Fig. 1.

Chromatin changes associated with stem cell aging. Changes in the structure and makeup of chromatin during aging have been characterized in HSCs and satellite cells. These changes include differences in the levels and distribution of chromatin-modifying enzymes (blue circles), histone modifications (green flag, activating; red flag, repressive; filled flag, increases during aging; empty flag, decreases during aging) and DNA methylation (pink star) patterns. Such changes result in regional loss of transcriptional silencing (yellow), altered cell fate decisions, decreased function and cellular senescence.