Nat. Immunol. 10, 109–115 (2009); published online 7 December 2008; corrected after print 9 April 2009

In the version of this article initially published, the Cre-transgenic mouse is identified incorrectly as Tg(SV40-cre)1Jrg. The correct mouse strain should be Tg(SCL6E5-Cre)1Jrg, and the citation describing this mouse (ref. 29) should be as follows: Gothert, J.R. et al. In vivo fate-tracing studies using the Scl stem cell enhancer: embryonic hematopoietic stem cells significantly contribute to adult hematopoiesis. Blood 105, 2724–2732 (2005). The error has been corrected in the HTML and PDF versions of the article.