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Updated: May 23, 2026
Structure-function Studies in Mouse Embryonic Stem Cells Using Recombinase-mediated Cassette Exchange
Published on: April 27, 2017
Junctophilin 2 knockdown interfere with mitochondrium status in ESC-CMs and cardiogenesis of ES cells
Xingguang Liang1, Yuqin Mei, Xin Huang
1Division of Cardio-Cerebral Vascular and Hepatic Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China.
Abstract:
In the present study, we explored the possible links between Junctophilin 2 (Jp2) and the mitochondrium-sarcoplasmic reticulum (SR) interaction in embryonic stem cell-derived cardiomyocytes (ESC-CMs), as well as the role of Jp2 in cardiogenesis of ES cells. We found that Ca(2+) transient was abnormal and mitochondria were de-energized within siJp2 ESC-CMs. The essential juxtaposition structure of mitochondrium with SR was destroyed accompanied by selectively downregulation of Pgc-1α, Nrf-1, and Mfn-2. Impaired co-localization of the JP2 and sarcomeres (α-Actinin or Troponin-T) appeared in embryoid bodies (EBs) after Jp2 knockdown. Calsequestrin2 and ryanodine receptor 2 within SR were expressed as early as the initiation of differentiation, while triadin and caveolin3 within t-tubules (TTs) did not appear until the terminal, indicating that JP2 probably did not contribute to anchoring the SR to TTs at the early cardiogenesis stage as usual. In addition, Jp2 knockdown selectively decreased gene transcription toward cardiogenesis (Brachyury, Isl1, and Nkx2.5), subsequently weaken EB beating activity by 60%. Taken together, reducing JP2 expression in ESC-CMs resulted in impaired mitochondrial status due to either abnormal cellular Ca(2+) homeostasis or disturbing of juxtaposition. A sensitive time window of JP2 necessary in cardiac differentiation was found at early stage via an extra non-TTs/SR anchor-dependent role.
Insights
Junctophilin 2 (Jp2) is crucial for cardiomyocyte development, impacting mitochondrial function and calcium handling. Reduced Jp2 expression impairs cardiac differentiation and embryonic stem cell-derived cardiomyocyte (ESC-CM) function.
Area of Science:
- Cardiovascular Research
- Stem Cell Biology
- Mitochondrial Biology
Background:
- Junctophilin 2 (Jp2) mediates interactions between mitochondria and the sarcoplasmic reticulum (SR) in cardiomyocytes.
- Understanding Jp2's role in cardiomyocyte development and function is critical for regenerative medicine.
Purpose of the Study:
- To investigate the role of Jp2 in the interaction between mitochondria and SR in embryonic stem cell-derived cardiomyocytes (ESC-CMs).
- To explore the function of Jp2 during the cardiogenesis of embryonic stem (ES) cells.
Main Methods:
- Utilized siRNA to knockdown Jp2 expression in ESC-CMs.
- Analyzed mitochondrial function, calcium transients, and gene expression related to cardiac differentiation and mitochondrial biogenesis.
- Examined the co-localization of Jp2 with sarcomeric proteins in embryoid bodies (EBs).
Main Results:
- Jp2 knockdown led to abnormal Ca(2+) transients and de-energized mitochondria in ESC-CMs.
- The structural integrity of mitochondria-SR interaction was disrupted, with downregulation of Pgc-1α, Nrf-1, and Mfn-2.
- Impaired Jp2 co-localization with sarcomeres was observed in EBs, and Jp2 knockdown weakened EB beating activity by 60%.
Conclusions:
- Reduced Jp2 expression in ESC-CMs impairs mitochondrial status due to abnormal Ca(2+) homeostasis and disrupted mitochondria-SR juxtaposition.
- A critical early-stage time window for Jp2 in cardiac differentiation was identified, involving a non-TTs/SR anchor-dependent role.
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