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Published November 2009 | Published + Supplemental Material
Journal Article Open

Reversing Blood Flows Act through klf2a to Ensure Normal Valvulogenesis in the Developing Heart


Heart valve anomalies are some of the most common congenital heart defects, yet neither the genetic nor the epigenetic forces guiding heart valve development are well understood. When functioning normally, mature heart valves prevent intracardiac retrograde blood flow; before valves develop, there is considerable regurgitation, resulting in reversing (or oscillatory) flows between the atrium and ventricle. As reversing flows are particularly strong stimuli to endothelial cells in culture, an attractive hypothesis is that heart valves form as a developmental response to retrograde blood flows through the maturing heart. Here, we exploit the relationship between oscillatory flow and heart rate to manipulate the amount of retrograde flow in the atrioventricular (AV) canal before and during valvulogenesis, and find that this leads to arrested valve growth. Using this manipulation, we determined that klf2a is normally expressed in the valve precursors in response to reversing flows, and is dramatically reduced by treatments that decrease such flows. Experimentally knocking down the expression of this shear-responsive gene with morpholine antisense oligonucleotides (MOs) results in dysfunctional valves. Thus, klf2a expression appears to be necessary for normal valve formation. This, together with its dependence on intracardiac hemodynamic forces, makes klf2a expression an early and reliable indicator of proper valve development. Together, these results demonstrate a critical role for reversing flows during valvulogenesis and show how relatively subtle perturbations of normal hemodynamic patterns can lead to both major alterations in gene expression and severe valve dysgenesis.

Additional Information

© 2009 Vermot et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received April 1, 2009; accepted October 9, 2009; published November 17, 2009. Academic Editor: Hiroshi Hamada, Osaka University, Japan. We are grateful to L. Trinh for sharing reagents and for providing probes, M. Lardelli, T. Zhong, and H. Clevers for ISH probes, the members of the Beckman Biological Imaging Center for discussions, the Bronner-Fraser laboratory for sharing tools and reagents, and Shigehisa Hirose for providing an aliquot of cx36.7 morpholino. Support received through a National Institutes of Health (NIH) grant to SEF (P01HD037105). JV was supported by a fellowship from the Human Frontier Science Program (HFSP), AF by a fellowship from the NIH, ML by a fellowship from the Swiss National Science Foundation (PA002-111433), DW by the NIH Medical Scientist Training Program at UCLA/Caltech, and DP by a fellowship from the Summer Undergraduate Research Fellowship (SURF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Author Contributions: The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: JV ASF ML MG SEF. Performed the experiments: JV ASF DW DP. Analyzed the data: JV ASF ML DW MG SEF. Contributed reagents/materials/analysis tools: DW. Wrote the paper: JV ASF ML MG SEF. Movie crafting: JV ASF ML.

Attached Files

Published - Vermot2009p6492Plos_Biol.pdf

Supplemental Material - journal.pbio.1000246.s001.tif

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August 21, 2023
August 21, 2023