Distribution of the titf2/foxe1 gene product is consistent with an important role in the development of foregut endoderm, palate, and hair

Disruption of the foxe1 gene in zebrafish reveals conserved functions in development of the craniofacial skeleton and the thyroid

Introduction: Mutations in the FOXE1 gene are implicated in cleft palate and thyroid dysgenesis in humans.

Methods: To investigate whether zebrafish could provide meaningful insights into the etiology of developmental defects in humans related to FOXE1, we generated a zebrafish mutant that has a disruption in the nuclear localization signal in the foxe1 gene, thereby restraining nuclear access of the transcription factor. We characterized skeletal development and thyroidogenesis in these mutants, focusing on embryonic and larval stages.

Results: Mutant larvae showed aberrant skeletal phenotypes in the ceratohyal cartilage and had reduced whole body levels of Ca, Mg and P, indicating a critical role for foxe1 in early skeletal development. Markers of bone and cartilage (precursor) cells were differentially expressed in mutants in post-migratory cranial neural crest cells in the pharyngeal arch at 1 dpf, at induction of chondrogenesis at 3 dpf and at the start of endochondral bone formation at 6 dpf. Foxe1 protein was detected in differentiated thyroid follicles, suggesting a role for the transcription factor in thyroidogenesis, but thyroid follicle morphology or differentiation were unaffected in mutants.

Discussion: Taken together, our findings highlight the conserved role of Foxe1 in skeletal development and thyroidogenesis, and show differential signaling of osteogenic and chondrogenic genes related to foxe1 mutation.

Analysis of candidate genes for cleft lip ± cleft palate using murine single-cell expression data

Introduction: Cleft lip ± cleft palate (CL/P) is one of the most common birth defects. Although research has identified multiple genetic risk loci for different types of CL/P (i.e., syndromic or non-syndromic forms), determining the respective causal genes and understanding the relevant functional networks remain challenging. The recent introduction of single-cell RNA sequencing (scRNA-seq) has provided novel opportunities to study gene expression patterns at cellular resolution. The aims of our study were to: (i) aggregate available scRNA-seq data from embryonic mice and provide this as a resource for the craniofacial community; and (ii) demonstrate the value of these data in terms of the investigation of the gene expression patterns of CL/P candidate genes. Methods and Results: First, two published scRNA-seq data sets from embryonic mice were re-processed, i.e., data representing the murine time period of craniofacial development: (i) facial data from embryonic day (E) E11.5; and (ii) whole embryo data from E9.5-E13.5 from the Mouse Organogenesis Cell Atlas (MOCA). Marker gene expression analyses demonstrated that at E11.5, the facial data were a high-resolution representation of the MOCA data. Using CL/P candidate gene lists, distinct groups of genes with specific expression patterns were identified. Among others we identified that a co-expression network including Irf6, Grhl3 and Tfap2a in the periderm, while it was limited to Irf6 and Tfap2a in palatal epithelia, cells of the ectodermal surface, and basal cells at the fusion zone. The analyses also demonstrated that additional CL/P candidate genes (e.g., Tpm1, Arid3b, Ctnnd1, and Wnt3) were exclusively expressed in Irf6+ facial epithelial cells (i.e., as opposed to Irf6- epithelial cells). The MOCA data set was finally used to investigate differences in expression profiles for candidate genes underlying different types of CL/P. These analyses showed that syndromic CL/P genes (syCL/P) were expressed in significantly more cell types than non-syndromic CL/P candidate genes (nsCL/P). Discussion: The present study illustrates how scRNA-seq data can empower research on craniofacial development and disease.

A new FOXE1 homozygous frameshift variant expands the genotypic and phenotypic spectrum of Bamforth-Lazarus syndrome

Bamforth-Lazarus syndrome is a rare autosomal recessive disease caused by biallelic loss-of-function variants in the FOXE1 gene. The condition is characterized by congenital hypothyroidism due to thyroid agenesis or thyroid hypoplasia, cleft palate, spiky hair, with or without choanal atresia, and bifid epiglottis. To date, seven pathogenic variants have been reported in the FOXE1 gene causing Bamforth-Lazarus syndrome. Here we report a novel homozygous loss-of-function variant in the FOXE1 gene NM_004473.4:c.141dupC:p.(Leu49Profs*75) leading to congenital hypothyroidism due to thyroid agenesis, scalp hair abnormalities, cleft palate, small areola, cafe-au-lait spots, mild bilateral hearing loss, skin abnormalities, and facial dysmorphism. We describe the evolving phenotype in the patient with age and review previous variants reported in FOXE1. This report further expands the clinical and molecular spectrum of Bamforth-Lazarus syndrome.

Immunohistochemical Evaluation of BARX1, DLX4, FOXE1, HOXB3, and MSX2 in Nonsyndromic Cleft Affected Tissue

Background

Nonsyndromic craniofacial clefts are relatively common congenital malformations which could create a significant negative effect on the health status and life quality of affected individuals within the pediatric population. Multiple cleft candidate genes and their coded proteins have been described with their possible involvement during cleft formation. Some of these proteins like Homeobox Protein BarH-like 1 (BARX1), Distal-Less Homeobox 4 (DLX4), Forkhead Box E1 (FOXE1), Homeobox Protein Hox-B3 (HOXB3), and Muscle Segment Homeobox 2 (MSX2) have been associated with the formation of craniofacial clefts. Understanding the pathogenetic mechanisms of nonsyndromic craniofacial cleft formation could provide a better knowledge in cleft management and could be a possible basis for development and improvement of cleft treatment options. This study investigates the presence of BARX1, DLX4, FOXE1, HOXB3, and MSX2 positive cells by using immunohistochemistry in different types of cleft-affected tissue while determining their possible connection with cleft pathogenesis process.

Materials and Methods

Craniofacial cleft tissue material was obtained during cleft-correcting surgery from patients with nonsyndromic craniofacial cleft diagnosis. Tissue material was gathered from patients who had unilateral cleft lip (n=36), bilateral cleft lip (n=13), and cleft palate (n=26). Control group (n=7) tissue material was received from individuals without any craniofacial clefts. The number of factor positive cells in the control group and patient group tissue was evaluated by using the semiquantitative counting method. Data was evaluated with the use of nonparametric statistical methods.

Results

Statistically significant differences were identified between the number of BARX1, FOXE1, HOXB3, and MSX2-containing cells in controls and cleft patient groups but no statistically significant difference was found for DLX4. Statistically significant correlations between the evaluated factors were also notified in cleft patient groups.

Conclusions

HOXB3 could be more associated with morphopathogenesis of unilateral cleft lip during postnatal course of the disorder. FOXE1 and BARX1 could be involved with both unilateral and bilateral cleft lip morphopathogenesis. The persistence of MSX2 in all evaluated cleft types could indicate its possible interaction within multiple cleft types. DLX4 most likely is not involved with postnatal cleft morphopathogenesis process.

