1 Heidelberg University Biochemistry Center Im Neuenheimer Feld 328, 69120 Heidelberg, Germany. Electronic address: walter.nickel@bzh.uni-heidelberg.de.
2 Hubrecht Institute of the KNAW & UMC Utrecht, 3584 CT Utrecht, The Netherlands; Department of Cell Biology, UMC Groningen, The Netherlands. Electronic address: c.rabouille@hubrecht.eu.