scholarly journals Atrial and Sinoatrial Node Development in the Zebrafish Heart

2021 ◽  
Vol 8 (2) ◽  
pp. 15
Author(s):  
Kendall E. Martin ◽  
Joshua S. Waxman
Keyword(s):  
Heart Development ◽  
Molecular Mechanisms ◽  
Sinoatrial Node ◽  
Genetic Manipulation ◽  
Heart Defects ◽  
Postnatal Life ◽  
And Function ◽  
Early Developmental ◽  
Node Development ◽  
Chamber Size

Proper development and function of the vertebrate heart is vital for embryonic and postnatal life. Many congenital heart defects in humans are associated with disruption of genes that direct the formation or maintenance of atrial and pacemaker cardiomyocytes at the venous pole of the heart. Zebrafish are an outstanding model for studying vertebrate cardiogenesis, due to the conservation of molecular mechanisms underlying early heart development, external development, and ease of genetic manipulation. Here, we discuss early developmental mechanisms that instruct appropriate formation of the venous pole in zebrafish embryos. We primarily focus on signals that determine atrial chamber size and the specialized pacemaker cells of the sinoatrial node through directing proper specification and differentiation, as well as contemporary insights into the plasticity and maintenance of cardiomyocyte identity in embryonic zebrafish hearts. Finally, we integrate how these insights into zebrafish cardiogenesis can serve as models for human atrial defects and arrhythmias.

scholarly journals Abnormal Cardiac Development in the Absence of Heart Glycogen

2004 ◽  
Vol 24 (16) ◽  
pp. 7179-7187 ◽  
Author(s):  
Bartholomew A. Pederson ◽  
Hanying Chen ◽  
Jill M. Schroeder ◽  
Weinian Shou ◽  
Anna A. DePaoli-Roach ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Cardiac Muscle ◽  
Heart Development ◽  
Congenital Heart ◽  
Cardiac Development ◽  
Glycogen Synthase ◽  
Heart Defects ◽  
Mendelian Inheritance ◽  
And Function ◽  
Impaired Cardiac Function

ABSTRACT Glycogen serves as a repository of glucose in many mammalian tissues. Mice lacking this glucose reserve in muscle, heart, and several other tissues were generated by disruption of the GYS1 gene, which encodes an isoform of glycogen synthase. Crossing mice heterozygous for the GYS1 disruption resulted in a significant underrepresentation of GYS1-null mice in the offspring. Timed matings established that Mendelian inheritance was followed for up to 18.5 days postcoitum (dpc) and that ∼90% of GYS1-null animals died soon after birth due to impaired cardiac function. Defects in cardiac development began between 11.5 and 14.5 dpc. At 18.5 dpc, the hearts were significantly smaller, with reduced ventricular chamber size and enlarged atria. Consistent with impaired cardiac function, edema, pooling of blood, and hemorrhagic liver were seen. Glycogen synthase and glycogen were undetectable in cardiac muscle and skeletal muscle from the surviving null mice, and the hearts showed normal morphology and function. Congenital heart disease is one of the most common birth defects in humans, at up to 1 in 50 live births. The results provide the first direct evidence that the ability to synthesize glycogen in cardiac muscle is critical for normal heart development and hence that its impairment could be a significant contributor to congenital heart defects.

Prenatal ethanol exposure impairs the conduction delay at the atrioventricular junction in the looping heart

2021 ◽  
Author(s):  
Shan Ling ◽  
Michael W Jenkins ◽  
Michiko Watanabe ◽  
Stephanie M Ford ◽  
Andrew M Rollins
Keyword(s):  
Heart Development ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Heart Defects ◽  
Ethanol Exposure ◽  
Cardiac Conduction ◽  
Conduction Delay ◽  
Prenatal Ethanol Exposure ◽  
Endocardial Cushions ◽  
Atrioventricular Junction

