In Extended Data Fig. 6a of this Letter, for consistency with the main figures, the labels ‘A’ and ‘P’ should be ‘Epi1’ and ‘Epi2’, respectively, and labels ‘EA’ and ‘EP’ should be ‘En1’ and ‘En2’, respectively. In Supplementary Table 6, the content of the table was wrongly calculated owing to an error during coding. In Supplementary Table 7, the label ‘Epi1.E7.5’ should be ‘Ect1.E7.5’ for consistency with the main figures. These errors do not affect the conclusions of the Letter. All errors have been corrected online.