Advances and Prospects in Understanding Vertebrate Cardiac Conduction System, Pacemaker Cell, and Cardiac Muscle Development: Toward Novel Biological Therapies

Round 1

Reviewer 1 Report

The review summarizes the current knowledge about vertebrate CCS and provides a strong motivation for cross-disciplined collaborative work on the identification of GRNs and their functional characterization. It is of great importance to multiple fields of research as collaborative research is lacking. However, with scientific point of view, review fails to create an impact.

1. Cardiac Conduction system has been abreviated as CCS in line 26. therefore it is needless to use as "Cardiac Conduction system" again in lines:82-83.

2. wordiness of certain sentences can be reduced to improve readability. for example,

(a) lines 86-88 can be split into two short sentences. 

(b).lines: 263-266: This needs a lot of seriously multi-disciplinary collaborative work (including work from system biologists, developmental biologists, and molecular biologists, and computational experts) and  funding to work in parallel to work and highlight and predict the important genes and their putative regulatory regions to test them functionally.

can be written as:

this warrants (a) an extensive interdisciplinary work plan across diverse disciplines ranging from systems biology, developmental and molecular biology to computational biology to identify putative regulatory regions, and, (b) requires intensive funding to drive the research focussed on functional characterization of putative regulatory regions.

Author Response

Thank you for highlighting the importance of cross-disciplinary collaboration in understanding the vertebrate CCS and GRNs. We've revised the manuscript to emphasise the impact of our work towards developing biological pacemaker cells for therapeutic intervention against cardiac dysfunction and its relevance to multiple research fields. Your feedback guided our improvements.

To ensure greater clarity and conciseness, we have eliminated the redundancy by refraining from using both the "Cardiac Conduction System" and its abbreviation "CCS" within the same context, as pointed out in lines 82-83.

Furthermore, we have restructured the sentences in lines 86-88 and 263-266 to enhance their clarity and flow.

Thank you once again for your thorough evaluation and constructive suggestions.

Reviewer 2 Report

The current review by Frew et al.,  entitled “The development of specialised cardiac muscle cells within a vertebrate heart requires a specialised regulatory network” describes the current knowledge about the myocardial Cardiac Conduction System (CCS) and the development of pacemaker cells through the description of key transcription factors and signaling pathways involved in CCS. Moreover, the authors mentioned the genetic network of CCS development.

Overall, I think that the review must be implemented. The authors should better revise the literature and extend the notions given.

It has been established that the restricted turnover of cardiomyocytes limits the regenerative potential of the adult mammalian heart. However, studies have shown a primitive regenerative capacity in the neonatal mouse heart and human hearts. After an injury, neonatal mouse cardiomyocytes are able re-enter the cell cycle to repopulate the injured myocardium. So far, it has been reported that it is possible to promote the recovery of injured myocardium through genetic manipulation of specific signaling pathways or by using cell therapy. In the last decade, significant advances have been made in understanding cardiac differentiation from mouse and human embryonic stem cells (ESCs), induced pluripotent stem cells (hiPSCs) and adult cardiac stem cells (CSCs) to induced cardiomyocytes (doi:10.1038/nature06894; doi:10.1016/j.stem.2010.12.008; doi.org/10.3390/cells12131793; doi: 10.3390/ijms222413180). While the major cardiac cell types, including cardiomyocytes, fibroblasts, endothelial cells and cardiac stem cells have been intensively studied during myocardial regeneration (doi.org/10.1016/j.eclinm.2022.101530), the role of the conduction system has yet to be fully investigated. In this study (doi: 10.1016/j.ydbio.2021.07.005) a new genetic tool is introduced for studying the physiology and pathology of the cardiac conduction system, including sinoatrial and atrioventricular nodal dysfunction and Purkinje fiber dysfunction. Moreover, in another interesting  study (doi.org/10.1161/CIRCRESAHA.118.314578) the authors give the transcriptional profiles from the entire CCS at single-cell resolution and provide a characterization in the context of development and disease.

There are a lots of typos in the main text. Please check the font style too.

Author Response

Thank you for your insightful feedback on our review.  We appreciate your positive assessment of our work and have carefully revised the manuscript to extend our discussion of key transcription factors and signalling pathways involved in CCS development. We have also incorporated literature references to emphasise recent advances in cardiac regeneration and differentiation, including studies involving neonatal mouse cardiomyocytes, stem cells, and the emergence of biological pacemakers for cardiac arrhythmias.

Furthermore, we have meticulously addressed the typos and font style issues in the main text to ensure the clarity and quality of our review.

Round 2

Reviewer 2 Report

The authors replied to all my requests and reorganized better the review.