Correctum Xuehong Xu, University of Maryland School of Medicine 22 November 2013 After publication of this article, Xu et al. Cell & Bioscience 2013, 3:27, it was noticed by the authors that there was an error in the affiliation of Yuexin Pan and Donald D Anthony. Case Western Reserve University is in Cleveland, OH not Baltimore, MD as was originally stated. Please accept our apologies for any inconvenience caused. Competing interests I am an auhtor of the article.