Role Of TBX2 Research Articles

SAT673 Novel Mutation Of TBX3 Associated With Morbid Obesity In Human

Abstract Disclosure: H.R. Alkaissi: None. B. Ji: None. S. McFarlane: None. Background: TBX3 is a transcription involved in the development of the heart conduction system, apocrine and mammary glands, limbs, and lung development and maturation, with variable oncogenic roles. Recently, the role of TBX3 and body weight control has been demonstrated in animal models, showing an essential role for TBX3 in hypothalamic arcuate neuronal maturation, function, and identity [1]. Case: 26-year-old woman referred for the management of morbid obesity and menstrual irregularities. The patient weighed 330 lbs, with a BMI of 55 kg/m2, with hypertension T2DM. The patient had a normal development until age five, after which she experienced regression in milestones and lost the ability to communicate, and was diagnosed with autism. She had a history of food-seeking behavior, leading to progressive weight gain, which was managed by blocking access to food, such as locking the fridge. The patient's weight fluctuated from 290 lbs to 330 lbs. Family history of T2DM in her maternal relatives. She was diagnosed with T2DM at the age of 18, with HbA1c level of 9.4%. Autoantibody testing was negative for glutamic acid decarboxylase (GAD), islet cell antibody (ICA), and zinc transporter 8 (ZnT8). The fasting C-peptide level was detectable at 1.87 ng/mL. T2DM was well controlled with an HbA1C range of 6.0-6.7% with the use of short and long-acting insulin regimen. However, with improved glycemic control, short-acting insulin was stopped and she was started on liraglutide. Syndromic obesity was suspected due to early-onset of the disease and the developmental regression. Testing for Prader-Willi syndrome was negative, based on a normal chromosome 15 methylation study. Leptin levels were elevated at 66 ng/mL, prompting further testing for obesity-related genetic mutations. Next-generation sequencing and targeted Sanger sequencing for 79 genes associated with obesity in human and animal models was performed. A novel mutation was identified in TBX3 activation domain, c. C1513T (p.P505S). UniProt peptide sequence alignment analyzed for sequence conservation. ClinVar, HGMD and GWAS Catalogue databases screened for similar variants. Discussion: We present the first case in human, where novel TBX3 mutation results in hypothalamic dysfunction, leptin resistance manifesting as morbid obesity, hyperphagia, and menstrual irregularities. The reported mutation in the activation domain (A) of TBX3. In silico analysis showed high evolutionary conservation of the mutated domain (across vertebrate species), indicating the mutation is likely pathogenic.

ScRNA-Seq Reveals New Enteric Nervous System Roles for GDNF, NRTN, and TBX3.

Background and AimsBowel function requires coordinated activity of diverse enteric neuron subtypes. Our aim was to define gene expression in these neuron subtypes to facilitate development of novel therapeutic approaches to treat devastating enteric neuropathies, and to learn more about enteric nervous system function.MethodsTo identify subtype–specific genes, we performed single-nucleus RNA-seq on adult mouse and human colon myenteric plexus, and single-cell RNA-seq on E17.5 mouse ENS cells from whole bowel. We used immunohistochemistry, select mutant mice, and calcium imaging to validate and extend results.ResultsRNA-seq on 635 adult mouse colon myenteric neurons and 707 E17.5 neurons from whole bowel defined seven adult neuron subtypes, eight E17.5 neuron subtypes and hundreds of differentially expressed genes. Manually dissected human colon myenteric plexus yielded RNA-seq data from 48 neurons, 3798 glia, 5568 smooth muscle, 377 interstitial cells of Cajal, and 2153 macrophages. Immunohistochemistry demonstrated differential expression for BNC2, PBX3, SATB1, RBFOX1, TBX2, and TBX3 in enteric neuron subtypes. Conditional Tbx3 loss reduced NOS1-expressing myenteric neurons. Differential Gfra1 and Gfra2 expression coupled with calcium imaging revealed that GDNF and neurturin acutely and differentially regulate activity of ∼50% of myenteric neurons with distinct effects on smooth muscle contractions.ConclusionSingle cell analyses defined genes differentially expressed in myenteric neuron subtypes and new roles for TBX3, GDNF and NRTN. These data facilitate molecular diagnostic studies and novel therapeutics for bowel motility disorders.

