Multicolor mapping of the cardiomyocyte proliferation dynamics that construct the atrium

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Zebrafish Models

Background:

• Cardiomyocyte division is crucial for heart chamber formation.
• Distinct morphologies of atrial and ventricular chambers are not fully understood.
• Zebrafish serve as a valuable model for studying cardiac development.

Purpose of the Study:

• To investigate the contribution of individual embryonic cardiomyocytes to zebrafish atrium formation.
• To compare atrial cardiomyocyte proliferation dynamics with those of ventricular cardiomyocytes.
• To elucidate the mechanisms driving the unique structural divergence of cardiac chambers.

Main Methods:

• Multicolor fate-mapping in zebrafish embryos.
• Analysis of cardiomyocyte proliferation dynamics.
• Comparison of atrial and ventricular cardiomyocyte behaviors.

Main Results:

• Atrial cardiomyocytes form a single-cell-thick, webbed myocardial wall.
• Inner pectinate myofibers develop via direct branching, distinct from ventricular delamination.
• Atrial wall cardiomyocyte proliferation results in diverse clonal patches, with dominant clones.
• A subpopulation of atrial myosin heavy chain-expressing cells contributes to ventricular development, indicating plasticity.

Conclusions:

• Cardiomyocyte proliferation and fate decisions are key to forming the distinct architecture of the zebrafish atrium.
• Direct branching is a primary mechanism for atrial myofiber formation.
• Cardiac chamber formation exhibits unexpected plasticity, with inter-chamber contributions.