The etiology of ethanol-related congenital heart defects has been the focus of much study, but most research has concentrated on cellular and molecular mechanisms. We have shown with optical coherence tomography (OCT) that ethanol exposure led to increased retrograde flow and smaller atrioventricular (AV) cushions compared to controls. Since AV cushions play a role in patterning the conduction delay at the atrioventricular junction (AVJ), this study aims to investigate whether ethanol exposure alters the AVJ conduction in early looping hearts and whether this alteration is related to the decreased cushion size. Quail embryos were exposed to a single dose of ethanol at gastrulation, and Hamburger-Hamilton stage 19 - 20 hearts were dissected for imaging. Cardiac conduction was measured using an optical mapping microscope and we imaged the endocardial cushions using OCT. Our results showed that, compared with controls, ethanol-exposed embryos exhibited abnormally fast AVJ conduction and reduced cushion size. However, this increased conduction velocity (CV) did not strictly correlate with decreased cushion volume and thickness. By matching the CV map to the cushion size map, we found that the slowest conduction location was consistently at the atrial side of the AVJ, which had the thinner cushions, not at the thickest cushion location at the ventricular side as expected. Our findings reveal regional differences in the AVJ myocardium even at this early stage in heart development. These findings reveal the early steps leading to the heterogeneity and complexity of conduction at the mature AVJ, a site where arrhythmias can be initiated.

scholarly journals Semaphorin3f as an intrinsic regulator of chamber-specific heart development

2021 ◽  
Author(s):  
Rami Halabi ◽  
Paula B. Cechmanek ◽  
Carrie L. Hehr ◽  
Sarah McFarlane
Keyword(s):  
Congenital Heart Defects ◽  
Heart Development ◽  
Congenital Heart ◽  
Molecular Mechanisms ◽  
Heart Defects ◽  
Border Region ◽  
Specific Gene ◽  
Atrioventricular Canal ◽  
Term Survival ◽  
Ventricular Cardiomyocytes

During development a pool of precursors form a heart with atrial and ventricular chambers that exhibit distinct transcriptional and electrophysiological properties. Normal development of these chambers is essential for full term survival of the fetus, and deviations result in congenital heart defects. The large number of genes that may cause congenital heart defects when mutated, and the genetic variability and penetrance of the ensuing phenotypes, reveals a need to understand the molecular mechanisms that allow for the formation of chamber-specific cardiomyocyte differentiation. We find that in the developing zebrafish heart, mRNA for a secreted Semaphorin (Sema), Sema3fb, is expressed by all cardiomyocytes, whereas mRNA for its receptor Plexina3 (Plxna3) is expressed by ventricular cardiomyocytes. In sema3fb CRISPR zebrafish mutants, ventricular chamber development is impaired; the ventricles of mutants are smaller in size than their wild type siblings, apparently because of differences in cell size and not cell numbers, with ventricular cardiomyocytes failing to undergo normal developmental hypertrophy. Analysis of chamber differentiation indicates defects in chamber specific gene expression at the border between the ventricular and atrial chambers, with spillage of ventricular chamber genes into the atrium, and vice versa, and a failure to restrict bmp4a mRNA to the atrioventricular canal. The disrupted atrioventricular border region in mutants is accompanied by hypoplastic heart chambers and impaired cardiac function. These data suggest a model whereby cardiomyocytes secrete a Sema cue that, through spatially restricted expression of the receptor, signals in a ventricular chamber-specific manner to establish a distinct border between atrial and ventricular chambers that is important for functional development of the heart.

scholarly journals Neddylation mediates ventricular chamber maturation through repression of Hippo signaling

2018 ◽  
Vol 115 (17) ◽  
pp. E4101-E4110 ◽  
Author(s):  
Jianqiu Zou ◽  
Wenxia Ma ◽  
Jie Li ◽  
Rodney Littlejohn ◽  
Hongyi Zhou ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Development ◽  
Molecular Mechanisms ◽  
Heart Defects ◽  
Left Ventricular ◽  
Late Gestation ◽  
Hippo Signaling ◽  
Cardiomyocyte Proliferation ◽  
Ventricular Noncompaction ◽  
Cullin 7