T-box Transcription Factor Tbx3 Contributes to Human Hepatocellular Carcinoma Cell Migration and Invasion by Repressing E-Cadherin Expression.

Tbx3, a member of the T-box family of transcription factors, contributes directly to tumor formation, migration, and invasion. However, the role of Tbx3 in the metastasis of HCC remains unclear. In the present study, Tbx3 expression was detected in HCC tissues and cells by Western blot, and Tbx3 expression was regulated by use of siRNAs or lentivirus-mediated vectors. Here we found that Tbx3 protein expression increased in HCC tissues and cell lines. Tbx3 expression was positively associated with multiple tumor nodes, venous infiltration, and advanced TNM tumor stage. Survival analysis demonstrated that Tbx3 expression was an independent prognostic factor for HCC patients. In vitro assays further validated that Tbx3 indeed prompted HCC cell migration and invasion. In addition, Tbx3 expression was negatively related with E-cadherin expression in HCC tissues. Mechanically, Tbx3 inhibited the expression of E-cadherin, and then facilitated epithelial–mesenchymal transition (EMT) of HCC cells. Furthermore, the effect of Tbx3 knockdown on HCC cells was attenuated by E-cadherin knockdown. In conclusion, Tbx3 may be a novel prognostic factor, and it contributes to HCC cell migration, invasion, and EMT by repressing E-cadherin expression. Thus, Tbx3 may be recommended as a therapeutic target for HCC patients.

The T-Box Transcription Factor TBX2 Regulates Cell Proliferation in the Retinal Pigment Epithelium

ABSTRACTPurpose: Vertebrate eye development and function critically depend on the regulation of proliferation of retinal pigment epithelium (RPE) cells. Hence, a thorough analysis of the molecular parameters controlling RPE cell proliferation is crucial for our understanding of the physiology of this cell type both in health and in disease. The T-box transcription factor TBX2 is an important cell cycle regulator in development and oncogenesis, but its specific role in RPE cell proliferation is far from clear. The purpose of the present study is to investigate whether TBX2 plays any role in regulating RPE cell proliferation.Materials and methods: The expression of TBX2 in RPE cells was analyzed in wildtype mice and ARPE-19 cells by co-staining for RPE-specific markers and cell proliferation. In vitro, the role of TBX2 was studied by manipulating its levels using RNAi and analyzing the effects on DNA synthesis and cell growth and on gene expression at the RNA and protein levels.Results: Here, we find that TBX2 is expressed in RPE cells both in vivo and in vitro. Specific knockdown of TBX2 in the human RPE cell line ARPE-19 leads to an accumulation of cells at G1. This cell cycle arrest is accompanied by changes in the levels of known cell cycle regulators and, in particular, by an increase in the levels of the tumor-suppressor gene CCAAT/enhancer-binding protein delta (CEBPD). In fact, simultaneous knockdown of both TBX2 and CEBPD interferes with the reduction in cell proliferation brought about by TBX2 reduction alone.Conclusions: Our results provide novel insights into the regulatory mechanisms of cell proliferation in the RPE and may contribute to our understanding of normal RPE maintenance and its pathology in degenerative and proliferative disorders of the eye.

Development of a subset of forelimb muscles and their attachment sites requires the ulnar-mammary syndrome gene Tbx3

In the vertebrate limb over 40 muscles are arranged in a precise pattern of attachment via muscle connective tissue and tendon to bone and provide an extensive range of motion. How the development of somite-derived muscle is coordinated with the development of lateral plate-derived muscle connective tissue, tendon and bone to assemble a functional limb musculoskeletal system is a long-standing question. Mutations in the T-box transcription factor, TBX3, have previously been identified as the genetic cause of ulnar-mammary syndrome (UMS), characterized by distinctive defects in posterior forelimb bones. Using conditional mutagenesis in mice, we now show that TBX3 has a broader role in limb musculoskeletal development. TBX3 is not only required for development of posterior forelimb bones (ulna and digits 4 and 5), but also for a subset of posterior muscles (lateral triceps and brachialis) and their bone eminence attachment sites. TBX3 specification of origin and insertion sites appears to be tightly linked with whether these particular muscles develop and may represent a newly discovered mechanism for specification of anatomical muscles. Re-examination of an individual with UMS reveals similar previously unrecognized muscle and bone eminence defects and indicates a conserved role for TBX3 in regulating musculoskeletal development.

