Project description:to study the effect of induced expression of TBX3 within the atrium of the heart Background: Treatment of congenital or acquired disorders of the sinus node or atrioventricular node requires insight into the molecular mechanisms for the development and homeostasis of these pacemaker tissues. In the developing heart, transcription factor TBX3 is required for pacemaker and conduction system development. Here, we explore the role of TBX3 in the adult heart and investigate whether TBX3 is able to reprogram terminally differentiated working cardiomyocytes into pacemaker cells. This would be an attractive approach in biological pacemaker formation. Methods and results: TBX3 expression was ectopically induced in cardiomyocytes of adult transgenic mice. Expression analysis revealed an efficient switch from the working myocardial expression profile to that of the pacemaker myocardium. This included suppression of genes encoding gap junction subunits (Cx40, Cx43), the cardiac Na+ channel (NaV1.5; INa) and inwardly rectifying K+ ion channels (Kir-genes; IK1). Concordantly, we observed conduction slowing in these hearts, and reductions in INa and IK1 in cardiomyocytes isolated from these hearts. The reduction in IK1 resulted in a more depolarized maximum diastolic potential, thus enabling spontaneous diastolic depolarization. Neither ectopic pacemaker activity nor pacemaker current, If, were observed. Lentiviral expression of TBX3 in ventricular cardiomyocytes resulted in conduction slowing and development of heterogeneous phenotypes, including depolarized and spontaneously active cardiomyocytes. Conclusions: TBX3 partially reprograms terminally differentiated working cardiomyocytes into pacemaker-like cells and induces important pacemaker properties. The ability of TBX3 to reduce intercellular coupling to overcome current-to-load mismatch and the ability to reduce IK1 density to enable diastolic depolarization, are very promising TBX3 characteristics for biological pacemaker formation strategies. 5 TBX3 expressing left atrial appendage samples (Tamoxifen-treated Myh6MCM;CTBX3 adult male mice) and 6 controls ((Tamoxifen-treated Myh6MCM adult male mice)
Project description:to study the effect of induced expression of TBX3 within the atrium of the heart Background: Treatment of congenital or acquired disorders of the sinus node or atrioventricular node requires insight into the molecular mechanisms for the development and homeostasis of these pacemaker tissues. In the developing heart, transcription factor TBX3 is required for pacemaker and conduction system development. Here, we explore the role of TBX3 in the adult heart and investigate whether TBX3 is able to reprogram terminally differentiated working cardiomyocytes into pacemaker cells. This would be an attractive approach in biological pacemaker formation. Methods and results: TBX3 expression was ectopically induced in cardiomyocytes of adult transgenic mice. Expression analysis revealed an efficient switch from the working myocardial expression profile to that of the pacemaker myocardium. This included suppression of genes encoding gap junction subunits (Cx40, Cx43), the cardiac Na+ channel (NaV1.5; INa) and inwardly rectifying K+ ion channels (Kir-genes; IK1). Concordantly, we observed conduction slowing in these hearts, and reductions in INa and IK1 in cardiomyocytes isolated from these hearts. The reduction in IK1 resulted in a more depolarized maximum diastolic potential, thus enabling spontaneous diastolic depolarization. Neither ectopic pacemaker activity nor pacemaker current, If, were observed. Lentiviral expression of TBX3 in ventricular cardiomyocytes resulted in conduction slowing and development of heterogeneous phenotypes, including depolarized and spontaneously active cardiomyocytes. Conclusions: TBX3 partially reprograms terminally differentiated working cardiomyocytes into pacemaker-like cells and induces important pacemaker properties. The ability of TBX3 to reduce intercellular coupling to overcome current-to-load mismatch and the ability to reduce IK1 density to enable diastolic depolarization, are very promising TBX3 characteristics for biological pacemaker formation strategies.
Project description:To understand the transcriptional landscape of Tbx18-induced cardiac pacemaker cells. The control cells were ventricular myocytes expressing GFP.
Project description:Understanding factors that drive development and function of the sinoatrial node (SAN) is crucial to development of potential therapies for sinus arrhythmias, including potential generation of biological pacemakers. Here, we identify a key cell autonomous role for the LIM homeodomain transcription factor ISL1 for survival, proliferation and function of pacemaker cells throughout development. Chromatin immunoprecipitation assays performed utilizing antibody to ISL1 in chromatin extracts from FACS purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes critical for normal pacemaker function, including subunits of the L-type calcium channel, Ank2, and Tbx3. Other genes implicated in abnormal heart rhythm in humans were also direct downstream targets of ISL1 in SAN cells. Our studies represent the first in vivo ChIP-seq studies for SAN cells which provide a basis for further exploration of factors critical to SAN formation and function and highlight the potential for utilization of ISL1 in combination with other SAN transcription factors for generating pacemaker cells for therapy or drug screening purposes. ISL1 ChIP-seq profiling was performed in Hcn4-H2BGFP SAN cells purified from neonatal hearts.
Project description:The sinus node is a collection of highly specialized cells that constitute the natural pacemaker activity of our heart. The protein expression landscape of the sinus node differs from the surrounding cardiac tissue, although it is primarily comprised of myocytes and fibroblasts like the rest of the cardiac tissue, endowing it with its unique ability to regulate heart rate. Here we performed quantitative proteomics experiments to profile protein expression in the pacemaker of the heart, and compared it to protein expression in the neighbouring atrial muscle. In summary, the quantitative proteomics data presented here offer a highly detailed insight into the unique composition of the pacemaker of our heart.
