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Anthony B. Firulli - One of the best experts on this subject based on the ideXlab platform.
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Defective HAND1 phosphoregulation uncovers essential roles for HAND1 in limb morphogenesis.
Development (Cambridge England), 2017Co-Authors: Beth A Firulli, Kevin P. Toolan, Hannah Milliar, Jade Harkin, Robyn K. Fuchs, Alexander G. Robling, Anthony B. FirulliAbstract:The morphogenesis of the vertebrate limbs is a complex process in which cell signaling and transcriptional regulation coordinate diverse structural adaptations in diverse species. In this study, we examine the consequences of altering HAND1 dimer choice regulation within developing vertebrate limbs. Although HAND1 deletion via the limb-specific Prrx1-Cre reveals a non-essential role for HAND1 in mouse limb morphogenesis, altering HAND1 phosphoregulation, and consequently HAND1 dimerization affinities, results in a severe truncation of proximal-anterior limb elements. Molecular analysis reveals a non-cell-autonomous mechanism that causes widespread cell death within the embryonic limb bud. In addition, we observe changes in proximal-anterior gene regulation, including a reduction in the expression of Irx3, Irx5, Gli3 and Alx4, all of which are upregulated in Hand2 limb conditional knockouts. A reduction of Hand2 and Shh gene dosage improves the integrity of anterior limb structures, validating the importance of the Twist-family bHLH dimer pool in limb morphogenesis.
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Hand factor ablation causes defective left ventricular chamber development and compromised adult cardiac function
2017Co-Authors: Joshua W Vincentz, Kevin P. Toolan, Wenjun Zhang, Anthony B. FirulliAbstract:Coordinated cardiomyocyte growth, differentiation, and morphogenesis are essential for heart formation. We demonstrate that the bHLH transcription factors HAND1 and Hand2 play critical regulatory roles for left ventricle (LV) cardiomyocyte proliferation and morphogenesis. Using an LV-specific Cre allele (HAND1LV-Cre), we ablate HAND1-lineage cardiomyocytes, revealing that DTA-mediated cardiomyocyte death results in a hypoplastic LV by E10.5. Once HAND1-linage cells are removed from the LV, and HAND1 expression is switched off, embryonic hearts recover by E16.5. In contrast, conditional LV loss-of-function of both HAND1 and Hand2 results in aberrant trabeculation and thickened compact zone myocardium resulting from enhanced proliferation and a breakdown of compact zone/trabecular/ventricular septal identity. Surviving HAND1;Hand2 mutants display diminished cardiac function that is rescued by concurrent ablation of Hand-null cardiomyocytes. Collectively, we conclude that, within a mixed cardiomyocyte population, removal of defective myocardium and replacement with healthy endogenous cardiomyocytes may provide an effective strategy for cardiac repair.
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A Phox2- and Hand2-dependent HAND1 cis-regulatory element reveals a unique gene dosage requirement for Hand2 during sympathetic neurogenesis.
The Journal of Neuroscience, 2012Co-Authors: Joshua W Vincentz, Andrew B. Fleming, Marthe J. Howard, Nathan J Vandusen, Beth A Firulli, Michael Rubart, Anthony B. FirulliAbstract:Neural crest cell specification and differentiation to a sympathetic neuronal fate serves as an important model for neurogenesis and depends upon the function of both bHLH transcription factors, notably Hand2, and homeodomain transcription factors, including Phox2b. Here, we define a 1007 bp cis -regulatory element 5′ of the HAND1 gene sufficient to drive reporter expression within the sympathetic chain of transgenic mice. Comparative genomic analyses uncovered evolutionarily conserved consensus-binding sites within this element, which chromatin immunoprecipitation and electrophoretic mobility shift assays confirm are bound by Hand2 and Phox2b. Mutational analyses revealed that the conserved Phox2 and E-box binding sites are necessary for proper cis -regulatory element activity, and expression analyses on both Hand2 conditionally null and hypomorphic backgrounds demonstrate that Hand2 is required for reporter activation in a gene dosage-dependent manner. We demonstrate that Hand2 and HAND1 differentially bind the E-boxes in this cis -regulatory element, establishing molecular differences between these two factors. Finally, we demonstrate that HAND1 is dispensable for normal tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH) expression in sympathetic neurons, even when Hand2 gene dosage is concurrently reduced by half. Together, these data define a tissue-specific HAND1 cis -regulatory element controlled by two factors essential for the development of the sympathetic nervous system and provide in vivo regulatory evidence to support previous findings that Hand2, rather than HAND1, is predominantly responsible for regulating TH, DBH, and HAND1 expression in developing sympathetic neurons.