Abstract 4131: Blocking endogenous TBX2 abrogates prostate cancer bone metastasis through WNT signaling

Abstract Bone metastasis is a crucial turning point in the progression of PCa and is seen in > 90% of the lethal cases. Identifying factors that mediate the metastatic spread and subsequent remodeling of the bone is highly relevant to successful therapeutic intervention in advanced human prostate cancer (PCa). TBX2, a transcription factor that belongs to the T-box family negatively regulates p21 cell cycle inhibitor and is known to play critical roles during embryonic development and cancer progression. Interestingly, a recent report found TBX2 over-expression in the bone metastases from patients with castrate resistant prostate cancer. We found TBX2 over-expression in human prostate cancer specimens and in aggressive androgen independent human PCa cell lines. Further, we found TBX2 over-expression in bone metastases in multiple xenograft mouse models of human PCa progression. Blocking endogenous TBX2 in PC3 and ARCaPM PCa cells through the use of a dominant negative construct resulted in decreased proliferation, colony formation and invasion in vitro. Utilizing various pre-clinical xenograft mouse models, we found that blocking endogenous TBX2 in PCa cells leads to decreased invasion and abrogation of bone and soft tissue metastasis in vivo. Further, utilizing the intra-tibial mouse model of growth in the bone microenvironment, we found that blocking endogenous TBX2 in PCa cells dramatically reduces bone remodeling. Additionally we found that TBX2 acts upstream of the canonical WNT (WNT3A) signaling in PCa and positively regulates its transcription by binding to its promoter. Further, rescue of WNT3A levels in PCa cells in the context of blocking endogenous TBX2 rescues the metastatic ability of the cells in vivo. Taken together, our findings highlight a novel and critical role of TBX2 in PCa progression, metastasis and the subsequent bone remodeling, and that TBX2 function in PCa is mediated through the canonical WNT signaling. Citation Format: Srinivas Nandana, Manisha Tripathi, Peng Duan, Gina Chu, Haiyen E. Zhau, Robert J. Matusik, Leland W.K. Chung. Blocking endogenous TBX2 abrogates prostate cancer bone metastasis through WNT signaling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4131.

The T-box transcription factor 3 is a promising biomarker and a key regulator of the oncogenic phenotype of a diverse range of sarcoma subtypes.

Sarcomas represent a complex group of malignant neoplasms of mesenchymal origin and their heterogeneity poses a serious diagnostic and therapeutic challenge. There is therefore a need to elucidate the molecular mechanisms underpinning the pathogenesis of the more than 70 distinguishable sarcoma subtypes. The transcription factor TBX3, a critical developmental regulator, is overexpressed in several cancers of epithelial origin where it contributes to tumorigenesis by different molecular mechanisms. However, the status and role of TBX3 in sarcomas have not been reported. Here we show that a diverse subset of soft tissue and bone sarcoma cell lines and patient-derived sarcoma tissues express high levels of TBX3. We further explore the significance of this overexpression using a small interferring RNA approach and demonstrate that TBX3 promotes the migratory ability of chondrosarcoma, rhabdomyosarcoma and liposarcoma cells but inhibits fibrosarcoma cell migration. This suggested that TBX3 may play a key role in the development of different sarcoma subtypes by functioning as either an oncoprotein or as a brake to prevent tumour progression. To further explore this, TBX3 knockdown and overexpression cell culture models were established using chondrosarcoma and fibrosarcoma cells as representatives of each scenario, and the resulting cells were characterized with regard to key features of tumorigenesis. Results from in vitro and in vivo assays reveal that, while TBX3 promotes substrate-dependent and -independent cell proliferation, migration and tumour formation in chondrosarcoma cells, it discourages fibrosarcoma formation. Our findings provide novel evidence linking TBX3 to cancers of mesenchymal origin. Furthermore, we show that TBX3 may be a biomarker for the diagnosis of histologically dynamic sarcoma subtypes and that it impacts directly on their oncogenic phenotype. Indeed, we reveal that TBX3 may exhibit oncogene or tumour suppressor activity in sarcomas, which suggests that its role in cancer progression may rely on cellular context.

