Stacked ER in motor neurons of wild-type VAPB overexpressing mice. A, B) Transmission electron photomicrographs showing stacked ER in motor neurons from a 30 week old wild-type VAPB overexpressing mouse (line VW3). The ER cisterns in the stacks are thin, while the cytosolic faces of the cisternal membranes are separated by a 17.2 ± 1.6 nm thick layers (A). In A“ the ER lumen is accentuated in green to outline the continuity of lumen of stacked cisterns with the surrounding ER cisterns. B illustrates stacked ER next to a synapse. C) Post-embedding anti-HA immunogold electron photomicrographs, showing that transgenic wild-type VAPB is concentrated in the stacked ER. D) Transmission electron photomicrograph of a motor neuron of an 8 week old mouse from line VW1 showing stacked ER (black arrow) and a variant of stacked ER (red arrows), consisting of curved more irregular ER cisterns, and electron dense intra-cisternal spaces (inserts in D). Color overlay: yellow, nucleus (A); purple, presynaptic bouton (B); green, lumen of ER (A, B). Scale bars: 2 μm (D), 500 nm (B), 100 nm (A”, C).