The Experts below are selected from a list of 12894 Experts worldwide ranked by ideXlab platform
Antonio Baldini - One of the best experts on this subject based on the ideXlab platform.
-
Pharmacological rescue of the brain cortex phenotype in TBX1 mouse mutants: significance for 22q11.2 deletion syndrome
2021Co-Authors: Ilaria Favicchia, Antonio Baldini, Gabriella Lania, Gemma Flore, Elizabeth IllingworthAbstract:Objectives: TBX1 mutant mice are a widely used model of 22q11.2 deletion syndrome (22q11.2DS) because they manifest a broad spectrum of physical and behavioral abnormalities that is similar to that found in 22q11.2DS patients. In TBX1 mutants, brain abnormalities include changes in cortical cytoarchitecture, hypothesized to be caused by the precocious differentiation of cortical progenitors. The objectives of this research are to identify drugs that have efficacy against the brain phenotype, and through a phenotypic rescue approach, gain insights into the pathogenetic mechanisms underlying TBX1 haploinsufficiency. Experimental approach: Disease model: TBX1 heterozygous and homozygous embryos. We tested the ability of two FDA-approved drugs, the LSD1 inhibitor Tranylcypromine and Vitamin B12, to rescue the TBX1 mutant cortical phenotype. Both drugs have proven efficacy against the cardiovascular phenotype, albeit at a much reduced level compared to the rescue achieved in the brain. Methods: in situ hybridization and immunostaining of histological brain sections using a subset of molecular markers that label specific cortical regions or cell types. Appropriate quantification and statistical analysis of gene and protein expression were applied to identify cortical abnormalities and to determine the level of phenotypic rescue achieved. Results: Cortical abnormalities observed in TBX1 mutant embryos were fully rescued by both drugs. Intriguingly, rescue was obtained with both drugs in TBX1 homozygous mutants, indicating that they function through mechanisms that do not depend upon TBX1 function. This was particularly surprising for Vitamin B12, which was identified through its ability to increase TBX1 gene expression. Conclusions: To our knowledge, this is only the second example of drugs to be identified that ameliorate phenotypes caused by the mutation of a single gene from the 22q11.2 homologous region of the mouse genome. This one drug-one gene approach might be important because there is evidence that the brain phenotype in 22q11.2DS patients is multigenic in origin, unlike the physical phenotypes, which are overwhelmingly attributable to TBX1 haploinsufficiency. Therefore, effective treatments will likely involve the use of multiple drugs that are targeted to the function of specific genes within the deleted region.
-
A dual role for TBX1 in cardiac lymphangiogenesis through genetic interaction with Vegfr3.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2020Co-Authors: Stefania Martucciello, Antonio Baldini, Marchesa Bilio, Li Chen, Sara Cioffi, Maria Giuseppina Turturo, Elizabeth IllingworthAbstract:The transcription factor TBX1 is the major gene implicated in 22q11.2 deletion syndrome (22q11.2DS). The complex clinical phenotype includes vascular anomalies and a recent report presented new cases of primary lymphedema in 22q11.2DS patients. We have previously shown that TBX1 is required for systemic lymphatic vessel development in prenatal mice and it is critical for their survival postnatally. Using loss-of-function genetics and transgenesis in the mouse, we show here a strong genetic interaction between TBX1 and Vegfr3 in cardiac lymphangiogenesis. Intriguingly, we found that different aspects of the cardiac lymphatic phenotype in TBX1-Vegfr3 compound heterozygotes were regulated independently by the two genes, with TBX1 primarily regulating vessel numbers and Vegfr3 vessel morphology. Consistent with this observation, TBX1Cre -activated expression of a Vegfr3 transgene rescued partially the cardiac lymphatic abnormalities in compound heterozygotes. Through time-controlled genetic experiments, we show that TBX1 is activated and required in cardiac lymphatic endothelial cell (LEC) progenitors between E10.5 and E11.5. Furthermore, we found that it is also required later in development for the growth of the cardiac lymphatics. Finally, our study revealed a differential sensitivity between ventral and dorsal cardiac lymphatics to the effects of altered TBX1 and Vegfr3 gene dosage, and we show that this likely results from an earlier requirement for TBX1 in ventral cardiac LEC progenitors.
-
TBX1 regulates extracellular matrix cell interactions in the second heart field
bioRxiv, 2018Co-Authors: Daniela Alfano, Robert G. Kelly, Alessandra Altomonte, Claudio Cortes, Marchesa Bilio, Antonio BaldiniAbstract:TBX1, the major candidate gene for DiGeorge or 22q11.2 deletion syndrome, is required for efficient incorporation of cardiac progenitors (CPs) of the second heart field (SHF) into the heart. However, the mechanisms by which TBX1 regulates this process are still unclear. Here, we have used two independent models, mouse embryos and cultured cells, to define the role of TBX1 in establishing morphological and dynamic characteristics of SHF in the mouse. We found that loss of TBX1 impairs extra cellular matrix (ECM)-integrin-focal adhesion (FA) signaling in both models. Mosaic analysis in embryos showed that this function is non-cell autonomous and, in cultured cells, loss of TBX1 impairs cell migration and focal adhesions. Additionally, we found that ECM-mediated outside-in integrin signaling is disrupted upon loss of TBX1. Finally, we show that interfering with the ECM-integrin-FA axis between E8.5 and E9.5 in mouse embryos, corresponding to the time window within which TBX1 is required in the SHF, causes outflow tract dysmorphogenesis. Our results demonstrate that TBX1 is required to maintain the integrity of ECM-cell interactions in the SHF, and that this interaction is critical for cardiac outflow tract development. More broadly, our data identifies a novel TBX1 downstream pathway as an important player in SHF tissue architecture and cardiac morphogenesis.
