Fndc5 knockdown induced suppression of mitochondrial integrity and significantly decreased cardiac differentiation of mouse embryonic stem cells

• Published in: Journal of cellular biochemistry 2018-06, Vol.119 (6), p.4528-4539
• Main Authors: Nazem, Shima, Rabiee, Farzaneh, Ghaedi, Kamran, Babashah, Sadegh, Sadeghizadeh, Majid, Nasr‐Esfahani, Mohammad Hossein
• Format: Article
• Language: English
• Subjects: Brain; cardiac differentiation; Cardiomyocytes; Differentiation; Doxycycline; Embryo cells; Fibronectin; Fndc5; Gene expression; Heart; Heart diseases; Membrane potential; Mitochondria; Mitochondrial DNA; mitochondrial function; Muscles; Ribonucleic acid; RNA; RNAi; Stem cell transplantation; Stem cells; Superoxide dismutase
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.26590

Fibronectin type III domain‐containing 5 protein (Fndc5) is a glycosylated protein with elevated expression in high energy demanded tissues as heart, brain, and muscle. It has been shown that upregulation of Fndc5 is regulated by peroxisome proliferator‐activated receptor‐γ coactivator‐1 alpha (PGC‐1α), which is known as a master regulator of mitochondrial function and biogenesis. Also, our group indicated that Fndc5 expression increases gradually during cardiac differentiation of mouse embryonic stem cells (mESCs). In this paper, to clarify the importance of Fndc5 in cardiac differentiation, we south to knock down Fndc5 expression by generation a stably transduced mESC line that derives the expression of a short hairpin RNA (shRNA) against Fndc5 gene following doxycycline (Dox) induction. Knock‐down of Fndc5 demonstrated a considerable decrease in expression of cardiac progenitor and cardiomyocyte markers. Considering the fact that mitochondria play a crucial role in cardiac differentiation of ESCs, we investigated the role of Fndc5, as a downstream target of PGC1‐α, on mitochondrial indices. Results showed that expression of nuclear encoded mitochondrial genes including PGC1‐α, Atp5b, Ndufb5, and SOD2 significantly decreased. Moreover, mitochondrial membrane potential (ΔΨm) and relative ATP content of cardiomyocytes decreased markedly with relative ROS level increase. Together, our results suggest that Fndc5 attenuates process of cardiac differentiation of mESCs which is associated with modulation of mitochondrial function and gene expression. (i) Fndc5 knockdown did not affect the expression of mesodermal markers during cardiac differentiation of mESCs. (ii) Fndc5 knockdown decreased the expression of cardiac progenitor and cardiomyocyte markers. (iii) Transcript level of nuclear encoded mitochondrial genes was decreased following Fndc5 down regulation in cardiac cells. (iv) Mitochondrial functions including ATP level and ΔΨm were modulated upon Fndc5 knockdown in cardiomyocytes.