Transcriptional repressor Tbx3 is required for the hormone-sensing cell lineage in mammary epithelium.

The transcriptional repressor Tbx3 is involved in lineage specification in several tissues during embryonic development. Germ-line mutations in the Tbx3 gene give rise to Ulnar-Mammary Syndrome (comprising reduced breast development) and Tbx3 is required for mammary epithelial cell identity in the embryo. Notably Tbx3 has been implicated in breast cancer, which develops in adult mammary epithelium, but the role of Tbx3 in distinct cell types of the adult mammary gland has not yet been characterized. Using a fluorescent reporter knock-in mouse, we show that in adult virgin mice Tbx3 is highly expressed in luminal cells that express hormone receptors, and not in luminal cells of the alveolar lineage (cells primed for milk production). Flow cytometry identified Tbx3 expression already in progenitor cells of the hormone-sensing lineage and co-immunofluorescence confirmed a strict correlation between estrogen receptor (ER) and Tbx3 expression in situ. Using in vivo reconstitution assays we demonstrate that Tbx3 is functionally relevant for this lineage because knockdown of Tbx3 in primary mammary epithelial cells prevented the formation of ER+ cells, but not luminal ER- or basal cells. Interestingly, genes that are repressed by Tbx3 in other cell types, such as E-cadherin, are not repressed in hormone-sensing cells, highlighting that transcriptional targets of Tbx3 are cell type specific. In summary, we provide the first analysis of Tbx3 expression in the adult mammary gland at a single cell level and show that Tbx3 is important for the generation of hormone-sensing cells.

High TBX2 expression predicts poor prognosis in non-small cell lung cancer.

Deregulated expression of T-box2 (TBX2) has been implicated in malignancies. However, the expression pattern and the role of TBX2 in non-small cell lung cancer (NSCLC) remain unclear. The aim of this study was to explore the clinical value of TBX2 in patients with NSCLC. We examined TBX2 expression in 40 NSCLC tissues and matched adjacent noncancerous tissues by quantitative RT-PCR (qRT-PCR) and Western blotting. Furthermore, the TBX2 protein expression was analyzed by immunohistochemistry in 416 NSCLC samples. Kaplan-Meier method and multivariate Cox regression model were used to evaluate the prognostic value of TBX2 expression in NSCLC for disease survival. The expression of TBX2 was significantly elevated in NSCLC tissues as compared with adjacent non-cancerous tissues (P<0.001). The high expression of TBX2 in NSCLC was significantly correlated with lymph node metastasis and tumor node metastasis (TNM) stage. Kaplan-Meier survival analysis revealed that high expression of TBX2 correlated with poor prognosis of NSCLC patients (P<0.01). Multivariate analysis showed that TBX2 expression was an independent prognostic marker for overall survival of NSCLC patients (HR=2.21, 95%CI=1.349-3.905, P=0.0015). Our results suggest that high TBX2 expression is associated with poor prognosis of NSCLC patients, and TBX2 may be a prognostic biomarker for NSCLC. Keywords: TBX2, non-small cell lung cancer, prognosis, biomarker.

Roles for Tbx3 in regulation of two-cell state and telomere elongation in mouse ES cells

Mouse embryonic stem (ES) cell cultures exhibit heterogeneity and recently are discovered to sporadically enter the 2-cell (2C)-embryo state, critical for ES potency. Zscan4 could mark the sporadic 2C-state of ES cells. However, factors that regulate the Zscan4+/2C state remain to be elucidated. We show that Tbx3 plays a novel role in regulation of Zscan4+/2C state. Tbx3 activates 2-cell genes including Zscan4 and Tcstv1/3, but not vise versa. Ectopic expression of Tbx3 results in telomere elongation, consistent with a role for Zscan4 in telomere lengthening. Mechanistically, Tbx3 decreases Dnmt3b and increases Tet2 protein levels, and reduces binding of Dnmt3b to subtelomeres, resulting in reduced DNA methylation and derepression of genes at subtelomeres, e.g. Zscan4. These data suggest that Tbx3 can activate Zscan4+/2C state by negative regulation of DNA methylation at repeated sequences, linking to telomere maintenance and self-renewal of ES cells.