-
TBX1 regulates extracellular matrix- and cell-cell interactions in the second heart field.
2018Co-Authors: Antonio Baldini, Daniela Alfano, Alessandra Altomonte, Marchesa BilioAbstract:TBX1, a gene involved in DiGeorge syndrome, is required for efficient incorporation of cardiac progenitors (CPs) of the second heart field (SHF) into the heart. However, the mechanisms by which TBX1 regulates this process are still unclear. Here, we have used two independent models, in vivo and in vitro, to define the role of TBX1 in establishing morphological and dynamic characteristics of target cells in the mouse. We found that loss of TBX1 impairs cell migration and adhesion in vitro and affects the axis extra cellular matrix (ECM)-integrin-focal adhesion in both models. In addition, the ECM-mediated outside-in signalling is disrupted in the absence of TBX1. Furthermore, we found that the epithelial-like layer of the SHF exhibits an apical-lateral adhesion domain containing E-cadherin, beta-catenin, paxillin, and non-muscle myosin II (NMIIB). Interestingly, loss of TBX1 affects this adhesion domain and causes loss of polarity and alteration of focal adhesion proteins. We propose that TBX1 is required for condensation of splanchnic mesodermal cells into the epithelial-like layer of the dorsal pericardial wall. In summary, our data identifies TBX1 as an important player in SHF tissue architecture via regulation of ECM-cell and cell-cell interactions.
-
Rebalancing gene haploinsufficiency in vivo by targeting chromatin
Nature Communications, 2016Co-Authors: Filomena Gabriella Fulcoli, Monica Franzese, Claudia Angelini, Zhen Zhang, Xiangyang Liu, Antonio BaldiniAbstract:Deficit in transcription factor TBX1 causes heart defects in humans and mice. Here the authors show that TBX1 regulates gene expression by recruiting histone methyltransferases that affect chromatin marks, and that a drug inhibiting histone demethylation ameliorates the cardiovascular phenotype in TBX1 haploinsufficient or hypomorphic mice.AbstractCongenital heart disease (CHD) affects eight out of 1,000 live births and is a major social and health-care burden. A common genetic cause of CHD is the 22q11.2 deletion, which is the basis of the homonymous deletion syndrome (22q11.2DS), also known as DiGeorge syndrome. Most of its clinical spectrum is caused by haploinsufficiency of TBX1 , a gene encoding a T-box transcription factor. Here we show that TBX1 positively regulates monomethylation of histone 3 lysine 4 (H3K4me1) through interaction with and recruitment of histone methyltransferases. Treatment of cells with tranylcypromine (TCP), an inhibitor of histone demethylases, rebalances the loss of H3K4me1 and rescues the expression of approximately one-third of the genes dysregulated by TBX1 suppression. In TBX1 mouse mutants, TCP treatment ameliorates substantially the cardiovascular phenotype. These data suggest that epigenetic drugs may represent a potential therapeutic strategy for rescue of gene haploinsufficiency phenotypes, including structural defects.
Bernice E Morrow - One of the best experts on this subject based on the ideXlab platform.
-
TBX1 and jag1 act in concert to modulate the fate of neurosensory cells of the mouse otic vesicle
Biology Open, 2017Co-Authors: Stephania Macchiarulo, Bernice E MorrowAbstract:ABSTRACT The domain within the otic vesicle (OV) known as the neurosensory domain (NSD), contains cells that will give rise to the hair and support cells of the otic sensory organs, as well as the neurons that form the cochleovestibular ganglion (CVG). The molecular dynamics that occur at the NSD boundary relative to adjacent OV cells is not well defined. The TBX1 transcription factor gene expression pattern is complementary to the NSD, and inactivation results in expansion of the NSD and expression of the Notch ligand, Jag1 mapping, in part of the NSD. To shed light on the role of Jag1 in NSD development, as well as to test whether TBX1 and Jag1 might genetically interact to regulate this process, we inactivated Jag1 within the TBX1 expression domain using a knock-in TBX1 Cre allele. We observed an enlarged neurogenic domain marked by a synergistic increase in expression of NeuroD and other proneural transcription factor genes in double TBX1 and Jag1 conditional loss-of-function embryos. We noted that neuroblasts preferentially expanded across the medial-lateral axis and that an increase in cell proliferation could not account for this expansion, suggesting that there was a change in cell fate. We also found that inactivation of Jag1 with TBX1 Cre resulted in failed development of the cristae and semicircular canals, as well as notably fewer hair cells in the ventral epithelium of the inner ear rudiment when inactivated on a TBX1 null background, compared to TBX1 Cre/− mutant embryos. We propose that loss of expression of TBX1 and Jag1 within the TBX1 expression domain tips the balance of cell fates in the NSD, resulting in an overproduction of neuroblasts at the expense of non-neural cells within the OV.
