were mated with previously established Prop1-cre and Tshb-cre transgenic lines. Both the Rosa26LSL-SV40-GFP/+; Prop1-cre and Rosa26LSL-SV40-GFP/+; Tshb-cre mice developed fully penetrant dwarfism and large tumors by 4 weeks. Tumors from both of these mouse lines were adapted to growth in cell culture. We have established a progenitor-like cell line (PIT-P1) that expresses Sox2 and Pitx1, and a thyrotrope-like cell line (PIT-T1) that expresses Pou1f1 and Cga. These studies demonstrate the utility of the novel, Rosa26LSL-SV40-GFP mouse line for reliable targeted oncogenesis and development of unique cell lines.

Novel insights into di­(2­ethylhexyl)phthalate activation: Implications for the hypothalamus­pituitary­thyroid axis.

Di (2­ethylhexyl) phthalate (DEHP), an environmental pollutant, is widely used as a plasticizer and causes serious pollution in the ecological environment. As previously reported, exposure to DEHP may cause thyroid dysfunction of the hypothalamic­pituitary­thyroid (HPT) axis. However, the underlying role of DEHP remains to be elucidated. The present study performed intragastrical administration of DEHP (150, 300 and 600 mg/kg) once a day for 90 consecutive days. DEHP­stimulated oxidative stress increased the thyroid follicular cavity diameter and caused thyrocyte oedema. Furthermore, DEHP exposure altered mRNA and protein levels. Thus, DEHP may perturb TH homeostasis by affecting biosynthesis, biotransformation, bio­transportation, receptor levels and metabolism through disruption of the HPT axis and activation of the thyroid­stimulating hormone (TSH)/TSH receptor signaling pathway. These results identified the formerly unappreciated endocrine­disrupting activities of phthalates and the molecular mechanisms of DEHP­induced thyrotoxicity.

Differential Regulation of the Expression of the Two Thyrotropin Beta Subunit Paralogs by Salmon Pituitary Cells In Vitro.

We recently characterized two paralogs of the thyrotropin (TSH) beta subunit in Atlantic salmon, tshßa and tshßb, issued from teleost-specific whole genome duplication. The transcript expression of tshßb, but not of tshßa, peaks at the time of smoltification, which revealed a specific involvement of tshßb paralog in this metamorphic event. Tshßa and tshßb are expressed by distinct pituitary cells in salmon, likely related to TSH cells from the pars distalis and pars tuberalis, respectively, in mammals and birds. The present study aimed at investigating the neuroendocrine and endocrine factors potentially involved in the differential regulation of tshßa and tshßb paralogs, using primary cultures of Atlantic salmon pituitary cells. The effects of various neurohormones and endocrine factors potentially involved in the control of development, growth, and metabolism were tested. Transcript levels of tshßa and tshßb were measured by qPCR, as well as those of growth hormone (gh), for comparison and validation. Corticotropin-releasing hormone (CRH) stimulated tshßa transcript levels in agreement with its potential role in the thyrotropic axis in teleosts, but had no effect on tshßb paralog, while it also stimulated gh transcript levels. Thyrotropin-releasing hormone (TRH) had no effect on neither tshß paralogs nor gh. Somatostatin (SRIH) had no effects on both tshß paralogs, while it exerted a canonical inhibitory effect on gh transcript levels. Thyroid hormones [triiodothyronine (T3) and thyroxine (T4)] inhibited transcript levels of both tshß paralogs, as well as gh, but with a much stronger effect on tshßa than on tshßb and gh. Conversely, cortisol had a stronger inhibitory effect on tshßb than tshßa, while no effect on gh. Remarkably, insulin-like growth factor 1 (IGF1) dose-dependently stimulated tshßb transcript levels, while it had no effect on tshßa, and a classical inhibitory effect on gh. This study provides the first data on the neuroendocrine factors involved in the differential regulation of the expression of the two tshß paralogs. It suggests that IGF1 may be involved in triggering the expression peak of the tshßb paralog at smoltification, thus representing a potential internal signal in the link between body growth and smoltification metamorphosis.

