1. ¹Department of Physiology, University of Kentucky, Lexington, KY, USA
2. ²Department of Internal Medicine, University of Kentucky, Lexington, KY, USA

Correspondence: Dr G Van Zant, Departments of Internal Medicine and Physiology, University of Kentucky, Markey Cancer Center, 800 Rose Street, Rm CC414, 800 Rose Street, Lexington, KY 40536-0093, USA. E-mail: gvzant1@uky.edu

Received 2 September 2006; Revised 6 November 2006; Accepted 8 November 2006; Published online 25 January 2007.

Abstract

Substantial progress in embryonic and adult stem cell research in the past several years has yielded a wealth of information regarding the mechanisms regulating self-renewal and differentiation, two processes often used to define stem cells. Recent evidence suggests that epigenetic as well as genetic processes maintain stem cells in a pluripotent state as well as dictate their transition to more restricted stages of development. In this review, we discuss two emerging themes in stem cell biology, epigenetic control of gene expression and post-transcriptional regulation via microRNAs. We summarize how these regulatory mechanisms facilitate various aspects of normal stem cell biology and extend the discussion to their involvement in aging and tumorigeneisis, two biological phenomena intimately tied to stem cells. We speculate that aberrant epigenetic events and altered miRNA expression profiles in aged stem cell populations play important roles in carcinogenesis.