Rnf20 shapes the endothelial control of heart morphogenesis and function

Linda Kessler, Rui Gao, Nalan Tetik-Elsherbiny, Olga Lityagina, Azhar Zhailauova, Yonggang Ren, Felix A. Trogisch, Julio Cordero, Yanliang Dou, Yinuo Wang, Evgeny Chichelnitskiy, Joscha Alexander Kraske, Patricia Laura Schäfer, Chi-Chung Wu, Guillermo Barreto, Michael Potente, Thomas Wieland, Roxana Ola, Joerg Heineke, Gergana Dobreva

Preprint posted on 17 September 2022 https://www.biorxiv.org/content/10.1101/2022.09.16.508288v1

Cellular Crosstalk: How Rnf20 communicates across cell types during cardiac development

Selected by Emma Armitage

Categories: cell biology, developmental biology, genetics

Background

The heart is a complex organ which is made up of distinct cell types which carry out different functions. Crosstalk between the two main cell types of the heart – the Endocardial Cells (EC) and Cardiomyocytes (CM) – is important for correct heart development, and when prevented can lead to disease. During early heart development the heart forms a linear tube, with the endocardium making up the inner layer, while the myocardium forms the outer layer. These tissues are separated by extracellular matrix (ECM) through which they communicate via paracrine signalling. The linear heart tube grows through the addition of a population of cells known as the Second Heart Field (SHF). These cells are multipotent and can give rise to either CM or EC. Despite signalling between CM and EC being important for correct heart development, it is greatly understudied. This preprint discusses the role of a gene called Rnf20, which is essential for EC-CM crosstalk during cardiac development. The authors’ aim was to understand how EC-specific deletion of Rnf20 leads to cardiac defects. This was achieved using Cre deleter lines in mice, to delete Rnf20 in specific cell types such as Isl1+ SHF progenitor cells, and Tie2+ endocardial cells.

Key Findings

Rnf20 is required in the SHF to control ECM dynamics

This study shows that Rnf20 is an important gene controlling EC-CM crosstalk during different stages of cardiac morphogenesis. Deletion of Rnf20 in Isl1+ SHF progenitor cells resulted in cardiac defects such as a shortened outflow tract and smaller right ventricle, along with abnormal trabeculation. This is thought to be due to a reduction in expression of genes associated with ECM degradation in Rnf20 depleted Isl1+ hearts, and ECM degradation is important for correct myocardial morphogenesis. Rnf20 depleted SHF cells being unable to degrade the ECM suggests an important role for Rnf20 in the SHF to control ECM dynamics during cardiac development.

Rnf20 inhibits EndoMT in ECs to maintain endothelial identify

Next, the authors showed that Rnf20 safeguards EC identify by inhibiting endothelial to mesenchymal transition (EndMT). This is a process during which endothelial cells lose cellular features associated with endothelial cells and obtain features associated with mesenchymal cells, such as becoming more migratory and increasing secretion of ECM proteins. Rnf20 deficient EC show increased migratory capacity and an upregulation of EndMT markers, indicating that Rnf20 is required within EC to maintain their endothelial state.

Loss of Rnf20 in EC results in increased ECM deposition

Finally, the authors found that Rnf20 is required within EC to maintain physiological angiocrine signalling using a novel cell-culture based system in which endothelial cells and cardiomyocytes are co-differentiated from mouse pluripotent stem cells. Upon deletion of Rnf20 in EC this led to upregulation of ECM proteins, resulting in defects in cardiac morphology and function due to excessive ECM deposition which can alter tissue stiffness. As levels of cardiac stiffness are required to mediate CM proliferation, maturation, and contractility, this increased cardiac stiffness caused by excessive ECM deposition led to CM binucleation and irregular contractility.

Overall, this preprint demonstrates the importance of Rnf20 in EC to control numerous aspects of heart morphogenesis.

What I like this preprint/Why it is important

I chose this preprint because I am interested in understanding the complex process of heart development and how congenital heart defects arise when this process goes wrong. This paper was particularly interesting to me as it shows that the same gene can be important in multiple different cell types to carry out distinct functions, and it also displays how crosstalk between different cell types is important during the development of an organ. This work is important to the field of heart development, and other biological fields, as it shows that mutating a gene in one cell type can have detrimental effects on the structure and function of a different cell type. Therefore, it is important to not only investigate the cell type which has been mutated, but to investigate neighbouring cell types which might rely on crosstalk to be able to function correctly.

Questions for authors

Rnf20 is required within both EC to prevent EndMT, but also required within SHF cells, which are known to migrate into the heart tube to assist heart growth¹. Do you think Rnf20 is playing a different role in the SHF cells e.g. enabling a more mesenchymal-like state to allow these cells to migrate, or is Rnf20 downregulated in these cells during their migration?
EndMT is required to form the cardiac valves². Is Rnf20 downregulated in EC undergoing valve formation?

References

Leung, C., Lu, X., Liu, M. & Feng, Q. Rac1 Signaling Is Critical to Cardiomyocyte Polarity and Embryonic Heart Development. J. Am. Heart Assoc. 3, (2014).
Monaghan, M. G. et al. A spatiotemporal observation of EndMT and mesenchymal cell colonization at the onset of human cardiac valve development. Development dev.133843 (2015) doi:10.1242/dev.133843.

Tags: development, heart

Posted on: 11 October 2022

doi: https://doi.org/10.1242/prelights.32869

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