Thyroid nuclear factor 1 (TTF-1) contains a homeodomain and displays a novel DNA binding specificity

NKX2-1 gene is targeted by H19 lncRNA and is found to be overexpressed in benign nodular goiter tissues

OBJECTIVE

Nodular goiter may increase the risk of thyroid cancer, but the genetic factors contributing to nodular goiter are not well understood. There is an overexpression of H19 lncRNA in goiter tissue and its target remains unknown. In this study, we attempted to identify a new target for H19 in the context of goiter development.

METHODS

Using interaction energy calculations, the interaction between NKX2-1 mRNA and H19 lncRNA was examined. Putative microRNAs were found at the H19 lncRNA target site with the highest affinity for NKX2-1. RNAseq data was analyzed to determine the tissue specificity of gene expression. Samples were taken from 18 goiter and 18 normal tissues during thyroidectomy. The expression of NKX2-1 was determined by RT-qPCR using specific primers.

RESULTS

The interaction between NKX2-1 and H19 was characterized by six local base-pairing connections, with a maximum energy of -20.56 kcal/moL. Specifically, the sequence that displayed the highest affinity for binding with H19 overlapped with the binding site of has-miR-1827 to NKX2-1. It was found that NKX2-1 is exclusively co-expressed with H19 in normal thyroid tissue. As compared to adjacent normal tissues, nodular goiter tissues have a significant overexpression of NKX2-1 (relative expression = 1.195, p =  0.038).

CONCLUSION

NKX2-1 has been identified as the putative target of H19 lncRNA, which is overexpressed in nodular goiter tissues significantly.

LEVEL OF EVIDENCE: 4

Polymorphism Pro64His within galectin-3 has functional consequences at proteome level in thyroid cells

Introduction

The single nucleotide polymorphism (SNP) rs4644 at codon 64 of galectin-3 (gal-3, gene name: LGALS3), specifying the variant proline (P64) to histidine (H64), is known to affect the protein's functions and has been associated with the risk of several types of cancer, including differentiated thyroid carcinoma (DTC).

Materials and methods

To deepen our understanding of the biological effects of this SNP, we analyzed the proteome of two isogenic cell lines (NC-P64 vs. NA-H64) derived from the immortalized non-malignant thyrocyte cell line Nthy-Ori, generated through the CRISPR-Cas9 technique to differ by rs4644 genotype. We compared the proteome of these cells to detect differentially expressed proteins and studied their proteome in relation to their transcriptome.

Results

Firstly, we found, consistently with previous studies, that gal-3-H64 could be detected as a monomer, homodimer, and heterodimer composed of one cleaved and one uncleaved monomer, whereas gal-3-P64 could be found only as a monomer or uncleaved homodimer. Moreover, results indicate that rs4644 influences the expression of several proteins, predominantly upregulated in NA-H64 cells. Overall, the differential protein expression could be attributed to the altered mRNA expression, suggesting that rs4644 shapes the function of gal-3 as a transcriptional co-regulator. However, this SNP also appeared to affect post-transcriptional regulatory mechanisms for proteins whose expression was oppositely regulated compared to mRNA expression. It is conceivable that the rs4644-dependent activities of gal-3 could be ascribed to the different modalities of self-dimerization.

Conclusion

Our study provided further evidence that rs4644 could affect the gal-3 functions through several routes, which could be at the base of differential susceptibility to diseases, as reported in case-control association studies.

The molecular and cellular choreography of early mammalian lung development

Mammalian lung development starts from a specific cluster of endodermal cells situated within the ventral foregut region. With the orchestrating of delicate choreography of transcription factors, signaling pathways, and cell-cell communications, the endodermal diverticulum extends into the surrounding mesenchyme, and builds the cellular and structural basis of the complex respiratory system. This review provides a comprehensive overview of the current molecular insights of mammalian lung development, with a particular focus on the early stage of lung cell fate differentiation and spatial patterning. Furthermore, we explore the implications of several congenital respiratory diseases and the relevance to early organogenesis. Finally, we summarize the unprecedented knowledge concerning lung cell compositions, regulatory networks as well as the promising prospect for gaining an unbiased understanding of lung development and lung malformations through state-of-the-art single-cell omics.

Functional characterization of two novel NKX2-1 frameshift variants that cause pulmonary surfactant dysfunction

BACKGROUND

We aim to report two unrelated patients with pulmonary surfactant dysfunction (PSD) that carried two novel NKX2-1 frameshift variants, and evaluated the impact of these variants in vitro.

METHODS

We enrolled children with PSD and NKX2-1 variants, and collected their clinical information and follow-up data. We constructed wild-type (WT) and variant NKX2-1 plasmids and transfected them into A549 and HEK293T cells. The functional characterization of variants was then evaluated by qRT-PCR, western blot, immunofluorescence, electrophoretic mobility shift assay, and dual-luciferase reporter assay.

RESULTS

Two novel heterozygous frameshift variants of NKX2-1, i.e., c.705delC (Gly236Alafs*29) and c.313_316 dup (Asn106Lysfs*304), were identified in children from two unrelated families. We discerned attenuated mRNA and protein expression in the Asn106Lysfs*304 variant, and reduced DNA -binding as well as transcriptional activation capabilities in both variants. While the Asn106Lysfs*304 variant lost its synergistic interactions with PAX8 and TAZ, the Gly236Alafs*29 variant partially retained its residual transcriptional activation capabilities and synergistic interactions with PAX8 and TAZ.

CONCLUSIONS

We reported on two children with two novel NKX2-1 frameshift variants. In vitro experiments revealed that the two frameshift variants have common and different mechanisms based on the loss or conservation of domains, which partially explained the phenotypical heterogeneity.

IMPACT

Pulmonary surfactant dysfunction is a rare heterogeneous disease that exhibits a great burden on children's quality of life. We reported two novel NKX2-1 frameshift variants carried by two children with different clinical phenotypes, thus broadening our knowledge base of gene variations and phenotypes in NKX2-1. We performed an in vitro study and uncovered different pathogenic mechanisms underlying the actions of two novel variants, and thereby partially explained the mechanisms of phenotypical heterogeneity caused by NKX2-1 variants.

Haploinsufficiency of NKX2-1 is likely to contribute to developmental delay involving 14q13 microdeletions

Nucleotide variations or deletions in the NK2 homeobox 1 gene (NKX2-1), located at 14q13.3, lead to symptoms associated with the brain, lungs, and thyroid, and the combination of these phenotypes is clinically recognized as the brain-lung-thyroid syndrome. Many types of nucleotide variants of NKX2-1 have been identified, and phenotypic variability has been reported. Chromosomal deletions involving NKX2-1 have also been reported; however, phenotypic differences between patients with nucleotide variants of NKX2-1 and patients with chromosomal deletions involving NKX2-1 have not been well established. Recently, we identified seven patients with 14q13 microdeletions involving the NKX2-1. Most patients exhibited developmental delay. This inquiry arises regarding the potential existence of haploinsufficiency effects beyond those attributed to NKX2-1 within the 14q13 microdeletion. However, a literature review has shown that developmental delay is not rare in patients with nucleotide alterations in NKX2-1. Rather, motor function impairment may have affected the total developmental assessment, and the haploinsufficiency of genes contiguous to NKX2-1 is unlikely to contribute to developmental delay.

Advances in Thyroid Organoids Research and Applications

INTRODUCTION

Organoids are three-dimensional cellular aggregates derived from stem cells or primary tissues that can self-organize into organotypic structures and showcase the physiological functions of that organ. Organoids typically comprise multiple organ-specific cell types that are responsible for organ function in vivo. They may also incorporate various cellular and molecular stromal components to recapitulate the in vivo microenvironment of the target organ.

METHODS

All articles related to thyroid-like organs were synthesized. Articles published between 1959 and 2023 were assessed, categorized, and analyzed using relevant keywords.