Thyroid stimulating hormone ß-subunit splice variant is expressed in all fractional subsets of bone marrow hematopoietic cells and peripheral blood leukocytes and is modulated during bacterial infection.

Thyroid stimulating hormone (TSH), a hormone produced in the anterior pituitary, is used to regulate thyroid hormone secretion. It has been known for over three decades that TSH is made by the cells of the immune system; however, the functional role of immune system TSH is unclear. We previously demonstrated that an alternatively-spliced isoform of TSHß, referred to as the TSHß splice variant (TSHßv), is the primary form of TSHß made by hematopoietic cells in mice and humans. Most studies have linked TSHßv expression to myeloid cells of the immune system; however, it has recently been demonstrated that plasma cells in patients with Hashimoto's thyroiditis may be a source of immune system TSHßv. Here, we demonstrate that TSHßv is expressed in bone marrow precursors of lymphoid cells, monocytes, and granulocytes, as well as in mesenteric lymph node (MLN) cells. Plasma cells generated by in vitro culture with bacterial lipopolysaccharide (LPS), and MLN cells from mice infected with L. monocytogenes expressed TSHßv. There was an increase in the intensity of intracellular TSHßv expression in MLN cells following exposure to LPS, and in the proportion of TSHßv+ CD138+ MLN cells following L. monocytogenes infection. The number of TSHßv+ cells increased in MLN cells, particularly among CD138+ cells, following bacterial infection. This was confirmed by an increase in gene expression of BLIMP-1, the transcription factor for CD138, following infection. Levels of circulating thyroxine dropped significantly in mice 24 hrs post-infection. These findings suggest that immune system TSHßv may contribute to the host immune response during bacterial infection.

Liganded T3 receptor ß2 inhibits the positive feedback autoregulation of the gene for GATA2, a transcription factor critical for thyrotropin production.

The serum concentration of thyrotropin (thyroid stimulating hormone, TSH) is drastically reduced by small increase in the levels of thyroid hormones (T3 and its prohormone, T4); however, the mechanism underlying this relationship is unknown. TSH consists of the chorionic gonadotropin α (CGA) and the ß chain (TSHß). The expression of both peptides is induced by the transcription factor GATA2, a determinant of the thyrotroph and gonadotroph differentiation in the pituitary. We previously reported that the liganded T3 receptor (TR) inhibits transactivation activity of GATA2 via a tethering mechanism and proposed that this mechanism, but not binding of TR with a negative T3-responsive element, is the basis for the T3-dependent inhibition of the TSHß and CGA genes. Multiple GATA-responsive elements (GATA-REs) also exist within the GATA2 gene itself and mediate the positive feedback autoregulation of this gene. To elucidate the effect of T3 on this non-linear regulation, we fused the GATA-REs at -3.9 kb or +9.5 kb of the GATA2 gene with the chloramphenicol acetyltransferase reporter gene harbored in its 1S-promoter. These constructs were co-transfected with the expression plasmids for GATA2 and the pituitary specific TR, TRß2, into kidney-derived CV1 cells. We found that liganded TRß2 represses the GATA2-induced transactivation of these reporter genes. Multi-dimensional input function theory revealed that liganded TRß2 functions as a classical transcriptional repressor. Then, we investigated the effect of T3 on the endogenous expression of GATA2 protein and mRNA in the gonadotroph-derived LßT2 cells. In this cell line, T3 reduced GATA2 protein independently of the ubiquitin proteasome system. GATA2 mRNA was drastically suppressed by T3, the concentration of which corresponds to moderate hypothyroidism and euthyroidism. These results suggest that liganded TRß2 inhibits the positive feedback autoregulation of the GATA2 gene; moreover this mechanism plays an important role in the potent reduction of TSH production by T3.

