Ultrastructural investigation of mitochondrial networks by serial block face scanning electron microscopy

Authors

• MA Aronova
• GN Calco
• BC Kuo
• JD Hoyne
• G Zhang
• RD Leapman

Abstract

Mitochondria have a central importance: they use electron transport chains and their associated molecular machinery to synthesize ATPs, which provide energy to drive chemical reactions within all eukaryotic cells. Mitochondria are also involved in heme synthesis and lipid metabolism and are highly dynamic, resulting in either large or discrete structures or networks. Characterization of these networks within cells can provide important information about the cells’ metabolic activity and their overall viability. We have used serial block-face scanning electron microscopy (SBF-SEM) to analyze distributions of mitochondrial network lengths in several types of cells. SBF-SEM can provide high-resolution three-dimensional ultrastructure of large volumes of resin-embedded biological tissue or cells at the nanometer scale, making it possible to image samples extending over >100 µm in three dimensions, at 10 nm spatial resolution in the plane of the block face (x and y) and 25 nm resolution in the perpendicular direction (z). We have explored a more efficient approach for segmenting mitochondrial networks, from which we have been able to obtain cross sectional areas, volumes and network lengths. For example, for insulin-secreting islet -cells, we found that approximately one-third of the total mitochondrial volume originated from short networks less than 3 µm in length, one-third came from tubules of length 3 to 10 µm, and one-third from networks of length 10 to 60 µm. We are in the process of further quantitatively analyzing these mitochondrial networks, as well as other cell/tissue networks.

Scientific Focus Area: Structural Biology

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