Nat. Genet. 38, 93–100 (2006); published online 27 November 2005; corrected after print 30 June 2006

In the version of this article initially published, the numbering of references 22–29 in the reference list was incorrect. The correct numbering is as follows:

22. Watkins, D. Cobalamin metabolism in methionine-dependent human tumour and leukemia cell lines. Clin. Invest. Med. 21, 151–158 (1998).

23. Watkins, D., Matiaszuk, N. & Rosenblatt, D.S. Complementation studies in the cblA class of inborn error of cobalamin metabolism: evidence for interallelic complementation and for a new complementation class (cblH). J. Med. Genet. 37, 510–513 (2000).

24. Ewing, B., Hillier, L., Wendl, M.C. & Green, P. Base-calling of automated sequencer traces using Phred I. Accuracy assesment. Genome Res. 8, 175–185 (1998).

25. Gordon, D., Abajian, C. & Green, P. Consed: a graphical tool for sequence finishing. Genome Res. 8, 195–202 (1998).

26. Miller, A.D. & Buttimore, C. Redesign of retrovirus packaging cell lines to avoid recombination leading to helper virus production. Mol. Cell Biol. 6, 2895–2902 (1986).

27. Yao, J. & Shoubridge, E.A. Expression and functional analysis of SURF1 in Leigh syndrome patients with cytochrome C oxidase deficiency. Hum. Mol. Genet. 8, 2541–2549 (1999).

The error has been corrected in the PDF version of this article.