ZFP36L2 Role in Thyroid Functionality

Thyroid hormone levels are usually genetically determined. Thyrocytes produce a unique set of enzymes that are dedicated to thyroid hormone synthesis. While thyroid transcriptional regulation is well-characterized, post-transcriptional mechanisms have been less investigated. Here, we describe the involvement of ZFP36L2, a protein that stimulates degradation of target mRNAs, in thyroid development and function, by in vivo and in vitro gene targeting in thyrocytes. Thyroid-specific Zfp36l2-/- females were hypothyroid, with reduced levels of circulating free Thyroxine (cfT4) and Triiodothyronine (cfT3). Their hypothyroidism was due to dyshormonogenesis, already evident one week after weaning, while thyroid development appeared normal. We observed decreases in several thyroid-specific transcripts and proteins, such as Nis and its transcriptional regulators (Pax8 and Nkx2.1), and increased apoptosis in Zfp36l2-/- thyroids. Nis, Pax8, and Nkx2.1 mRNAs were also reduced in Zfp36l2 knock-out thyrocytes in vitro (L2KO), in which we confirmed the increased apoptosis. Finally, in L2KO cells, we showed an altered response to TSH stimulation regarding both thyroid-specific gene expression and cell proliferation and survival. This result was supported by increases in P21/WAF1 and p-P38MAPK levels. Mechanistically, we confirmed Notch1 as a target of ZFP36L2 in the thyroid since its levels were increased in both in vitro and in vivo models. In both models, the levels of Id4 mRNA, a potential inhibitor of Pax8 activity, were increased. Overall, the data indicate that the regulation of mRNA stability by ZFP36L2 is a mechanism that controls the function and survival of thyrocytes.

Expression Analysis of FGF/FGFR and FOX Family Proteins in Mucosal Tissue Obtained from Orofacial Cleft-Affected Children

Orofacial clefts affect hundreds of thousands of children worldwide annually and are usually corrected by a series of surgeries extending to childhood. The underlying mechanisms that lead to clefts are still unknown, mainly because of the multifactorial etiology and the myriad of interactions between genes and environmental factors. In the present study, we investigated the role and expression of candidate genes belonging to the FGF/FGFR signaling pathway and FOX family in tissue material obtained from 12 pediatric patients undergoing cleft correction surgery. The expression was investigated using immunohistochemistry (IHC) and chromogenic in-situ hybridization (CISH) in three cell/tissue types-epithelial cells, connective tissue, and endothelial cells. We found elevated expression of FGFR1 in epithelial cells while no expression was observed in endothelial cells. Further, our results elucidate the potential pathogenetic role of FGFR1 in cellular proliferation, local site inflammation, and fibrosis in cleft patients. Along with bFGF (also called FGF2), FGFR1 could play a pro-inflammatory role in clefts. Over-amplification of FGFR2 in some patients, along with bFGF, could potentially suggest roles for these genes in angiogenesis. Additionally, increased expression of FOXE1 (also called TTF2) contributes to local site inflammation. Finally, zero to low amplification of FOXO1 could suggest its potential role in inducing oxidative stress in the endothelium along with reduced epithelial apoptosis.

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.

Association between forkhead box E1 polymorphisms and risk of non-syndromic cleft lip with or without cleft palate: A meta-analysis

OBJECTIVE

The purpose of the present work was to investigate the association between forkhead box E1 (FOXE1) and the risk of non-syndromic cleft lip with or without cleft palate (NSCL/P).

MATERIALS AND METHODS

Relevant studies were searched in several professional databases up to 31 July 2019. The pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using a fixed-effect model or a random-effect model to analyse the relationship between FOXE1 polymorphisms and NSCL/P.

RESULTS

A total of four single nucleotide polymorphisms (SNPs), including rs3758249, rs4460498, rs1443434 and rs10217225, were analysed. The overall findings showed that FOXE1 rs4460498 was statistically associated with NSCL/P (including cleft lip with or without cleft palate (CL/P) and cleft palate only (CPO)). Genotypes CC and CT of rs4460498 were significantly more closely correlated with NSCL/P (including CL/P and CPO) than genotype TT (NSCL/P: TT vs CC, OR = 0.630, P = .000; TT vs TC + CC, OR = 0.775, P = .020; CL/P: TT vs CC, OR = 0.664, P = .000; TT vs TC + CC, OR = 0.738, P = .006. CPO: TT vs CC, OR = 0.761, P = .027; TT vs TC + CC, OR = 0.792, P = .045). For rs10217225, only the TT genotype might have contributed to the elevated risk of CL/P (TT vs CC OR = 2.236, P = .000). The other FOXE1 polymorphisms were not associated with NSCLP, CL/P or CPO.

CONCLUSION

The meta-analysis provided confirmation that the polymorphism of FOXE1 rs10217225 was correlated with an increased risk of CL/P, and the polymorphism of FOXE1 rs4460498 was a protective factor for NSCL/P, including CLP and CPO.

Association of rs944289, rs965513, and rs1443434 in TITF1/TITF2 with Risks of Papillary Thyroid Carcinoma and with Nodular Goiter in Northern Chinese Han Populations

OBJECTIVE

In this study, we aimed to investigate the associations of three single-nucleotide polymorphisms (SNPs) on TITF1/TITF2 (rs944289, rs965513, and rs1443434) with susceptibility to papillary thyroid carcinoma (PTC) and with nodular goiter (NG) in northern Chinese Han populations.

METHODS

We performed a case-control study comprising 861 PTC patients, 562 NG patients, and 896 normal controls (NCs). One TITF1 SNP (rs944289) and two TITF2 SNPs (rs965513 and rs1443434) were genotyped. Departures from Hardy-Weinberg equilibrium (HWE) in the control group were evaluated using chi-square test. Associations of the SNPs with PTC and with NG were assessed by unconditional logistic regression using the online SNPStats program. Bonferroni correction was performed for multiple tests in genotype analyses. Data analysis was performed by SPSS24.0 unless otherwise specified.

RESULTS

For rs944289, T allele was associated with increased risks for both PTC (OR = 1.23, 95% CI: 1.08-1.41, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50, P=0.002) and NG (OR = 1.28, 95% CI: 1.10-1.50.

CONCLUSIONS

There are associations of rs944289 and rs1443434 polymorphisms with PTC risk and association of rs944289 polymorphism with NG risk. Haplotypes T-G-G and T-G-T are risk haplotypes of PTC and NG, respectively.

