Caspase 3/caspase-activated DNase promote cell differentiation by inducing DNA strand breaks

doi:10.1073/pnas.0913089107

Caspase 3/caspase-activated DNase promote cell differentiation by inducing DNA strand breaks

^aOttawa Hospital Research Institute, Sprott Centre for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital, Ottawa, ON K1H 8L6, Canada;
^bFaculty of Medicine, Department of Cellular and Molecular Medicine, Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON K1H 8M5, Canada

Edited by Eric N. Olson, University of Texas Southwestern, Dallas, TX, and approved January 25, 2010 (received for review November 12, 2009)

Abstract

Caspase 3 is required for the differentiation of a wide variety of cell types, yet it remains unclear how this apoptotic protein could promote such a cell-fate decision. Caspase signals often result in the activation of the specific nuclease caspase-activated DNase (CAD), suggesting that cell differentiation may be dependent on a CAD-mediated modification in chromatin structure. In this study, we have investigated if caspase 3/CAD plays a role in initiating the DNA strand breaks that are known to occur during the terminal differentiation of skeletal muscle cells. Here, we show that inhibition of caspase 3 or reduction of CAD expression leads to a dramatic loss of strand-break formation and a block in the myogenic program. Caspase-dependent induction of differentiation results in CAD targeting of the p21 promoter, and loss of caspase 3 or CAD leads to a significant down-regulation in p21 expression. These results show that caspase 3/CAD promotes cell differentiation by directly modifying the DNA/nuclear microenvironment, which enhances the expression of critical regulatory genes.

Footnotes

¹To whom correspondence should be addressed. E-mail: lmegeney{at}ohri.ca.
Author contributions: B.D.L., F.J.D., and L.A.M. designed research; B.D.L., S.R., L.E.B., and S.B. performed research; B.D.L., L.E.B., and L.A.M. analyzed data; and B.D.L. and L.A.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0913089107/DCSupplemental.