Nature Communications 6: Article number: 6793 (2015); Published: 9 April 2015; Updated: 13 March 2018

In the originally published version of this Article, there were errors in the Methods section and in Supplementary Figure 2. In the Methods section entitled ‘Quality control’, and in Supplementary Figure 2, references to ‘MAF>0.0001’ were incorrectly given as ‘MAF>0.01’. These errors have now been corrected in both the PDF and HTML versions of the Article and in the Supplementary Information File.