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Hand factors as regulators of cardiac morphogenesis and implications for congenital heart defects.
Birth defects research. Part A Clinical and molecular teratology, 2011Co-Authors: Joshua W Vincentz, Ralston M. Barnes, Anthony B. FirulliAbstract:Almost 15 years of careful study have established the related basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 as critical for heart development across evolution. Hand factors make broad contributions, revealed through animal models, to the development of multiple cellular lineages that ultimately contribute to the heart. They perform critical roles in ventricular cardiomyocyte growth, differentiation, morphogenesis, and conduction. They are also important for the proper development of the cardiac outflow tract, epicardium, and endocardium. Molecularly, they function both through DNA binding and through protein-protein interactions, which are regulated transcriptionally, posttranscriptionally by microRNAs, and posttranslationally through phosphoregulation. Although direct Hand factor transcriptional targets are progressively being identified, confirmed direct targets of Hand factor transcriptional activity in the heart are limited. Identification of these targets will be critical to model the mechanisms by which Hand factor bHLH interactions affect developmental pathways. Improved understanding of Hand factor-mediated transcriptional cascades will be necessary to determine how Hand factor dysregulation translates to human disease phenotypes. This review summarizes the insight that animal models have provided into the regulation and function of these factors during heart development, in addition to the recent findings that suggest roles for HAND1 and HAND2 in human congenital heart disease.
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Hand2 Loss-of-Function in HAND1-Expressing Cells Reveals Distinct Roles in Epicardial and Coronary Vessel Development
Circulation Research, 2011Co-Authors: Ralston M. Barnes, Simon J. Conway, Peter Cserjesi, Yuka Morikawa, Nathan J Vandusen, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:Rationale: The basic helix–loop–helix (bHLH) transcription factors HAND1 and Hand2 are essential for embryonic development. Given their requirement for cardiogenesis, it is imperative to determine their impact on cardiovascular function. Objective: To deduce the role of Hand2 within the epicardium. Method and Results: We engineered a HAND1 allele expressing Cre recombinase. Cardiac HAND1 expression is largely limited to cells of the primary heart field, overlapping little with Hand2 expression. HAND1 is expressed within the septum transversum, and the HAND1 lineage marks the proepicardial organ and epicardium. To examine Hand factor functional overlap, we conditionally deleted Hand2 from HAND1 -expressing cells. Hand2 mutants display defective epicardialization and fail to form coronary arteries, coincident with altered extracellular matrix deposition and Pdgfr expression. Conclusions: These data demonstrate a hierarchal relationship whereby transient HAND1 septum transversum expression defines epicardial precursors that are subsequently dependent on Hand2 function.
Beth A Firulli - One of the best experts on this subject based on the ideXlab platform.
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Defective HAND1 phosphoregulation uncovers essential roles for HAND1 in limb morphogenesis.