A recurrent mutation in tshb gene underlying central congenital hypothyroidism undetectable in neonatal screening / Uma mutação recorrente no gene tshb resultando em hipotireoidismo congênito central não detectável na triagem neonatal

ABSTRACT Objective: To describe the case of a patient with central congenital hypothyroidism (CCH) due to a recurrent mutation in the TSHB gene, as well as to conduct a genetic study of his family. Case description: It is presented a case report of a 5-month-old boy with a delayed diagnosis of isolated CCH in whom the molecular analysis was performed 12 years later and detected a recurrent mutation (c.373delT) in TSHB gene. The parents and sister were carriers of the mutant allele. Comments: The c.373delT mutation has previously been reported in patients from Brazil, Germany, Belgium, United States, Switzerland, Argentina, France, Portugal, United Kingdom and Ireland. In summary, our case and other ones reported in the literature support the theory that this mutation may be a common cause of isolated TSH deficiency. Isolated TSH deficiency is not detected by routine TSH-based neonatal screening, representing a clinical challenge. Therefore, when possible, molecular genetic study is indicated. Identification of affected and carriers allows the diagnosis, treatment and adequate genetic counseling.

RESUMO Objetivo: Descrever o caso de um paciente com hipotireoidismo congênito central (HCC) por conta de uma mutação recorrente no gene TSHB, bem como realizar um estudo genético de sua família. Descrição do caso: Relato de caso de um menino de 5 meses de idade com diagnóstico tardio de HCC isolado, em quem a análise molecular foi realizada 12 anos depois e detectou uma mutação recorrente (c.373delT) no gene TSHB. Os pais e a irmã eram portadores do alelo mutante. Comentários: A mutação c.373delT já foi relatada em pacientes do Brasil, da Alemanha, da Bélgica, dos Estados Uinidos, da Suíça, da Argentina, da França, de Portugal, do Reino Unido e da Irlanda. Em resumo, nosso caso e outros relatados na literatura reforçam a teoria de que essa mutação pode ser uma causa comum de deficiência isolada de TSH. A deficiência isolada de TSH não é detectada na triagem neonatal com base na dosagem de TSH, representando um desafio clínico. Portanto, quando possível, o estudo genético molecular é indicado. A identificação dos afetados e dos portadores permite o diagnóstico, o tratamento e o aconselhamento genético adequado.

The Pathogenic TSH ß-subunit Variant C105Vfs114X Causes a Modified Signaling Profile at TSHR.

1) Background: Central congenital hypothyroidism (CCH) is a rare endocrine disorder that can be caused by mutations in the ß-subunit of thyrotropin (TSHB). The TSHB mutation C105Vfs114X leads to isolated thyroid-stimulating-hormone-(TSH)-deficiency and results in a severe phenotype. The aim of this study was to gain more insight into the underlying molecular mechanism and the functional effects of this mutation based on two assumptions: a) the three-dimensional (3D) structure of TSH should be modified with the C105V substitution, and/or b) whether the C-terminal modifications lead to signaling differences. 2) Methods: wild-type (WT) and different mutants of hTSH were generated in human embryonic kidney 293 cells (HEK293 cells) and TSH preparations were used to stimulate thyrotropin receptor (TSHR) stably transfected into follicular thyroid cancer cells (FTC133-TSHR cells) and transiently transfected into HEK293 cells. Functional characterization was performed by determination of Gs, mitogen activated protein kinase (MAPK) and Gq/11 activation. 3) Results: The patient mutation C105Vfs114X and further designed TSH mutants diminished cyclic adenosine monophosphate (cAMP) signaling activity. Surprisingly, MAPK signaling for all mutants was comparable to WT, while none of the mutants induced PLC activation. 4) Conclusion: We characterized the patient mutation C105Vfs114X concerning different signaling pathways. We identified a strong decrease of cAMP signaling induction and speculate that this could, in combination with diverse signaling regarding the other pathways, accounting for the patient's severe phenotype.

A RECURRENT MUTATION IN TSHB GENE UNDERLYING CENTRAL CONGENITAL HYPOTHYROIDISM UNDETECTABLE IN NEONATAL SCREENING.