Double knock-out of Hmga1 and Hipk2 genes causes perinatal death associated to respiratory distress and thyroid abnormalities in mice

The serine–threonine kinase homeodomain-interacting protein kinase 2 (HIPK2) modulates important cellular functions during development, acting as a signal integrator of a wide variety of stress signals, and as a regulator of transcription factors and cofactors. We have previously demonstrated that HIPK2 binds and phosphorylates High-Mobility Group A1 (HMGA1), an architectural chromatinic protein ubiquitously expressed in embryonic tissues, decreasing its binding affinity to DNA. To better define the functional role of HIPK2 and HMGA1 interaction in vivo, we generated mice in which both genes are disrupted. About 50% of these Hmga1/Hipk2 double knock-out (DKO) mice die within 12 h of life (P1) for respiratory failure. The DKO mice present an altered lung morphology, likely owing to a drastic reduction in the expression of surfactant proteins, that are required for lung development. Consistently, we report that both HMGA1 and HIPK2 proteins positively regulate the transcriptional activity of the genes encoding the surfactant proteins. Moreover, these mice display an altered expression of thyroid differentiation markers, reasonably because of a drastic reduction in the expression of the thyroid-specific transcription factors PAX8 and FOXE1, which we demonstrate here to be positively regulated by HMGA1 and HIPK2. Therefore, these data indicate a critical role of HIPK2/HMGA1 cooperation in lung and thyroid development and function, suggesting the potential involvement of their impairment in the pathogenesis of human lung and thyroid diseases.

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.

Chromosomal microarray and whole exome sequencing identify genetic causes of congenital hypothyroidism with extra-thyroidal congenital malformations

BACKGROUND

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder. Although most patients present with isolated CH, some patients present with CH and extra-thyroidal congenital malformations (ECMs), for which less is known about the underlying genetics. The aim of this study was to investigate the genetic mechanisms in patients with CH and ECMs using chromosomal microarray (CMA) and whole exome sequencing (WES).

METHODS

Peripheral venous blood samples were collected from 16 patients with CH and ECMs. Genomic DNA was extracted from peripheral blood leukocytes. CMA and WES were performed to detect copy number and single nucleotide variants.

RESULTS

CMA identified clinically significant copy number variants in 7 patients consistent with their phenotypes. For 6 of them, the genotype and phenotype suggested a syndromic diagnosis, and the remaining patient carried a pathogenic microdeletion and microduplication including GLIS3. WES analysis identified 9 different variants in 7 additional patients. The variants included 2 known mutations (c.1096C>T (p.Arg366Trp) in KCNQ1 and c.848C>A (p.Pro283Gln) in NKX2-5) and 7 novel variants: one nonsense mutation (c.4330C>T (p.Arg1444*) in ASXL3), one frameshift mutation (c.1253_1259delACTCTGG (p.Asp418fs) in TG), three missense variants (c.1472C>T (p.Thr491Ile) in TG, c.4604A>G (p.Asp1535Gly) in TG, and c.2139G>T (p.Glu713Asp) in DUOX2, and two splice site variants (c.944-1G>C and c.3693 + 1G>T) in DUOX2.

CONCLUSIONS

We report the first genetic study of CH patients with ECMs using CMA and WES. Overall, our detection rate for pathogenic and possibly pathogenic variants was 87.5% (14/16). We report 7 novel variants, expanding the mutational spectrum of TG, DUOX2, and ASXL3.

3D Modeling of Esophageal Development using Human PSC-Derived Basal Progenitors Reveals a Critical Role for Notch Signaling

Pluripotent stem cells (PSCs) could provide a powerful system to model development of the human esophagus, whose distinct tissue organization compared to rodent esophagus suggests that developmental mechanisms may not be conserved between species. We therefore established an efficient protocol for generating esophageal progenitor cells (EPCs) from human PSCs. We found that inhibition of TGF-ß and BMP signaling is required for sequential specification of EPCs, which can be further purified using cell-surface markers. These EPCs resemble their human fetal counterparts and can recapitulate normal development of esophageal stratified squamous epithelium during in vitro 3D cultures and in vivo. Importantly, combining hPSC differentiation strategies with mouse genetics elucidated a critical role for Notch signaling in the formation of this epithelium. These studies therefore not only provide an efficient approach to generate EPCs, but also offer a model system to study the regulatory mechanisms underlying development of the human esophagus.

rs965513 polymorphism as a common risk marker is associated with papillary thyroid cancer

Papillary thyroid cancer (PTC) is the most common type of thyroid cancer. With the rapid development of genome-wide association studies (GWAS), many genome variants associated with susceptibility to PTC have been identified, including the single nucleotide polymorphism rs965513 (9q22.33) near FOXE1. To evaluate the association between rs965513 and PTC in different ethnicities and countries, we conducted a meta-analysis using relatively large-scale samples from 23 studies (N = 163,136; 20,736 cases and 142,400 controls) by searching the PubMed and Google Scholar databases. Significant heterogeneity caused by different populations among the selected studies was observed. The A allele of rs965513 polymorphism was shown to be highly associated with risk of thyroid cancer, with odds ratios of 1.58 (95% CI 1.32–1.90) in all populations, 1.65 (95% CI 1.31–2.07)) in Caucasian populations and 1.49 in Asian populations. Compared to the dominant and recessive models, we observed the highest odds ratio (OR = 2.80, 95% CI 2.12–3.69) in the homozygous model. These results revealed that the rs965513 polymorphism is a risk factor for thyroid cancer

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.

Mice lacking microRNAs in Pax8-expressing cells develop hypothyroidism and end-stage renal failure

BACKGROUND

Non-coding RNAs have gained increasing attention during the last decade. The first large group of non-coding RNAs to be characterized systematically starting at the beginning of the 21st century were small oligonucleotides--the so-called microRNAs (miRNAs). By now we have learnt that microRNAs are indispensable for most biological processes including organogenesis and maintenance of organ structure and function. The role of microRNAs has been studied extensively in the development of a number of organs, so far most studies focussed on e.g. the heart or the brain whilst the role of microRNAs in the development and maintenance of complex epithelial organs is less well understood. Furthermore most analyses regarding microRNA function in epithelial organs employed conditional knockout mouse models of the RNAse III Dicer to abrogate microRNA biogenesis. However, there is increasing evidence for Dicer to have multiple functions independent from microRNA maturation. Therefore Dicer independent models are needed to gain further insight into the complex biology of miRNA dependent processes.

RESULTS

Here we analyze the contribution of microRNA-dependent transcriptional control in Pax8-expressing epithelial cells. Pax8 is a transcription factor that is crucial to the development of epithelial organs. The miRNA machinery was disrupted by crossing conditional DiGeorge syndrome critical region 8 (Dgcr8) fl/fl mice to Pax8Cre mice. The Dgcr8/Drosha complex processes pri-miRNAs in the nucleus before they are exported as pre-miRNAs for further maturation by Dicer in the cytoplasm. Dgcr8 fl/fl; Pax8Cre+ knockout mice died prematurely, developed massive hypothyroidism and end stage renal disease due to a loss of miRNAs in Pax8 expressing tissue.

CONCLUSION

Pax8Cre-mediated conditional loss of DiGeorge syndrome critical region 8 (Dgcr8), an essential component of the nuclear machinery that is required for microRNA biogenesis, resulted in severe hypothyroidism, massively reduced body weight and ultimately led to renal failure and death of the animals. These data provide further insight into the importance of miRNAs in organ homeostasis using a Dicer independent model.