During development, ventricular chamber maturation is a crucial step in the formation of a functionally competent postnatal heart. Defects in this process can lead to left ventricular noncompaction cardiomyopathy and heart failure. However, molecular mechanisms underlying ventricular chamber development remain incompletely understood. Neddylation is a posttranslational modification that attaches ubiquitin-like protein NEDD8 to protein targets via NEDD8-specific E1-E2-E3 enzymes. Here, we report that neddylation is temporally regulated in the heart and plays a key role in cardiac development. Cardiomyocyte-specific knockout of NAE1, a subunit of the E1 neddylation activating enzyme, significantly decreased neddylated proteins in the heart. Mice lacking NAE1 developed myocardial hypoplasia, ventricular noncompaction, and heart failure at late gestation, which led to perinatal lethality. NAE1 deletion resulted in dysregulation of cell cycle-regulatory genes and blockade of cardiomyocyte proliferation in vivo and in vitro, which was accompanied by the accumulation of the Hippo kinases Mst1 and LATS1/2 and the inactivation of the YAP pathway. Furthermore, reactivation of YAP signaling in NAE1-inactivated cardiomyocytes restored cell proliferation, and YAP-deficient hearts displayed a noncompaction phenotype, supporting an important role of Hippo-YAP signaling in NAE1-depleted hearts. Mechanistically, we found that neddylation regulates Mst1 and LATS2 degradation and that Cullin 7, a NEDD8 substrate, acts as the ubiquitin ligase of Mst1 to enable YAP signaling and cardiomyocyte proliferation. Together, these findings demonstrate a role for neddylation in heart development and, more specifically, in the maturation of ventricular chambers and also identify the NEDD8 substrate Cullin 7 as a regulator of Hippo-YAP signaling.

scholarly journals A heterogeneously expressed gene family modulates biofilm architecture and hypoxic growth of Aspergillus fumigatus

2020 ◽  
Author(s):  
Caitlin H. Kowalski ◽  
Kaesi A. Morelli ◽  
Jason E. Stajich ◽  
Carey D. Nadell ◽  
Robert A. Cramer
Keyword(s):  
Aspergillus Fumigatus ◽  
Gene Family ◽  
Molecular Mechanisms ◽  
Genetic Manipulation ◽  
Large Population ◽  
Colony Morphology ◽  
Low Oxygen ◽  
Biofilm Architecture ◽  
Biofilm Development ◽  
And Function

AbstractThe genus Aspergillus encompasses human pathogens such as Aspergillus fumigatus and industrial powerhouses such as Aspergillus niger. In both cases, Aspergillus biofilms have consequences for infection outcomes and yields of economically important products. Yet, the molecular components influencing filamentous fungal biofilm development, structure, and function remain ill-defined. Macroscopic colony morphology is an indicator of underlying biofilm architecture and fungal physiology. A hypoxia-locked colony morphotype of A. fumigatus has abundant colony furrows that coincide with a reduction in vertically-oriented hyphae within biofilms and increased low oxygen growth and virulence. Investigation of this morphotype has led to the identification of the causative gene, biofilm architecture factor A (bafA), a small cryptic open reading frame within a subtelomeric gene cluster. BafA is sufficient to induce the hypoxia-locked colony morphology and biofilm architecture in A. fumigatus. Analysis across a large population of A. fumigatus isolates identified a larger family of baf genes, all of which have the capacity to modulate hyphal architecture, biofilm development, and hypoxic growth. Furthermore, introduction of A. fumigatus bafA into A. niger is sufficient to generate the hypoxia-locked colony morphology, biofilm architecture, and increased hypoxic growth. Together these data indicate the potential broad impacts of this previously uncharacterized family of small genes to modulate biofilm architecture and function in clinical and industrial settings.ImportanceThe manipulation of microbial biofilms in industrial and clinical applications remains a difficult task. The problem is particularly acute with regard to filamentous fungal biofilms for which molecular mechanisms of biofilm formation, maintenance, and function are only just being elucidated. Here we describe a family of small genes heterogeneously expressed across Aspergillus fumigatus strains that are capable of modifying colony biofilm morphology and microscopic hyphal architecture. Specifically, these genes are implicated in the formation of a hypoxia-locked colony morphotype that is associated with increased virulence of A. fumigatus. Synthetic introduction of these gene family members, here referred to as biofilm architecture factors, in both A. fumigatus and A. niger additionally modulates low oxygen growth and surface adherence. Thus, these genes are candidates for genetic manipulation of biofilm development in Aspergilli.