Development (Cambridge England), 2017Co-Authors: Beth A Firulli, Kevin P. Toolan, Hannah Milliar, Jade Harkin, Robyn K. Fuchs, Alexander G. Robling, Anthony B. FirulliAbstract:The morphogenesis of the vertebrate limbs is a complex process in which cell signaling and transcriptional regulation coordinate diverse structural adaptations in diverse species. In this study, we examine the consequences of altering HAND1 dimer choice regulation within developing vertebrate limbs. Although HAND1 deletion via the limb-specific Prrx1-Cre reveals a non-essential role for HAND1 in mouse limb morphogenesis, altering HAND1 phosphoregulation, and consequently HAND1 dimerization affinities, results in a severe truncation of proximal-anterior limb elements. Molecular analysis reveals a non-cell-autonomous mechanism that causes widespread cell death within the embryonic limb bud. In addition, we observe changes in proximal-anterior gene regulation, including a reduction in the expression of Irx3, Irx5, Gli3 and Alx4, all of which are upregulated in Hand2 limb conditional knockouts. A reduction of Hand2 and Shh gene dosage improves the integrity of anterior limb structures, validating the importance of the Twist-family bHLH dimer pool in limb morphogenesis.
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A Phox2- and Hand2-dependent HAND1 cis-regulatory element reveals a unique gene dosage requirement for Hand2 during sympathetic neurogenesis.
The Journal of Neuroscience, 2012Co-Authors: Joshua W Vincentz, Andrew B. Fleming, Marthe J. Howard, Nathan J Vandusen, Beth A Firulli, Michael Rubart, Anthony B. FirulliAbstract:Neural crest cell specification and differentiation to a sympathetic neuronal fate serves as an important model for neurogenesis and depends upon the function of both bHLH transcription factors, notably Hand2, and homeodomain transcription factors, including Phox2b. Here, we define a 1007 bp cis -regulatory element 5′ of the HAND1 gene sufficient to drive reporter expression within the sympathetic chain of transgenic mice. Comparative genomic analyses uncovered evolutionarily conserved consensus-binding sites within this element, which chromatin immunoprecipitation and electrophoretic mobility shift assays confirm are bound by Hand2 and Phox2b. Mutational analyses revealed that the conserved Phox2 and E-box binding sites are necessary for proper cis -regulatory element activity, and expression analyses on both Hand2 conditionally null and hypomorphic backgrounds demonstrate that Hand2 is required for reporter activation in a gene dosage-dependent manner. We demonstrate that Hand2 and HAND1 differentially bind the E-boxes in this cis -regulatory element, establishing molecular differences between these two factors. Finally, we demonstrate that HAND1 is dispensable for normal tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH) expression in sympathetic neurons, even when Hand2 gene dosage is concurrently reduced by half. Together, these data define a tissue-specific HAND1 cis -regulatory element controlled by two factors essential for the development of the sympathetic nervous system and provide in vivo regulatory evidence to support previous findings that Hand2, rather than HAND1, is predominantly responsible for regulating TH, DBH, and HAND1 expression in developing sympathetic neurons.
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Hand2 Loss-of-Function in HAND1-Expressing Cells Reveals Distinct Roles in Epicardial and Coronary Vessel Development
Circulation Research, 2011Co-Authors: Ralston M. Barnes, Simon J. Conway, Peter Cserjesi, Yuka Morikawa, Nathan J Vandusen, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:Rationale: The basic helix–loop–helix (bHLH) transcription factors HAND1 and Hand2 are essential for embryonic development. Given their requirement for cardiogenesis, it is imperative to determine their impact on cardiovascular function. Objective: To deduce the role of Hand2 within the epicardium. Method and Results: We engineered a HAND1 allele expressing Cre recombinase. Cardiac HAND1 expression is largely limited to cells of the primary heart field, overlapping little with Hand2 expression. HAND1 is expressed within the septum transversum, and the HAND1 lineage marks the proepicardial organ and epicardium. To examine Hand factor functional overlap, we conditionally deleted Hand2 from HAND1 -expressing cells. Hand2 mutants display defective epicardialization and fail to form coronary arteries, coincident with altered extracellular matrix deposition and Pdgfr expression. Conclusions: These data demonstrate a hierarchal relationship whereby transient HAND1 septum transversum expression defines epicardial precursors that are subsequently dependent on Hand2 function.
