There were errors in the e-press version of the article published in J. Cell Sci. 122, 1665-1679.
In the e-press version of 28 April 2009, the equations were missing and there were errors in the colour reproduction of the figures. The correct version was published on e-press on 30 April 2009. The print version is correct.
We apologise for this mistake.
© The Company of Biologists Limited 2009
2009