scholarly journals Calreticulin reveals a critical Ca2+ checkpoint in cardiac myofibrillogenesis

2002 ◽  
Vol 158 (1) ◽  
pp. 103-113 ◽  
Author(s):  
Jian Li ◽  
Michel Pucéat ◽  
Carmen Perez-Terzic ◽  
Annabelle Mery ◽  
Kimitoshi Nakamura ◽  
...  
Keyword(s):  
Heart Development ◽  
Molecular Mechanisms ◽  
Es Cells ◽  
Embryonic Stem ◽  
Cardiac Cells ◽  
Embryoid Bodies ◽  
Cell Functions ◽  
Myosin Light Chain 2 ◽  
And Function

Calreticulin (crt) is an ubiquitously expressed and multifunctional Ca2+-binding protein that regulates diverse vital cell functions, including Ca2+ storage in the ER and protein folding. Calreticulin deficiency in mice is lethal in utero due to defects in heart development and function. Herein, we used crt−/− embryonic stem (ES) cells differentiated in vitro into cardiac cells to investigate the molecular mechanisms underlying heart failure of knockout embryos. After 8 d of differentiation, beating areas were prominent in ES-derived wild-type (wt) embryoid bodies (EBs), but not in ES-derived crt−/− EBs, despite normal expression levels of cardiac transcription factors. Crt−/− EBs exhibited a severe decrease in expression and a lack of phosphorylation of ventricular myosin light chain 2 (MLC2v), resulting in an impaired organization of myofibrils. Crt−/− phenotype could be recreated in wt cells by chelating extracellular or cytoplasmic Ca2+ with EGTA or BAPTA, or by inhibiting Ca2+/calmodulin-dependent kinases (CaMKs). An imposed ionomycin-triggered cystolic-free Ca2+ concentration ([Ca2+]c) elevation restored the expression, phosphorylation, and insertion of MLC2v into sarcomeric structures and in turn the myofibrillogenesis. The transcription factor myocyte enhancer factor C2 failed to accumulate into nuclei of crt−/− cardiac cells in the absence of ionomycin-triggered [Ca2+]c increase. We conclude that the absence of calreticulin interferes with myofibril formation. Most importantly, calreticulin deficiency revealed the importance of a Ca2+-dependent checkpoint critical for early events during cardiac myofibrillogenesis.

scholarly journals From Stem Cells to Populations—Using hiPSC, Next-Generation Sequencing, and GWAS to Explore the Genetic and Molecular Mechanisms of Congenital Heart Defects

Genes ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 921
Author(s):  
Martin Broberg ◽  
Johanna Hästbacka ◽  
Emmi Helle
Keyword(s):  
Stem Cells ◽  
Congenital Heart Defects ◽  
Heart Development ◽  
Congenital Heart ◽  
Molecular Mechanisms ◽  
Association Studies ◽  
Heart Defects ◽  
Cell Types ◽  
Mendelian Inheritance ◽  
Genome Wide Association Studies