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analysis of the HAND1 cell lineage reveals novel contributions to cardiovascular neural crest extra embryonic and lateral mesoderm derivatives
Developmental Dynamics, 2010Co-Authors: Ralston M. Barnes, Simon J. Conway, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:The basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of HAND1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of β-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of HAND1-expressing cells. HAND1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between HAND1 expression and HAND1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel HAND1 functions in structures not thought to be HAND1-dependent. Developmental Dynamics 239:3086–3097, 2010. © 2010 Wiley-Liss, Inc.
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Analysis of the HAND1 cell lineage reveals novel contributions to cardiovascular, neural crest, extra‐embryonic, and lateral mesoderm derivatives
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Ralston M. Barnes, Simon J. Conway, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:The basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of HAND1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of β-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of HAND1-expressing cells. HAND1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between HAND1 expression and HAND1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel HAND1 functions in structures not thought to be HAND1-dependent. Developmental Dynamics 239:3086–3097, 2010. © 2010 Wiley-Liss, Inc.
Eric N. Olson - One of the best experts on this subject based on the ideXlab platform.
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Abstract 786: Hand Genes in the Mammalian Heart Chamber Formation
Circulation, 2007Co-Authors: Jun Maeda, Hiroyuki Yamagishi, Takatoshi Tsuchihashi, Eric N. Olson, Deepak SrivastavaAbstract:Hand genes ( HAND1/eHand and Hand2/dHand ) encode critical transcription factors required for cardiovascular development. HAND1 and Hand2 are complementally expressed during the murine heart development; Hand2 is expressed throughout the heart predominantly in right ventricle, whereas HAND1 is restricted in left ventricle. Although HAND1 null ( HAND1 −/− ) mice die before the cardiac looping, cardiac-specific HAND1 −/− mice survive until birth and display defects in left ventricle and endocardial cushion. Hand2 null ( Hand2 −/− ) mice die at embryonic day (E) 10.5 due to the heart failure and display severe hypoplasia of right ventricle poor trabeculation in left ventricle along with developmental defects of pharyngeal arches and limb buds. To delineate the genetic redundancy and regional function of Hand genes in ventricular development we generated genetically engineered Hand2 HAND1/HAND1 mice where a Hand2 gene was replaced by the HAND1 cDNA using homologous recombination so that HAND1 , but not Hand2 , was driven under control of endogenous Hand2 promoter, and Hand2 HAND1/ − mice from mating of Hand2 HAND1/+ mice with Hand2 +/ − mice. Our observation reveled that Hand2 HAND1/HAND1 mice had hypoplastic right ventricle, but no sign of heart failure before E12.5, and survived until E13.5. This phenotype was milder than that of Hand2 −/− or Hand2 HAND1/ − mice, suggesting that HAND1 could partially compensate the function of Hand2 in ventricular formation. In contrast, pharyngeal arch development was not affected until E13.5 whereas developmental arrest was observed in the posterior region of limb buds where Hand2 regulates the Sonic hedgehog expression. These results indicate that in mammalian heart, Hand genes may have common function and partial genetic redundancy for ventricular formation, and that Hand genes are genetically redundant in tissue-specific manner during murine development. The complementally expression of Hand genes may be essential for regionalization of right and left ventricles.
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Hand transcription factors cooperatively regulate development of the distal midline mesenchyme.
