Characterization of sinoatrial node in four conduction system marker mice

Viswanathan, Shiv Kumar; Burch, John; Fishman, Glenn I.; Moskowitz, Ivan P.; Benson, D. Woodrow

doi:10.1016/j.yjmcc.2007.02.008

Cited by 24 publications

(17 citation statements)

References 40 publications

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“…Tamoxifen inductions were performed at distinct stages of embryonic development, harvesting at E16.5 when the CCS is well defined 29, 30 (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

HCN4 Dynamically Marks the First Heart Field and Conduction System Precursors

et al. 2013

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Rationale To date, there has been no specific marker of the first heart field to facilitate understandings of contributions of the first heart field to cardiac lineages. Cardiac arrhythmia is a leading cause of death, often resulting from abnormalities in the cardiac conduction system (CCS). Understanding origins and identifying markers of CCS lineages is an essential step toward modeling diseases of the CCS and for development of biological pacemakers. Objective To investigate HCN4 as a marker for the first heart field and for precursors of distinct components of the CCS, and gain insight into contributions of first and second heart lineages to the CCS. Methods and Results HCN4-CreERT2, -nuclear LacZ and -H2BGFP mouse lines were generated. HCN4 expression was examined by means of immunostaining with HCN4 antibody and reporter gene expression. Lineage studies were performed using HCN4CreERT2, Isl1Cre, Nkx2.5Cre, and Tbx18Cre, coupled to co-immunostaining with CCS markers. Results demonstrated that, at cardiac crescent stages, HCN4 marks the first heart field, with HCN4CreERT2 allowing assessment of cell fates adopted by first heart field myocytes. Throughout embryonic development, HCN4 expression marked distinct CCS precursors at distinct stages, marking the entire CCS by late fetal stages. We also noted expression of HCN4 in distinct subsets of endothelium at specific developmental stages. Conclusions This study provides insight into contributions of first and second heart lineages to the CCS and highlights the potential utility of HCN4 in conjunction with other markers for optimization of protocols for generation and isolation of specific conduction system precursors.

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“…Tamoxifen inductions were performed at distinct stages of embryonic development, harvesting at E16.5 when the CCS is well defined 29, 30 (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

HCN4 Dynamically Marks the First Heart Field and Conduction System Precursors

et al. 2013

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“…However, due to lack of specifi c markers to distinguish or isolate pacemaker cells from working cardiomyocytes at early embryonic stages [ 20 ], it has not been possible to apply single-cell recordings to evaluate the mechanisms of automaticity in early pacemaker cells. Nonetheless, dominant pacemaker cells in CSs would be expected to dictate the BR and a change of BR by applied drugs, in turn, would implicate the mechanism of dominant automaticity.…”

Section: Contribution Of Intracellular Ca 2+ Signaling To Automaticitmentioning

confidence: 99%

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Kim

Majdi

Xia

et al. 2010

Stem Cells and Development

160

149

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Various types of cardiomyocytes undergo changes in automaticity and electrical properties during fetal heart development. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs), like fetal cardiomyocytes, are electrophysiologically immature and exhibit automaticity. We used hESC-CMs to investigate developmental changes in mechanisms of automaticity and to determine whether electrophysiological maturation is driven by an intrinsic developmental clock and/or is regulated by interactions with non-cardiomyocytes in embryoid bodies (EBs). We isolated pure populations of hESC-CMs from EBs by lentivirus-engineered Puromycin resistance at various stages of differentiation. Using pharmacological agents, calcium (Ca 2+ ) imaging, and intracellular recording techniques, we found that intracellular Ca 2+ -cycling mechanisms developed early and contributed to dominant automaticity throughout hESC-CM differentiation. Sarcolemmal ion channels evolved later upon further differentiation within EBs and played an increasing role in controlling automaticity and electrophysiological properties of hESC-CMs. In contrast to the development of intracellular Ca 2+ -handling proteins, ion channel development and electrophysiological maturation of hESC-CMs did not occur when hESC-CMs were isolated from EBs early and maintained in culture without further interaction with non-cardiomyocytes. Adding back non-cardiomyocytes to early-isolated hESC-CMs rescued the arrest of electrophysiological maturation, indicating that non-cardiomyocytes in EBs drive electrophysiological maturation of early hESC-CMs. Non-cardiomyocytes in EBs contain most cell types present in the embryonic heart that are known to infl uence early cardiac development. Our study is the fi rst to demonstrate that non-cardiomyocytes infl uence electrophysiological maturation of early hESC-CMs in cultures. Defi ning the nature of these extrinsic signals will aid in the directed maturation of immature hESC-CMs to mitigate arrhythmogenic risks of cell-based therapies.

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“…However, it has been difficult to identify and validate CREs that control gene expression in subsets of functionally specialized cardiomyocytes as occur in the cardiac conduction system. In recent years, just one AV node CRE has been cloned and characterized (Munshi et al, 2009), a few enhancers with activity in the AV bundle and Purkinje Fibers have been described (Arnolds et al, 2012; Moskowitz et al, 2007; van den Boogaard et al, 2012), and no autonomous CREs with specific activity in the SA node have been identified, despite the functional importance of these structures, their unique patterns of gene expression, and numerous attempts(Stroud et al, 2007; Viswanathan et al, 2007). The difficulty in identifying CREs that recapitulate highly patterned gene expression may reflect a requirement for multiple interacting CREs.…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal regulation of an Hcn4 enhancer defines a role for Mef2c and HDACs in cardiac electrical patterning

Vedantham

Evangelista

Huang

et al. 2013

Developmental Biology

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Regional differences in cardiomyocyte automaticity permit the sinoatrial node (SAN) to function as the leading cardiac pacemaker and the atrioventricular (AV) junction as a subsidiary pacemaker. The regulatory mechanisms controlling the distribution of automaticity within the heart are not understood. To understand regional variation in cardiac automaticity, we carried out an in vivo analysis of cis-regulatory elements that control expression of the hyperpolarization-activated cyclic-nucleotide gated ion channel 4 (Hcn4). Using transgenic mice, we found that spatial and temporal patterning of Hcn4 expression in the AV conduction system required cis-regulatory elements with multiple conserved fragments. One highly conserved region, which contained a myocyte enhancer factor 2C (Mef2C) binding site previously described in vitro, induced reporter expression specifically in the embryonic non-chamber myocardium and the postnatal AV bundle in a Mef2c-dependent manner in vivo. Inhibition of histone deacetylase (HDAC) activity in cultured transgenic embryos showed expansion of reporter activity to working myocardium. In adult animals, hypertrophy induced by transverse aortic constriction, which causes translocation of HDACs out of the nucleus, resulted in ectopic activation of the Hcn4 enhancer in working myocardium, recapitulating pathological electrical remodeling. These findings reveal mechanisms that control the distribution of automaticity among cardiomyocytes during development and in response to stress.

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Characterization of sinoatrial node in four conduction system marker mice

Cited by 24 publications

References 40 publications

HCN4 Dynamically Marks the First Heart Field and Conduction System Precursors

HCN4 Dynamically Marks the First Heart Field and Conduction System Precursors

Non-Cardiomyocytes Influence the Electrophysiological Maturation of Human Embryonic Stem Cell-Derived Cardiomyocytes During Differentiation

Spatiotemporal regulation of an Hcn4 enhancer defines a role for Mef2c and HDACs in cardiac electrical patterning

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