OBJECTIVE: To describe the case of a patient with central congenital hypothyroidism (CCH) due to a recurrent mutation in the TSHB gene, as well as to conduct a genetic study of his family. CASE DESCRIPTION: It is presented a case report of a 5-month-old boy with a delayed diagnosis of isolated CCH in whom the molecular analysis was performed 12 years later and detected a recurrent mutation (c.373delT) in TSHB gene. The parents and sister were carriers of the mutant allele. COMMENTS: The c.373delT mutation has previously been reported in patients from Brazil, Germany, Belgium, United States, Switzerland, Argentina, France, Portugal, United Kingdom and Ireland. In summary, our case and other ones reported in the literature support the theory that this mutation may be a common cause of isolated TSH deficiency. Isolated TSH deficiency is not detected by routine TSH-based neonatal screening, representing a clinical challenge. Therefore, when possible, molecular genetic study is indicated. Identification of affected and carriers allows the diagnosis, treatment and adequate genetic counseling.

HPT axis­independent TSHß splice variant regulates the synthesis of thyroid hormone in mice.

Thyroid stimulating hormone (TSH) consists of an α­subunit and a unique ß­subunit. The first in­frame TSHß splice variant produced by the cells of immune system was identified in 2009. The TSHß splice variant and native TSHß exhibit different expression profiles, and research has been conducted to elucidate the role of the TSHß splice variant in different diseases. However, understanding of the fundamental physiological characteristics of the TSHß splice variant is currently limited. To verify whether the TSHß splice variant has the potential to induce thyroid follicular cells to synthesize thyroid hormone, in vivo and in vitro stimulation experiments were conducted in the present study. A total of 60 C57BL/6 mice were divided into control­, 5 and 10 µg TSHß splice variant­treated groups at random. Mice were sacrificed at 0.5, 1 and 4 h after intraperitoneal injection, and serum levels of tri­iodothyronine (T3) and thyroxine (T4) were determined using a radioimmunoassay. Thyroid follicular cells were isolated from the thyroids of mice, and stimulated with 2 µg/ml TSHß splice variant. Supernatants were collected, and the levels of T3 and T4 were detected. The protein expression levels of the sodium­iodide symporter, thyroperoxidase and thyroglobulin in thyroid follicular cells were quantified using western blot analysis. To verify whether the TSHß splice variant expression was regulated by the hypothalamus­pituitary­thyroid (HPT) axis, similar to native TSHß, a total of 60 C57BL/6 mice were equally divided into control, 2 mg/kg T3 intraperitoneal injection and 0.05 mg/kg thyroid­releasing hormone intraperitoneal injection groups at random. Mice were sacrificed at 1 and 4 h after injection. Alterations in the expression of the TSHß splice variant in the pituitary, thyroid, peripheral blood leukocytes and spleen tissues were detected using western blot analysis. The present study demonstrated that the TSHß splice variant is not regulated by the HPT axis and may affect thyroid hormone synthesis. Modifications in the expression of the TSHß splice variant may occur in a uniquely regulated manner to provide peripheral immunological compartments with a source of activated cells, particularly under immune stress.

Functional divergence of thyrotropin beta-subunit paralogs gives new insights into salmon smoltification metamorphosis.

Smoltification is a metamorphic event in salmon life history, which initiates downstream migration and pre-adapts juvenile salmon for seawater entry. While a number of reports concern thyroid hormones and smoltification, few and inconclusive studies have addressed the potential role of thyrotropin (TSH). TSH is composed of a α-subunit common to gonadotropins, and a ß-subunit conferring hormone specificity. We report the presence and functional divergence of duplicated TSH ß-subunit paralogs (tshßa and tshßb) in Atlantic salmon. Phylogeny and synteny analyses allowed us to infer that they originated from teleost-specific whole genome duplication. Expression profiles of both paralogs in the pituitary were measured by qPCR throughout smoltification in Atlantic salmon from the endangered Loire-Allier population raised in a conservation hatchery. This revealed a striking peak of tshßb expression in April, concomitant with downstream migration initiation, while tshßa expression remained relatively constant. In situ hybridization showed two distinct pituitary cell populations, tshßa cells in the anterior adenohypophysis, and tshßb cells near to the pituitary stalk, a location comparable to the pars tuberalis TSH cells involved in seasonal physiology and behaviour in birds and mammals. Functional divergence of tshß paralogs in Atlantic salmon supports a specific role of tshßb in smoltification.