TITF1 and TITF2 loci variants indicate significant associations with thyroid cancer

A number of studies have investigated the influence of TITF1 and TITF2 genetic variants on thyroid carcinogenesis, but their associations remain unclear due to the controversial results. The objective of this study was to test the hypothesis that TITF1 and TITF2 variants modulate thyroid cancer susceptibility. Eligible studies were identified through online searches supplemented by manual search. Either the DerSimonian and Laird method or the Mantel-Haenszel method was used to estimate the risk of thyroid cancer (ORs and 95 % CIs). The pooled ORs were calculated assuming the allele model. We identified a total of 10 publications concerning the topic of interest. Overall, meta-analysis of rs944289 showed 1.11-fold increased risk of thyroid cancer related to the risk T allele (T vs. C: OR 1.11, 95 % CI 1.05-1.17). For rs965513, individuals carrying the risk A allele, compared to individuals with the G allele, had 31 % higher risk of thyroid cancer (A vs. G: OR 1.31, 95 % CI 1.17-1.46). Analyses in total samples for rs1867277, rs1443434, and rs907580 yielded similar associations (A vs. G: OR 1.22, 95 % CI 1.06-1.39; G vs. T: OR 1.26, 95 % CI 1.09-1.45; T vs. C: OR 1.42, 95 % CI 1.21-1.66, respectively). The significant association persisted among Caucasians in subgroup analyses for rs944289 and rs965513. The genetic susceptibility of thyroid cancer seems likely to be associated with the risk allele at rs944289 in the TITF1 gene and at rs1867277, rs965513, rs1443434, and rs907580 in the TITF2 gene.

Thyroid transcription factors in development, differentiation and disease

Identification of the thyroid transcription factors (TTFs), NKX2-1, FOXE1, PAX8 and HHEX, has considerably advanced our understanding of thyroid development, congenital thyroid disorders and thyroid cancer. The TTFs are fundamental to proper formation of the thyroid gland and for maintaining the functional differentiated state of the adult thyroid; however, they are not individually required for precursor cell commitment to a thyroid fate. Although knowledge of the mechanisms involved in thyroid development has increased, the full complement of genes involved in thyroid gland specification and the signals that trigger expression of the genes that encode the TTFs remain unknown. The mechanisms involved in thyroid organogenesis and differentiation have provided clues to identifying the genes that are involved in human congenital thyroid disorders and thyroid cancer. Mutations in the genes that encode the TTFs, as well as polymorphisms and epigenetic modifications, have been associated with thyroid pathologies. Here, we summarize the roles of the TTFs in thyroid development and the mechanisms by which they regulate expression of the genes involved in thyroid differentiation. We also address the implications of mutations in TTFs in thyroid diseases and in diseases not related to the thyroid gland.

Application of Immunohistochemistry in Thyroid Pathology

Context

Accurate classification of follicular-patterned thyroid lesions is not always an easy task on routine surgical hematoxylin-eosin–stained or cytologic fine-needle aspiration specimens. The diagnostic challenges are partially due to differential diagnostic criteria that are often subtle and subjective. In the past decades, tremendous advances have been made in molecular gene profiling of tumors and diagnostic immunohistochemistry, aiding in diagnostic accuracy and proper patient management.

Objective

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of thyroid pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine) from 1976–2013.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method may complement the morphologic assessment and aid in the accurate classification of difficult thyroid lesions.

Palatogenesis and cutaneous repair: A two-headed coin

BACKGROUND

The reparative mechanism that operates following post-natal cutaneous injury is a fundamental survival function that requires a well-orchestrated series of molecular and cellular events. At the end, the body will have closed the hole using processes like cellular proliferation, migration, differentiation and fusion.

RESULTS

These processes are similar to those occurring during embryogenesis and tissue morphogenesis. Palatogenesis, the formation of the palate from two independent palatal shelves growing towards each other and fusing, intuitively, shares many similarities with the closure of a cutaneous wound from the two migrating epithelial fronts.

CONCLUSIONS

In this review, we summarize the current information on cutaneous development, wound healing, palatogenesis and orofacial clefting and propose that orofacial clefting and wound healing are conserved processes that share common pathways and gene regulatory networks.

The paired box transcription factor Pax8 is essential for function and survival of adult thyroid cells

The transcription factor Pax8 is already known to be essential at very early stages of mouse thyroid gland development, before the onset of thyroid hormone production. In this paper we show, using a conditional inactivation strategy, that the removal of the Pax8 protein late in gland development results in severe hypothyroidism, consequent to a reduced gland size and a deranged differentiation. These results demonstrate that Pax8 is also an essential player in controlling survival and differentiation of adult thyroid follicular cells.

Role for tissue-dependent methylation differences in the expression of FOXE1 in nontumoral thyroid glands

BACKGROUND

Discordance of monozygotic twins for thyroid dysgenesis suggests that epigenetic mechanisms may underlie defects in thyroid gland development. This prompted us to evaluate whether differentially methylated regions (DMRs) can be found between human thyroids (either eutopic or ectopic) and matched leukocytes.

METHODS

To compare the genome-wide methylation profile of thyroids and leukocytes, immunoprecipitated methylated DNA was interrogated on human promoter plus CpG island tiling arrays. In addition, the methylation profile of the human FOXE1, PAX8, and NKX2.1 promoter was examined using bisulfite sequencing. Finally, the functional impact of CpG methylation of the promoter on FOXE1 expression was assessed with luciferase assays.

RESULTS

Genome-wide methylation profiling and bisulfite sequencing of CpG islands of PAX8 and NKX2.1 promoters revealed no DMR between thyroid and leukocytes. However, bisulfite sequencing revealed that the methylation level of two consecutive CpG dinucleotides (CpG14 and CpG15, which were not covered by the genome-wide array) in one CpG island of the FOXE1 promoter (-1600 to -1140 from the transcription start site) is significantly higher in leukocytes than in eutopic or ectopic thyroid tissues, suggesting that methylation of this region may decrease FOXE1 gene expression. Indeed, luciferase activities were decreased when FOXE1 promoter constructs were methylated in vitro. Moreover, derepression of luciferase activity was observed when the methylation of CpG14 and CpG15 was prevented by mutations.

CONCLUSION

We report a tissue-dependent DMR in the FOXE1 promoter. This DMR contains two consecutive CpG dinucleotides, which are epigenetic modifiers of FOXE1 expression in nontumoral tissues.

A novel FOXE1 mutation (R73S) in Bamforth-Lazarus syndrome causing increased thyroidal gene expression

BACKGROUND

Homozygous loss-of-function mutations in the FOXE1 gene have been reported in several patients with partial or complete Bamforth-Lazarus syndrome: congenital hypothyroidism (CH) with thyroid dysgenesis (usually athyreosis), cleft palate, spiky hair, with or without choanal atresia, and bifid epiglottis. Here, our objective was to evaluate potential functional consequences of a FOXE1 mutation in a patient with a similar clinical phenotype.

