Electron microscopic examination of the nuclear morphology in AD-EDMD patient cells. Electron microscopic analysis of lymphoblastoids (a-b'), fibroblasts (c-d') and frozen muscle sections (e-f') from AD-EDMD patient 99-3 (b,b',d,d',f,f') and from control (a,a',c,c',e,e'). In the control a largely continuous layer of heterochromatin is in contact with the inner face of the nuclear envelope [visible at low (a,c,e) and higher magnification (a',c',e')]. In the lymphoblastoid cells with mutation LMNA R377H the condensed peripheral heterochromatin appears clearly detached from the nuclear envelope (arrows in b), the double membrane surrounding the chromatin contains numerous blebs and the inner pore fibrils become visible as shown at higher magnification (b', arrows). In patient fibroblast cells and muscle sections, nuclei showed nuclear membrane invaginations while the morphology of the membrane and nuclear pores was not disturbed as shown at higher magnification (d',f', arrows). In patient mature muscle cells, condensation of the peripheral chromatin was observed (f) compared to control (e). Bars (a-f): 2 µm; (a'-f') 0.2 µm.