Activation of RXR and RAR signaling promotes myogenic differentiation of myoblastic C2C12 cells.
Differentiation of embryonic and adult myogenic progenitors undergoes a complex series of cell rearrangements and specification events which are controlled by distinct gene regulatory networks. Delineation of the molecular mechanisms that regulate skeletal muscle specification and formation should be important for understanding congenital myopathies and muscular degenerative diseases. Retinoic acid (RA) signaling plays an important role in development. However, the role of RA signaling in adult myogenic progenitors is poorly understood. Here, we investigate the role of RA signaling in regulating myogenic differentiation of myoblastic progenitor cells. Using the mouse myoblast progenitor C2C12 line as a model, we have found that the endogenous expression of most RAR and RXR isotypes is readily detected. While the nuclear receptor co-repressors are highly expressed, two of the three nuclear receptor co-activators and the enzymes involved in RA synthesis are expressed at low level or undetectable, suggesting that the RA signaling pathway may be repressed in myogenic progenitors. Using the alpha-myosin heavy chain promoter-driven reporter (MyHC-GLuc), we have demonstrated that either ATRA or 9CRA is able to effectively induce myogenic differentiation, which can be synergistically enhanced when both ATRA and 9CRA are used. Upon ATRA and 9CRA treatment of C2C12 cells the expression of late myogenic markers significantly increases. We have further shown that adenovirus-mediated exogenous expression of RARalpha and/or RXRalpha is able to effectively induce myogenic differentiation in a ligand-independent fashion. Morphologically, ATRA- and 9CRA-treated C2C12 cells exhibit elongated cell body and become multi-nucleated myoblasts, and even form myoblast fusion. Ultrastructural analysis under transmission electron microscope reveals that RA-treated myogenic progenitor cells exhibit an abundant presence of muscle fibers. Therefore, our results strongly suggest that RA signaling may play an important role in regulating myogenic differentiation.
Zhu
Gao-Hui
GH
Key Laboratory of Diagnostic Medicine designated by Chinese Ministry of Education, and The Affiliated Hospitals of Chongqing Medical University, Chongqing, China.
Huang
Jiayi
J
Bi
Yang
Y
Su
Yuxi
Y
Tang
Yi
Y
He
Bai-Cheng
BC
He
Yun
Y
Luo
Jinyong
J
Wang
Yi
Y
Chen
Liang
L
Zuo
Guo-Wei
GW
Jiang
Wei
W
Luo
Qing
Q
Shen
Jikun
J
Liu
Bo
B
Zhang
Wen-Li
WL
Shi
Qiong
Q
Zhang
Bing-Qiang
BQ
Kang
Quan
Q
Zhu
Jing
J
Tian
Jie
J
Luu
Hue H
HH
Haydon
Rex C
RC
Chen
Yuan
Y
He
Tong-Chuan
TC
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D017930:Genes, Reporter; D049409:Luciferases, Firefly / Q000378:metabolism; D051379:Mice; D032446:Myoblasts / Q000378:metabolism* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*; D013997:Time Factors; D014212:Tretinoin / Q000494:pharmacology
D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014212:Tretinoin; D049409:Luciferases, Firefly