METHODS

FOXE1 was sequenced in eight patients with thyroid dysgenesis and cleft palate. Transient transfection was performed in HEK293 cells using the thyroglobulin (TG) and thyroid peroxidase (TPO) promoters in luciferase reporter plasmids to assess the functional impact of the FOXE1 mutations. Primary human thyrocytes transfected with wild type and mutant FOXE1 served to assess the impact of the mutation on endogenous TG and TPO expression.

RESULTS

We identified and characterized the function of a new homozygous FOXE1 missense mutation (p.R73S) in a boy with a typical phenotype (athyreosis, cleft palate, and partial choanal atresia). This new mutation located within the forkhead domain was inherited from the heterozygous healthy consanguineous parents. In vitro functional studies in HEK293 cells showed that this mutant gene enhanced the activity of the TG and TPO gene promoters (1.5-fold and 1.7-fold respectively vs. wild type FOXE1; p<0.05), unlike the five mutations previously reported in Bamforth-Lazarus syndrome. The gain-of-function effect of the FOXE1-p.R73S mutant gene was confirmed by an increase in endogenous TG production in primary human thyrocytes.

CONCLUSION

We identified a new homozygous FOXE1 mutation responsible for enhanced expression of the TG and TPO genes in a boy whose phenotype is similar to that reported previously in patients with loss-of-function FOXE1 mutations. This finding further delineates the role for FOXE1 in both thyroid and palate development, and shows that enhanced gene activity should be considered among the mechanisms underlying Bamforth-Lazarus syndrome.

Digital imaging analysis to assess scar phenotype

In order to understand the link between the genetic background of patients and wound clinical outcomes, it is critical to have a reliable method to assess the phenotypic characteristics of healed wounds. In this study, we present a novel imaging method that provides reproducible, sensitive, and unbiased assessments of postsurgical scarring. We used this approach to investigate the possibility that genetic variants in orofacial clefting genes are associated with suboptimal healing. Red-green-blue digital images of postsurgical scars of 68 patients, following unilateral cleft lip repair, were captured using the 3dMD imaging system. Morphometric and colorimetric data of repaired regions of the philtrum and upper lip were acquired using ImageJ software, and the unaffected contralateral regions were used as patient-specific controls. Repeatability of the method was high with intraclass correlation coefficient score > 0.8. This method detected a very significant difference in all three colors, and for all patients, between the scarred and the contralateral unaffected philtrum (p ranging from 1.20(-05) to 1.95(-14) ). Physicians' clinical outcome ratings from the same images showed high interobserver variability (overall Pearson coefficient = 0.49) as well as low correlation with digital image analysis results. Finally, we identified genetic variants in TGFB3 and ARHGAP29 associated with suboptimal healing outcome.

Quantitative assessment of common genetic variants on FOXE1 and differentiated thyroid cancer risk

Forkhead box E1 encodes the transcription factor FOXE1 (or TTF-2), which together with Homeobox protein NKX2-1, PAX8 and HHEX, are pivotal proteins required for thyroid gland formation, differentiation and function. Recently, genome-wide association studies have identified FOXE1 as a thyroid cancer (TC) susceptibility gene in populations of European descent. After that, a number of studies reported that the rs965513, rs1867277, and rs71369530 polymorphism in FOXE1 has been implicated in TC risk. However, the causal variants remain unknown. To derive a more precise estimation of the relationship, a meta-analysis of 9,828 TC cases and 109,995 controls from 14 case–control studies was performed. Overall, significant results were observed for rs965513 (OR = 1.71, 95% CI: 1.59–1.85, P<10⁻⁵), rs1867277 (OR = 1.64, 95% CI: 1.51–1.78, P<10⁻⁵) and rs71369530 (OR = 2.01, 95% CI: 1.66–2.44, P<10⁻⁵) polymorphism. In the subgroup analysis by ethnicity, we found that rs965513 polymorphism confer high risk for Caucasians with per-allele OR of 1.80 (95% CI: 1.69–1.92, P<10⁻⁵) compared to East Asians of 1.35 (95% CI: 1.09–1.67, P = 0.006). There was strong evidence of heterogeneity, which largely disappeared after stratification by ethnicity. In the subgroup analysis by sample size, and study design, significantly increased risks were found for the polymorphism. In conclusion, this meta-analysis demonstrated that common variations of FOXE1 are a risk factor associated with increased TC susceptibility.

The molecular causes of thyroid dysgenesis: a systematic review

BACKGROUND

Congenital hypothyroidism (CH) is a frequent disease occurring with an incidence of about 1/2500 newborns/year. In 80-85% of the cases CH is caused by alterations in thyroid morphogenesis, generally indicated by the term "thyroid dysgenesis" (TD). TD is generally a sporadic disease, but in about 5% of the cases a genetic origin has been demonstrated. In these cases, mutations in genes playing a role during thyroid morphogenesis (NKX2-1, PAX8, FOXE1, NKX2-5, TSHR) have been reported.

AIM

This work reviews the main steps of thyroid morphogenesis and all the genetic alterations associated with TD and published in the literature.

Suppression of estrogen receptor-alpha transactivation by thyroid transcription factor-2 in breast cancer cells

Estrogen receptors (ERs), which mediate estrogen actions, regulate cell growth and differentiation of a variety of normal tissues and hormone-responsive tumors through interaction with cellular factors. In this study, we show that thyroid transcription factor-2 (TTF-2) is expressed in mammary gland and acts as ERα co-repressor. TTF-2 inhibited ERα transactivation in a dose-dependent manner in MCF-7 breast cancer cells. In addition, TTF-2 directly bound to and formed a complex with ERα, colocalizing with ERα in the nucleus. In MCF-7/TTF-2 stable cell lines, TTF-2 repressed the expression of endogenous ERα target genes such as pS2 and cyclin D1 by interrupting ERα binding to target promoters and also significantly decreased cell proliferation. Taken together, these data suggest that TTF-2 may modulate the function of ERα as a corepressor and play a role in ER-dependent proliferation of mammary cells.

Novel cell surface genes expressed in the stomach primordium during gastrointestinal morphogenesis of mouse embryos

The mechanisms of gastrointestinal morphogenesis in mammals are not well understood. This is partly due to the lack of appropriate markers that are expressed with spatiotemporal specificity in the gastrointestinal tract during development. Using mouse embryos, we surveyed markers of the prospective stomach region during gastrointestinal morphogenesis. The initiation of organ bud formation occurs at E10.5 in mice. These primordia for the digestive organs protrude from a tube-like structured endoderm and have their own distinct morphogenesis. We identified 3 cell surface genes -Adra2a, Fzd5, and Trpv6 - that are expressed in the developing stomach region during gastrointestinal morphogenesis using a microarray-based screening. These novel genes will be useful in expanding our understanding of the mechanisms of gastrointestinal development.