Project description:We established an efficient strategy to derive functional human SAN like pacemaker cells for disease modeling and drug screening. And we found SARS-CoV-2 infection causes dysfunction of human SAN like pacemaker cells and induces ferroptosis. And we also found that Deferoxamine and imatinib can block SARS-CoV-2 infection and infection-associated ferroptosis. Our study using functional human SAN like pacemaker cells demonstrates a potential mechanism for some COVID-19 cardiac abnormalities and identifies candidate drugs to protect the SAN like pacemaker from SARS-CoV-2 infection.
Project description:Each heartbeat is triggered by the sinoatrial node (SAN), the primary pacemaker of the heart. Studies in animal models have revealed that pacemaker cells share a common progenitor with the (pro)epicardium, and that the pacemaker cardiomyocytes further diversify into “transitional”, “tail” and “head” subtypes. However, the underlying molecular mechanisms, especially of human pacemaker cell development are poorly understood. Here, we performed single cell RNA sequencing (scRNA-seq) and trajectory inference on human induced pluripotent stem cells (hiPSCs) differentiating to SAN-like cardiomyocytes (SANCM) to construct a roadmap of transcriptional changes and lineage decisions. In differentiated SANCM, we identified distinct clusters that closely resemble different subpopulations of the in vivo SAN. Moreover, the presence of a side population of proepicardial cells suggested their shared ontogeny with SANCM, as also reported in vivo. Our results demonstrate that the divergence of SANCM and proepicardial lineages is determined by WNT signaling. Furthermore, we uncovered roles for TGFβ and WNT signaling in the branching of transitional and head SANCM subtypes, respectively. These findings provide new insights into the molecular processes involved in human pacemaker cell differentiation, opening new avenues for complex disease modeling in vitro and inform approaches for cell-therapy based regeneration of the SAN.
Project description:Background: Ion channels are key determinants for the function of excitable cells but little is known about their role and involvement during cardiac development. Earlier work identified Ca2+-activated potassium channels of small and intermediate conductance (SKCas) as important regulators of neural stem cell fate. Here, we have investigated their impact on the differentiation of pluripotent cells towards the cardiac lineage. Methods and Results: We have applied the SKCa-activator EBIO on embryonic stem cells and identified this particular ion channel family as a new critical target involved in the generation of cardiac pacemaker-like cells: SKCa-activation led to rapid remodeling of the actin cytoskeleton, inhibition of proliferation, induction of differentiation and diminished teratoma formation. Time-restricted SKCa-activation induced cardiac mesoderm and commitment to the cardiac lineage as shown by gene regulation, protein and functional electrophysiological studies. In addition, the differentiation into cardiomyocytes was modulated in a qualitative fashion, resulting in a strong enrichment of pacemaker-like cells. This was accompanied by induction of the sino-atrial gene program and in parallel by a loss of the chamber-specific myocardium. In addition, SKCa activity induced activation of the Ras-Mek-Erk signaling cascade, a signaling pathway involved in the EBIO-induced effects. Conclusions: SKCa-activation drives the fate of pluripotent cells towards the cardiac lineage and preferentially into pacemaker-like cardiomyocytes. This provides a novel strategy for the enrichment of cardiomyocytes and in particular, the generation of a specific subtype of cardiomyocytes, pacemaker-like cells, without genetic modification. Untreated ES cells in three independent experiments: - Untreated control ES cells sample 1 (Con_1) - Untreated control ES cells sample 2 (Con_2) - Untreated control ES cells sample 3 (Con_3) EBIO-treated ES cells in three independent experiments: - EBIO-treated ES cells sample 1 (EBIO_1) - EBIO-treated ES cells sample 2 (EBIO_2) - EBIO-treated ES cells sample 3 (EBIO_3) Untreated differentiated ES cells in two independent experiments: - Untreated control differentiated ES cells sample 1 (Con_day5+10_1) - Untreated control differentiated ES cells sample 2 (Con_day5+10_2) EBIO-treated differentiated ES cells in two independent experiments: - EBIO-treated differentiated ES cells sample 1 (EBIO_day5+10_1) - EBIO-treated differentiated ES cells sample 2 (EBIO_day5+10_2)
Project description:Background: Ion channels are key determinants for the function of excitable cells but little is known about their role and involvement during cardiac development. Earlier work identified Ca2+-activated potassium channels of small and intermediate conductance (SKCas) as important regulators of neural stem cell fate. Here, we have investigated their impact on the differentiation of pluripotent cells towards the cardiac lineage. Methods and Results: We have applied the SKCa-activator EBIO on embryonic stem cells and identified this particular ion channel family as a new critical target involved in the generation of cardiac pacemaker-like cells: SKCa-activation led to rapid remodeling of the actin cytoskeleton, inhibition of proliferation, induction of differentiation and diminished teratoma formation. Time-restricted SKCa-activation induced cardiac mesoderm and commitment to the cardiac lineage as shown by gene regulation, protein and functional electrophysiological studies. In addition, the differentiation into cardiomyocytes was modulated in a qualitative fashion, resulting in a strong enrichment of pacemaker-like cells. This was accompanied by induction of the sino-atrial gene program and in parallel by a loss of the chamber-specific myocardium. In addition, SKCa activity induced activation of the Ras-Mek-Erk signaling cascade, a signaling pathway involved in the EBIO-induced effects. Conclusions: SKCa-activation drives the fate of pluripotent cells towards the cardiac lineage and preferentially into pacemaker-like cardiomyocytes. This provides a novel strategy for the enrichment of cardiomyocytes and in particular, the generation of a specific subtype of cardiomyocytes, pacemaker-like cells, without genetic modification.