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TISSUE-SPECIFIC STEM CELLS

Myocardin A Enhances Telomerase Activities in Adipose Tissue Mesenchymal Cells and Embryonic Stem Cells Undergoing Cardiovascular Myogenic Differentiation

The University of Texas Health Science Center at Houston and the Texas Heart Institute, Houston, Texas, USA

Key Words. Stem cell • Telomerase • Myocardin • Heart • Development • Myogenesis

Correspondence: Correspondence: Yong-Jian Geng, M.D., Ph.D., The Center for Cardiovascular Biology and Atherosclerosis Research, Cardiology Division, Department of Internal Medicine, University of Texas Houston Medical School, 6431 Fannin Street, MSB 6.037, Houston, Texas 77030, USA. Telephone: 713-500-6077; Fax: 713-500-6556; e-mail: yong-jian.geng{at}uth.tmc.edu

Received on June 20, 2007; accepted for publication on September 26, 2007.

First published online in STEM CELLS EXPRESS  October 4, 2007.


Acting as a reverse transcriptase that maintains nuclear telomere length and replication potential, telomerase usually decreases in expression and activities when mammalian stem cells undergo terminal differentiation. This study identified, in adult adipose tissue, a subpopulation of mesenchymal stem cells (MSCs) that coexpresses telomerase and myocardin A, a key regulator of cardiovascular myogenic development. The telomerase/myocardin A-positive MSCs differentiated into cardiovascular myogenic cells while retaining expression and activation of the telomerase catalytic unit, telomerase reverse transcriptase (TERT), at a level comparable to that of ESCs. Both myocardin A and TERT could be coimmunoprecipitated from the developing MSCs and ESC-derived EBs with either anti-TERT or anti-myocardin A antibodies, suggesting the formation of TERT-myocardin A complexes in the MSCs and EBs. The proteins pulled down with anti-myocardin antibodies showed almost the same levels of telomerase activities as those precipitated with anti-TERT antibodies. Overexpression of myocardin A by cDNA transfection significantly increased telomerase activities and promoted telomere synthesis by MSCs. The data from this study indicate a potentially novel function of myocardin A in maintaining the myogenic stemness in developing MSCs and EBs by enhancing telomerase activation and promoting myogenic gene expression.

Disclosure of potential conflicts of interest is found at the end of this article.

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