Fig. 8.

Electron micrographs of cell nuclei in the cerebral cortex of E17.5 Lmnb1^+/+, Lmnb1^CS/CS, Lmnb2^CS/+, and Lmnb2^CS/CS embryos. (A and B) Low-magnification electron micrographs. Many cortical cells in Lmnb1^CS/CS embryos, but not wild-type or Lmnb2^CS/CS embryos, exhibited nuclear blebs (arrowheads). (Scale bars: 4 µm in A; 3 µm in B.) (C) A higher-magnification image of a nuclear bleb in the cortex of an Lmnb1^CS/CS embryo. Only a small amount of chromatin was present in the bleb (arrow). (Scale bar, 1 µm.) (D) EM tomography of the cerebral cortex of an Lmnb1^CS/CS embryo. (Left and Center) Two sections from a total of 135 sections spanning 200 nm of the cell nucleus. (Right) 3D modeling of the inner (red) and outer (green) nuclear membranes, generated by tracing the membranes in every fifth section (14 total sections) of the tomogram. In many sections, the outer and inner nuclear membranes overlapped because of the plane of sectioning. The inner and outer nuclear membranes were generally closely associated in nuclear blebs but were occasionally separated. (Scale bar, 1 µm.)