RESULTS

As such, organoids provide a model of greater physiological relevance than 2D cell culture for basic and translational research. Murine and human organoids of the thyroid have been established from embryonic stem cells (ESCs), pluripotent stem cells (PSCs) and from various healthy or diseased thyroid tissues. These thyroid organoids have been used in basic and translation research on thyroid-related diseases including hyperthyroidism, Graves' disease, and Hashimoto's thyroiditis. In addition, organoids derived from patients with thyroid cancer retain histopathological features and mutational profile of the original tumor. These patient-derived organoids have been successfully used in in vitro evaluation of drug response of individual patients, demonstrating their potential application in personalized treatment of thyroid cancer.

CONCLUSION

In this review article, we have discussed various techniques for establishing thyroid organoids and their applications in thyroid-related diseases as disease models, regenerative medicines, or a tool for drug testing.

Transcription factors in microcephaly

Higher cognition in humans, compared to other primates, is often attributed to an increased brain size, especially forebrain cortical surface area. Brain size is determined through highly orchestrated developmental processes, including neural stem cell proliferation, differentiation, migration, lamination, arborization, and apoptosis. Disruption in these processes often results in either a small (microcephaly) or large (megalencephaly) brain. One of the key mechanisms controlling these developmental processes is the spatial and temporal transcriptional regulation of critical genes. In humans, microcephaly is defined as a condition with a significantly smaller head circumference compared to the average head size of a given age and sex group. A growing number of genes are identified as associated with microcephaly, and among them are those involved in transcriptional regulation. In this review, a subset of genes encoding transcription factors (e.g., homeobox-, basic helix-loop-helix-, forkhead box-, high mobility group box-, and zinc finger domain-containing transcription factors), whose functions are important for cortical development and implicated in microcephaly, are discussed.

Sirtuin1-Mediated Deacetylation of Hypothalamic TTF-1 Contributes to the Energy Deficiency Response

TTF-1 stimulates appetite by regulating the expression of agouti-related peptide (AgRP) and proopiomelanocortin (POMC) genes in the hypothalamus of starving animals. However, the mechanism underlying TTF-1's response to decreased energy levels remains elusive. Here, we provide evidence that the NAD+-dependent deacetylase, sirtuin1 (Sirt1), activates TTF-1 in response to energy deficiency. Energy deficiency leads to a twofold increase in the expression of both Sirt1 and TTF-1, leading to the deacetylation of TTF-1 through the interaction between the two proteins. The activation of Sirt1, induced by energy deficiency or resveratrol treatment, leads to a significant increase in the deacetylation of TTF-1 and promotes its nuclear translocation. Conversely, the inhibition of Sirt1 prevents these Sirt1 effects. Notably, a point mutation in a lysine residue of TTF-1 significantly disrupts its deacetylation and thus nearly completely hinders its ability to regulate AgRP and POMC gene expression. These findings highlight the importance of energy-deficiency-induced deacetylation of TTF-1 in the control of AgRP and POMC gene expression.

HDAC3 is critical in tumor development and therapeutic resistance in Kras-mutant non-small cell lung cancer

HDAC3 is one of the main targets of histone deacetylase (HDAC) inhibitors in clinical development as cancer therapies, yet the in vivo role of HDAC3 in solid tumors is unknown. We identified a critical role for HDAC3 in Kras-mutant lung cancer. Using genetically engineered mouse models (GEMMs), we found that HDAC3 is required for lung tumor growth in vivo. HDAC3 was found to direct and enhance the transcription effects of the lung cancer lineage transcription factor NKX2-1 to mediate expression of a common set of target genes. We identified FGFR1 as a critical previously unidentified target of HDAC3. Leveraging this, we identified that an HDAC3-dependent transcriptional cassette becomes hyperactivated as Kras/LKB1-mutant cells develop resistance to the MEK inhibitor trametinib, and this can be reversed by treatment with the HDAC1/HDAC3 inhibitor entinostat. We found that the combination of entinostat plus trametinib treatment elicits therapeutic benefit in the Kras/LKB1 GEMM.

TTF1 suppresses neuroblastoma growth and induces neuroblastoma differentiation by targeting TrkA and the miR-204/TrkB axis

Neuroblastoma (NB) is the most common extracranial malignant solid tumor in children. We found that TTF1, TrkA, and miR-204 were lowly expressed, whereas TrkB was highly expressed in undifferentiated NB tissues. Meanwhile, TTF1 expression correlated positively with TrkA and miR-204 expression but negatively with TrkB expression. The TTF1 promoter was hypermethylated in undifferentiated NB tissues and SK-N-BE cells, leading to TTF1 downregulation. We also identified miR-204, which directly targets TrkB, as a transcriptional target of TTF1. Functionally, TTF1 suppressed proliferation, migration, and invasion of NB cells, whereas induced cell cycle arrest, apoptosis, and autophagy of NB cells by regulating TrkA and the miR-204-TrkB axis. Furthermore, TTF1 suppressed tumor growth and promoted neurogenic differentiation in a NB xenograft mouse model. Our study demonstrates that TTF1 reduces tumor growth and induces neurogenic differentiation in NB by directly targeting TrkA and the miR-204/TrkB axis.

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TTF1, TrkA, and miR-204 were lowly expressed in undifferentiated NB tissues

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TTF1 promoter was hypermethylated in undifferentiated NB tissues and cells

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TTF1 suppressed proliferation of NB cells by regulating TrkA and the miR-204-TrkB axis

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TTF1 suppressed tumor growth and promoted neurogenic differentiation in vivo

Genetic Regulation of Vertebrate Forebrain Development by Homeobox Genes

Forebrain development in vertebrates is regulated by transcription factors encoded by homeobox, bHLH and forkhead gene families throughout the progressive and overlapping stages of neural induction and patterning, regional specification and generation of neurons and glia from central nervous system (CNS) progenitor cells. Moreover, cell fate decisions, differentiation and migration of these committed CNS progenitors are controlled by the gene regulatory networks that are regulated by various homeodomain-containing transcription factors, including but not limited to those of the Pax (paired), Nkx, Otx (orthodenticle), Gsx/Gsh (genetic screened), and Dlx (distal-less) homeobox gene families. This comprehensive review outlines the integral role of key homeobox transcription factors and their target genes on forebrain development, focused primarily on the telencephalon. Furthermore, links of these transcription factors to human diseases, such as neurodevelopmental disorders and brain tumors are provided.

Tracheal separation is driven by NKX2-1-mediated repression of Efnb2 and regulation of endodermal cell sorting

The mechanisms coupling fate specification of distinct tissues to their physical separation remain to be understood. The trachea and esophagus differentiate from a single tube of definitive endoderm, requiring the transcription factors SOX2 and NKX2-1, but how the dorsoventral site of tissue separation is defined to allocate tracheal and esophageal cell types is unknown. Here, we show that the EPH/EPHRIN signaling gene Efnb2 regulates tracheoesophageal separation by controlling the dorsoventral allocation of tracheal-fated cells. Ventral loss of NKX2-1 results in disruption of separation and expansion of Efnb2 expression in the trachea independent of SOX2. Through chromatin immunoprecipitation and reporter assays, we find that NKX2-1 likely represses Efnb2 directly. Lineage tracing shows that loss of NKX2-1 results in misallocation of ventral foregut cells into the esophagus, while mosaicism for NKX2-1 generates ectopic NKX2-1/EPHRIN-B2 boundaries that organize ectopic tracheal separation. Together, these data demonstrate that NKX2-1 coordinates tracheal specification with tissue separation through the regulation of EPHRIN-B2 and tracheoesophageal cell sorting.

Lewis et al. show that, in the development of the mammalian trachea and esophagus, cell fate specification is coupled with morphogenesis by NKX2-1-mediated repression of Efnb2. This establishes an EPH/EPHRIN boundary that drives cell allocation and physical separation of the trachea and esophagus.

