Figure 7.

Full-length L1 and SpORF2 expression triggers senescence-like phenotype in normal human fibroblasts and human adult stem cells. (A) Normal human fibroblasts transfected with the empty vector, vectors expressing wt L1, or SpORF2, or treated with a DNA damaging agent zeocin. Blue color represents cells that express senescence-associated β-galactosidase. (B) Quantitation of the L1-induced senescence in normal human fibroblasts, BJ, immortalized with human telomerase. Black bars represent relative amount of senescent cells among human fibroblasts treated as described in (A). Grey bars represent relative amount of cells observed after each treatment in any given field. Asterisks indicate statistically significant difference between the cell numbers of cells transfected with the empty vector and cells transfected with the wt L1 expression cassette or zeocin treatment (t-test, P-value 0.014 and 0.00025, respectively). Untransfected (untr.) is mock-transfected cells. (C) Quantitation of the L1-induced senescence in human adult stem cells. Black and gray bars represent relative amount of senescent cells and total cells as described in (B). Asterisks indicate statistically significant difference between the cell numbers of cells transfected with the empty vector and cells transfected with the wt L1 expression cassette, zeocin treatment, or SpORF2 vectors (t-test, P-value 0.01, 0.0002 and 0.013, respectively).