Vol. 188 No. 6, March 22, 2010. Pages 821–832.

The authors regret errors in the Materials and methods section of this paper pertaining to the acquisition of the electron micrographs shown in Fig. 4 D. The correct methods for this acquisition are as follows:

Pancreatic tissue was fixed by immersion in 2.5% glutaraldehyde and 2.0% paraformaldehyde in 0.1M sodium cacodylate buffer (pH 7.2), postfixed in 1% osmium tetroxide, and en bloc stained with 1% uranyl acetate. The tissue was dehydrated in ethanol embedded in Epon (Electron Microscopy Sciences). Ultrathin sections were post-stained with uranyl acetate and lead citrate and examined using an electron microscope (model CM12; FEI) at 120 kV. Images were recorded digitally using a camera system (4k 3 2.7k; Gatan, Inc.) with DigitalMicrograph software (Gatan, Inc.).

We are indebted to Alice Liang and Eric Roth from the Imaging Core Facility at the NYU School of Medicine (New York, NY) for processing the samples and acquiring the images.