Accelerated evolution of 3'avian FOXE1 genes, and thyroid and feather specific expression of chicken FoxE1

Background

The forkhead transcription factor gene E1 (FOXE1) plays an important role in regulation of thyroid development, palate formation and hair morphogenesis in mammals. However, avian FOXE1 genes have not been characterized and as such, codon evolution of FOXE1 orthologs in a broader evolutionary context of mammals and birds is not known.

Results

In this study we identified the avian FOXE1 gene in chicken, turkey and zebra finch, all of which consist of a single exon. Chicken and zebra finch FOXE1 are uniquely located on the sex-determining Z chromosome. In situ hybridization shows that chicken FOXE1 is specifically expressed in the developing thyroid. Its expression is initiated at the placode stage and is maintained during the stages of vesicle formation and follicle primordia. Based on this expression pattern, we propose that avian FOXE1 may be involved in regulating the evagination and morphogenesis of thyroid. Chicken FOXE1 is also expressed in growing feathers. Sequence analysis identified two microdeletions in the avian FOXE1 genes, corresponding to the loss of a transferable repression domain and an engrailed homology motif 1 (Eh1) C-terminal to the forkhead domain. The avian FOXE1 proteins exhibit a significant sequence divergence of the C-terminus compared to those of amphibian and mammalian FOXE1. The codon evolution analysis (dN/dS) of FOXE1 shows a significantly increased dN/dS ratio in the avian lineages, consistent with either a relaxed purifying selection or positive selection on a few residues in avian FOXE1 evolution. Further site specific analysis indicates that while relaxed purifying selection is likely to be a predominant cause of accelerated evolution at the 3'-region of avian FOXE1, a few residues might have evolved under positive selection.

Conclusions

We have identified three avian FOXE1 genes based on synteny and sequence similarity as well as characterized the expression pattern of the chicken FOXE1 gene during development. Our evolutionary analyses suggest that while a relaxed purifying selection is likely to be the dominant force driving accelerated evolution of avian FOXE1 genes, a few residues may have evolved adaptively. This study provides a basis for future genetic and comparative biochemical studies of FOXE1.

Palatogenesis: engineering, pathways and pathologies

Cleft palate represents the second most common birth defect and carries substantial physiologic and social challenges for affected patients, as they often require multiple surgical interventions during their lifetime. A number of genes have been identified to be associated with the cleft palate phenotype, but etiology in the majority of cases remains elusive. In order to better understand cleft palate and both surgical and potential tissue engineering approaches for repair, we have performed an in-depth literature review into cleft palate development in humans and mice, as well as into molecular pathways underlying these pathologic developments. We summarize the multitude of pathways underlying cleft palate development, with the transforming growth factor beta superfamily being the most commonly studied. Furthermore, while the majority of cleft palate studies are performed using a mouse model, studies focusing on tissue engineering have also focused heavily on mouse models. A paucity of human randomized controlled studies exists for cleft palate repair, and so far, tissue engineering approaches are limited. In this review, we discuss the development of the palate, explain the basic science behind normal and pathologic palate development in humans as well as mouse models and elaborate on how these studies may lead to future advances in palatal tissue engineering and cleft palate treatments.

Clinical review: The emerging cell biology of thyroid stem cells

CONTEXT

Stem cells are undifferentiated cells with the property of self-renewal and give rise to highly specialized cells under appropriate local conditions. The use of stem cells in regenerative medicine holds great promise for the treatment of many diseases, including those of the thyroid gland.

EVIDENCE ACQUISITION

This review focuses on the progress that has been made in thyroid stem cell research including an overview of cellular and molecular events (most of which were drawn from the period 1990-2011) and discusses the remaining problems encountered in their differentiation.

EVIDENCE SYNTHESIS

Protocols for the in vitro differentiation of embryonic stem cells, based on normal developmental processes, have generated thyroid-like cells but without full thyrocyte function. However, agents have been identified, including activin A, insulin, and IGF-I, which are able to stimulate the generation of thyroid-like cells in vitro. In addition, thyroid stem/progenitor cells have been identified within the normal thyroid gland and within thyroid cancers.

CONCLUSIONS

Advances in thyroid stem cell biology are providing not only insight into thyroid development but may offer therapeutic potential in thyroid cancer and future thyroid cell replacement therapy.

Expression of FOXL2 in human normal pituitaries and pituitary adenomas

Many transcription factors have important roles in the function and differentiation of the human pituitary adenomas. Forkhead box gene transcription factor L2, Foxl2, is expressed during mouse pituitary development and co-localizes with the expression of α-glycoprotein hormone subunit (αGSU). In addition, Foxl2 regulates expression of the αGSU gene (Cga) in cell culture. To elucidate the functional role of FOXL2 in the human pituitary, we examined the expression and localization of FOXL2 in normal human pituitaries and various types of pituitary adenomas. Human pituitary adenomas were obtained by trans-sphenoidal surgery from 67 patients. Three normal adult pituitaries were obtained from autopsies of non-endocrine cases. The localization of FOXL2 and pituitary hormones in these pituitary patients was examined by immunohistochemical staining and RT-PCR. Quantitative analysis of FOXL2 protein was performed by immunoblotting. FOXL2 was localized in the nuclei of ∼20% of normal pituitary cells that also co-expressed gonadotropins including follicule-stimulating hormone β (FSHβ), luteinizing hormone β (LHβ), and αGSU, whereas it was observed in minor proportion of thyroid-stimulating hormone (TSH)-producing cells, prolactin (PRL)-producing cells, and precursor of adrenocorticotropic hormone (ACTH)-producing cells. FOXL2 immunoreactivity was not detected in growth hormone (GH)-producing cells or S100-positive folliculo-stellate cells. In human pituitary adenomas, FOXL2 was expressed in the nuclei of the adenoma cells. FOXL2 was detected in 13 of 15 gonadotropin-subunit-producing adenoma (Gn-oma) cases and 8 of 11 null cell adenoma cases, but its incidence was reduced or not detected in the other types of adenomas. The results of this study suggest that FOXL2 contributes to the human-specific functional expression and the differentiation of gonadotroph cells and adenomas.

Thyroid-specific transcription factors and their roles in thyroid cancer

Homeodomain, forkhead domain, and paired domain-containing transcription factors play a major role in development, tissue-specific gene expression, and tissue homeostasis in organs where they are expressed. Recently, their roles in stem cell and cancer biology are emerging. In the thyroid, NKX2-1, FOXE1, and PAX8 transcription factors are responsible for thyroid organogenesis and expression of thyroid-specific genes critical for thyroid hormone synthesis. In contrast to their known roles in gene regulation, thyroid development and homeostasis, their involvement in stem cell, and/or cancer biology are still elusive. In order to further understand the nature of thyroid cancer, it is critical to determine their roles in thyroid cancer.