Tbx2a Is Required for Specification of Endodermal Pouches during Development of the Pharyngeal Arches

Tbx2 is a member of the T-box family of transcription factors essential for embryo- and organogenesis. A deficiency in the zebrafish paralogue tbx2a causes abnormalities of the pharyngeal arches in a p53-independent manner. The pharyngeal arches are formed by derivatives of all three embryonic germ layers: endodermal pouches, mesenchymal condensations and neural crest cells. While tbx2a expression is restricted to the endodermal pouches, its function is required for the normal morphogenesis of the entire pharyngeal arches. Given the similar function of Tbx1 in craniofacial development, we explored the possibility of an interaction between Tbx1 and Tbx2a. The use of bimolecular fluorescence complementation revealed the interaction between Tbx2a and Tbx1, thus providing support for the idea that functional interaction between different, co-expressed Tbx proteins could be a common theme across developmental processes in cell lineages and tissues. Together, this work provides mechanistic insight into the role of TBX2 in human disorders affecting the face and neck.

Increased expression of TBX2 is a novel independent prognostic biomarker of a worse outcome in colorectal cancer patients after curative surgery and a potential therapeutic target

T-box2 (TBX2) plays a critical role in embryonic development. Recently, deregulated expression of TBX2 has been implicated in several malignancies. However, the expression and the role of TBX2 in colorectal cancer (CRC) remain unclear. In this study, we found that TBX2 was obviously up-regulated in CRC in comparison with the corresponding normal mucosa at transcriptional and protein level. Up-expression of TBX2 was significantly associated with depth of tumor invasion (P = 0.006), distant metastasis (P = 0.038), advanced AJCC stage (P = 0.008), and relapse (P = 0.003). TBX2 was a significantly prognostic factor for decreased survival and increased disease recurrence independent of tumor stage(II, III stage) and functioned as a biomarker to identify prognosis of patients with CRC (OS: HR 2.154; 95% CI 1.019-4.551; P = 0.044, DFS: HR 2.253; 95% CI 1.109-4.575; P = 0.025). Furthermore, TBX2 could serve as a potential target of cancer drug therapy.

Msx1andTbx2antagonistically regulateBmp4expression during the bud-to-cap stage transition in tooth development

Bmp4 expression is tightly regulated during embryonic tooth development, with early expression in the dental epithelial placode leading to later expression in the dental mesenchyme. Msx1 is among several transcription factors that are induced by epithelial Bmp4 and that, in turn, are necessary for the induction and maintenance of dental mesenchymal Bmp4 expression. Thus, Msx1(-/-) teeth arrest at early bud stage and show loss of Bmp4 expression in the mesenchyme. Ectopic expression of Bmp4 rescues this bud stage arrest. We have identified Tbx2 expression in the dental mesenchyme at bud stage and show that this can be induced by epithelial Bmp4. We also show that endogenous Tbx2 and Msx1 can physically interact in mouse C3H10T1/2 cells. In order to ascertain a functional relationship between Msx1 and Tbx2 in tooth development, we crossed Tbx2 and Msx1 mutant mice. Our data show that the bud stage tooth arrest in Msx1(-/-) mice is partially rescued in Msx1(-/-);Tbx2(+/-) compound mutants. This rescue is accompanied by formation of the enamel knot (EK) and by restoration of mesenchymal Bmp4 expression. Finally, knockdown of Tbx2 in C3H10T1/2 cells results in an increase in Bmp4 expression. Together, these data identify a novel role for Tbx2 in tooth development and suggest that, following their induction by epithelial Bmp4, Msx1 and Tbx2 in turn antagonistically regulate odontogenic activity that leads to EK formation and to mesenchymal Bmp4 expression at the key bud-to-cap stage transition.