Sox9 is involved in the thyroid differentiation program and is regulated by crosstalk between TSH, TGFβ and thyroid transcription factors

While the signaling pathways and transcription factors involved in the differentiation of thyroid follicular cells, both in embryonic and adult life, are increasingly well understood, the underlying mechanisms and potential crosstalk between the thyroid transcription factors Nkx2.1, Foxe1 and Pax8 and inductive signals remain unclear. Here, we focused on the transcription factor Sox9, which is expressed in Nkx2.1-positive embryonic thyroid precursor cells and is maintained from embryonic development to adulthood, but its function and control are unknown. We show that two of the main signals regulating thyroid differentiation, TSH and TGFβ, modulate Sox9 expression. Specifically, TSH stimulates the cAMP/PKA pathway to transcriptionally upregulate Sox9 mRNA and protein expression, a mechanism that is mediated by the binding of CREB to a CRE site within the Sox9 promoter. Contrastingly, TGFβ signals through Smad proteins to inhibit TSH-induced Sox9 transcription. Our data also reveal that Sox9 transcription is regulated by the thyroid transcription factors, particularly Pax8. Interestingly, Sox9 significantly increased the transcriptional activation of Pax8 and Foxe1 promoters and, consequently, their expression, but had no effect on Nkx2.1. Our study establishes the involvement of Sox9 in thyroid follicular cell differentiation and broadens our understanding of transcription factor regulation of thyroid function.

Thyroid Transcription Factor-1: Structure, Expression, Function and Its Relationship with Disease

Thyroid transcription factor-1 (TTF-1/NKx2.1) is a member of the NKx2 tissue-specific transcription factor family, which is expressed in thyroid follicle, parathyroid gland, alveolar epithelium, and diencephalon which originated from ectoderm, and participates in the differentiation, development, and functional maintenance of the above organs. Recent studies have shown that the abnormal expression of TTF-1 is closely related to the occurrence of a variety of human diseases and can be used as a potential new target for the diagnosis and treatment of related diseases. In this article, in order to strengthen the systematic understanding of TTF-1 and promote the progress of related research, we reviewed the structure, expression regulation, biological functions of TTF-1, and its role in the occurrence and development of human-related clinical diseases. Meanwhile, we prospect the future research direction of TTF-1, which might ultimately contribute to the understanding of the pathogenesis of related clinical diseases and the development of new prevention and treatment strategies.

Pro64His (rs4644) Polymorphism Within Galectin-3 Is a Risk Factor of Differentiated Thyroid Carcinoma and Affects the Transcriptome of Thyrocytes Engineered via CRISPR/Cas9 System

Background: Galectin-3 (LGALS3) is an important glycoprotein involved in the malignant transformation of thyrocytes acting in the extracellular matrix, cytoplasm, and nucleus where it regulates TTF-1 and TCF4 transcription factors. Within LGALS3 gene, a common single-nucleotide polymorphism (SNP) (c.191C>A, p.Pro64His; rs4644) encoding for the variant Proline to Histidine at codon 64 has been extensively studied. However, data on rs4644 in the context of thyroid cancer are lacking. Thus, the aim of the present work was to evaluate the role of the rs4644 SNP as risk factor for differentiated thyroid cancer (DTC) and to determine the effect on the transcriptome in thyrocytes. Methods: A case/control association study in 1223 controls and 1142 unrelated consecutive DTC patients was carried out to evaluate the association between rs4644-P64H and the risk of DTC. We used the nonmalignant cell line Nthy-Ori (rs4644-C/A) and the CRISPR/Cas9 technique to generate isogenic cells carrying either the rs4644-A/A or rs4644-C/C homozygosis. Then, the transcriptome of the derivative and unmodified parental cells was analyzed by RNA-seq. Genes differentially expressed were validated by quantitative reverse transcription PCR and further tested in the parental Nthy-Ori cells after LGALS3 gene silencing, to investigate whether the expression of target genes was dependent on galectin-3 levels. Results: rs4644 AA genotype was associated with a reduced risk of DTC (compared with CC, OR_adj = 0.66; 95% confidence interval = 0.46-0.93; P_ass = 0.02). We found that rs4644 affects galectin-3 as a transcriptional coregulator. Among 34 genes affected by rs4644, HES1, HSPA6, SPC24, and NHS were of particular interest since their expression was rs4644-dependent (CC>AA for the first and AA>CC for the others), also in 574 thyroid tissues of Genotype-Tissue Expression (GTEx) biobank. Moreover, the expression of these genes was regulated by LGALS3-silencing. Using the proximity ligation assay in Nthy-Ori cells, we found that the TTF-1 interaction was genotype dependent. Conclusions: Our data show that in thyroid, rs4644 is a trans-expression quantitative trait locus that can modify the transcriptional expression of downstream genes, through the modulation of TTF-1.

Genetics of Familial Non-Medullary Thyroid Carcinoma (FNMTC)

Non-medullary thyroid carcinoma (NMTC) is the most frequent endocrine tumor and originates from the follicular epithelial cells of the thyroid. Familial NMTC (FNMTC) has been defined in pedigrees where two or more first-degree relatives of the patient present the disease in absence of other predisposing environmental factors. Compared to sporadic cases, FNMTCs are often multifocal, recurring more frequently and showing an early age at onset with a worse outcome. FNMTC cases show a high degree of genetic heterogeneity, thus impairing the identification of the underlying molecular causes. Over the last two decades, many efforts in identifying the susceptibility genes in large pedigrees were carried out using linkage-based approaches and genome-wide association studies, leading to the identification of susceptibility loci and variants associated with NMTC risk. The introduction of next-generation sequencing technologies has greatly contributed to the elucidation of FNMTC predisposition, leading to the identification of novel candidate variants, shortening the time and cost of gene tests. In this review we report the most significant genes identified for the FNMTC predisposition. Integrating these new molecular findings in the clinical data of patients is fundamental for an early detection and the development of tailored therapies, in order to optimize patient management.

Deletion of conserved non-coding sequences downstream from NKX2-1: A novel disease-causing mechanism for benign hereditary chorea

Background

Benign hereditary chorea (BHC) is an autosomal dominant disorder characterized by early‐onset non‐progressive involuntary movements. Although NKX2‐1 mutations or deletions are the cause of BHC, some BHC families do not have pathogenic alterations in the NKX2‐1 gene, indicating that mutations of non‐coding regulatory elements of NKX2‐1 may also play a role.

Methods and Results

By using whole‐genome microarray analysis, we identified a 117 Kb founder deletion in three apparently unrelated BHC families that were negative for NKX2‐1 sequence variants. Targeted next generation sequencing analysis confirmed the deletion and showed that it was part of a complex local genomic rearrangement. In addition, we also detected a 648 Kb de novo deletion in an isolated BHC case. Both deletions are located downstream from NKX2‐1 on chromosome 14q13.2‐q13.3 and share a 33 Kb smallest region of overlap with six previously reported cases. This region has no gene but contains multiple evolutionarily highly conserved non‐coding sequences.

Conclusion

We propose that the deletion of potential regulatory elements necessary for NKX2‐1 expression in this critical region is responsible for BHC phenotype in these patients, and this is a novel disease‐causing mechanism for BHC.

Unraveling the Complex Interplay Between Transcription Factors and Signaling Molecules in Thyroid Differentiation and Function, From Embryos to Adults

Thyroid differentiation of progenitor cells occurs during embryonic development and in the adult thyroid gland, and the molecular bases of these complex and finely regulated processes are becoming ever more clear. In this Review, we describe the most recent advances in the study of transcription factors, signaling molecules and regulatory pathways controlling thyroid differentiation and development in the mammalian embryo. We also discuss the maintenance of the adult differentiated phenotype to ensure the biosynthesis of thyroid hormones. We will focus on endoderm-derived thyroid epithelial cells, which are responsible for the formation of the thyroid follicle, the functional unit of the thyroid gland. The use of animal models and pluripotent stem cells has greatly aided in providing clues to the complicated puzzle of thyroid development and function in adults. The so-called thyroid transcription factors - Nkx2-1, Foxe1, Pax8 and Hhex - were the first pieces of the puzzle identified in mice. Other transcription factors, either acting upstream of or directly with the thyroid transcription factors, were subsequently identified to, almost, complete the puzzle. Among them, the transcription factors Glis3, Sox9 and the cofactor of the Hippo pathway Taz, have emerged as important players in thyroid differentiation and development. The involvement of signaling molecules increases the complexity of the puzzle. In this context, the importance of Bmps, Fgfs and Shh signaling at the onset of development, and of TSH, IGF1 and TGFβ both at the end of terminal differentiation in embryos and in the adult thyroid, are well recognized. All of these aspects are covered herein. Thus, readers will be able to visualize the puzzle of thyroid differentiation with most - if not all - of the pieces in place.

