Nature Cell Biol. 11, 1150–1156 (2009); published online 16 August 2009; corrected after print, 11 November 2009

In both in the HTML and PDF versions of this letter, statements regarding the functions of HPS4 and 1 have been altered as follows: on page1150 (right column, second paragraph, line 4 to line 12), the following text has replaced the previous text,

“Its etiology has been related to defects in eight genes, all of which act in endosome pathways that form lysosome-related organelles5. In skin melanocytes, a complex of the HPS4 and HPS1 proteins is required for the biogenesis of melanosomes12. The complex is also required for normal localization of late endocytic organelles11. The presence of SNARE-like domains in HPS4 and HPS1 supports a role for those proteins in the synthesis and trafficking of lysosome-related organelles13. The yeast Ccz1 and Mon1 proteins, which possess similar SNARE-like domains, act as a complex to promote tethering of late endosomes for fusion to the vacuole10.”

On page 1151 (left column, second paragraph, line 1), the following text has replaced the previous text,

“To explore whether HPS4 affects RNAi because of its putative role in endosomal trafficking.”

On page 1151 (left column, second paragraph, line 7) the following sentence has been deleted,

“It is in this turnover step that HPS4 functions.”