Related Experiment Video
Updated: Jul 3, 2026
Assessing Cardiomyocyte Subtypes Following Transcription Factor-mediated Reprogramming of Mouse Embryonic Fibroblasts
Published on: March 22, 2017
Down-regulation of cardiac lineage protein (CLP-1) expression in CLP-1 +/- mice affords
Eduardo Mascareno1, Irena Manukyan1, Dipak K Das2
1Center for Cardiovascular and Muscle Research, Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY, USA.
Abstract:
In order to understand the transcriptional mechanism that underlies cell protection to stress, we evaluated the role of CLP-1, a known inhibitor of the transcription elongation complex (pTEFb), in CLP-1 +/- mice hearts. Using the isolated heart model, we observed that the CLP-1 +/- hearts, when subjected to ischaemic stress and evaluated by haemodynamic measurements, exhibit significant cardioprotection. CLP-1 remains associated with the pTEFb complex in the heterozygous hearts, where as it is released in the wild-type hearts suggesting the involvement of pTEFb regulation in cell protection. There was a decrease in Cdk7 and Cdk9 kinase activity and consequently in phosphorylation of serine-5 and serine-2 of Pol II CTD in CLP-1 +/- hearts. However, the levels of mitochondrial proteins, PGC-1alpha and HIF-1alpha, which enhance mitochondrial activity and are implicated in cell survival, were increased in CLP-1 +/- hearts subjected to ischaemic stress compared to that in wild-type CLP-1 +/- hearts treated identically. There was also an increase in the expression of pyruvate dehydrogenase kinase (PDK-1), which facilitates cell adaptation to hypoxic stress. Taken together, our data suggest that regulation of the CLP-1 levels is critical to cellular adaptation of the survival program that protects cardiomyocytes against stress due collectively to a decrease in RNA Pol II phosphorylation but an increase in expression of target proteins that regulate mitochondrial function and metabolic adaptation to stress.
Insights
CLP-1 protects heart cells from stress by regulating transcription. CLP-1 +/- hearts showed reduced RNA Pol II phosphorylation but increased mitochondrial proteins, enhancing survival during ischemic stress.
Area of Science:
- Cardiovascular Biology
- Molecular Mechanisms of Stress Response
- Transcriptional Regulation
Background:
- Cellular protection against stress involves intricate transcriptional mechanisms.
- CLP-1 is a known inhibitor of the transcription elongation complex, positive transcription elongation factor b (pTEFb).
Purpose of the Study:
- To investigate the role of CLP-1 in the transcriptional response to ischemic stress in the heart.
- To elucidate the mechanism by which CLP-1 influences cardioprotection.
Main Methods:
- Utilized an isolated heart model subjected to ischemic stress.
- Evaluated hemodynamic measurements, protein levels (PGC-1alpha, HIF-1alpha, PDK-1), kinase activity (Cdk7, Cdk9), and RNA Polymerase II (Pol II) CTD phosphorylation.
- Assessed CLP-1 association with the pTEFb complex.
Main Results:
- CLP-1 +/- hearts exhibited significant cardioprotection against ischemic stress.
- CLP-1 remained associated with pTEFb in heterozygous hearts, unlike wild-type hearts.
- Decreased Cdk7/Cdk9 activity and Pol II CTD phosphorylation were observed in CLP-1 +/- hearts.
- Increased levels of mitochondrial proteins PGC-1alpha and HIF-1alpha, and PDK-1 expression were found in CLP-1 +/- hearts.
Conclusions:
- Regulation of CLP-1 levels is critical for cellular adaptation to stress.
- Cardioprotection involves decreased RNA Pol II phosphorylation coupled with enhanced mitochondrial function and metabolic adaptation.
- CLP-1 plays a key role in activating a survival program that protects cardiomyocytes from stress.