Neuronal tangential migration from Nkx2.1-positive hypothalamus

During the development of the central nervous system, the immature neurons suffer different migration processes. It is well known that Nkx2.1-positive ventricular layer give rise to critical tangential migrations into different regions of the developing forebrain. Our aim was to study this phenomenon in the hypothalamic region. With this purpose, we used a transgenic mouse line that expresses the tdTomato reporter driven by the promotor of Nkx2.1. Analysing the Nkx2.1-positive derivatives at E18.5, we found neural contributions to the prethalamic region, mainly in the zona incerta and in the mes-diencephalic tegmental region. We studied the developing hypothalamus along the embryonic period. From E10.5 we detected that the Nkx2.1 expression domain was narrower than the reporter distribution. Therefore, the Nkx2.1 expression fades in a great number of the early-born neurons from the Nkx2.1-positive territory. At the most caudal positive part, we detected a thin stream of positive neurons migrating caudally into the mes-diencephalic tegmental region using time-lapse experiments on open neural tube explants. Late in development, we found a second migratory stream into the prethalamic territory. All these tangentially migrated neurons developed a gabaergic phenotype. In summary, we have described the contribution of interneurons from the Nkx2.1-positive hypothalamic territory into two different rostrocaudal territories: the mes-diencephalic reticular formation through a caudal tangential migration and the prethalamic zona incerta complex through a dorsocaudal tangential migration.

Identification and functional characterization of a novel PAX8 mutation (p.His39Pro) causing familial thyroid hypoplasia

Mutations in PAX8, the gene for a thyroid-specific transcription factor, causes congenital hypothyroidism (CH) with autosomal dominant inheritance. All previously detected PAX8 mutations except one are located in the DNA-binding paired domain. The proband, a 1-yr-old boy, was diagnosed with CH in the frame of newborn screening. He had high serum TSH level (180 mU/L) and low serum free T₄ level (0.4 ng/dL). Ultrasonography revealed that the proband had thyroid hypoplasia. Importantly, he had a family history of CH, i.e., his mother also had CH and hypoplasia. Next generation sequencing-based mutation screening revealed a novel heterozygous PAX8 mutation (c.116A>C, p.His39Pro) that was transmitted to the proband from the mother. Expression experiments with HeLa cells confirmed that His39Pro-PAX8 exhibited defective transactivation of the TG promoter–luciferase reporter. In conclusion, we identified and described a novel loss-of-function PAX8 mutation in a family with thyroid hypoplasia. Patients with dominantly inherited CH and no extrathyroidal abnormalities could have PAX8 mutations.

A transgene targeted to the zebrafish nkx2.4b locus drives specific green fluorescent protein expression and disrupts thyroid development

BACKGROUND

With the goal of labeling and manipulating the zebrafish hypothalamus, we sought to target a green fluorescent protein (gfp) transgene to the expression domains of nkx2.4b, a gene expressed during hypothalamic and thyroid development. We combined transcription activator-like effector nucleases (TALENs)-mediated mutagenesis with a targeting construct to enable insertion of a gfp transgene into the endogenous nkx2.4b genomic locus.

RESULTS

Injection of TALENs targeted to the first exon of nkx2.4b created a predicted null allele, and homozygous mutant embryos displayed loss of thyroid markers. From embryos injected with both TALENs and a targeting construct carrying a gfp transgene, we recovered a line in which GFP was expressed specifically in the hypothalamus and thyroid. Fish homozygous for this allele lacked exon 1 of nkx2.4b and exhibited hypothyroid phenotypes.

CONCLUSIONS

By combining TALENs injections with a targeting construct that contained a gfp transgene, we were able to recover an allele in which GFP is expressed in the nkx2.4b expression domains, with homozygous phenotypes suggesting the creation of a loss-of-function transgenic line. These results demonstrate the creation of a useful tool for studying hypothalamus and thyroid development.

Delineating the early transcriptional specification of the mammalian trachea and esophagus

The genome-scale transcriptional programs that specify the mammalian trachea and esophagus are unknown. Though NKX2-1 and SOX2 are hypothesized to be co-repressive master regulators of tracheoesophageal fates, this is untested at a whole transcriptomic scale and their downstream networks remain unidentified. By combining single-cell RNA-sequencing with bulk RNA-sequencing of Nkx2-1 mutants and NKX2-1 ChIP-sequencing in mouse embryos, we delineate the NKX2-1 transcriptional program in tracheoesophageal specification, and discover that the majority of the tracheal and esophageal transcriptome is NKX2-1 independent. To decouple the NKX2-1 transcriptional program from regulation by SOX2, we interrogate the expression of newly-identified tracheal and esophageal markers in Sox2/Nkx2-1 compound mutants. Finally, we discover that NKX2-1 binds directly to Shh and Wnt7b and regulates their expression to control mesenchymal specification to cartilage and smooth muscle, coupling epithelial identity with mesenchymal specification. These findings create a new framework for understanding early tracheoesophageal fate specification at the genome-wide level.

Impaired Gene Expression Due to Iodine Excess in the Development and Differentiation of Endoderm and Thyroid Is Associated with Epigenetic Changes

Background: Thyroid hormone (TH) synthesis is essential for the control of development, growth, and metabolism in vertebrates and depends on a sufficient dietary iodine intake. Importantly, both iodine deficiency and iodine excess (IE) impair TH synthesis, causing serious health problems especially during fetal/neonatal development. While it is known that IE disrupts thyroid function by inhibiting thyroid gene expression, its effects on thyroid development are less clear. Accordingly, this study sought to investigate the effects of IE during the embryonic development/differentiation of endoderm and the thyroid gland. Methods: We used the murine embryonic stem (ES) cell model of in vitro directed differentiation to assess the impact of IE on the generation of endoderm and thyroid cells. Additionally, we subjected endoderm and thyroid explants obtained during early gestation to IE and evaluated gene and protein expression of endodermal markers in both models. Results: ES cells were successfully differentiated into endoderm cells and, subsequently, into thyrocytes expressing the specific thyroid markers Tshr, Slc5a5, Tpo, and Tg. IE exposure decreased the messenger RNA (mRNA) levels of the main endoderm markers Afp, Crcx4, Foxa1, Foxa2, and Sox17 in both ES cell-derived endoderm cells and embryonic explants. Interestingly, IE also decreased the expression of the main thyroid markers in ES cell-derived thyrocytes and thyroid explants. Finally, we demonstrate that DNA methyltransferase expression was increased by exposure to IE, and this was accompanied by hypermethylation and hypoacetylation of histone H3, pointing to an association between the gene repression triggered by IE and the observed epigenetic changes. Conclusions: These data establish that IE treatment is deleterious for embryonic endoderm and thyroid gene expression.

Knock-in mutations of scarecrow, a Drosophila homolog of mammalian Nkx2.1, reveal a novel function required for development of the optic lobe in Drosophila melanogaster

scarecrow (scro) gene encodes a Drosophila homolog of mammalian Nkx2.1 that belongs to an evolutionally conserved NK2 family. Nkx2.1 has been well known for its role in the development of hypothalamus, lung, thyroid gland, and brain. However, little is known about biological roles of scro. To understand scro functions, we generated two types of knock-in mutant alleles, substituting part of either exon-2 or exon-3 for EGFP (or Gal4) by employing the CRISPR/Cas9 genome editing tool. Using these mutations, we characterized spatio-temporal expression patterns of the scro gene and its mutant phenotypes. Homozygous knock-in mutants are lethal during embryonic and early larval development. In developing embryos, scro is exclusively expressed in the pharyngeal primordia and numerous neural clusters in the central nervous system (CNS). In postembryonic stages, the most prominent scro expression is detected in the larval and adult optic lobes, suggesting that scro plays a role for the development and/or function of this tissue type. Notch signaling is the earliest factor known to act for the development of the optic lobe. scro mutants lacked mitotic cells and Delta expression in the optic anlagen, and showed altered expression of several proneural and neurogenic genes including Delta and Notch. Furthermore, scro mutants showed grossly deformed neuroepithelial (NE) cells in the developing optic lobe and severely malformed adult optic lobes, the phenotypes of which are shown in Notch or Delta mutants, suggesting scro acting epistatic to the Notch signaling. From these data together, we propose that scro plays an essential role for the development of the optic lobe, possibly acting as a regional specification factor.

