Poster Presentation 2014 International Biophysics Congress

3D Ultra-structural analysis of insulin granules in pancreatic β-cells using STEM and FIB/SEM (#574)

Wei Zhao 1 , Lu-sheng Gu 2 , Yan-hong Xue 1 , Tao Xu 1
  1. Institute of Biophysics, CAS, Beijing, China
  2. College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
Insulin and proinsulin are stored in secretory granules known as dense core vesicles (DCVs) in pancreatic β-cells. Insulin granule trafficking is a key step in the insulin secretion process. Abnormalities in the ultrastructure and distribution of DCVs reflect different physiological conditions. However, because of its small size (around 350 nm), it’s difficult to study the morphological parameters and distribution of DCVs. We applied tomography based on scanning transmission electron microscopy (STEM) to image 1 μm thick sections of β-cells of mouse pancreatic islets which contain hundreds of intact insulin granules with resolution less than 5 nm. After reconstruction, we calculated density and DCV size and compared the distribution differences between wt and conditional knockout mice. To calculate the distance between DCVs and plasma membrane, we used focused ion beam scanning electron microscopy (FIB/SEM) to acquire large volumes (13.8×13.8×20 μm) of resin-embedded beta cells. DCVs were recognized and distances were calculated automatically using self-designed programs. In conclusion, we used STEM and FIB/SEM to study the 3D ultrastructure and distribution of DCVs with high resolution, and conducted a statistic analysis of different distributions of DCVs under different physiological conditions.