-
endoderm specific deletion of TBX1 reveals an fgf independent role for TBX1 in pharyngeal apparatus morphogenesis
Developmental Dynamics, 2014Co-Authors: Abigail L. Jackson, Bernice E Morrow, Sahrunizam Kasah, Suzanne L. Mansour, Albert M BassonAbstract:Background: The T-box transcription factor TBX1, is essential for the normal development of multiple organ systems in the embryo. One of the most striking phenotypes in TBX1−/− embryos is the failure of the caudal pharyngeal pouches to evaginate from the foregut endoderm. Despite considerable interest in the role of TBX1 in development, the mechanisms whereby TBX1 controls caudal pouch formation have remained elusive. In particular, the question as to how TBX1 expression in the pharyngeal endoderm regulates pharyngeal pouch morphogenesis in the mouse embryo is not known. Results: To address this question, we produced mouse embryos in which TBX1 was specifically deleted from the pharyngeal endoderm and, as expected, embryos failed to form caudal pharyngeal pouches. To determine the molecular mechanism, we examined expression of Fgf3 and Fgf8 ligands and downstream effectors. Although Fgf8 expression is greatly reduced in TBX1-deficient endoderm, FGF signaling levels are unaffected. Furthermore, pouch morphogenesis is only partially perturbed by the loss of both Fgf3 and Fgf8 from the endoderm, indicating that neither are required for pouch formation. Conclusions: TBX1 deletion from the pharyngeal endoderm is sufficient to cause caudal pharyngeal arch segmentation defects by FGF-independent effectors that remain to be identified. Developmental Dynamics 243:1143–1151, 2014. © 2014 Wiley Periodicals, Inc.
-
Endoderm‐specific deletion of TBX1 reveals an FGF‐independent role for TBX1 in pharyngeal apparatus morphogenesis
Developmental dynamics : an official publication of the American Association of Anatomists, 2014Co-Authors: Abigail L. Jackson, Bernice E Morrow, Sahrunizam Kasah, Suzanne L. Mansour, M. Albert BassonAbstract:Background: The T-box transcription factor TBX1, is essential for the normal development of multiple organ systems in the embryo. One of the most striking phenotypes in TBX1−/− embryos is the failure of the caudal pharyngeal pouches to evaginate from the foregut endoderm. Despite considerable interest in the role of TBX1 in development, the mechanisms whereby TBX1 controls caudal pouch formation have remained elusive. In particular, the question as to how TBX1 expression in the pharyngeal endoderm regulates pharyngeal pouch morphogenesis in the mouse embryo is not known. Results: To address this question, we produced mouse embryos in which TBX1 was specifically deleted from the pharyngeal endoderm and, as expected, embryos failed to form caudal pharyngeal pouches. To determine the molecular mechanism, we examined expression of Fgf3 and Fgf8 ligands and downstream effectors. Although Fgf8 expression is greatly reduced in TBX1-deficient endoderm, FGF signaling levels are unaffected. Furthermore, pouch morphogenesis is only partially perturbed by the loss of both Fgf3 and Fgf8 from the endoderm, indicating that neither are required for pouch formation. Conclusions: TBX1 deletion from the pharyngeal endoderm is sufficient to cause caudal pharyngeal arch segmentation defects by FGF-independent effectors that remain to be identified. Developmental Dynamics 243:1143–1151, 2014. © 2014 Wiley Periodicals, Inc.
-
Conditional and constitutive expression of a TBX1-GFP fusion protein in mice
BMC developmental biology, 2013Co-Authors: Laina Freyer, Antonio Baldini, Sonja Nowotschin, Melinda K. Pirity, Bernice E MorrowAbstract:Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is caused by a 1.5-3 Mb microdeletion of chromosome 22q11.2, frequently referred to as 22q11.2 deletion syndrome (22q11DS). This region includes TBX1, a T-box transcription factor gene that contributes to the etiology of 22q11DS. The requirement for TBX1 in mammalian development is dosage-sensitive, such that loss-of-function (LOF) and gain-of-function (GOF) of TBX1 in both mice and humans results in disease relevant congenital malformations. To further gain insight into the role of TBX1 in development, we have targeted the Rosa26 locus to generate a new GOF mouse model in which a TBX1-GFP fusion protein is expressed conditionally using the Cre/LoxP system. TBX1-GFP expression is driven by the endogenous Rosa26 promoter resulting in ectopic and persistent expression. TBX1 is pivotal for proper ear and heart development; ectopic activation of TBX1-GFP in the otic vesicle by Pax2-Cre and Foxg1-Cre represses neurogenesis and produces morphological defects of the inner ear. Overexpression of a single copy of TBX1-GFP using TBX1 Cre/+ was viable, while overexpression of both copies resulted in neonatal lethality with cardiac outflow tract defects. We have partially rescued inner ear and heart anomalies in TBX1 Cre/- null embryos by expression of TBX1-GFP. We have generated a new mouse model to conditionally overexpress a GFP-tagged TBX1 protein in vivo. This provides a useful tool to investigate in vivo direct downstream targets and protein binding partners of TBX1.