Thyrotropin, but Not Thyroid-Stimulating Antibodies, Induces Biphasic Regulation of Gene Expression in Human Thyrocytes

Background: Thyrotropin (TSH) and thyroid-stimulating antibodies (TSAbs) activate TSH receptor (TSHR) signaling by binding to its extracellular domain. TSHR signaling has been studied extensively in animal thyrocytes and in engineered cell lines, and differences in signaling have been observed in different cell systems. We, therefore, decided to characterize and compare TSHR signaling mediated by TSH and monoclonal TSAbs in human thyrocytes in primary culture. Methods: We used quantitative reverse transcription-polymerase chain reaction to measure mRNA levels of thyroid-specific genes thyroglobulin (TG), thyroperoxidase (TPO), iodothyronine deiodinase type 2 (DIO2), sodium-iodide symporter (NIS), and TSHR after stimulation by TSH or two monoclonal TSAbs, KSAb1 and M22. We also compared secreted TG protein after TSHR activation by TSH and TSAbs using an enzyme-linked immunosorbent assay. TSHR cell surface expression was determined using fluorescence activated cell sorting (FACS). Results: We found that TSH at low doses increases and at high doses (>1 mU/mL) decreases levels of gene expression for TSHR, TG, TPO, NIS, and DIO2. The biphasic effect of TSH on signaling was not caused by downregulation of cell surface TSHRs. This bell-shaped biphasic dose-response curve has been termed an inverted U-shaped dose-response curve (IUDRC). An IUDRC was also found for TSH-induced regulation of TG secretion. In contrast, KSAb1- and M22-induced regulation of TSHR, TG, TPO, NIS, and DIO2 gene expression, and secreted TG followed a monotonic dose-response curve that plateaus at high doses of activating antibody. Conclusions: Our data demonstrate that the physiological activation of TSHRs by TSH in primary cultures of human thyrocytes is characterized by a regulatory mechanism that may inhibit thyrocyte overstimulation. In contrast, TSAbs do not exhibit biphasic regulation. Although KSAb1 and M22 may not be representative of all TSAbs found in patients with Graves' disease, we suggest that persistent robust stimulation of TSHRs by TSAbs, unrelieved by a decrease at high TSAb levels, fosters chronic stimulation of thyrocytes in Graves' hyperthyroidism.

Persistent Respiratory Distress in the Term Neonate: Genetic Surfactant Deficiency Diseases

Respiratory distress is one of the most common clinical presentations in newborns requiring admission to a Neonatal Intensive Care Unit (NICU). Many of these infants develop respiratory distress secondary to surfactant deficiency, which causes an interstitial lung disease that can occur in both preterm and term infants. Pulmonary surfactant is a protein and lipid mixture made by type II alveolar cells, which reduces alveolar surface tension and prevents atelectasis. The etiology of surfactant deficiency in preterm infants is pulmonary immaturity and inadequate production. Term infants may develop respiratory insufficiency secondary to inadequate surfactant, either from exposure to factors that delay surfactant synthesis (such as maternal diabetes) or from dysfunctional surfactant arising from a genetic mutation. The genetics of surfactant deficiencies are very complex. Some mutations are lethal in the neonatal period, while others cause a wide range of illness severity from infancy to adulthood. Genes that have been implicated in surfactant deficiency include SFTPA1, SFTPA2, SFTPB, SFTPC, and SFTPD (which encode for surfactant proteins A, B, C, and D, respectively); ABCA3 (crucial for surfactant packaging and secretion); and NKX2 (a transcription factor that regulates the expression of the surfactant proteins in lung tissue). This article discusses the interplay between the genotypes and phenotypes of newborns with surfactant deficiency to assist clinicians in determining which patients warrant a genetic evaluation.

Molecular defects in thyroid dysgenesis

Congenital hypothyroidism (CH) is a neonatal endocrine disorder that might occur as itself or be associated to congenital extra-thyroidal defects. About 85% of affected subjects experience thyroid dysgenesis (TD), characterized by defect in thyroid gland development. In vivo experiments on null mice paved the way for the identification of genes involved thyroid morphogenesis and development, whose mutation has been strongly associated to TD. Most of them are thyroid-specific transcription factors expressed during early thyroid development. Despite the arduous effort in unraveling the genetics of TD in animal models, up to now these data have been discontinuously confirmed in humans and only 5% of TD have associated with known null mice-related mutations (mainly PAX8 and TSHR). Notwithstanding, the advance in genetic testing represented by the next-generation sequencing (NGS) approach is steadily increasing the list of genes whose highly penetrant mutation predisposes to TD. In this review we intend to outline the molecular bases of TD, summarizing the current knowledge on thyroid development in both mice and humans and delineating the genetic features of its monogenetic forms. We will also highlight current strategies to enhance the insight into the non-Mendelian mechanisms of abnormal thyroid development.

Generation of a NKX2.1 knock-in reporter cell line from human induced pluripotent stem cells (MHHi006-A-2)

NK homeobox 1 (NKX2.1; also known as thyroid transcription factor 1, TTF-1) encodes for a transcription factor involved in the development of thyroid, lung and brain. Here, we established a NKX2.1 knock-in reporter cell line from human induced pluripotent stem cells (iPSCs) using TALEN technology. The reporter enables the optimization and monitoring of the differentiation of pluripotent stem cells (PSCs) into NKX2.1 expressing cells on a single cell level, as well as the enrichment of NKX2.1 positive cells.

Regulation of Foxe1 by Thyrotropin and Transforming Growth Factor Beta Depends on the Interplay Between Thyroid-Specific, CREB and SMAD Transcription Factors

Background: Thyroid follicular cells are characterized by the expression of a specific set of genes necessary for the synthesis and secretion of thyroid hormones, which are in turn regulated by the transcription factors Nkx2-1, Pax8, and Foxe1. Thyroid differentiation is finely tuned by the balance between positive regulatory signals, including thyrotropin (TSH), and by negative regulatory signals, such as transforming growth factor beta (TGF-β), which counteracts the action of TSH. A role for Foxe1 as a mediator of hormonal and growth-factor control of thyroid differentiation has been previously suggested. Therefore, the aim of this work was to study the mechanisms governing Foxe1 expression to define the ligands and signals that regulate one of the important factors in thyroid differentiation. Methods: Expression of Foxe1 was evaluated in rat PCCl3 thyroid follicular cells under different treatments. The mouse Foxe1 promoter was cloned, and site-directed mutagenesis was undertaken to study its transcriptional regulation and to identify response elements. Protein/DNA binding assays were performed to evaluate the binding of different transcription factors, and gene-silencing approaches were used to elucidate their functional roles. Results:In silico analysis of the Foxe1 promoter identified binding sites for Nkx2-1, Pax8, Foxe1, and Smad proteins, as well as cAMP-response element (CRE) sites. It was found that both CRE-binding protein and CRE modulator were necessary for the TSH-mediated induction of Foxe1 expression via the cAMP/PKA signaling pathway. Moreover, transcription of Foxe1 was regulated by Nkx2-1 and Pax8 and by itself, suggesting an autoregulatory mechanism of activation and an important role for thyroid transcription factors. Finally, TGF-β, through Smad proteins, inhibited the TSH-induced Foxe1 expression. Conclusions: This study shows that Foxe1 is the final target of TSH/cAMP and TGF-β regulation that mediates expression of thyroid differentiation genes, and provides evidence of an interplay between CRE-binding proteins, thyroid transcription factors, and Smad proteins in its regulation. Thus, Foxe1 plays an important role in the complex transcriptional network that regulates thyroid follicular cell differentiation.