A novel role for Tbx3 in regulating digit number in the developing limb by Shh dependent and independent mechanisms

The crucial roles of TBX3 in development are evident in the fact that heterozygous mutations of TBX3 cause human Ulnar–mammary syndrome (UMS) including limb malformations, apocrine and mammary gland hypoplasia, dental and genital defects. Although germline deletion of Tbx3 in mice generates UMS‐like phenotypes, embryonic lethality has previously prevented investigating its precise role during limb development. To overcome this, we conditionally ablated Tbx3 in critical signaling compartments in the developing forelimb and discovered distinct functions in anterior and posterior mesenchyme. We found that Tbx3 promotes posterior digit development by positively regulating the Hand2/Shh signaling pathway. In anterior mesenchyme, Tbx3 constrains digit number by increasing the level of Gli3R and preventing expression of Hand1. The molecular basis for the effect of Tbx3 on Gli3R is at least in part via post‐transcriptional regulation of Suppressor of fused (Sufu). Loss of Tbx3 results in increased Sufu protein and altered Gli3R processing in primary cilia. Furthermore, mutants with complete loss of Tbx3 phenocopy the severe limb defects of Shh and Hand2 null mutants. In total, Tbx3 controls digit number by regulating Shh signaling in both ligand dependent (posterior mesenchyme) and ligand independent (anterior mesenchyme) mechanisms.This work was supported by a March of Dimes Basil O'Connor Award (AMM), and NIH R01HD046767 (AMM).Grant Funding Source: N/A

The T Box Transcription Factor TBX2 Promotes Epithelial-Mesenchymal Transition and Invasion of Normal and Malignant Breast Epithelial Cells

The T box transcription factor TBX2, a master regulator of organogenesis, is aberrantly amplified in aggressive human epithelial cancers. While it has been shown that overexpression of TBX2 can bypass senescence, a failsafe mechanism against cancer, its potential role in tumor invasion has remained obscure. Here we demonstrate that TBX2 is a strong cell-autonomous inducer of the epithelial-mesenchymal transition (EMT), a latent morphogenetic program that is key to tumor progression from noninvasive to invasive malignant states. Ectopic expression of TBX2 in normal HC11 and MCF10A mammary epithelial cells was sufficient to induce morphological, molecular, and behavioral changes characteristic of EMT. These changes included loss of epithelial adhesion and polarity gene (E-cadherin, ß-catenin, ZO1) expression, and abnormal gain of mesenchymal markers (N-cadherin, Vimentin), as well as increased cell motility and invasion. Conversely, abrogation of endogenous TBX2 overexpression in the malignant human breast carcinoma cell lines MDA-MB-435 and MDA-MB-157 led to a restitution of epithelial characteristics with reciprocal loss of mesenchymal markers. Importantly, TBX2 inhibition abolished tumor cell invasion and the capacity to form lung metastases in a Xenograft mouse model. Meta-analysis of gene expression in over one thousand primary human breast tumors further showed that high TBX2 expression was significantly associated with reduced metastasis-free survival in patients, and with tumor subtypes enriched in EMT gene signatures, consistent with a role of TBX2 in oncogenic EMT. ChIP analysis and cell-based reporter assays further revealed that TBX2 directly represses transcription of E-cadherin, a tumor suppressor gene, whose loss is crucial for malignant tumor progression. Collectively, our results uncover an unanticipated link between TBX2 deregulation in cancer and the acquisition of EMT and invasive features of epithelial tumor cells.

Microdeletion of 17q22q23.2 encompassing TBX2 and TBX4 in a patient with congenital microcephaly, thyroid duct cyst, sensorineural hearing loss, and pulmonary hypertension