Congenital heart defects (CHD) are developmental malformations affecting the heart and the great vessels. Early heart development requires temporally regulated crosstalk between multiple cell types, signaling pathways, and mechanical forces of early blood flow. While both genetic and environmental factors have been recognized to be involved, identifying causal genes in non-syndromic CHD has been difficult. While variants following Mendelian inheritance have been identified by linkage analysis in a few families with multiple affected members, the inheritance pattern in most familial cases is complex, with reduced penetrance and variable expressivity. Furthermore, most non-syndromic CHD are sporadic. Improved sequencing technologies and large biobank collections have enabled genome-wide association studies (GWAS) in non-syndromic CHD. The ability to generate human to create human induced pluripotent stem cells (hiPSC) and further differentiate them to organotypic cells enables further exploration of genotype–phenotype correlations in patient-derived cells. Here we review how these technologies can be used in unraveling the genetics and molecular mechanisms of heart development.

scholarly journals Cardiomyopathy in Irx4-Deficient Mice Is Preceded by Abnormal Ventricular Gene Expression

2001 ◽  
Vol 21 (5) ◽  
pp. 1730-1736 ◽  
Author(s):  
Benoit G. Bruneau ◽  
Zheng-Zheng Bao ◽  
Diane Fatkin ◽  
Jose Xavier-Neto ◽  
Dimitrios Georgakopoulos ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cardiac Hypertrophy ◽  
Heart Development ◽  
Contractile Function ◽  
Specific Gene ◽  
Postnatal Life ◽  
Helix Loop Helix ◽  
And Function ◽  
Expression Program ◽  
Deficient Mice

ABSTRACT To define the role of Irx4, a member of the Iroquoisfamily of homeobox transcription factors in mammalian heart development and function, we disrupted the murine Irx4 gene. Cardiac morphology in Irx4-deficient mice (designatedIrx4 Δex2/Δex2) was normal during embryogenesis and in early postnatal life. AdultIrx4 Δex2/Δex2 mice developed a cardiomyopathy characterized by cardiac hypertrophy and impaired contractile function. Prior to the development of cardiomyopathy,Irx4 Δex2/Δex2 hearts had abnormal ventricular gene expression: Irx4-deficient embryos exhibited reduced ventricular expression of the basic helix-loop-helix transcription factor eHand (Hand1), increasedIrx2 expression, and ventricular induction of an atrial chamber-specific transgene. In neonatal hearts, ventricular expression of atrial natriuretic factor and α-skeletal actin was markedly increased. Several weeks subsequent to these changes in embryonic and neonatal gene expression, increased expression of hypertrophic markers BNP and β-myosin heavy chain accompanied adult-onset cardiac hypertrophy. Cardiac expression of Irx1, Irx2, and Irx5 may partially compensate for loss of Irx4 function. We conclude that Irx4 is not sufficient for ventricular chamber formation but is required for the establishment of some components of a ventricle-specific gene expression program. In the absence of genes under the control of Irx4, ventricular function deteriorates and cardiomyopathy ensues.

scholarly journals Autism: A “Critical Period” Disorder?

2011 ◽  
Vol 2011 ◽  
pp. 1-17 ◽  
Author(s):  
Jocelyn J. LeBlanc ◽  
Michela Fagiolini
Keyword(s):  
Critical Period ◽  
Molecular Mechanisms ◽  
Neurodevelopmental Disorder ◽  
Repetitive Behaviors ◽  
Postnatal Life ◽  
Critical Periods ◽  
Restricted Interests ◽  
Behavioral Impairments ◽  
And Function ◽  
The Brain

Cortical circuits in the brain are refined by experience during critical periods early in postnatal life. Critical periods are regulated by the balance of excitatory and inhibitory (E/I) neurotransmission in the brain during development. There is now increasing evidence of E/I imbalance in autism, a complex genetic neurodevelopmental disorder diagnosed by abnormal socialization, impaired communication, and repetitive behaviors or restricted interests. The underlying cause is still largely unknown and there is no fully effective treatment or cure. We propose that alteration of the expression and/or timing of critical period circuit refinement in primary sensory brain areas may significantly contribute to autistic phenotypes, including cognitive and behavioral impairments. Dissection of the cellular and molecular mechanisms governing well-established critical periods represents a powerful tool to identify new potential therapeutic targets to restore normal plasticity and function in affected neuronal circuits.

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