Systematic alanine scanning of PAX8 paired domain reveals functional importance of the N-subdomain

Thyroid-specific transcription factor PAX8 has an indispensable role in the thyroid gland development, which is evidenced by the facts that PAX8/Pax8 mutations cause congenital hypothyroidism in humans and mice. More than 90% of known PAX8 mutations were located in the paired domain, suggesting the central role of the domain in exerting the molecular function. Structure-function relationships of PAX8, as well as other PAX family transcription factors, have never been investigated in a systematic manner. Here, we conducted the first alanine scanning mutagenesis study, in which 132 alanine variants located in the paired domain of PAX8 were created and systematically evaluated in vitro. We found that 76 alanine variants (55%) were loss of function (LOF) variants (defined by <30% activity as compared with wild type PAX8). Importantly, the distribution of LOF variants were skewed, with more frequently observed in the N-subdomain (65% of the alanine variants in the N-subdomain) than in the C-subdomain (45%). Twelve out of 13 alanine variants in residues that have been affected in patients with congenital hypothyroidism were actually LOF, suggesting that the alanine scanning data can be used to evaluate the functional importance of mutated residues. Using our in vitro data, we tested the accuracy of seven computational algorithms for pathogenicity prediction, showing that they are sensitive but not specific to evaluate on the paired domain alanine variants. Collectively, our experiment-based data would help better understand the structure-function relationships of the paired domain, and would provide a unique resource for pathogenicity prediction of future PAX8 variants.

Correlation of Thyroid Transcription Factor-1 Expression with EGFR Mutations in Non-Small-Cell Lung Cancer: A Meta-Analysis

OBJECTIVES

This meta-analysis investigated the relationship between thyroid transcription factor-1 (TTF-1) expression and epidermal growth factor receptor (EGFR) mutations in non-small-cell lung cancer (NSCLC) to clarify whether TTF-1 can be a potential surrogate marker for EGFR mutation status in advanced NSLCL.

METHODS

A systematic searching of databases, including PubMed, EMBASE, Cochrane Library, and Google Scholar, was performed to identify studies assessing the correlation of TTF-1 expression with EGFR mutations. From 17 studies, 9764 patients were included in the combined analysis of odds ratio (OR) for the correlation between TTF-1 expression and EGFR mutations.

RESULTS

Compared with NSCLCs showing negative TTF-1 expression, tumors harboring TTF-1 overexpression showed a significantly higher rate of EGFR mutations (OR = 5.19, 95% confidence interval: 3.60⁻7.47, p < 0.00001). This correlation was observed in both subgroups of East Asian (OR = 4.33, 95% CI: 3.46⁻5.41, p < 0.00001) and European patients (OR = 4.64, 95% CI: 1.41⁻15.28, p < 0.01). In addition, TTF-1 expression was significantly associated with EGFR mutations in exon 19 (OR = 4.63, 95% CI: 2.89⁻7.41, p < 0.00001) as well as exon 21 (OR = 3.16, 95% CI: 1.04⁻9.60, p = 0.04).

CONCLUSIONS

This meta-analysis demonstrates a significant correlation between TTF-1 expression and EGFR mutations in patients with NSCLC. The status of TTF-1 expression may be a biomarker to guide anticancer treatment in patients with NSCLC and unknown EGFR mutation status.

Nkx2-3-A Slippery Slope From Development Through Inflammation Toward Hematopoietic Malignancies

The development of peripheral lymphoid tissues from the mesoderm is the result of a complex convergence combining lymphohematopoietic differentiation with the local specification of nonhematopoietic mesenchymal components. Although the various transcriptional regulators with fate-determining effects in diversifying the mobile leukocyte subsets have been thoroughly studied and identified, the tissue-specific determinants promoting the regional differentiation of resident mesenchyme are less understood. Of these factors, various members of the NK-class Nkx paralogues have emerged as key regulators for the organogenesis of spleen and mucosal lymphoid tissues, and recent data have also indicated their involvement in various pathological events, including gut inflammation and hematopoietic malignancies. Here, we summarize available data on the roles of Nkx2-3 in lymphoid tissue development and discuss its possible value as a developmental marker and disease-associated pathogenic trait.

Pulmonary anatomy and a case of unilateral aplasia in a common snapping turtle (Chelydra serpentina): developmental perspectives on cryptodiran lungs

The common snapping turtle (Chelydra serpentina) is a well studied and broadly distributed member of Testudines; however, very little is known concerning developmental anomalies and soft tissue pathologies of turtles and other reptiles. Here, we present an unusual case of unilateral pulmonary aplasia, asymmetrical carapacial kyphosis, and mild scoliosis in a live adult C. serpentina. The detailed three-dimensional (3D) anatomy of the respiratory system in both the pathological and normal adult C. serpentina, and a hatchling are visualized using computed tomography (CT), microCT, and 3D digital anatomical models. In the pathological turtle, the right lung consists of an extrapulmonary bronchus that terminates in a blind stump with no lung present. The left lung is hyperinflated relative to the normal adult, occupying the extra coelomic space facilitated by the unusual mid-carapacial kyphotic bulge. The bronchial tree of the left lung retains the overall bauplan of the normal specimens, with some minor downstream variation in the number of secondary airways. The primary difference between the internal pulmonary structure of the pathological individual and that of a normal adult is a marked increase in the surface area and density of the parenchymal tissue originating from the secondary airways, a 14.3% increase in the surface area to volume ratio. Despite this, the aplasia has not had an impact upon the ability of the turtle to survive; however, it did interfere with aquatic locomotion and buoyancy control under water. This turtle represents a striking example of a non-fatal congenital defect and compensatory visceral hypertrophy.

Rapid Immunohistochemistry With Thyroid Transcription Factor-1 for Pulmonary Adenocarcinoma

BACKGROUND

Intraoperative pathologic diagnosis of solitary pulmonary tumors to differentiate between metastatic and primary lung cancer is extremely important to determine the appropriate range of excision. Accurate intraoperative pathologic evaluation may be often difficult, however, and needs additional immunohistochemical (IHC) evaluation to support the diagnosis. Although conventional IHC is a powerful tool for diagnosis, its clinical use is limited intraoperatively because of time constraints. To address this issue, we developed a device that enables complete and rapid IHC (R-IHC) analyses within 20 minutes. We aimed to evaluate the discriminative ability of the R-IHC with anti-thyroid transcription factor-1 (TTF-1) antibody, which is a highly specific IHC marker for primary lung adenocarcinoma.

METHODS

A total of 61 pulmonary tumors that were resected at our institute from May 2011 to September 2013 were retrospectively examined. The samples were sectioned, labeled with anti-TTF-1 antibody using the R-IHC method, and pathologically evaluated. The standard used for evaluation was conventional IHC with TTF-1.

RESULTS

With the R-IHC procedure, analyses were completed within 20 minutes, with a diagnostic accuracy of 96.7% (59 of 61). Among the 47 primary lung adenocarcinomas, the R-IHC detected 31 (66%) tumors that were positive for TTF-1, with a positive predictive value of 100% (31 of 31).

CONCLUSIONS

Our newly developed method of R-IHC with anti-TTF-1 antibody was useful for diagnosing and differentiation of solitary pulmonary tumors. This technology may prove to be an important supplement to standard intraoperative pathologic diagnosis in routine practice.