-
TBX1 and Brn4 regulate retinoic acid metabolic genes during cochlear morphogenesis
BMC developmental biology, 2009Co-Authors: Evan M. Braunstein, Vimla Aggarwal, Dennis C. Monks, Jelena S. Arnold, Bernice E MorrowAbstract:In vertebrates, the inner ear is comprised of the cochlea and vestibular system, which develop from the otic vesicle. This process is regulated via inductive interactions from surrounding tissues. TBX1, the gene responsible for velo-cardio-facial syndrome/DiGeorge syndrome in humans, is required for ear development in mice. TBX1 is expressed in the otic epithelium and adjacent periotic mesenchyme (POM), and both of these domains are required for inner ear formation. To study the function of TBX1 in the POM, we have conditionally inactivated TBX1 in the mesoderm while keeping expression in the otic vesicle intact. Conditional mutants (TCre-KO) displayed malformed inner ears, including a hypoplastic otic vesicle and a severely shortened cochlear duct, indicating that TBX1 expression in the POM is necessary for proper inner ear formation. Expression of the mesenchyme marker Brn4 was also lost in the TCre-KO. Brn4-;TBX1+/-embryos displayed defects in growth of the distal cochlea. To identify a potential signal from the POM to the otic epithelium, expression of retinoic acid (RA) catabolizing genes was examined in both mutants. Cyp26a1 expression was altered in the TCre-KO, while Cyp26c1 showed reduced expression in both TCre-KO and Brn4-;TBX1+/- embryos. These results indicate that TBX1 expression in the POM regulates cochlear outgrowth potentially via control of local retinoic acid activity.
Vincent M. Christoffels - One of the best experts on this subject based on the ideXlab platform.
-
TBX2 is expressed in the proepicardium and epicardium.
2016Co-Authors: Franziska Greulich, Henner F. Farin, Vincent M. Christoffels, Carsten Rudat, Andreas KispertAbstract:(A) Epifluorescence of a Tbx2cre/+;R26mTmG/+ embryo at E9.5 reveals the contribution of formerly Tbx2-expressing cells to the atrio-ventricular canal (AVC), the otic vesicle (OV), the eye (E) and the proepicardium (PE) (n = 5). The scale bar is 500 μm. (B) Lineage tracing of Tbx2-expressing cells on sections of E9.5 embryos by immunofluorescent detection of a GFP reporter and/or the epicardial markers TBX18 and WT1 (left row) confirms the contribution of Tbx2-expressing cells to the proepicardium (n = 3). Double immunofluorescence against GFP and TBX2 or TBX3, respectively, (right row) shows expression of TBX2 in the caudal part of the proepicardium. Note that the anti-TBX2 antibody recognizes cells that do not recombine after cre expression from the Tbx2 promoter. The third picture of the lower row shows an in silico overlay of the expression domains of TBX2 and TBX3 co-stained with the Tbx2-lineage label GFP on neighboring sections. Only TBX2-positive (red), TBX3-negative and GFP-positive (blue) domains relate to Tbx2 expression domains (white arrowhead). The scale bars are 50 μm. (C) TBX2 but not TBX3 protein was detected by immunofluorescence against TBX2 and TBX3 in epicardial and subepicardial cells of TBX18cre/+;R26mTmG/+ embryos at E13.5 (white arrows, n = 2). Co-staining against the TBX18-lineage label GFP clearly identifies epicardial and epicardium-derived cells. The scale bars are 50 μm. CA, common atrium; Epi, epicardium; RV, right ventricle; SV, sinus venosus.
-
Development of the human aortic arch system captured in an interactive three-dimensional reference model.
American Journal of Medical Genetics Part A, 2013Co-Authors: M Sameer Rana, Vincent M. Christoffels, Aleksander Sizarov, Antoon F.m. MoormanAbstract:Variations and mutations in the human genome, such as 22q11.2 microdeletion, can increase the risk for congenital defects, including aortic arch malformations. Animal models are increasingly expanding our molecular and genetic insights into aortic arch development. However, in order to justify animal-to-human extrapolations, a human morphological, and molecular reference model would be of great value, but is currently lacking. Here, we present interactive three-dimensional reconstructions of the developing human aortic arch system, supplemented with the protein distribution of developmental markers for patterning and growth, including T-box transcription factor TBX1, a major candidate for the phenotypes found in patients with the 22q11.2 microdeletion. These reconstructions and expression data facilitate unbiased interpretations, and reveal previously unappreciated aspects of human aortic arch development. Based on our reconstructions and on reported congenital anomalies of the pulmonary trunk and tributaries, we postulate that the pulmonary arteries originate from the aortic sac, rather than from the sixth pharyngeal arch arteries. Similar to mouse, TBX1 is expressed in pharyngeal mesenchyme and epithelia. The endothelium of the pharyngeal arch arteries is largely negative for TBX1 and family member TBX2 but expresses neural crest marker AP2α, which gradually decreases with ongoing development of vascular smooth muscle. At early stages, the pharyngeal arch arteries, aortic sac, and the dorsal aortae in particular were largely negative for proliferation marker Ki67, potentially an important parameter during aortic arch system remodeling. Together, our data support current animal-to-human extrapolations and future genetic and molecular analyses using animal models of congenital heart disease. © 2013 Wiley Periodicals, Inc.
