Data were collected using a Leica DMIRB microscope equipped with a 100x objective (N.A. 1.4) and appropriate filter sets, and images captured using a Quantix 57 CCD camera (Roper Scientific Photometrics). For high resolution spatial mapping, three-dimensional optical stacks (containing 21 consecutive 0.25 micron slices) were captured using a PIFOC microscope focusing drive (Polytec PI). Images were dark current subtracted and intensity scaled See Fig 1 CD in Politz et al., 2005 Mol Biol Cell 16:3401-3410.