Role of thyroid transcription factor-1 in the diagnosis of feline lung-digit syndrome

Objectives The aim of this study was to investigate the role of thyroid transcription factor-1 (TTF-1) in the diagnosis of feline lung-digit syndrome (FLDS) and to investigate the associations between the morphological features of FLDS and TTF-1 expression. We also compared the reliability of TTF-1 and transmission electron microscopy (TEM) in establishing the diagnosis of FLDS. Methods Histology records of feline digit tumours were retrieved, including patients from 2008-2015. If formalin-fixed, paraffin-embedded tissues were available for review, patients were included in the study. As a control group we included 12 feline primary tumours of the digits. All the histological slides of the study group were blindly reviewed by the same veterinary pathologist. Representative sections of the lesions were selected for immunohistochemistry (IHC) analysis. To confirm the respiratory origin of the neoplastic tissue, TEM was used as a gold standard in all cases. Results Five cases of FLDS were included. TTF-1 was weakly to moderately positive in 60% of the cases, showing no correlation with the microscopic presence of ciliated epithelium. When IHC results were combined with the presence of cilia, 80% of the cases from the study group could be identified as FLDS. TEM confirmed the presence of ciliated epithelium in all five cases, confirming the respiratory origin of the neoplastic tissue and therefore the diagnosis of FLDS. Conclusions and relevance TTF-1 expression is maintained in FLDS. While the combination of TTF-1 and identification of cilia confirms FLDS, TEM should be considered in those cases where diagnosis is uncertain and FLDS is suspected.

Nkx2.1 regulates the generation of telencephalic astrocytes during embryonic development

The homeodomain transcription factor Nkx2.1 (NK2 homeobox 1) controls cell differentiation of telencephalic GABAergic interneurons and oligodendrocytes. Here we show that Nkx2.1 also regulates astrogliogenesis of the telencephalon from embryonic day (E) 14.5 to E16.5. Moreover we identify the different mechanisms by which Nkx2.1 controls the telencephalic astrogliogenesis. In Nkx2.1 knockout (Nkx2.1^−/−) mice a drastic loss of astrocytes is observed that is not related to cell death. Further, in vivo analysis using BrdU incorporation reveals that Nkx2.1 affects the proliferation of the ventral neural stem cells that generate early astrocytes. Also, in vitro neurosphere assays showed reduced generation of astroglia upon loss of Nkx2.1, which could be due to decreased precursor proliferation and possibly defects in glial specification/differentiation. Chromatin immunoprecipitation analysis and in vitro co-transfection studies with an Nkx2.1-expressing plasmid indicate that Nkx2.1 binds to the promoter of glial fibrillary acidic protein (GFAP), primarily expressed in astrocytes, to regulate its expression. Hence, Nkx2.1 controls astroglial production spatiotemporally in embryos by regulating proliferation of the contributing Nkx2.1-positive precursors.

Disorders of thyroid morphogenesis

Developmental anomalies of the thyroid gland, defined as thyroid dysgenesis, underlie the majority of cases of congenital hypothyroidism. Thyroid dysgenesis is predominantly a sporadic disorder although a reported familial enrichment, variation of incidence by ethnicity and the monogenic defects associated mainly with athyreosis or orthotopic thyroid hypoplasia, suggest a genetic contribution. Of note, the most common developmental anomaly, thyroid ectopy, remains unexplained. Ectopy may result from multiple genetic or epigenetic variants in the germline and/or at the somatic level. This review provides a brief overview of the monogenic defects in candidate genes that have been identified so far and of the syndromes which are known to be associated with thyroid dysgenesis.

Thyroid transcription factor-1 distinguishes subependymal giant cell astrocytoma from its mimics and supports its cell origin from the progenitor cells in the medial ganglionic eminence

Subependymal giant cell astrocytoma is a benign brain tumor mostly associated with tuberous sclerosis complex. However, it may be misinterpreted as other high-grade brain tumors due to the presence of large tumor cells with conspicuous pleomorphism and occasional atypical features, such as tumor necrosis and endothelial proliferation. In this study, we first investigated thyroid transcription factor-1 (TTF-1) expression in a large series of subependymal giant cell astrocytomas and other histologic and locational mimics to validate the diagnostic utility of this marker. We then examined TTF-1 expression in non-neoplastic brain tissue to determine the cell origin of subependymal giant cell astrocytoma. Twenty-four subependymal giant cell astrocytoma specimens were subjected to tissue microarray construction. For comparison, a selection of tumors, including histologic mimics (21 gemistocytic astrocytomas and 24 gangliogliomas), tumors predominantly occurring at the ventricular system (50 ependymomas, 19 neurocytomas, and 7 subependymomas), and 134 astrocytomas (3 pleomorphic xanthoastrocytomas, 45 diffuse astrocytomas, 46 anaplastic astrocytomas, and 40 glioblastomas) were used. Immunohistochemical stain for TTF-1 was positive in all 24 subependymal giant cell astrocytomas, whereas negative in all astrocytomas, gangliogliomas, ependymomas, and subependymomas. Neurocytomas were positive for TTF-1 in 4/19 (21%) of cases using clone 8G7G3/1 and in 9/19 (47%) of cases using clone SPT24. In the three fetal brains that we examined, TTF-1 expression was seen in the medial ganglionic eminence, a transient fetal structure between the caudate nucleus and the thalami. There was no BRAF^V600E mutation identified by direct sequencing in the 20 subependymal giant cell astrocytomas that we studied. In conclusion, TTF-1 is a useful marker in distinguishing subependymal giant cell astrocytoma from its mimics. Expression of TTF-1 in the fetal medial ganglionic eminence indicates that subependymal giant cell astrocytoma may originate from the progenitor cells in this region.

Usefulness of Thyroid Transcription Factor-1 Immunohistochemical Staining in the Differential Diagnosis of Primary Pulmonary Tumors of Dogs

In a previous study, we characterized the reactivity of monoclonal antibody (MoAb) 8G7G3/1 to thyroid transcription factor-1 (TTF-1) in canine thyroid tumors. In this study, we have examined the reactivity of this antibody in 120 canine pulmonary tumors, including 78 primary epithelial tumors. Tissues had been fixed in formalin and routinely processed for histopathology. Nuclear staining for TTF-1 was detected in 64.2% of primary pulmonary epithelial tumors. The most common TTF-1-reactive tumor types were bronchioloalveolar carcinomas and bronchogenic carcinomas. Staining was diffuse, heterogeneous, or patchy. Nonpulmonary, metastatic epithelial tumors, except two of two thyroid carcinomas, did not react with antibody 8G7G3/1. Mesotheliomas and other mesenchymal tumors were also negative for this marker. A reduction or loss of reactivity was apparent in pulmonary epithelial tumors archived in paraffin blocks for 7-8 years. There was slight reduction in the number of positive cells or the intensity of the reaction in control tissues fixed longer than 1 week. On the basis of our limited studies and the human literature, it appears that MoAb 8G7G3/1 to TTF-1 is a highly specific (with the exception of thyroid tumors) and moderately sensitive marker for canine pulmonary epithelial tumors.

Integrated microRNA, gene expression and transcription factors signature in papillary thyroid cancer with lymph node metastasis

Background. Papillary thyroid carcinoma (PTC) is the commonest thyroid malignancy originating from the follicle cells in the thyroid. Despite a good overall prognosis, certain high-risk cases as in those with lymph node metastasis (LNM) have progressive disease and poorer prognosis. MicroRNAs are a class of non-protein-coding, 19–24 nucleotides single-stranded RNAs which regulate gene expression and these molecules have been shown to play a role in LNM. The integrated analysis of miRNAs and gene expression profiles together with transcription factors (TFs) has been shown to improve the identification of functional miRNA-target gene-TF relationships, providing a more complete view of molecular events underlying metastasis process.

Objectives. We reanalyzed The Cancer Genome Atlas (TCGA) datasets on PTC to identify differentially expressed miRNAs/genes in PTC patients with LNM-positive (LNM-P) versus lymph node negative (LNN) PTC patients and to investigate the miRNA-gene-TF regulatory circuit that regulate LNM in PTC.