-
Identification of a TBX1/Tbx2/Tbx3 genetic pathway governing pharyngeal and arterial pole morphogenesis.
Human Molecular Genetics, 2012Co-Authors: Karim Mesbah, Virginia E. Papaioannou, Robert G. Kelly, M Sameer Rana, Alexandre Francou, Karel Van Duijvenboden, Antoon F Moorman, Vincent M. ChristoffelsAbstract:The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion disorder and is characterized by abnormal development of the pharyngeal apparatus and heart. Cardiovascular malformations (CVMs) affecting the outflow tract (OFT) are frequently observed in 22q11.2DS and are among the most commonly occurring heart defects. The gene encoding T-box transcription factor 1 (TBX1) has been identified as a major candidate for 22q11.2DS. However, CVMs are generally considered to have a multigenic basis and single-gene mutations underlying these malformations are rare. The T-box family members Tbx2 and Tbx3 are individually required in regulating aspects of OFT and pharyngeal development. Here, using expression and three-dimensional reconstruction analysis, we show that TBX1 and Tbx2/Tbx3 are largely uniquely expressed but overlap in the caudal pharyngeal mesoderm during OFT development, suggesting potential combinatorial requirements. Cross-regulation between TBX1 and Tbx2/Tbx3 was analyzed using mouse genetics and revealed that TBX1 deficiency affects Tbx2 and Tbx3 expression in neural crest-derived cells and pharyngeal mesoderm, whereas Tbx2 and Tbx3 function redundantly upstream of TBX1 and Hh ligand expression in pharyngeal endoderm and bone morphogenetic protein- and fibroblast growth factor-signaling in cardiac progenitors. Moreover, in vivo, we show that loss of two of the three genes results in severe pharyngeal hypoplasia and heart tube extension defects. These findings reveal an indispensable T-box gene network governing pharyngeal and OFT development and identify TBX2 and TBX3 as potential modifier genes of the cardiopharyngeal phenotypes found in TBX1-haploinsufficient 22q11.2DS patients.
-
identification of a TBX1 tbx2 tbx3 genetic pathway governing pharyngeal and arterial pole morphogenesis
Human Molecular Genetics, 2012Co-Authors: Karim Mesbah, Virginia E. Papaioannou, Robert G. Kelly, Alexandre Francou, Karel Van Duijvenboden, Antoon F Moorman, Sameer M Rana, Vincent M. ChristoffelsAbstract:The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion disorder and is characterized by abnormal development of the pharyngeal apparatus and heart. Cardiovascular malformations (CVMs) affecting the outflow tract (OFT) are frequently observed in 22q11.2DS and are among the most commonly occurring heart defects. The gene encoding T-box transcription factor 1 (TBX1) has been identified as a major candidate for 22q11.2DS. However, CVMs are generally considered to have a multigenic basis and single-gene mutations underlying these malformations are rare. The T-box family members Tbx2 and Tbx3 are individually required in regulating aspects of OFT and pharyngeal development. Here, using expression and three-dimensional reconstruction analysis, we show that TBX1 and Tbx2/Tbx3 are largely uniquely expressed but overlap in the caudal pharyngeal mesoderm during OFT development, suggesting potential combinatorial requirements. Cross-regulation between TBX1 and Tbx2/Tbx3 was analyzed using mouse genetics and revealed that TBX1 deficiency affects Tbx2 and Tbx3 expression in neural crest-derived cells and pharyngeal mesoderm, whereas Tbx2 and Tbx3 function redundantly upstream of TBX1 and Hh ligand expression in pharyngeal endoderm and bone morphogenetic protein- and fibroblast growth factor-signaling in cardiac progenitors. Moreover, in vivo, we show that loss of two of the three genes results in severe pharyngeal hypoplasia and heart tube extension defects. These findings reveal an indispensable T-box gene network governing pharyngeal and OFT development and identify TBX2 and TBX3 as potential modifier genes of the cardiopharyngeal phenotypes found in TBX1-haploinsufficient 22q11.2DS patients.
Robert G. Kelly - One of the best experts on this subject based on the ideXlab platform.
-
TBX1 regulates extracellular matrix cell interactions in the second heart field
bioRxiv, 2018Co-Authors: Daniela Alfano, Robert G. Kelly, Alessandra Altomonte, Claudio Cortes, Marchesa Bilio, Antonio BaldiniAbstract:TBX1, the major candidate gene for DiGeorge or 22q11.2 deletion syndrome, is required for efficient incorporation of cardiac progenitors (CPs) of the second heart field (SHF) into the heart. However, the mechanisms by which TBX1 regulates this process are still unclear. Here, we have used two independent models, mouse embryos and cultured cells, to define the role of TBX1 in establishing morphological and dynamic characteristics of SHF in the mouse. We found that loss of TBX1 impairs extra cellular matrix (ECM)-integrin-focal adhesion (FA) signaling in both models. Mosaic analysis in embryos showed that this function is non-cell autonomous and, in cultured cells, loss of TBX1 impairs cell migration and focal adhesions. Additionally, we found that ECM-mediated outside-in integrin signaling is disrupted upon loss of TBX1. Finally, we show that interfering with the ECM-integrin-FA axis between E8.5 and E9.5 in mouse embryos, corresponding to the time window within which TBX1 is required in the SHF, causes outflow tract dysmorphogenesis. Our results demonstrate that TBX1 is required to maintain the integrity of ECM-cell interactions in the SHF, and that this interaction is critical for cardiac outflow tract development. More broadly, our data identifies a novel TBX1 downstream pathway as an important player in SHF tissue architecture and cardiac morphogenesis.
