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Analysis of Cardiomyocyte Development using Immunofluorescence in Embryonic Mouse Heart
10:56

Analysis of Cardiomyocyte Development using Immunofluorescence in Embryonic Mouse Heart

Published on: March 26, 2015

Rac1 signaling is critical to cardiomyocyte polarity and embryonic heart development

Carmen Leung1, Xiangru Lu2, Murong Liu3

  • 1Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada (C.L., X.L., Q.F.) Collaborative Program in Developmental Biology, The University of Western Ontario, London, Ontario, Canada (C.L.).

Journal of the American Heart Association
|October 16, 2014
PubMed
Abstract

Insights

Rac1 signaling in the second heart field is crucial for cardiomyocyte polarity and embryonic heart development, preventing congenital septal defects and ensuring proper right ventricle formation.

Area of Science:

  • Cardiovascular Biology
  • Developmental Biology
  • Cell Biology

Background:

  • Congenital heart defects, particularly cardiac septation defects, are common but their underlying mechanisms remain unclear.
  • The role of small GTPase Rac1 in mammalian cardiomyocyte polarity is not well understood.
  • Rac1 is known to influence planar cell polarity in Drosophila epithelial cells.

Purpose of the Study:

  • To investigate the role of Rac1 signaling in the second heart field during embryonic heart development.
  • To determine if Rac1 regulates cardiomyocyte polarity, chamber septation, and right ventricle development.
  • To test the hypothesis that Rac1 is essential for normal heart formation.

Main Methods:

  • Generated mice with second heart field-specific deficiency of Rac1 (Rac1(SHF)).
  • Utilized fate-mapping analysis to track cell contributions.
  • Examined cardiomyocyte morphology, F-actin organization, and expression of key polarity and transcription factors.
  • Assessed cell migration, projection formation, and apoptosis.

Main Results:

  • Rac1(SHF) mice displayed ventricular/atrial septal defects, thin right ventricle myocardium, and bifid cardiac apex.
  • Cardiomyocytes in Rac1(SHF) hearts were spherical with disrupted F-actin, unlike controls.
  • Loss of Scrib, WAVE, and Arp2/3 expression was observed, impairing cell migration.
  • Rac1 deficiency led to defects in cell projections, lamellipodia, and increased apoptosis.

Conclusions:

  • Rac1 deficiency in the second heart field severely impairs cardiomyocyte elongation and cytoskeleton organization.
  • This leads to congenital septal defects, reduced right ventricle myocardium thickness, and a bifid cardiac apex.
  • Rac1 signaling is essential for cardiomyocyte polarity and proper embryonic heart development.
Keywords:
Rac1congenital heart defectsheart septal defectssecond heart field

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