Adipose tissue TSH as a new modulator of human adipocyte mitochondrial function.

BACKGROUND/OBJECTIVES: Recent studies indicate a possible role of TSH/TSHR signalling axis on adipogenesis and adipose tissue physiology. Here, we aimed to investigate the relationship between adipose tissue TSHB and adipose tissue physiology-related gene expression. SUBJECTS/METHODS: Subcutaneous and visceral adipose tissue TSHB gene expression was analysed in two independent cohorts [Cohort1 (N = 96) and Cohort2 (N = 45)] and after bariatric surgery-induced weight loss [Cohort3 (N = 22)]. Adipose tissue TSH protein expression was also analysed in a subgroup of participants from Cohort 1 (N = 16). The effects of recombinant TSH on human subcutaneous preadipocytes and adipocytes were investigated. RESULTS: In cohort 1, both visceral and subcutaneous adipose tissue TSHB gene expression was positively correlated with the expression of mitochondrial function (PPARGC1A, ISCA2, CISD1, SIRT1, NFE2L2, NRF1) and fatty acid mobilization (CAV1, ENGL1), but not with adipogenic-related genes. Of note, adipose tissue TSH protein levels were also associated with some of these markers of mitochondrial function and fatty acid mobilization. These associations were replicated in cohort 2. Bariatric surgery-induced weight loss resulted in increased subcutaneous adipose tissue TSHB in parallel to increased PPARGC1A. In human subcutaneous adipocytes, rh-TSH administration led to increased mitochondrial respiratory capacity in parallel to increased mitochondrial function- and adipogenic-related gene expression, but no significant effects were observed during differentiation of human preadipocytes. CONCLUSION: These data point to a possible role of adipose tissue TSH in the maintenance of adipocyte mitochondrial function.

Central Congenital Hypothyroidism Caused by a Novel Mutation, C47W, in the Cysteine Knot Region of TSHß.

BACKGROUND: Isolated central congenital hypothyroidism (ICCH) is a rare form (1:50,000 newborns) of congenital hypothyroidism, which can present with growth and neuropsychological retardation. Unlike the more common primary CH (1:1,500-1:4,000), which presents on newborn screening with elevated serum thyroid-stimulating hormone (TSH) and low thyroxine (T4) and triiodothyronine (T3), ICCH presents with low TSH and low thyroid hormone levels. ICCH, therefore, may be missed in most newborn screens that are based only on elevated TSH. Most cases of ICCH have been associated with mutations in the TSHß gene. PATIENT: We present a consanguineous Sudanese family where the proband was diagnosed with "atypical" CH (serum TSH was low, not high). INTERVENTION AND OUTCOME: The propositus underwent whole-exome sequencing, and the C47W TSHß mutation was identified. Sanger sequencing confirmed the proband to be homozygous for C47W, and both parents were heterozygous for the same mutation. The mutation was predicted by several in silico methods to have a deleterious effect (SIFT 0.0, Damaging; Polyphen2_HDIV 0.973, probably damaging; MutationTaster 1, disease causing; and CADD 3.17, 16.62). C47W affects the first cysteine of the cysteine knot of the TSHß subunit. The cysteine knot region of TSHß is highly conserved across species and is critical for binding to the TSH receptor. Only two other mutations were previously reported along the cysteine knot and showed consistently low or undetectable serum TSH and low T4 and T3 levels. Other TSHß gene mutations causing ICCH have been reported in the "seatbelt" region, necessary for TSHß dimerization with the alpha subunit. CONCLUSIONS: Identification of a mutation in the TSHß gene reinforces the importance of identifying ICCH that can occur in the absence of elevated serum TSH and demonstrates the functional significance of the TSHß cysteine knot.

Adipose TSHB in Humans and Serum TSH in Hypothyroid Rats Inform About Cellular Senescence.