-
Identification of a TBX1/Tbx2/Tbx3 genetic pathway governing pharyngeal and arterial pole morphogenesis.
Human Molecular Genetics, 2012Co-Authors: Karim Mesbah, Virginia E. Papaioannou, Robert G. Kelly, M Sameer Rana, Alexandre Francou, Karel Van Duijvenboden, Antoon F Moorman, Vincent M. ChristoffelsAbstract:The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion disorder and is characterized by abnormal development of the pharyngeal apparatus and heart. Cardiovascular malformations (CVMs) affecting the outflow tract (OFT) are frequently observed in 22q11.2DS and are among the most commonly occurring heart defects. The gene encoding T-box transcription factor 1 (TBX1) has been identified as a major candidate for 22q11.2DS. However, CVMs are generally considered to have a multigenic basis and single-gene mutations underlying these malformations are rare. The T-box family members Tbx2 and Tbx3 are individually required in regulating aspects of OFT and pharyngeal development. Here, using expression and three-dimensional reconstruction analysis, we show that TBX1 and Tbx2/Tbx3 are largely uniquely expressed but overlap in the caudal pharyngeal mesoderm during OFT development, suggesting potential combinatorial requirements. Cross-regulation between TBX1 and Tbx2/Tbx3 was analyzed using mouse genetics and revealed that TBX1 deficiency affects Tbx2 and Tbx3 expression in neural crest-derived cells and pharyngeal mesoderm, whereas Tbx2 and Tbx3 function redundantly upstream of TBX1 and Hh ligand expression in pharyngeal endoderm and bone morphogenetic protein- and fibroblast growth factor-signaling in cardiac progenitors. Moreover, in vivo, we show that loss of two of the three genes results in severe pharyngeal hypoplasia and heart tube extension defects. These findings reveal an indispensable T-box gene network governing pharyngeal and OFT development and identify TBX2 and TBX3 as potential modifier genes of the cardiopharyngeal phenotypes found in TBX1-haploinsufficient 22q11.2DS patients.
-
identification of a TBX1 tbx2 tbx3 genetic pathway governing pharyngeal and arterial pole morphogenesis
Human Molecular Genetics, 2012Co-Authors: Karim Mesbah, Virginia E. Papaioannou, Robert G. Kelly, Alexandre Francou, Karel Van Duijvenboden, Antoon F Moorman, Sameer M Rana, Vincent M. ChristoffelsAbstract:The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion disorder and is characterized by abnormal development of the pharyngeal apparatus and heart. Cardiovascular malformations (CVMs) affecting the outflow tract (OFT) are frequently observed in 22q11.2DS and are among the most commonly occurring heart defects. The gene encoding T-box transcription factor 1 (TBX1) has been identified as a major candidate for 22q11.2DS. However, CVMs are generally considered to have a multigenic basis and single-gene mutations underlying these malformations are rare. The T-box family members Tbx2 and Tbx3 are individually required in regulating aspects of OFT and pharyngeal development. Here, using expression and three-dimensional reconstruction analysis, we show that TBX1 and Tbx2/Tbx3 are largely uniquely expressed but overlap in the caudal pharyngeal mesoderm during OFT development, suggesting potential combinatorial requirements. Cross-regulation between TBX1 and Tbx2/Tbx3 was analyzed using mouse genetics and revealed that TBX1 deficiency affects Tbx2 and Tbx3 expression in neural crest-derived cells and pharyngeal mesoderm, whereas Tbx2 and Tbx3 function redundantly upstream of TBX1 and Hh ligand expression in pharyngeal endoderm and bone morphogenetic protein- and fibroblast growth factor-signaling in cardiac progenitors. Moreover, in vivo, we show that loss of two of the three genes results in severe pharyngeal hypoplasia and heart tube extension defects. These findings reveal an indispensable T-box gene network governing pharyngeal and OFT development and identify TBX2 and TBX3 as potential modifier genes of the cardiopharyngeal phenotypes found in TBX1-haploinsufficient 22q11.2DS patients.
