Movie 2. The chromatin ultrastructure and 3D organization of the human genome in the nucleus.
ChromEM staining and multitilt EMT enable the ultrastructure of individual chromatin chains to be resolved and their 3D organization to be visualized as a continuum in the context of the nuclear architecture. Resting human SAECs were fixed, stained with ChromEM, and an eight-tilt EM tomogram (29,000×) was collected of a 250-nm-thick section (SAEC #1 from Fig. 4B). The reconstructed EMT volume is 1206 nm (x) by 1418 nm (y) by 155 nm (z) and comprises 121 TSs (each 1.28 nm thick). We compiled serial TS slices (TS #0 to TS #120) into a movie that enables chromatin to be visualized as a continuum from the top to the bottom of the nuclear volume. Chromatin is a disordered particulate chain that is packed together at different concentrations in the nucleus, with higher densities at the nuclear lamina. The gaps in the nuclear membrane correspond to the insertion sites of nuclear pores.