Hand1 regulates cardiomyocyte proliferation versus differentiation in the developing heart
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Updated: Jul 19, 2026
Generation and Expansion of Human Cardiomyocytes from Patient Peripheral Blood Mononuclear Cells
Published on: February 12, 2021
Catherine A Risebro1, Nicola Smart, Laurent Dupays
1Molecular Medicine Unit, UCL Institute of Child Health, London WC1N 1EH, UK.
Insights
The basic helix-loop-helix (bHLH) transcription factor Hand1 is crucial for heart development. It balances cardioblast proliferation and differentiation, preventing congenital heart defects by regulating myocyte precursor pools.
Area of Science:
- Cardiovascular Biology
- Developmental Biology
- Molecular Cardiology
Background:
- Precise origins and regulation of myocardial progenitors are key to understanding heart development.
- Identifying factors controlling cardioblast proliferation and differentiation is essential for preventing congenital heart disease.
Purpose of the Study:
- To investigate the role of the transcription factor Hand1 in regulating myocardial progenitor cell fate.
- To elucidate how Hand1 influences the balance between proliferation and differentiation in developing cardiomyocytes.
Main Methods:
- Studied Hand1 function through gain-of-function and loss-of-function approaches in embryonic stem cell-derived cardiomyocytes.
- Analyzed effects on cardioblast proliferation, differentiation, and cell-cycle progression.
Main Results:
- Hand1 upregulation in specific cells extends the heart tube and increases cardioblast proliferation.
- Hand1 deficiency leads to elevated cardiomyocyte differentiation, suggesting a default mesodermal pathway.
- Hand1 gain of function delays differentiation by maintaining proliferating precursors and preventing cell-cycle exit.
Conclusions:
- Hand1 is a critical cardiac regulatory protein controlling the proliferation-differentiation balance in the embryonic heart.
- This study clarifies Hand1's role in establishing the myocardium and preventing organ hypoplasia.
Abstract:
The precise origins of myocardial progenitors and their subsequent contribution to the developing heart has been an area of considerable activity within the field of cardiovascular biology. How these progenitors are regulated and what signals are responsible for their development are, however, much less well understood. Clearly, not only is there a need to identify factors that regulate the transition from proliferation of cardioblasts to differentiation of cardiac muscle, but it is also necessary to identify factors that maintain an adequate pool of undifferentiated myocyte precursors as a prerequisite to preventing organ hypoplasia and congenital heart disease. Here, we report how upregulation of the basic helix-loop-helix (bHLH) transcription factor Hand1, restricted exclusively to Hand1-expressing cells, brings about a significant extension of the heart tube and extraneous looping caused by the elevated proliferation of cardioblasts in the distal outflow tract. This activity is independent of the further recruitment of extracardiac cells from the secondary heart field and permissive for the continued differentiation of adjacent myocardium. Culture studies using embryonic stem (ES) cell-derived cardiomyocytes revealed that, in a Hand1-null background, there is significantly elevated cardiomyocyte differentiation, with an apparent default mesoderm pathway to a cardiomyocyte fate. However, Hand1 gain of function maintains proliferating precursors resulting in delayed and significantly reduced cardiomyocyte differentiation that is mediated by the prevention of cell-cycle exit, by G1 progression and by increased cell division. Thus, this work identifies Hand1 as a crucial cardiac regulatory protein that controls the balance between proliferation and differentiation in the developing heart, and fills a significant gap in our understanding of how the myocardium of the embryonic heart is established.
