CKAP2 and Hutchinson-Gilford progeria syndrome: Because spontaneous NE rupture is frequently observed in skin fibroblasts derived from a HGPS patient and mouse smooth muscle cells (SMCs) expressing PG (31, 33), we first examined whether G609G/+ MEFs also exhibit deformed nuclei, the leakage of NLS-sfCherry to the cytoplasm, the mis-localization, or decreased expression of LB1, which are indicative of spontaneous NE rupture and nuclear blebbing (15, 43).