-
hes1 expression is reduced in TBX1 null cells and is required for the development of structures affected in 22q11 deletion syndrome
Developmental Biology, 2010Co-Authors: Kelly Lammerts Van Bueren, Catherine Roberts, Robert G. Kelly, Amélie Calmont, Irinna Papangeli, Francesca Rochais, Kerra Pearce, Dorota Szumska, Shoumo Bhattacharya, Peter J. ScamblerAbstract:22q11 deletion syndrome (22q11DS) is characterised by aberrant development of the pharyngeal apparatus and the heart with haploinsufficiency of the transcription factor TBX1 being considered the major underlying cause of the disease. TBX1 mutations in mouse phenocopy the disorder. In order to identify the transcriptional dysregulation in TBX1-expressing lineages we optimised fluorescent-activated cell sorting of β-galactosidase expressing cells (FACS-Gal) to compare the expression profile of Df1/TBX1lacZ (effectively TBX1 null) and TBX1 heterozygous cells isolated from mouse embryos. Hes1, a major effector of Notch signalling, was identified as downregulated in TBX1−/− mutants. Hes1 mutant mice exhibited a partially penetrant range of 22q11DS-like defects including pharyngeal arch artery (PAA), outflow tract, craniofacial and thymic abnormalities. Similar to TBX1 mice, conditional mutagenesis revealed that Hes1 expression in embryonic pharyngeal ectoderm contributes to thymus and pharyngeal arch artery development. These results suggest that Hes1 acts downstream of TBX1 in the morphogenesis of pharyngeal-derived structures.
-
properties of branchiomeric and somite derived muscle development in TBX1 mutant embryos
Developmental Dynamics, 2008Co-Authors: Raphälle Grifone, Thérèse Jarry, Mathieu Dandonneau, Julien Grenier, Delphine Duprez, Robert G. KellyAbstract:Vertebrate craniofacial and trunk myogenesis are regulated by distinct genetic programs. TBX1, homologue of the del22q11.2 syndrome candidate gene TBX1, controls branchiomeric craniofacial muscle development. Here, we demonstrate using immunohistochemistry that myogenic regulatory factors are activated in TBX1-positive cells within pharyngeal mesoderm. These cells are also Islet1 and Capsulin-positive and in the absence of TBX1 persist in the core of the first arch. Sporadic hypoplastic mandibular muscles in TBX1-/- embryos contain Pax7-positive myocytes with indistinguishable differentiation properties from wild-type muscles and have normal tendon attachments and fiber-type patterning. In contrast to TBX1 haploinsufficient del22q11.2 syndrome patients, no alteration in fiber-type distribution was detected in TBX1+/- adult masseter and pharyngeal constrictor muscles. Furthermore, TBX1-expressing limb muscles display normal patterning, differentiation, fiber-type growth, fiber-type distribution and fetal maturation in the absence of TBX1. The critical requirement for TBX1 during muscle development is thus in the robust onset of myogenic specification in pharyngeal mesoderm.
Peter J. Scambler - One of the best experts on this subject based on the ideXlab platform.
-
Defective Vagal Innervation in Murine TBX1 Mutant Hearts
MDPI AG, 2018Co-Authors: Amélie Calmont, Naomi Anderson, Jenifer P. Suntharalingham, Richard Ang, Andrew Tinker, Peter J. ScamblerAbstract:Haploinsufficiency of the T-box transcription factor TBX1 is responsible for many features of 22q11.2 deletion syndrome. TBX1 is expressed dynamically in the pharyngeal apparatus during mouse development and TBX1 homozygous mutants display numerous severe defects including abnormal cranial ganglion formation and neural crest cell defects. These abnormalities prompted us to investigate whether parasympathetic (vagal) innervation of the heart was affected in TBX1 mutant embryos. In this report, we used an allelic series of TBX1 mouse mutants, embryo tissue explants and cardiac electrophysiology to characterise, in detail, the function of TBX1 in vagal innervation of the heart. We found that total nerve branch length was significantly reduced in TBX1+/− and TBX1neo2/− mutant hearts expressing 50% and 15% levels of TBX1. We also found that neural crest cells migrated normally to the heart of TBX1+/−, but not in TBX1neo2 mutant embryos. In addition, we showed that cranial ganglia IXth and Xth were fused in TBX1neo2/− but neuronal differentiation appeared intact. Finally, we used telemetry to monitor heart response to carbachol, a cholinergic receptor agonist, and found that heart rate recovered more quickly in TBX1+/− animals versus controls. We speculate that this condition of decreased parasympathetic drive could result in a pro-arrhythmic substrate in some 22q11.2DS patients
-
TBX1 genetically interacts with the transforming growth factor β bone morphogenetic protein inhibitor smad7 during great vessel remodeling
Circulation Research, 2013Co-Authors: Irinna Papangeli, Peter J. ScamblerAbstract:Rationale: Growth and remodeling of the pharyngeal arch arteries are vital for the development of a mature great vessel system. Dysmorphogenesis of the fourth arch arteries can result in interruption of the aortic arch type B, typically found in DiGeorge syndrome. TBX1 haploinsufficient embryos, which model DiGeorge syndrome, display fourth arch artery defects during formation of the vessels. Recovery from such defects is a documented yet unexplained phenotype in TBX1 haploinsufficiency. Objective: To understand the nature of fourth arch artery growth recovery in TBX1 haploinsufficiency and its underlying genetic control. Methods and Results: We categorized vessel phenotypes of TBX1 heterozygotes as hypoplastic or aplastic at the conclusion of pharyngeal artery formation and compared these against the frequency of vessel defects scored at the end of great vessel development. The frequency of hypoplastic vessels decreased during embryogenesis, whereas no reduction of vessel aplasia was seen, implying recovery is attributable to remodeling of hypoplastic vessels. We showed that Smad7 , an inhibitory Smad within the transforming growth factor-β pathway, is regulated by TBX1, is required for arch artery remodeling, and genetically interacts with TBX1 in this process. TBX1 and TBX1 ; Smad7 haploinsufficiency affected several remodeling processes; however, concurrent haploinsufficiency particularly impacted on the earliest stage of vascular smooth muscle cell vessel coverage and subsequent fibronectin deposition. Conditional reconstitution of Smad7 with a TBX1Cre driver indicated that the interaction between the 2 genes is cell autonomous. Conclusions: TBX1 acts upstream of Smad7 controlling vascular smooth muscle and extracellular matrix investment of the fourth arch artery.