BACKGROUND/AIMS: Thyroid hormones have been recently linked to senescence and longevity. Given the recent description of TSHB mRNA in human adipose tissue (AT), we aimed to investigate the relationship between local AT TSH and adipose tissue senescence. METHODS: TSHB mRNA (measured by real-time PCR) and markers of adipose tissue senescence [BAX, DBC1, TP53, TNF (real-time PCR), telomere length (Telo TAGGG Telomere Length Assay) and lipidomics (liquid chromatography mass spectrometry)] were analysed in subcutaneous (SAT) and visceral (VAT) AT from euthyroid subjects. The chronic effects of TSH were also investigated in AT from hypothyroid rats and after recombinant human TSH (rhTSH) administration in human adipocytes. RESULTS: Both VAT and SAT TSHB gene expression negatively correlated with markers of AT cellular senescence (BAX, DBC1, TP53, TNF gene expression and specific glucosylceramides) and positively associated with telomere length. Supporting these observations, both rhTSH administration in human adipocytes and increased TSH in hypothyroid rats resulted in decreased markers of cellular senescence (Bax and Tp53 mRNA) in both gonadal and subcutaneous white adipose tissue. CONCLUSION: These data point to a possible role of TSH in AT cellular senescence.

Effects of bisphenol analogs on thyroid endocrine system and possible interaction with 17ß-estradiol using GH3 cells.

This study was conducted using a rat pituitary (GH3) cell line to understand the effects of bisphenol analogs (BPs) on the thyroid endocrine system, in the presence of 17ß-estradiol (E2). In the first series of experiments, changes in cell proliferation were examined after exposure to each of ten BPs, in the absence or presence of a median effective concentration (6.4 × 10-10 M) of triiodothyronine (T3). All tested BPs significantly increased cell proliferation, suggesting thyroid hormone (TH) agonistic effects of BPs. BPs did not potentiate the T3-induced cell proliferation at 48 h exposure, while several tested BPs including BPA, BPAF, BPB, BPF, BPS, and BPZ elicited a potentiating effect on the T3-induced cell proliferation at 96 h exposure. These results indicate that TH-antagonistic effects of BPs depend on the tested dose and exposure time. In the second set of experiments, one of the most potent BPs, i.e., BPAF, was selected, and its possible interaction with E2 on the thyroid endocrine system was evaluated. Co-exposure of GH3 cells to 10-12 M E2 showed an additive-like effect. The extent of increase in cell proliferation was more pronounced with a combination of BPAF and E2 than with that of BPA and E2. Significant down-regulation of Trα, Trß, and Dio2 genes and up-regulation of the Tshß gene were observed in GH3 cells following co-exposure to BPAF and E2. Our results showed that some BP analogs might influence the thyroid endocrine system, and such perturbation appeared to be enhanced in the presence of E2.

Posttranscriptional actions of triiodothyronine on Tshb expression in TαT1 cells: New insights into molecular mechanisms of negative feedback.

Rapid actions of triiodothyronine (T3) on thyrotropin (TSH) synthesis and secretion have been described in hypothyroid male rats. However, the molecular mechanisms remain unknown. TαT1 cells, a thyrotroph cell line, was used herein to characterize the possible non-genomic actions of T3 on the expression of alpha (Cga) and Tshb genes, and the posttranscriptional processing and translation of both transcripts. The involvement of αVß3 integrin was also assessed. T3 quickly reduced Tshb mRNA content, poly(A) tail length and its association with ribosomes. The effect of T3 on Tshb gene expression was detected even in the presence of a transcription inhibitor. The decrease in Tshb mRNA content and polyadenylation depend on T3 interaction with αVß3 integrin, while T3 reduced Cga mRNA content by transcriptional action. The translational rate of both transcripts was reduced by a mechanism, which does not depend on T3-αVß3 integrin interaction. Results indicate that, in parallel with the inhibitory transcriptional action in Cga and Tshb gene expression, T3 rapidly triggers additional posttranscriptional mechanisms, reducing the TSH synthesis. These non-genomic actions partially depend on T3-αVß3 integrin interaction at the plasma membrane of thyrotrophs and add new insights to the molecular mechanisms involved in T3 negative feedback loop.