Microdeletions of the long arm of chromosome 17 are being reported with increasing frequency. Deletions of 17q22q23.2 may represent a genetically recognizable phenotype although its spectrum of genomic abnormalities, clinical manifestations, and critical regions are not fully delineated. Isolated reports and small case series suggest that deletions of 17q22q23.2 result in haploinsufficiency of dosage sensitive genes NOG, TBX2, and TBX4, which may be responsible for many aspects of the phenotype. Shared clinical features in this group of patients include microcephaly, prenatal onset growth restriction, heart defects, tracheoesophageal fistula, and esophageal atresia (TEF/EA), skeletal anomalies, and moderate to severe global developmental delay. We describe a female patient who presented with severe congenital microcephaly, thyroglossal duct cyst, sensorineural hearing loss, mild tracheomalacia, abnormal auricles, pulmonary hypertension, developmental delay, and postnatal onset growth delay. She had no TEF/EA or heart defects. Using a high density oligonucleotide microarray, we identified a microdeletion at 17q22q23.2, resulting in the heterozygous loss of several genes, including TBX2 and TBX4 but not NOG. The breakpoints did not lie within known segmental duplications. This case helps to further delineate the critical region for TEF/EA, which is likely confined to the chromosomal region proximal to 17q23.1, and suggests that genes in 17q23.1q23.2 may be associated with thyroglossal duct cysts. The role of TBX2 and TBX4 in pulmonary hypertension warrants investigation.

Role of Tbx2 in defining the territory of the pronephric nephron

Despite extensive study of the development of the nephron, which is the functional unit of the kidney, the molecular mechanisms underlying the determination of nephron size remain largely unknown. Using the Xenopus pronephros, we demonstrate here that Tbx2, a T-box transcriptional repressor, functions to demarcate the territory of the pronephric nephron. Tbx2 is specifically expressed around three distinct components of the pronephric nephron: the tubule, duct and glomus. Gain of function of Tbx2 inhibits nephric mesoderm formation. Conversely, Tbx2 loss of function expands the boundary of each component of the pronephric nephron, resulting in an enlarged pronephros. BMP signals induce Tbx2 in the non-nephric mesoderm, which inhibits the expression of the nephric markers Hey1 and Gremlin. Importantly, these pronephric molecules repress Tbx2 expression by antagonizing BMP signals in the nephric mesoderm. These results suggest that the negative regulatory loops between BMP/Tbx2 and Gremlin or Hey1 are responsible for defining the territory of the pronephric nephron.

The Role of TBX3 in the Regulation of Tumor Suppressor p14ARF Expression in Human Liver Carcinoma Cells

TBX3 is a transcription factor in the T‐box gene family. Mutations of TBX3 in humans are associated with Ulnar‐Mammary syndrome, an autosomal dominant condition with multiple organ abnormalities. The recent studies showed that overexpression of TBX3 is associated with breast cancer, probably by interacting with HDACs and inhibiting p14ARF. The tumor suppressor p14ARF is a vital biomarker for cancer development. To determine if the misregulation of TBX3 gene expression could disrupt the expression of tumor suppressor p14ARF in human liver carcinoma cells, we established an inducible expression of the TBX3 cell model with the Tet‐off Advanced System. The results showed that the expression of endogenous p14ARF in human liver carcinoma cells was suppressed by TBX3 in a dose‐dependent manner. This experiment will facilitate our understanding of the molecular mechanisms underlying the TBX3‐initiated liver tumorigenesis, as we as provide potential for liver cancer diagnostics and therapeutics.

The role of Tbx2 in pancreatic cancers and its regulation by Wnt/β-catenin signaling

Objective To investigate the expression of Tbx2 protein in pancreatic cancer tissues and its molecular regulation mechanism by Wnt/β-catenin signaling.

A role for Tbx2 in the regulation of the α2(1) collagen gene in human fibroblasts

The T-box gene family encodes highly conserved transcription factors that play important roles in embryonic development and have been implicated in carcinogenesis. One member of the family, Tbx2, is generally regarded as a transcriptional repressor but appears to be capable of functioning as an activator depending on the cellular context. This study shows that Tbx2 is expressed in normal human fibroblasts but is drastically reduced in several transformed fibroblast cell lines. This pattern of Tbx2 expression correlated with that observed for the human alpha2(1) collagen gene (COL1A2). Interestingly, stable expression of transfected Tbx2 in transformed fibroblast cell lines further reduces expression of the human endogenous COL1A2 gene. This ability of Tbx2 to repress the human COL1A2 gene was confirmed in luciferase reporter assays and shown to be independent of the consensus T-box binding element.