MSX1 and TGF-beta3 are novel target genes functionally regulated by FOXE1

FOXE1 mutations cause the Bamforth-Lazarus syndrome characterized by thyroid and craniofacial defects. Although a pioneer activity of FOXE1 in thyroid development has been reported, FOXE1 regulation in other contexts remains unexplored. We pointed to: (i) a role of FOXE1 in controlling the expression of MSX1 and TGF-β3 relevant in craniofacial development and (ii) a causative part of FOXE1 mutations or mice Foxe1(-/-) genotype in the pathogenesis of cleft palate in the Bamforth-Lazarus syndrome. The MSX1 and TGF-β3 up-regulation in response to FOXE1 at both transcriptional and translational levels and the recruitment of FOXE1 to specific binding motifs, together with the transactivation of the promoters of these genes, indicate that MSX1 and TGF-β3 are direct FOXE1 targets. Moreover, we showed that all the known forkhead-domain mutations, but not the polyalanine-stretch polymorphisms, affect the FOXE1 ability to bind to and transactivate MSX1 and TGF-β3 promoters. In 14-day Foxe1(-/-) mice embryos, Tgf-β3 and Msx1 mRNAs were almost absent in palatal shelves compared with Foxe1(+/-) embryos. Our findings give new insights into the genetic mechanisms underlying the Bamforth-Lazarus syndrome-associated facial defects.

Cranial neural crest cells on the move: their roles in craniofacial development

The craniofacial region is assembled through the active migration of cells and the rearrangement and sculpting of facial prominences and pharyngeal arches, which consequently make it particularly susceptible to a large number of birth defects. Genetic, molecular, and cellular processes must be temporally and spatially regulated to culminate in the three-dimension structures of the face. The starting constituent for the majority of skeletal and connective tissues in the face is a pluripotent population of cells, the cranial neural crest cells (NCCs). In this review we discuss the newest scientific findings in the development of the craniofacial complex as related to NCCs. Furthermore, we present recent findings on NCC diseases called neurocristopathies and, in doing so, provide clinicians with new tools for understanding a growing number of craniofacial genetic disorders.

A locus on mouse chromosome 2 is involved in susceptibility to congenital hypothyroidism and contains an essential gene expressed in thyroid

We report here the mapping of a chromosomal region responsible for strain-specific development of congenital hypothyroidism in mice heterozygous for null mutations in genes encoding Nkx2-1/Titf1 and Pax8. The two strains showing a differential predisposition to congenital hypothyroidism contain several single-nucleotide polymorphisms in this locus, one of which leads to a nonsynonymous amino acid change in a highly conserved region of Dnajc17, a member of the type III heat-shock protein-40 (Hsp40) family. We demonstrate that Dnajc17 is highly expressed in the thyroid bud and had an essential function in development, suggesting an important role of this protein in organogenesis and/or function of the thyroid gland.

Forkhead transcription factor foxe1 regulates chondrogenesis in zebrafish

Forkhead transcription factor (Fox) e1 is a causative gene for Bamforth-Lazarus syndrome, which is characterized by hypothyroidism and cleft palate. Applying degenerate polymerase chain reaction using primers specific for the conserved forkhead domain, we identified zebrafish foxe1 (foxe1). Foxe1 is expressed in the thyroid, pharynx, and pharyngeal skeleton during development; strongly expressed in the gill and weakly expressed in the brain, eye, and heart in adult zebrafish. A loss of function of foxe1 by morpholino antisense oligo (MO) exhibited abnormal craniofacial development, shortening of Meckel's cartilage and the ceratohyals, and suppressed chondrycytic proliferation. However, at 27 hr post fertilization, the foxe1 MO-injected embryos showed normal dlx2, hoxa2, and hoxb2 expression, suggesting that the initial steps of pharyngeal skeletal development, including neural crest migration and specification of the pharyngeal arch occurred normally. In contrast, at 2 dpf, a severe reduction in the expression of sox9a, colIIaI, and runx2b, which play roles in chondrocytic proliferation and differentiation, was observed. Interestingly, fgfr2 was strongly upregulated in the branchial arches of the foxe1 MO-injected embryos. Unlike Foxe1-null mice, normal thyroid development in terms of morphology and thyroid-specific marker expression was observed in foxe1 MO-injected zebrafish embryos. Taken together, our results indicate that Foxe1 plays an important role in chondrogenesis during development of the pharyngeal skeleton in zebrafish, probably through regulation of fgfr2 expression. Furthermore, the roles reported for FOXE1 in mammalian thyroid development may have been acquired during evolution.

SOX2 is an amplified lineage-survival oncogene in lung and esophageal squamous cell carcinomas

Lineage-survival oncogenes are activated by somatic DNA alterations in cancers arising from the cell lineages in which these genes play a role in normal development. Here we show that a peak of genomic amplification on chromosome 3q26.33 found in squamous cell carcinomas (SCCs) of the lung and esophagus contains the transcription factor gene SOX2, which is mutated in hereditary human esophageal malformations, is necessary for normal esophageal squamous development, promotes differentiation and proliferation of basal tracheal cells and cooperates in induction of pluripotent stem cells. SOX2 expression is required for proliferation and anchorage-independent growth of lung and esophageal cell lines, as shown by RNA interference experiments. Furthermore, ectopic expression of SOX2 here cooperated with FOXE1 or FGFR2 to transform immortalized tracheobronchial epithelial cells. SOX2-driven tumors show expression of markers of both squamous differentiation and pluripotency. These characteristics identify SOX2 as a lineage-survival oncogene in lung and esophageal SCC.

[New aspects of genetics and molecular mechanisms on thyroid morphogenesis for the understanding of thyroid dysgenesia]

The elucidation of the molecular mechanisms underlying the very early steps of thyroid organogenesis and the etiology of most cases of thyroid dysgenesis are poorly understood. Many genes have been identified as important contributors to survival, proliferation and migration of thyroid cells precursors, acting as an integrated and complex regulatory network. Moreover, by generation of mouse mutants, the studies have provided better knowledge of the role of these genes in the thyroid morphogenesis. In addition, it is likely that a subset of patients has thyroid dysgenesis as a result of mutations in regulatory genes expressed during embryogenesis. This review summarizes molecular aspects of thyroid development, describes the animal models and phenotypes known to date and provides information about novel insights into the ontogeny and pathogenesis of human thyroid dysgenesis.

FOXE1 association with both isolated cleft lip with or without cleft palate, and isolated cleft palate

Nonsyndromic orofacial clefts are a common complex birth defect caused by genetic and environmental factors and/or their interactions. A previous genome-wide linkage scan discovered a novel locus for cleft lip with or without cleft palate (CL/P) at 9q22-q33. To identify the etiologic gene, we undertook an iterative and complementary fine mapping strategy using family-based CL/P samples from Colombia, USA and the Philippines. Candidate genes within 9q22-q33 were sequenced, revealing 32 new variants. Concurrently, 397 SNPs spanning the 9q22-q33 2-LOD-unit interval were tested for association. Significant SNP and haplotype association signals (P = 1.45E - 08) narrowed the interval to a 200 kb region containing: FOXE1, C9ORF156 and HEMGN. Association results were replicated in CL/P families of European descent and when all populations were combined the two most associated SNPs, rs3758249 (P = 5.01E - 13) and rs4460498 (P = 6.51E - 12), were located inside a 70 kb high linkage disequilibrium block containing FOXE1. Association signals for Caucasians and Asians clustered 5' and 3' of FOXE1, respectively. Isolated cleft palate (CP) was also associated, indicating that FOXE1 plays a role in two phenotypes thought to be genetically distinct. Foxe1 expression was found in the epithelium undergoing fusion between the medial nasal and maxillary processes. Mutation screens of FOXE1 identified two family-specific missense mutations at highly conserved amino acids. These data indicate that FOXE1 is a major gene for CL/P and provides new insights for improved counseling and genetic interaction studies.

