Figure 4.

ATUM-SEM Analysis of Mitochondrial Protrusions in Neurons of the Mouse Cortex

(A) A representative micrograph showing mitochondria in axonal or dendritic compartments of neurons. Box-a shows a mitochondrion with a protrusion (arrowheads); note that the tip but not neck of this protrusion stays visible in subsequent micrographs in the z direction (arrowheads). The z resolution of the ATUM-SEM for the cortex is 30 nm. The number on the micrograph indicates its z position in the SEM image stack.

(B) Micrographs showing three different protrusions from the same mitochondrion, as shown in Aa.

(C) An example of a mitochondrial protrusion (arrowheads) and a part of this protrusion is high density (dark).

(D and E) Additional examples illustrating mitochondrial protrusions in different shapes and sizes (arrowheads).

(F and G) Percentage of mitochondria with protrusions. A total of 400 axonal mitochondria and 200 dendritic mitochondria were examined in their entirety in z dimensions.

Scale bar in (A), 1 μm; scale bars in a, and (B)–(E), 100 nm. A 3D reconstruction of the mitochondrion shown in a, and additional examples of protrusions are shown in Figure S4.