Developmental biology, 2007Co-Authors: Ana C. Barbosa, Eric N. Olson, Noriko Funato, Shelby L. Chapman, Marc D. Mckee, James A. Richardson, Hiromi YanagisawaAbstract:Hand proteins are evolutionally conserved basic helix-loop-helix (bHLH) transcription factors implicated in development of neural crest-derived tissues, heart and limb. HAND1 is expressed in the distal (ventral) zone of the branchial arches, whereas the Hand2 expression domain extends ventrolaterally to occupy two-thirds of the mandibular arch. To circumvent the early embryonic lethality of HAND1 or Hand2-null embryos and to examine their roles in neural crest development, we generated mice with neural crest-specific deletion of HAND1 and various combinations of mutant alleles of Hand2. Ablation of HAND1 alone in neural crest cells did not affect embryonic development, however, further removing one Hand2 allele or deleting the ventrolateral branchial arch expression of Hand2 led to a novel phenotype presumably due to impaired growth of the distal midline mesenchyme. Although we failed to detect changes in proliferation or apoptosis between the distal mandibular arch of wild-type and HAND1/Hand2 compound mutants at embryonic day (E)10.5, dysregulation of Pax9, Msx2 and Prx2 was observed in the distal mesenchyme at E12.5. In addition, the inter-dental mesenchyme and distal symphysis of Meckel's cartilage became hypoplastic, resulting in the formation of a single fused lower incisor within the hypoplastic fused mandible. These findings demonstrate the importance of Hand transcription factors in the transcriptional circuitry of craniofacial and tooth development.
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The HAND1 and Hand2 transcription factors regulate expansion of the embryonic cardiac ventricles in a gene dosage-dependent manner
Development (Cambridge England), 2004Co-Authors: David G. Mcfadden, Deepak Srivastava, Ana C. Barbosa, James A. Richardson, Michael D. Schneider, Eric N. OlsonAbstract:The basic helix-loop-helix transcription factors HAND1 and Hand2 display dynamic and spatially restricted expression patterns in the developing heart. Mice that lack Hand2 die at embryonic day 10.5 from right ventricular hypoplasia and vascular defects, whereas mice that lack HAND1 die at embryonic day 8.5 from placental and extra-embryonic abnormalities that preclude analysis of its potential role in later stages of heart development. To determine the cardiac functions of HAND1, we generated mice harboring a conditional HAND1-null allele and excised the gene by cardiac-specific expression of Cre recombinase. Embryos homozygous for the cardiac HAND1 gene deletion displayed defects in the left ventricle and endocardial cushions, and exhibited dysregulated ventricular gene expression. However, these embryos survived until the perinatal period when they died from a spectrum of cardiac abnormalities. Creation of HAND1/2 double mutant mice revealed gene dose-sensitive functions of Hand transcription factors in the control of cardiac morphogenesis and ventricular gene expression. These findings demonstrate that Hand factors play pivotal and partially redundant roles in cardiac morphogenesis, cardiomyocyte differentiation and cardiac-specific transcription.
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heart and extra embryonic mesodermal defects in mouse embryos lacking the bhlh transcription factor HAND1
Nature Genetics, 1998Co-Authors: Anthony B. Firulli, Deepak Srivastava, David G. Mcfadden, Qing Lin, Eric N. OlsonAbstract:The basic helix-loop-helix (bHLH) transcription factors, HAND1 and Hand2 (refs 1,2), also called eHand/Hxt/Thing1 and dHand/Hed/Thing2 (refs 3,4), respectively, are expressed in the heart and certain neural-crest derivatives during embryogenesis. In addition, HAND1 is expressed in extraembryonic membranes, whereas Hand2 is expressed in the deciduum. Previous studies have demonstrated that Hand2 is required for formation of the right ventricle of the heart and the aortic arch arteries. We have generated a germline mutation in the mouse HAND1 gene by replacing the first coding exon with a beta-galactosidase reporter gene. Embryos homozygous for the HAND1 null allele died between embryonic days 8.5 and 9.5 and exhibited yolk sac abnormalities due to a deficiency in extraembryonic mesoderm. Heart development was also perturbed and did not progress beyond the cardiac-looping stage. Our results demonstrate important roles for HAND1 in extraembryonic mesodermal and heart development.
Ralston M. Barnes - One of the best experts on this subject based on the ideXlab platform.
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Hand factors as regulators of cardiac morphogenesis and implications for congenital heart defects.
Birth defects research. Part A Clinical and molecular teratology, 2011Co-Authors: Joshua W Vincentz, Ralston M. Barnes, Anthony B. FirulliAbstract:Almost 15 years of careful study have established the related basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 as critical for heart development across evolution. Hand factors make broad contributions, revealed through animal models, to the development of multiple cellular lineages that ultimately contribute to the heart. They perform critical roles in ventricular cardiomyocyte growth, differentiation, morphogenesis, and conduction. They are also important for the proper development of the cardiac outflow tract, epicardium, and endocardium. Molecularly, they function both through DNA binding and through protein-protein interactions, which are regulated transcriptionally, posttranscriptionally by microRNAs, and posttranslationally through phosphoregulation. Although direct Hand factor transcriptional targets are progressively being identified, confirmed direct targets of Hand factor transcriptional activity in the heart are limited. Identification of these targets will be critical to model the mechanisms by which Hand factor bHLH interactions affect developmental pathways. Improved understanding of Hand factor-mediated transcriptional cascades will be necessary to determine how Hand factor dysregulation translates to human disease phenotypes. This review summarizes the insight that animal models have provided into the regulation and function of these factors during heart development, in addition to the recent findings that suggest roles for HAND1 and HAND2 in human congenital heart disease.
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Hand2 Loss-of-Function in HAND1-Expressing Cells Reveals Distinct Roles in Epicardial and Coronary Vessel Development
Circulation Research, 2011Co-Authors: Ralston M. Barnes, Simon J. Conway, Peter Cserjesi, Yuka Morikawa, Nathan J Vandusen, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:Rationale: The basic helix–loop–helix (bHLH) transcription factors HAND1 and Hand2 are essential for embryonic development. Given their requirement for cardiogenesis, it is imperative to determine their impact on cardiovascular function. Objective: To deduce the role of Hand2 within the epicardium. Method and Results: We engineered a HAND1 allele expressing Cre recombinase. Cardiac HAND1 expression is largely limited to cells of the primary heart field, overlapping little with Hand2 expression. HAND1 is expressed within the septum transversum, and the HAND1 lineage marks the proepicardial organ and epicardium. To examine Hand factor functional overlap, we conditionally deleted Hand2 from HAND1 -expressing cells. Hand2 mutants display defective epicardialization and fail to form coronary arteries, coincident with altered extracellular matrix deposition and Pdgfr expression. Conclusions: These data demonstrate a hierarchal relationship whereby transient HAND1 septum transversum expression defines epicardial precursors that are subsequently dependent on Hand2 function.
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analysis of the HAND1 cell lineage reveals novel contributions to cardiovascular neural crest extra embryonic and lateral mesoderm derivatives
Developmental Dynamics, 2010Co-Authors: Ralston M. Barnes, Simon J. Conway, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:The basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of HAND1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of β-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of HAND1-expressing cells. HAND1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between HAND1 expression and HAND1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel HAND1 functions in structures not thought to be HAND1-dependent. Developmental Dynamics 239:3086–3097, 2010. © 2010 Wiley-Liss, Inc.
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Analysis of the HAND1 cell lineage reveals novel contributions to cardiovascular, neural crest, extra‐embryonic, and lateral mesoderm derivatives
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Ralston M. Barnes, Simon J. Conway, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:The basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of HAND1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of β-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of HAND1-expressing cells. HAND1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between HAND1 expression and HAND1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel HAND1 functions in structures not thought to be HAND1-dependent. Developmental Dynamics 239:3086–3097, 2010. © 2010 Wiley-Liss, Inc.
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Analysis of a HAND1 hypomorphic allele reveals a critical threshold for embryonic viability
Developmental dynamics : an official publication of the American Association of Anatomists, 2010Co-Authors: Beth A Firulli, Ralston M. Barnes, Joshua W Vincentz, David P. Mcconville, James S. Byers, Anthony B. FirulliAbstract:Loss-of-function analysis of the basic helix–loop–helix (bHLH) transcription factor HAND1 indicates critical roles in development. In an effort to generate a HAND1 cDNA knock-in reporter mouse, we generated two hypomorphic alleles, which extend embryonic survival to between embryonic day (E) 10.5 and E12.5. Heart morphogenesis appears largely normal; however, hypomorphic mice display thin left ventricular myocardium and reduction in pharyngeal mesoderm. Caudal defects, large allantois, and thickened yolk sac are observed and consistent with systemic HAND1 gene deletion. HAND1 mRNA is expressed at 30% of wild-type littermates and known HAND1-dependent genes show intermediate expression compared with wild-type and HAND1 null mice. Interestingly, putative bHLH partners, Hand2 and Twist1, show altered expression in both HAND1 null and hypomorphic backgrounds and intercrossing the HAND1 hypomorphic mice onto the Hand2 systemic null background exacerbates the cardiac and lateral mesoderm phenotypes. Together, these data define a critical threshold of HAND1 expression that is necessary for embryonic survival. Developmental Dynamics 239:2748–2760, 2010. © 2010 Wiley-Liss, Inc.
Joshua W Vincentz - One of the best experts on this subject based on the ideXlab platform.
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Hand factor ablation causes defective left ventricular chamber development and compromised adult cardiac function
2017Co-Authors: Joshua W Vincentz, Kevin P. Toolan, Wenjun Zhang, Anthony B. FirulliAbstract:Coordinated cardiomyocyte growth, differentiation, and morphogenesis are essential for heart formation. We demonstrate that the bHLH transcription factors HAND1 and Hand2 play critical regulatory roles for left ventricle (LV) cardiomyocyte proliferation and morphogenesis. Using an LV-specific Cre allele (HAND1LV-Cre), we ablate HAND1-lineage cardiomyocytes, revealing that DTA-mediated cardiomyocyte death results in a hypoplastic LV by E10.5. Once HAND1-linage cells are removed from the LV, and HAND1 expression is switched off, embryonic hearts recover by E16.5. In contrast, conditional LV loss-of-function of both HAND1 and Hand2 results in aberrant trabeculation and thickened compact zone myocardium resulting from enhanced proliferation and a breakdown of compact zone/trabecular/ventricular septal identity. Surviving HAND1;Hand2 mutants display diminished cardiac function that is rescued by concurrent ablation of Hand-null cardiomyocytes. Collectively, we conclude that, within a mixed cardiomyocyte population, removal of defective myocardium and replacement with healthy endogenous cardiomyocytes may provide an effective strategy for cardiac repair.
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A Phox2- and Hand2-dependent HAND1 cis-regulatory element reveals a unique gene dosage requirement for Hand2 during sympathetic neurogenesis.
The Journal of Neuroscience, 2012Co-Authors: Joshua W Vincentz, Andrew B. Fleming, Marthe J. Howard, Nathan J Vandusen, Beth A Firulli, Michael Rubart, Anthony B. FirulliAbstract:Neural crest cell specification and differentiation to a sympathetic neuronal fate serves as an important model for neurogenesis and depends upon the function of both bHLH transcription factors, notably Hand2, and homeodomain transcription factors, including Phox2b. Here, we define a 1007 bp cis -regulatory element 5′ of the HAND1 gene sufficient to drive reporter expression within the sympathetic chain of transgenic mice. Comparative genomic analyses uncovered evolutionarily conserved consensus-binding sites within this element, which chromatin immunoprecipitation and electrophoretic mobility shift assays confirm are bound by Hand2 and Phox2b. Mutational analyses revealed that the conserved Phox2 and E-box binding sites are necessary for proper cis -regulatory element activity, and expression analyses on both Hand2 conditionally null and hypomorphic backgrounds demonstrate that Hand2 is required for reporter activation in a gene dosage-dependent manner. We demonstrate that Hand2 and HAND1 differentially bind the E-boxes in this cis -regulatory element, establishing molecular differences between these two factors. Finally, we demonstrate that HAND1 is dispensable for normal tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH) expression in sympathetic neurons, even when Hand2 gene dosage is concurrently reduced by half. Together, these data define a tissue-specific HAND1 cis -regulatory element controlled by two factors essential for the development of the sympathetic nervous system and provide in vivo regulatory evidence to support previous findings that Hand2, rather than HAND1, is predominantly responsible for regulating TH, DBH, and HAND1 expression in developing sympathetic neurons.
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Hand factors as regulators of cardiac morphogenesis and implications for congenital heart defects.
Birth defects research. Part A Clinical and molecular teratology, 2011Co-Authors: Joshua W Vincentz, Ralston M. Barnes, Anthony B. FirulliAbstract:Almost 15 years of careful study have established the related basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 as critical for heart development across evolution. Hand factors make broad contributions, revealed through animal models, to the development of multiple cellular lineages that ultimately contribute to the heart. They perform critical roles in ventricular cardiomyocyte growth, differentiation, morphogenesis, and conduction. They are also important for the proper development of the cardiac outflow tract, epicardium, and endocardium. Molecularly, they function both through DNA binding and through protein-protein interactions, which are regulated transcriptionally, posttranscriptionally by microRNAs, and posttranslationally through phosphoregulation. Although direct Hand factor transcriptional targets are progressively being identified, confirmed direct targets of Hand factor transcriptional activity in the heart are limited. Identification of these targets will be critical to model the mechanisms by which Hand factor bHLH interactions affect developmental pathways. Improved understanding of Hand factor-mediated transcriptional cascades will be necessary to determine how Hand factor dysregulation translates to human disease phenotypes. This review summarizes the insight that animal models have provided into the regulation and function of these factors during heart development, in addition to the recent findings that suggest roles for HAND1 and HAND2 in human congenital heart disease.
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Hand2 Loss-of-Function in HAND1-Expressing Cells Reveals Distinct Roles in Epicardial and Coronary Vessel Development
Circulation Research, 2011Co-Authors: Ralston M. Barnes, Simon J. Conway, Peter Cserjesi, Yuka Morikawa, Nathan J Vandusen, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:Rationale: The basic helix–loop–helix (bHLH) transcription factors HAND1 and Hand2 are essential for embryonic development. Given their requirement for cardiogenesis, it is imperative to determine their impact on cardiovascular function. Objective: To deduce the role of Hand2 within the epicardium. Method and Results: We engineered a HAND1 allele expressing Cre recombinase. Cardiac HAND1 expression is largely limited to cells of the primary heart field, overlapping little with Hand2 expression. HAND1 is expressed within the septum transversum, and the HAND1 lineage marks the proepicardial organ and epicardium. To examine Hand factor functional overlap, we conditionally deleted Hand2 from HAND1 -expressing cells. Hand2 mutants display defective epicardialization and fail to form coronary arteries, coincident with altered extracellular matrix deposition and Pdgfr expression. Conclusions: These data demonstrate a hierarchal relationship whereby transient HAND1 septum transversum expression defines epicardial precursors that are subsequently dependent on Hand2 function.
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analysis of the HAND1 cell lineage reveals novel contributions to cardiovascular neural crest extra embryonic and lateral mesoderm derivatives
Developmental Dynamics, 2010Co-Authors: Ralston M. Barnes, Simon J. Conway, Joshua W Vincentz, Beth A Firulli, Anthony B. FirulliAbstract:The basic Helix-Loop-Helix (bHLH) transcription factors HAND1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of HAND1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of β-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of HAND1-expressing cells. HAND1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between HAND1 expression and HAND1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel HAND1 functions in structures not thought to be HAND1-dependent. Developmental Dynamics 239:3086–3097, 2010. © 2010 Wiley-Liss, Inc.
