Fig. 7. Conserved structure and dynamics of pore-free islands in human normal diploid fibroblast IMR90 cells. (A) Dynamic changes in nuclear pore distributions during the cell cycle of human normal diploid IMR90 fibroblasts. In the G1 nucleus (center), the pore distribution displayed a patched pattern (see also supplementary material Fig. S3), but upon cell-cycle progression, pore distribution becomes uniform, coupled with an increase in pore number (top left). Quiescent cells induced by serum depletion still have patched pore distribution (bottom left), whereas the senescent cell nucleus shows a uniform pore distribution with a high density of pores (right). Note that DAPI staining of the senescent nucleus shows typical heterochromatic foci in the nucleoplasm (SAHF). (B) Lamin A/C is enriched in the pore-free islands of G1 nuclei of IMR90 cells (arrows), suggesting the structural conservation of the pore-free islands. 1, DAPI; 2, nuclear pores; 3, lamin A/C; 4, merged images of nuclear pores and lamin A/C.