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Circu ML, Aw TY.Circu ML, et al.Semin Cell Dev Biol. 2012 Sep;23(7):729-37. doi: 10.1016/j.semcdb.2012.03.014. Epub 2012 Mar 30.Semin Cell Dev Biol. 2012.PMID: 22484611Free PMC article.Review.