Results. PTC patients with LNM (PTC LNM-P) have a significantly shorter disease-free survival rate compared to PTC patients without LNM (PTC LNN) (Log-rank Mantel Cox test, p = 0.0049). We identified 181 significantly differentially expressed miRNAs in PTC LNM-P versus PTC LNN; 110 were upregulated and 71 were downregulated. The five topmost deregulated miRNAs were hsa-miR-146b, hsa-miR-375, hsa-miR-31, hsa-miR-7-2 and hsa-miR-204. In addition, 395 miRNAs were differentially expressed between PTC LNM-P and normal thyroid while 400 miRNAs were differentially expressed between PTC LNN and normal thyroid. We found four significant enrichment pathways potentially involved in metastasis to the lymph nodes, namely oxidative phosphorylation (OxPhos), cell adhesion molecules (CAMs), leukocyte transendothelial migration and cytokine–cytokine receptor interaction. OxPhos was the most significantly perturbed pathway (p = 4.70E−06) involving downregulation of 90 OxPhos-related genes. Significant interaction of hsa-miR-301b with HLF, HIF and REL/NFkB transcription factors were identified exclusively in PTC LNM-P versus PTC LNN.

Conclusion. We found evidence of five miRNAs differentially expressed in PTC LNM-P. Alteration in OxPhos pathway could be the central event in metastasis to the lymph node in PTC. We postulate that hsa-miR-301b might be involved in regulating LNM in PTC via interactions with HLF, HIF and REL/NFkB. To the best of our knowledge, the roles of these TFs have been studied in PTC but the precise role of this miRNA with these TFs in LNM in PTC has not been investigated.

Gene expression of thyroid-specific transcription factors may help diagnose thyroid lesions but are not determinants of tumor progression

PURPOSE

The role of thyroid-specific transcription factors in thyroid malignancy is still poorly understood, so we investigate thyroid-specific transcription factors gene expression both in benign and in malignant thyroid nodules, aiming to study a possible clinical utility of these molecules.

METHODS

We quantified TTF-1, FOXE1 and PAX8 mRNA levels, relating their expression to diagnostic and prognostic features of thyroid tumors. RNA was extracted from 4 normal thyroid tissues, 101 malignant [99 papillary thyroid carcinomas (PTC) and 2 anaplastic thyroid carcinomas] and 99 benign thyroid lesion tissues [49 goiter and 50 follicular adenomas (FA)].

RESULTS

Levels of mRNA of both FOXE1 (P < 0.0001) and PAX8 (P < 0.0001) genes, but not TTF-1 (P = 0.7056), were higher in benign than in malignant thyroid lesions. FOXE1 was able to identify malignant nodules with 75.8 % sensitivity, 76.1 % specificity, 75.8 % positive predictive value, 76.1 % negative predictive value and 75.9 % accuracy. PAX8 was able to identify malignancy with 60.6 % sensitivity, 81.1 % specificity, 76.9 % positive predictive value, 66.4 % negative predictive value and 70.6 % accuracy. Both FOXE1 and PAX8 gene expression patterns were also able to differentiate FA from the follicular variant of PTC-FVPTC. However, the investigated gene expression was neither associated with any clinical feature of tumor aggressiveness nor associated with recurrence or survival.

CONCLUSIONS

We suggest that FOXE1 and PAX8 gene expression patterns may help to diagnose thyroid nodules, identifying malignancy and characterizing follicular-patterned thyroid lesions, but are not determinants of thyroid tumor progression.

Increased Thyroid Hormone Activation Accompanies the Formation of Thyroid Hormone-Dependent Negative Feedback in Developing Chicken Hypothalamus

The hypothalamic-pituitary-thyroid axis is governed by hypophysiotropic TRH-synthesizing neurons located in the hypothalamic paraventricular nucleus under control of the negative feedback of thyroid hormones. The mechanisms underlying the ontogeny of this phenomenon are poorly understood. We aimed to determine the onset of thyroid hormone-mediated hypothalamic-negative feedback and studied how local hypothalamic metabolism of thyroid hormones could contribute to this process in developing chicken. In situ hybridization revealed that whereas exogenous T4 did not induce a statistically significant inhibition of TRH expression in the paraventricular nucleus at embryonic day (E)19, T4 treatment was effective at 2 days after hatching (P2). In contrast, TRH expression responded to T3 treatment in both age groups. TSHβ mRNA expression in the pituitary responded to T4 in a similar age-dependent manner. Type 2 deiodinase (D2) was expressed from E13 in tanycytes of the mediobasal hypothalamus, and its activity increased between E15 and P2 both in the mediobasal hypothalamus and in tanycyte-lacking hypothalamic regions. Nkx2.1 was coexpressed with D2 in E13 and P2 tanycytes and transcription of the cdio2 gene responded to Nkx2.1 in U87 glioma cells, indicating its potential role in the developmental regulation of D2 activity. The T3-degrading D3 enzyme was also detected in tanycytes, but its level was not markedly changed before and after the period of negative feedback acquisition. These findings suggest that increasing the D2-mediated T3 generation during E18-P2 could provide the sufficient local T3 concentration required for the onset of T3-dependent negative feedback in the developing chicken hypothalamus.

KRAS and NKX2-1 Mutations in Invasive Mucinous Adenocarcinoma of the Lung

INTRODUCTION

Mucinous differentiation is observed in a subset of lung adenocarcinomas with unique clinical and pathological features, but the biology of these neoplasms is poorly understood.

METHODS

We apply targeted next-generation sequencing to characterize the mutational profiles of 21 invasive mucinous adenocarcinomas, mixed mucinous/nonmucinous adenocarcinomas, and adenocarcinomas with mucinous features of the lung and validate key findings on 954 additional lung adenocarcinomas from our institution and 514 lung adenocarcinomas from The Cancer Genome Atlas.

RESULTS

Sequencing identifies pathogenic mutations in the oncogenes Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), erb-b2 receptor tyrosine kinase 2 (ERBB2), and anaplastic lymphoma receptor tyrosine kinase (ALK) and recurrent mutations in tumor protein p53 (TP53), serine/threonine kinase 11 (STK11), NK2 homeobox 1 (NKX2-1), and SET domain containing 2 (SETD2). In the combined discovery and validation cohorts, we identify nine neoplasms with distinct molecular and pathological features. All are invasive mucinous adenocarcinomas or mixed mucinous/nonmucinous adenocarcinomas with mutations of KRAS and frameshift or nonsense mutations of NKX2-1. Immunohistochemical analysis shows that these neoplasms are associated with altered differentiation states, including loss of expression of the pulmonary marker thyroid transcription factor 1 (also called Nkx2.1) and expression of gastrointestinal markers.

CONCLUSIONS

These findings describe recurrent NKX2-1 mutations in invasive mucinous adenocarcinomas of the lung and support NKX2-1 as a lineage-specific tumor suppressor gene in lung carcinogenesis.

Distinct Characteristics of Small Cell Lung Cancer Correlate With Central or Peripheral Origin: Subtyping Based on Location and Expression of Transcription Factor TTF-1

Small-cell lung carcinoma (SCLC) is a type of lung cancer with neuroendocrine differentiation and a poor prognosis that is widely believed to arise in the central lung. Thyroid transcription factor-1 (TTF-1) is a peripheral marker of lung adenocarcinoma that is also highly expressed in SCLC. In this study, we examined whether SCLC is really a central-type tumor and the relationship between tumor location, TTF-1 expression and prognosis of SCLC.Ninety six SCLCs, diagnosed from biopsies or surgical materials, for which detailed computed tomography (CT) images were available, were collected consecutively from Japanese patients between 2004 and 2011. We examined the location of the primary tumor (central or peripheral) using thin-sliced CT, a TTF-1 immunohistochemical expression, and clinicopathology including prognosis.Of the 96 SCLCs, 74% (71/96) were of the peripheral type and found to have a significantly worse prognosis than central-type tumors. TTF-1 immunoreactivity was identified in 79 tumors (82%), 78% of which (62/79) were of the peripheral type and 22% of which were central. TTF-1 expression was significantly correlated with peripheral location (P = 0.030). Multivariate analysis revealed that high TNM stages and the peripheral location were independent markers for poor survival.The majority of SCLCs were of the peripheral type. The peripheral-type SCLC expressed TTF-1 more frequently and had a poorer prognosis than central-type tumors did. Further analysis on original sites of SCLC, using molecular methodology, or based on another ethnicity, should be warranted.

Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site

CONTEXT

-Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes.

OBJECTIVES

-To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features.

DATA SOURCES

-Literature review, the authors' practice experience, and authors' research.

CONCLUSIONS

-With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls.