Showing papers by "Victor Chang Cardiac Research Institute published in 2010"
TL;DR: Central haemodynamic indexes are independent predictors of future CV events and all-cause mortality andAugmentation index predicts clinical events independently of peripheral pressures, while central PP has a marginally but not significantly better predictive ability when compared with peripheral PP.
Abstract: We meta-analysed 11 longitudinal studies that had employed measures of central haemodynamics and had followed 5648 subjects for a mean follow-up of 45 months. The age- and risk-factor-adjusted pooled relative risk (RR) of total CV events was 1.088 (95% CI 1.040-1.139) for a 10 mmHg increase of central systolic pressure, 1.137 (95% CI 1.063-1.215) for a 10 mmHg increase of central pulse pressure (PP), and 1.318 (95% CI 1.093-1.588) for a 10% absolute increase of central augmentation index (AIx). Furthermore, we found that a 10% increase of central AIx was associated with a RR of 1.384 (95% CI 1.192-1.606) for all-cause mortality. When compared with brachial PP, central PP was associated with marginally but not significantly higher RR of clinical events (P ¼ 0.057). Conclusion Central haemodynamic indexes are independent predictors of future CV events and all-cause mortality. Augmenta- tion index predicts clinical events independently of peripheral pressures, while central PP has a marginally but not significantly (P ¼ 0.057) better predictive ability when compared with peripheral PP.
1,223 citations
TL;DR: This review examines the key concept that proteins embedded in the lipid bilayer can respond to the changes in the mechanical environment the lipid Bilayer provides.
Abstract: All cells, including microbes, detect and respond to mechanical forces, of which osmotic pressure is most ancient and universal. Channel proteins have evolved such that they can be directly stretched open when the membrane is under turgor pressure. Osmotic downshock, as in rain, opens bacterial mechanosensitive (MS) channels to jettison osmolytes, relieving pressure and preventing cell lysis. The ion flux through individual channel proteins can be observed directly with a patch clamp. MS channels of large and small conductance (MscL and MscS, respectively) have been cloned, crystallized, and subjected to biophysical and genetic analyses in depth. They are now models to scrutinize how membrane forces direct protein conformational changes. Eukaryotic microbes have homologs from animal sensory channels of the TRP superfamily. The MS channel in yeast is also directly sensitive to membrane stretch. This review examines the key concept that proteins embedded in the lipid bilayer can respond to the changes in the mechanical environment the lipid bilayer provides.
275 citations
TL;DR: The role of redox-active disulfides as switches in proteins is discussed, including the helical CXXC motif, often associated with thioredoxin-fold proteins; and forbiddendisulfides, a group of metastable disulfide that disobey elucidated rules of protein stereochemistry.
Abstract: The molecular mechanisms underlying thiol-based redox control are poorly defined. Disulfide bonds between Cys residues are commonly thought to confer extra rigidity and stability to their resident protein, forming a type of proteinaceous spot weld. Redox biologists have been redefining the role of disulfides over the last 30-40 years. Disulfides are now known to form in the cytosol under conditions of oxidative stress. Isomerization of extracellular disulfides is also emerging as an important regulator of protein function. The current paradigm is that the disulfide proteome consists of two subproteomes: a structural group and a redox-sensitive group. The redox-sensitive group is less stable and often associated with regions of stress in protein structures. Some characterized redox-active disulfides are the helical CXXC motif, often associated with thioredoxin-fold proteins; and forbidden disulfides, a group of metastable disulfides that disobey elucidated rules of protein stereochemistry. Here we discuss the role of redox-active disulfides as switches in proteins.
219 citations
TL;DR: The hypothesis that amyloid-β itself, a known causative factor of AD, causes neuronal miRNA deregulation, which could contribute to the pathomechanisms of AD is addressed.
Abstract: Normal brain development and function depends on microRNA (miRNA) networks to fine tune the balance between the transcriptome and proteome of the cell. These small non-coding RNA regulators are highly enriched in brain where they play key roles in neuronal development, plasticity and disease. In neurodegenerative disorders such as Alzheimer's disease (AD), brain miRNA profiles are altered; thus miRNA dysfunction could be both a cause and a consequence of disease. Our study dissects the complexity of human AD pathology, and addresses the hypothesis that amyloid-β (Aβ) itself, a known causative factor of AD, causes neuronal miRNA deregulation, which could contribute to the pathomechanisms of AD. We used sensitive TaqMan low density miRNA arrays (TLDA) on murine primary hippocampal cultures to show that about half of all miRNAs tested were down-regulated in response to Aβ peptides. Time-course assays of neuronal Aβ treatments show that Aβ is in fact a powerful regulator of miRNA levels as the response of certain mature miRNAs is extremely rapid. Bioinformatic analysis predicts that the deregulated miRNAs are likely to affect target genes present in prominent neuronal pathways known to be disrupted in AD. Remarkably, we also found that the miRNA deregulation in hippocampal cultures was paralleled in vivo by a deregulation in the hippocampus of Aβ42-depositing APP23 mice, at the onset of Aβ plaque formation. In addition, the miRNA deregulation in hippocampal cultures and APP23 hippocampus overlaps with those obtained in human AD studies. Taken together, our findings suggest that neuronal miRNA deregulation in response to an insult by Aβ may be an important factor contributing to the cascade of events leading to AD.
205 citations
TL;DR: The ‘Vascular Aging Continuum’ which is introduced, dovetails with the late phases of the Cardiovascular Continuum and provides a more comprehensive explanation, especially for vascular diseases in nations with little atherosclerosis.
Abstract: The 'Cardiovascular Continuum' was described by Dzau and colleagues in 2006 to explain the development over many years of coronary disease with its complications, then end-stage heart failure. The Continuum identified different points along the way where the process could be interrupted by drug therapies or interventions, then described the trials that have been undertaken over the last three decades to establish their value. The approach summarized the major steps in cardiology through modern times, but it had an emphasis on coronary atherosclerosis in prosperous nations, and did not account fully for the problems of aging, which occur in all societies. Aging of the aorta and elastic arteries causes arterial stiffening and leads to development of cardiac failure and microvascular disease in highly perfused organs such as the brain and kidneys. The 'Vascular Aging Continuum' which we introduce, dovetails with the late phases of the Cardiovascular Continuum and provides a more comprehensive explanation, especially for vascular diseases in nations with little atherosclerosis. It will become more common in the Western World where attention to risk factors and widespread use of statins are responsible for a decrease in atherosclerotic disease, prolongation of life, and dominance of macrovascular and microvascular arterial disease, as well as of cardiac failure.
204 citations
TL;DR: The modular nature of MNAzymes provides potential for their integration into diverse devices such as diagnostic biosensors, molecular computers, and/or nanoscale machines and for their capacity to function as molecular switches and to work in series to create a molecular cascade.
Abstract: To increase the versatility and utility of nucleic acid enzymes, we developed multicomponent complexes, known as MNAzymes, which produce amplified "output" signals in response to specific "input" signals. Multiple oligonucleotide partzymes assemble into active MNAzymes only in the presence of an input assembly facilitator such as a target nucleic acid. Once formed, MNAzymes catalytically modify a generic substrate, generating an amplified output signal that heralds the presence of the target while leaving the target intact. We demonstrated several applications including sensitive, isothermal target detection; discrimination of polymorphisms; and highly specific monitoring of real-time polymerase chain reaction (PCR). Furthermore, we showed their capacity to function as molecular switches and to work in series to create a molecular cascade. The modular nature of MNAzymes, together with the separation of input and output functionalities, provides potential for their integration into diverse devices such as diagnostic biosensors, molecular computers, and/or nanoscale machines.
198 citations
TL;DR: A new mechanism of p53 regulation in cancer and stem cells is demonstrated and a potential therapeutic target for neuroblastoma is uncovered.
Abstract: Inactivation of the p53 tumor suppressor pathway allows cell survival in times of stress and occurs in many human cancers; however, normal embryonic stem cells and some cancers such as neuroblastoma maintain wild-type human TP53 and mouse Trp53 (referred to collectively as p53 herein). Here we describe a miRNA, miR-380-5p, that represses p53 expression via a conserved sequence in the p53 3' untranslated region (UTR). miR-380-5p is highly expressed in mouse embryonic stem cells and neuroblastomas, and high expression correlates with poor outcome in neuroblastomas with neuroblastoma derived v-myc myelocytomatosis viral-related oncogene (MYCN) amplification. miR-380 overexpression cooperates with activated HRAS oncoprotein to transform primary cells, block oncogene-induced senescence and form tumors in mice. Conversely, inhibition of endogenous miR-380-5p in embryonic stem or neuroblastoma cells results in induction of p53, and extensive apoptotic cell death. In vivo delivery of a miR-380-5p antagonist decreases tumor size in an orthotopic mouse model of neuroblastoma. We demonstrate a new mechanism of p53 regulation in cancer and stem cells and uncover a potential therapeutic target for neuroblastoma.
190 citations
TL;DR: The molecular structure of the full-length FliG protein is reported, conformational changes that are involved in rotational switching are identified and the structural basis for the formation of theFliG torque ring is uncovered.
Abstract: The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation.
155 citations
TL;DR: In this article, the authors present crystallographic evidence of interdependent gates in the conduction pathway and reveal the mechanism of polyamine block, where reorientation of the intracellular domains, concomitant with activation, instigates polyamine release from the binding sites to block the permeation pathway.
148 citations
TL;DR: Switching between beta1-selective Beta-blockers and the nonselective beta-blocker carvedilol is well tolerated but results in demonstrable changes in airway function, most marked in patients with COPD.
129 citations
TL;DR: The data indicate that functional variants of MYH6 are associated with cardiac malformations in addition to ASD and provide a novel potential mechanism, and phenotypic heterogeneity has been observed in other genes mutated in CHD.
Abstract: Congenital heart defects (CHD) are collectively the most common form of congenital malformation. Studies of human cases and animal models have revealed that mutations in several genes are responsible for both familial and sporadic forms of CHD. We have previously shown that a mutation in MYH6 can cause an autosomal dominant form of atrial septal defect (ASD), whereas others have identified mutations of the same gene in patients with hypertrophic and dilated cardiomyopathy. In the present study, we report a mutation analysis of MYH6 in patients with a wide spectrum of sporadic CHD. The mutation analysis of MYH6 was performed in DNA samples from 470 cases of isolated CHD using denaturing high-performance liquid chromatography and sequence analysis to detect point mutations and small deletions or insertions, and multiplex amplifiable probe hybridization to detect partial or complete copy number variations. One non-sense mutation, one splicing site mutation and seven non-synonymous coding mutations were identified. Transfection of plasmids encoding mutant and non-mutant green fluorescent protein-MYH6 fusion proteins in mouse myoblasts revealed that the mutations A230P and A1366D significantly disrupt myofibril formation, whereas the H252Q mutation significantly enhances myofibril assembly in comparison with the non-mutant protein. Our data indicate that functional variants of MYH6 are associated with cardiac malformations in addition to ASD and provide a novel potential mechanism. Such phenotypic heterogeneity has been observed in other genes mutated in CHD.
TL;DR: It is demonstrated that selective TG inhibition broadly corrects transcriptional dysregulation in HD and defines a novel HDAC‐independent epigenetic strategy for treating neurodegeneration.
Abstract: Caused by a polyglutamine expansion in the huntingtin protein, Huntington's disease leads to striatal degeneration via the transcriptional dysregulation of a number of genes, including those involved in mitochondrial biogenesis. Here we show that transglutaminase 2, which is upregulated in HD, exacerbates transcriptional dysregulation by acting as a selective corepressor of nuclear genes; transglutaminase 2 interacts directly with histone H3 in the nucleus. In a cellular model of HD, transglutaminase inhibition de-repressed two established regulators of mitochondrial function, PGC-1α and cytochrome c and reversed susceptibility of human HD cells to the mitochondrial toxin, 3-nitroproprionic acid; however, protection mediated by transglutaminase inhibition was not associated with improved mitochondrial bioenergetics. A gene microarray analysis indicated that transglutaminase inhibition normalized expression of not only mitochondrial genes but also 40% of genes that are dysregulated in HD striatal neurons, including chaperone and histone genes. Moreover, transglutaminase inhibition attenuated degeneration in a Drosophila model of HD and protected mouse HD striatal neurons from excitotoxicity. Altogether these findings demonstrate that selective TG inhibition broadly corrects transcriptional dysregulation in HD and defines a novel HDAC-independent epigenetic strategy for treating neurodegeneration.
TL;DR: Comparisons with other cytoplasmic membrane proteins suggest that CL-dependent polar localization in E. coli cells is not a general characteristic of transporters, channels, or osmoregulatory proteins.
Abstract: Fluorescence microscopy has revealed that the phospholipid cardiolipin (CL) and FlAsH-labeled transporters ProP and LacY are concentrated at the poles of Escherichia coli cells. The proportion of CL among E. coli phospholipids can be varied in vivo as it is decreased by cls mutations and it increases with the osmolality of the growth medium. In this report we compare the localization of CL, ProP, and LacY with that of other cytoplasmic membrane proteins. The proportion of cells in which FlAsH-labeled membrane proteins were concentrated at the cell poles was determined as a function of protein expression level and CL content. Each tagged protein was expressed from a pBAD24-derived plasmid; tagged ProP was also expressed from the chromosome. The osmosensory transporter ProP and the mechanosensitive channel MscS concentrated at the poles at frequencies correlated with the cellular CL content. The lactose transporter LacY was found at the poles at a high and CL-independent frequency. ProW (a component of the osmoregulatory transporter ProU), AqpZ (an aquaporin), and MscL (a mechanosensitive channel) were concentrated at the poles in a minority of cells, and this polar localization was CL independent. The frequency of polar localization was independent of induction (at arabinose concentrations up to 1 mM) for proteins encoded by pBAD24-derived plasmids. Complementation studies showed that ProW, AqpZ, MscS, and MscL remained functional after introduction of the FlAsH tag (CCPGCC). These data suggest that CL-dependent polar localization in E. coli cells is not a general characteristic of transporters, channels, or osmoregulatory proteins. Polar localization can be frequent and CL independent (as observed for LacY), frequent and CL dependent (as observed for ProP and MscS), or infrequent (as observed for AqpZ, ProW, and MscL).
TL;DR: Weight loss in both normal and overweight mothers during the periconceptional period results in epigenetic modification of IGF2 in the adrenal gland, adrenal overgrowth, and increased vulnerability to stress in offspring.
Abstract: Adverse conditions in early life result in increased activation of the hypothalamo-pituitary-adrenal axis and in stress responsiveness in offspring. We have developed a model in which "donor" ewes are either normally nourished or overnourished prior to a period of dietary restriction, before transfer of the embryo at 6-7 d after conception to a ewe of normal weight and nutritional history. A moderate restriction of energy intake during the periconceptional period in both normal weight and overweight ewes resulted in increased adrenal mass in male and female lambs and an increased cortisol response to stress in female lambs. The increase in adrenal weight in lambs exposed to periconceptional undernutrition was associated with a decrease in the adrenal mRNA expression of IGF2 and decreased methylation in the proximal CTCF-binding site in the differentially methylated region of the IGF2/H19 gene. Thus, weight loss in both normal and overweight mothers during the periconceptional period results in epigenetic modification of IGF2 in the adrenal gland, adrenal overgrowth, and increased vulnerability to stress in offspring. Determining the appropriate approach to weight loss in the periconceptional period may therefore be important in overweight or obese women seeking to become pregnant.
TL;DR: It is suggested that diverse observations of 'Classic' enzymes 'moonlighting' might herald the existence of currently hidden post-transcriptional regulatory networks between intermediary metabolism and gene expression based on RNA, enzyme and metabolite interactions.
TL;DR: The crystal structure of the peripheral stalk of the A-type ATPase/synthase from Thermus thermophilus, which contains a heterodimeric right-handed coiled coil, a protein fold never observed before, is determined and fitted into the 23 Å resolution EM density of the intact A-ATPase complex.
Abstract: The crystal structure of the peripheral stalk of the A-type ATPase/synthase (A-ATPase) from Thermus thermophilus reveals a heterodimeric right-handed coiled coil, a protein fold never observed before. Fitting of the stalk structure into the EM density of intact A-ATPase provides the most complete composite model so far.
TL;DR: Transcriptional decay patterns induced by reduced Nrg1 suggest a novel mechanism for cardiac transcriptional regulation and dysfunction in disease, potentially linking biomechanical feedback to molecular pathways for growth and differentiation.
Abstract: Rationale: The cardiac gene regulatory network (GRN) is controlled by transcription factors and signaling inputs, but network logic in development and it unraveling in disease is poorly understood. In development, the membrane-tethered signaling ligand Neuregulin (Nrg)1, expressed in endocardium, is essential for ventricular morphogenesis. In adults, Nrg1 protects against heart failure and can induce cardiomyocytes to divide.
Objective: To understand the role of Nrg1 in heart development through analysis of null and hypomorphic Nrg1 mutant mice.
Methods and Results: Chamber domains were correctly specified in Nrg1 mutants, although chamber-restricted genes Hand1 and Cited1 failed to be activated. The chamber GRN subsequently decayed with individual genes exhibiting decay patterns unrelated to known patterning boundaries. Both trabecular and nontrabecular myocardium were affected. Network demise was spatiotemporally dynamic, the most sensitive region being the central part of the left ventricle, in which the GRN underwent complete collapse. Other regions were partially affected with graded sensitivity. In vitro, Nrg1 promoted phospho-Erk1/2–dependent transcription factor expression, cardiomyocyte maturation and cell cycle inhibition. We monitored cardiac pErk1/2 in embryos and found that expression was Nrg1-dependent and levels correlated with cardiac GRN sensitivity in mutants.
Conclusions: The chamber GRN is fundamentally labile and dependent on signaling from extracardiac sources. Nrg1–ErbB1/4–Erk1/2 signaling critically sustains elements of the GRN in trabecular and nontrabecular myocardium, challenging our understanding of Nrg1 function. Transcriptional decay patterns induced by reduced Nrg1 suggest a novel mechanism for cardiac transcriptional regulation and dysfunction in disease, potentially linking biomechanical feedback to molecular pathways for growth and differentiation.
# Novelty and Significance {#article-title-51}
TL;DR: It is shown that structural rearrangements of the protein can be measured in similar conditions as patch clamp recordings while controlling the state of the pore in its natural lipid environment by modifying the lateral pressure distribution via the lipid bilayer.
Abstract: Mechanosensitive channels act as molecular transducers of mechanical force exerted on the membrane of living cells by opening in response to membrane bilayer deformations occurring in physiological processes such as touch, hearing, blood pressure regulation, and osmoregulation. Here, we determine the likely structure of the open state of the mechanosensitive channel of large conductance using a combination of patch clamp, fluorescence resonance energy transfer (FRET) spectroscopy, data from previous electron paramagnetic resonance experiments, and molecular and Brownian dynamics simulations. We show that structural rearrangements of the protein can be measured in similar conditions as patch clamp recordings while controlling the state of the pore in its natural lipid environment by modifying the lateral pressure distribution via the lipid bilayer. Transition to the open state is less dramatic than previously proposed, while the N terminus remains anchored at the surface of the membrane where it can either guide the tilt of or directly translate membrane tension to the conformation of the pore-lining helix. Combining FRET data obtained in physiological conditions with simulations is likely to be of great value for studying conformational changes in a range of multimeric membrane proteins.
TL;DR: A detailed analysis of concomitant betaine uptake and efflux under hyperosmotic conditions indicates that MscCG may act in osmoregulation in C. glutamicum by fine-tuning the steady state concentration of compatible solutes in the cytoplasm which are accumulated in response to hyperOSmotic stress.
TL;DR: It is reported that Smyd 2 is differentially expressed during cardiac development with highest expression in the neonatal heart and evidence for a potential role of Smyd2 in the transcriptional regulation of genes associated with translation is provided and it is revealed that SmyD2, similar to Smyd3, interacts with RNA Polymerase II as well as to the RNA helicase, HELZ.
Abstract: Chromatin modifying enzymes play a critical role in cardiac differentiation. Previously, it has been shown that the targeted deletion of the histone methyltransferase, Smyd1, the founding member of the SET and MYND domain containing (Smyd) family, interferes with cardiomyocyte maturation and proper formation of the right heart ventricle. The highly related paralogue, Smyd2 is a histone 3 lysine 4- and lysine 36-specific methyltransferase expressed in heart and brain. Here, we report that Smyd2 is differentially expressed during cardiac development with highest expression in the neonatal heart. To elucidate the functional role of Smyd2 in the heart, we generated conditional knockout (cKO) mice harboring a cardiomyocyte-specific deletion of Smyd2 and performed histological, functional and molecular analyses. Unexpectedly, cardiac deletion of Smyd2 was dispensable for proper morphological and functional development of the murine heart and had no effect on global histone 3 lysine 4 or 36 methylation. However, we provide evidence for a potential role of Smyd2 in the transcriptional regulation of genes associated with translation and reveal that Smyd2, similar to Smyd3, interacts with RNA Polymerase II as well as to the RNA helicase, HELZ.
TL;DR: Current concepts of the molecular pathogenesis, clinical presentation, natural history, and management of familial DCM are outlined in this review.
TL;DR: The data suggest that factors other than mechanical stress-induced apoptosis contribute to DCM and provide the first demonstration that regular moderate exercise and carvedilol can modify disease progression in lamin A/C–deficient hearts.
Abstract: Rationale: Mutations in the LMNA gene, which encodes the nuclear lamina proteins lamin A and lamin C, are the most common cause of familial dilated cardiomyopathy (DCM). Mechanical stress-induced apoptosis has been proposed as the mechanism underpinning DCM in lamin A/C–deficient hearts, but supporting in vivo evidence has been lacking. Objective: Our aim was to study interventions to modify mechanical stress in heterozygous Lmna knockout (Lmna+/−) mice. Methods and Results: Cardiac structure and function were evaluated before and after exercise training, thoracic aortic constriction, and carvedilol treatment. Lmna+/− mice develop adult-onset DCM with relatively more severe disease in males. Lmna+/− cardiomyocytes show altered nuclear morphology and perinuclear desmin organization, with enhanced responses to hypo-osmotic stress indicative of cytoskeletal instability. Despite these structural defects that provide a template for mechanical stress-induced damage, young Lmna+/− mice subjected to 6 weeks of mo...
TL;DR: Epigenetics as a mediator of disease risk in response to nutritional cues is discussed and the potential for maternal nutrition to heritably alter epigenetic states may have implications for population health and adaptive evolution.
Abstract: Within the Western world's aging and increasingly overweight population, we are seeing an increasing prevalence of adult-onset, lifestyle-related disease such as diabetes, hypertension and atherosclerosis. There is significant evidence that suboptimal nutrition in pregnancy can lead to an increased risk of these diseases developing in offspring, and that this increased risk can be heritable. Thus, poor in utero nutrition may be a major contributor to the current cycle of obesity. While the molecular basis of this phenomenon is unknown, available evidence suggests that it can be mediated by epigenetic changes to gene expression. Here, we discuss epigenetics as a mediator of disease risk in response to nutritional cues. The potential for maternal nutrition to heritably alter epigenetic states may have implications for population health and adaptive evolution.
TL;DR: The spectrum of mutations associated with cardiac septal defects is expanded and two novel putative mutations identified in five patients with atrial or ventricular septals that were not seen in control subjects do not support GATA4 mutations as a common cause of CHD.
Abstract: Congenital heart disease (CHD) represents one of the most common birth defects, but the genetic causes remain largely unknown. Mutations in GATA4, encoding a zinc finger transcription factor with a pivotal role in heart development, have been associated with CHD in several familial cases and a small subset of sporadic patients. To estimate the pathogenetic role of GATA4 in CHD, we screened for mutations in 357 unrelated patients with different congenital heart malformations. In addition to nine synonymous changes, we identified two known (A411V and D425N) and two novel putative mutations (G69D and P163R) in five patients with atrial or ventricular septal defects that were not seen in control subjects. The four mutations did not show altered GATA4 transcriptional activity in synergy with the transcription factors NKX2-5 and TBX20. Our data expand the spectrum of mutations associated with cardiac septal defects but do not support GATA4 mutations as a common cause of CHD.
TL;DR: The data provide a potential mechanistic link between Zac1 in cardiogenesis and congenital heart disease manifestations associated with genetic or epigenetic defects in an imprinted gene network.
Abstract: Rationale: The transcriptional networks guiding heart development remain poorly understood, despite the identification of several essential cardiac transcription factors. Objective: To isolate novel cardiac transcription factors, we performed gene chip analysis and found that Zac1 , a zinc finger-type transcription factor, was strongly expressed in the developing heart. This study was designed to investigate the molecular and functional role of Zac1 as a cardiac transcription factor. Methods and Results: Zac1 was strongly expressed in the heart from cardiac crescent stages and in the looping heart showed a chamber-restricted pattern. Zac1 stimulated luciferase reporter constructs driven by ANF, BNP , or α MHC promoters. Strong functional synergy was seen between Zac1 and Nkx2-5 on the ANF promoter, which carries adjacent Zac1 and Nkx2-5 DNA-binding sites. Zac1 directly associated with the ANF promoter in vitro and in vivo, and Zac1 and Nkx2-5 physically associated through zinc fingers 5 and 6 in Zac1, and the homeodomain in Nkx2-5. Zac1 is a maternally imprinted gene and is the first such gene found to be involved in heart development. Homozygous and paternally derived heterozygous mice carrying an interruption in the Zac1 locus showed decreased levels of chamber and myofilament genes, increased apoptotic cells, partially penetrant lethality and morphological defects including atrial and ventricular septal defects, and thin ventricular walls. Conclusions: Zac1 plays an essential role in the cardiac gene regulatory network. Our data provide a potential mechanistic link between Zac1 in cardiogenesis and congenital heart disease manifestations associated with genetic or epigenetic defects in an imprinted gene network.