-
Absence of the vagus nerve in the stomach of TBX1-/- mutant mice.
Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society, 2010Co-Authors: Amélie Calmont, Peter J. Scambler, Nikhil Thapar, Alan J. BurnsAbstract:Background TBX1 is a member of the Tbox family of binding domain transcription factors. TBX1 maps within the region of chromosome 22q11 deleted in humans with DiGeorge syndrome (DGS), a common genetic disorder characterized by numerous physical manifestations including craniofacial and cardiac anomalies. Mice with homozygous null mutations in TBX1 phenocopy this disorder and have defects including abnormal cranial ganglia formation and cardiac neural crest cell migration. These defects prompted us to investigate whether extrinsic vagus nerve or intrinsic enteric nervous system abnormalities are prevalent in the gastrointestinal tract of TBX1 mutant mice. Methods We used in situ hybridization for Ret, and immunohistochemical staining for neurofilament, HuC/D and βIII-tubulin to study cranial ganglia, vagus nerve, and enteric nervous system development in TBX1 mutant and control mice. Key Results In TBX1−/− embryos, cranial ganglia of the glossopharyngeal (IXth) and vagus (Xth) nerves were malformed and abnormally fused. In the gastrointestinal tract, the vagus nerves adjacent to the esophagus were severely hypoplastic and they did not extend beyond the gastro-esophageal junction nor project branches within the stomach wall, as was observed in TBX1+/+ mice. Conclusions & Inferences Although cranial ganglia morphology appeared normal in TBX1+/− mice, these animals had a spectrum of stomach vagus innervation defects ranging from mild to severe. In all TBX1 genotypes, the intrinsic enteric nervous system developed normally. The deficit in vagal innervation of the stomach in mice mutant for a gene implicated in DGS raises the possibility that similar defects may underlie a number of as yet unidentified/unreported congenital disorders affecting gastrointestinal function.
-
hes1 expression is reduced in TBX1 null cells and is required for the development of structures affected in 22q11 deletion syndrome
Developmental Biology, 2010Co-Authors: Kelly Lammerts Van Bueren, Catherine Roberts, Robert G. Kelly, Amélie Calmont, Irinna Papangeli, Francesca Rochais, Kerra Pearce, Dorota Szumska, Shoumo Bhattacharya, Peter J. ScamblerAbstract:22q11 deletion syndrome (22q11DS) is characterised by aberrant development of the pharyngeal apparatus and the heart with haploinsufficiency of the transcription factor TBX1 being considered the major underlying cause of the disease. TBX1 mutations in mouse phenocopy the disorder. In order to identify the transcriptional dysregulation in TBX1-expressing lineages we optimised fluorescent-activated cell sorting of β-galactosidase expressing cells (FACS-Gal) to compare the expression profile of Df1/TBX1lacZ (effectively TBX1 null) and TBX1 heterozygous cells isolated from mouse embryos. Hes1, a major effector of Notch signalling, was identified as downregulated in TBX1−/− mutants. Hes1 mutant mice exhibited a partially penetrant range of 22q11DS-like defects including pharyngeal arch artery (PAA), outflow tract, craniofacial and thymic abnormalities. Similar to TBX1 mice, conditional mutagenesis revealed that Hes1 expression in embryonic pharyngeal ectoderm contributes to thymus and pharyngeal arch artery development. These results suggest that Hes1 acts downstream of TBX1 in the morphogenesis of pharyngeal-derived structures.
-
22q11 Deletion Syndrome: A Role for TBX1 in Pharyngeal and Cardiovascular Development
Pediatric Cardiology, 2010Co-Authors: Peter J. ScamblerAbstract:TBX1 is a member of the Tbox family of binding domain transcription factors. TBX1 maps within the region of 22q11 deleted in humans with DiGeorge or velocardiofacial syndrome. Mice haploinsufficient for TBX1 have phenotypes that recapitulate major features of the syndrome, notably abnormal growth and remodelling of the pharyngeal arch arteries. The TBX1 haploinsufficiency phenotype is modified by genetic background and by mutations in putative downstream targets. Homozygous null mutations of TBX1 have more severe defects including failure of outflow tract septation, and absence of the caudal pharyngeal arches. TBX1 is a transcriptional activator, and loss of this activity has been linked to alterations in the expression of various genes involved in cardiovascular morphogenesis. In particular, Fgf and retinoic acid signalling are dysregulated in TBX1 mutants. This article summarises the tissue specific and temporal requirements for TBX1 , and attempts to synthesis what is know about the developmental pathways under its control.
