Fig 2: Normal muscle architecture with discrete ultrastructural changes due to reduced MACF1 gene product.Transmission electron microscopic analyses of muscle biopsies from the proband (a–g) and his youngest sister (proband 2, h–l). In (a) a satellite cell from the proband is shown, and the cell periphery having a severely affected membrane structure is magnified in (d, arrows). In (b) an endothelial cell from the proband is shown, and this cell displays membrane foldings facing the myofiber (magnified in (c), arrows). In (e) and (f) another satellite cell from the proband is shown, again displaying an abnormal cell membrane structure that appears folded or whorled at the cell periphery (f, arrows). In (g) normal organization of myofibrils and z-bands in the proband is shown. In (h) and (i) a satellite cell presenting the same phenomenon in proband 2 as for the proband, with folded cell membrane structure at the periphery, is shown (i, arrows). In (j) an endothelial cell from proband 2 is shown. This endothelial cell displays a normal tight junction (j, white arrow) but also an abnormal, folded membrane structure at a tight junction (j, black arrows). An electron dense cylindrical membrane structure with membrane whorls at the periphery is observed in proband 2 (k, arrows). Proband 2 further displays large membranous whorl structures (l, arrows). These structures were also detected in the proband (m, arrows). In (n) normal ultrastructure from a control is shown. In (o) two satellite cells from control muscle are shown and in (p) an endothelial cell surrounding a vessel from a normal control is shown. SC = satellite cell, EC = endothelial cell, L = vessel lumen, M = membrane structure, TJ = tight junction, TJ* = abnormal tight junction, C = cylindrical membrane structure, MW = membranous whorl. Scale bars in a: 2000 nm; b: 5000 nm; c: 1000 nm; d: 2000 nm, e: 2000 nm, f: 1000 nm, g: 2000 nm; h: 1000 nm; i: 500 nm; j: 1000 nm; k: 1000 nm; l: 1000 nm; m: 500 nm; n: 2000 nm; o: 5000 nm; p: 5000 nm.