Genome scan, fine-mapping, and candidate gene analysis of non-syndromic cleft lip with or without cleft palate reveals phenotype-specific differences in linkage and association results

OBJECTIVES

Non-syndromic orofacial clefts, i.e. cleft lip (CL) and cleft palate (CP), are among the most common birth defects. The goal of this study was to identify genomic regions and genes for CL with or without CP (CL/P).

METHODS

We performed linkage analyses of a 10 cM genome scan in 820 multiplex CL/P families (6,565 individuals). Significant linkage results were followed by association analyses of 1,476 SNPs in candidate genes and regions, utilizing a weighted false discovery rate (wFDR) approach to control for multiple testing and incorporate the genome scan results.

RESULTS

Significant (multipoint HLOD >or=3.2) or genome-wide-significant (HLOD >or=4.02) linkage results were found for regions 1q32, 2p13, 3q27-28, 9q21, 12p11, 14q21-24 and 16q24. SNPs in IRF6 (1q32) and in or near FOXE1 (9q21) reached formal genome-wide wFDR-adjusted significance. Further, results were phenotype dependent in that the IRF6 region results were most significant for families in which affected individuals have CL alone, and the FOXE1 region results were most significant in families in which some or all of the affected individuals have CL with CP.

CONCLUSIONS

These results highlight the importance of careful phenotypic delineation in large samples of families for genetic analyses of complex, heterogeneous traits such as CL/P.

Thyrotropin-independent induction of thyroid endoderm from embryonic stem cells by activin A

To model the differentiation of thyroid epithelial cells, we examined embryoid bodies derived from undifferentiated murine embryonic stem cells treated with activin A to induce endoderm differentiation, the germ layer from which thyroid cells occur. The resulting endodermal cells were then further exposed to TSH and/or IGF-I for up to 21 d. Oct-4 and REX1 expression, required to sustain stem cell self-renewal and pluripotency, were appropriately down-regulated, whereas GATA-4, and alpha-fetoprotein, both endodermal-specific markers, increased as the embryonic stem cells were exposed to activin A. By d 5 culture, TSH receptor (TSHR) and sodium iodide symporter (NIS) gene and protein expression were markedly induced. Cells isolated by the fluorescence-activated cell sorter simultaneously expressed not only TSHR and NIS proteins but also PAX8 mRNA, an expression pattern unique to thyroid cells and expected in committed thyroid progenitor cells. Such expression continued until d 21 with no influence seen by the addition of TSH or IGF-I. The sequence of gene expression changes observed in these experiments demonstrated the emergence of definitive thyroid endoderm. The activin A induction of thyroid-specific markers, NIS and TSHR, occurred in the absence of TSH stimulation, and, therefore, the emergence of thyroid endoderm in vitro paralleled the emergence of thyroid cells in TSHR-knockout mice. Activin A is clearly a major regulator of thyroid endoderm.

Transcriptional dynamics of endodermal organ formation

Although endodermal organs including the liver, pancreas, and intestine are of significant therapeutic interest, the mechanism by which the endoderm is divided into organ domains during embryogenesis is not well understood. To better understand this process, global gene expression profiling was performed on early endodermal organ domains. This global analysis was followed up by dynamic immunofluorescence analysis of key transcription factors, uncovering novel expression patterns as well as cell surface proteins that allow prospective isolation of specific endodermal organ domains. Additionally, a repressive interaction between Cdx2 and Sox2 was found to occur at the prospective stomach-intestine border, with the hepatic and pancreatic domains forming at this boundary, and Hlxb9 was revealed to have graded expression along the dorsal-ventral axis. These results contribute to understanding the mechanism of endodermal organogenesis and should assist efforts to replicate this process using pluripotent stem cells.

Common variants on 9q22.33 and 14q13.3 predispose to thyroid cancer in European populations

In order to search for sequence variants conferring risk of thyroid cancer we conducted a genome-wide association study in 192 and 37,196 Icelandic cases and controls, respectively, followed by a replication study in individuals of European descent. Here we show that two common variants, located on 9q22.33 and 14q13.3, are associated with the disease. Overall, the strongest association signals were observed for rs965513 on 9q22.33 (OR = 1.75; P = 1.7 x 10(-27)) and rs944289 on 14q13.3 (OR = 1.37; P = 2.0 x 10(-9)). The gene nearest to the 9q22.33 locus is FOXE1 (TTF2) and NKX2-1 (TTF1) is among the genes located at the 14q13.3 locus. Both variants contribute to an increased risk of both papillary and follicular thyroid cancer. Approximately 3.7% of individuals are homozygous for both variants, and their estimated risk of thyroid cancer is 5.7-fold greater than that of noncarriers. In a study on a large sample set from the general population, both risk alleles are associated with low concentrations of thyroid stimulating hormone (TSH), and the 9q22.33 allele is associated with low concentration of thyroxin (T(4)) and high concentration of triiodothyronine (T(3)).

The forkhead factor FoxE1 binds to the thyroperoxidase promoter during thyroid cell differentiation and modifies compacted chromatin structure

The Forkhead box (Fox) transcription factors play diverse roles in differentiation, development, hormone responsiveness, and aging. A pioneer activity of the Forkhead factors in developmental processes has been reported, but how this may apply to other contexts of Forkhead factor regulation remains unexplored. In this study, we address the pioneer activity of the thyroid-specific factor FoxE1 during thyroid differentiation. In response to hormone induction, FoxE1 binds to the compacted chromatin of the inactive thyroperoxidase (TPO) promoter, which coincides with the appearance of strong DNase I hypersensitivity at the FoxE1 binding site. In vitro, FoxE1 can bind to its site even when this is protected by a nucleosome, and it creates a local exposed domain specifically on H1-compacted TPO promoter-containing nucleosome arrays. Furthermore, nuclear factor 1 binds to the TPO promoter simultaneously with FoxE1, and this binding has an additive effect on FoxE1-mediated chromatin structure alteration. On the basis of our findings, we propose that FoxE1 is a pioneer factor whose primary mechanistic role in mediating the hormonal regulation of the TPO gene is to enable other regulatory factors to access the chromatin. The presented model extends the reported pioneer activity of the Forkhead factors to processes involved in hormone-induced differentiation.