TL;DR: Two new missense mutations in the HES7 gene in a single family are identified, with only individuals carrying both mutant alleles being affected by SCD.
Abstract: Spondylocostal dysostosis (SCD) is an inherited disorder with abnormal vertebral segmentation that results in extensive hemivertebrae, truncal shortening and abnormally aligned ribs. It arises during embryonic development by a disruption of formation of somites (the precursor tissue of the vertebrae, ribs and associated tendons and muscles). Four genes causing a subset of autosomal recessive forms of this disease have been identified: DLL3 (SCDO1: MIM 277300), MESP2 (SCDO2: MIM 608681), LFNG (SCDO3: MIM609813) and HES7 (SCDO4). These genes are all essential components of the Notch signalling pathway, which has multiple roles in development and disease. Previously, only a single SCD-causative missense mutation was described in HES7. In this study, we have identified two new missense mutations in the HES7 gene in a single family, with only individuals carrying both mutant alleles being affected by SCD. In vitro functional analysis revealed that one of the mutant HES7 proteins was unable to repress gene expression by DNA binding or protein heterodimerization.
TL;DR: A novel role for SF1 is suggested in promoting ovarian development in addition to its roles in testis differentiation, according to the reduced levels of Sf1 expression in Cited2(-/-) mice.
Abstract: Sex determination is regulated by a molecular antagonism between testis- and ovary-determining pathways in the supporting cell lineage of the gonadal primordia. Genes important for maintaining this lineage play critical roles in early gonadal development, but their influence on testis and ovary differentiation is unclear due to the severity of loss-of-function phenotypes. The transcription factor SF1 (Nr5a1/Ad4BP) is one such factor, required for establishing the supporting cell lineage, and for propagating the male pathway. In the gonad, Sf1 expression is enhanced by the transcriptional co-factor Cited2. We have used the reduced levels of Sf1 expression in Cited2 -/- mice as a hypomorphic model to gain insight into the sex-specific roles of SF1 function in gonadal development. In XY mutant mice, we found that testis development was delayed in Cited2 -/- gonads, and that testis structure was permanently disrupted. In XX Cited2 -/- gonads, ectopic cell migration was observed which correlated with a transient upregulation of Fgf9, and a delay in Wnt4 then Foxl2 expression. These data suggest a novel role for SF1 in promoting ovarian development in addition to its roles in testis differentiation.
TL;DR: It is shown that two structurally distinct TG2 protein isoforms, the full-length ( TG2-L) and the short form (TG2-S), exert opposing effects on cell differentiation, which highlights the potential importance of repressing the GTP binding activity of TG1-L or activating the transamidase activity ofTG1-S for the treatment of neuroblastoma, and possibly also other Myc-induced malignancies, and for enhancing retinoid antic
TL;DR: Functional studies indicated that induction of 14-3-3 binding to EDC3 causes morphological changes in processing body structures, inhibition of microRNA-mediated mRNA post-transcriptional regulation, and alterations in the protein- protein interactions of EDC 3.
TL;DR: It is demonstrated by in situ hybridization that multiple Slit ligands and Robo receptors are expressed in the developing mouse heart and suggested that patterned Slit‐Robo signaling may contribute to the control of oriented cell growth during chamber morphogenesis of the mammalian heart.
Abstract: Development of the mammalian heart is mediated by complex interactions between myocardial, endocardial, and neural crest-derived cells. Studies in Drosophila have shown that the Slit-Robo signaling pathway controls cardiac cell shape changes and lumen formation of the heart tube. Here, we demonstrate by in situ hybridization that multiple Slit ligands and Robo receptors are expressed in the developing mouse heart. Slit3 is the predominant ligand transcribed in the early mouse heart and is expressed in the ventral wall of the linear heart tube and subsequently in chamber but not in atrioventricular canal myocardium. Furthermore, we identify that the homeobox gene Nkx2-5 is required for early ventral restriction of Slit3 and that the T-box transcription factor Tbx2 mediates repression of Slit3 in nonchamber myocardium. Our results suggest that patterned Slit-Robo signaling may contribute to the control of oriented cell growth during chamber morphogenesis of the mammalian heart.