Figure 4.

Genetic instability induced by Rint1 deficiency. (a) Metaphase spreads show increased genomic instability after Rint1 inactivation in MEFs. Magnified regions show chromosomes without two telomeres (sister chromatid fusion, SCF) and nearby small DNA fragments with two telomeres (fused telomeres, FT). Evaluations in the right panel show a significant increase in these chromosomal aberrations after Rint1 inactivation. (b) Projection of confocal images of the defective mitosis with co-stained telomeres (green) and centromeres (red) demonstrating DNA bridges between two centromeres of daughter cells and micronuclei with two telomeres. (c) Mechanism of bridge and micronuclei formation in case of fusion of wrong DNA ends of DSBs in close proximity. (d) Mechanism of bridge and micronuclei formation in case of telomere loss. After replication the telomere-less chromatids are fused forming SCF and FT. Rint1^Nes-Cre brains (n=5) have a reduced pool of neural stem cells (e) with altered capacity to proliferate in comparison with Rint1^Ctrl mice (n=17) (f). (g) Representative images of neurospheres isolated from Rint1^Ctrl and Rint1^Nes-Cre mice brains. (h) A significant increase in mitotic defects in primary neuronal stem cells from Rint1^Cre-ER(T2) mice 2 days after 4-OHT treatment. (i) Projection of confocal images of the defective mitosis in neuronal progenitor cell 2 days after 4-OHT treatment, co-stained against telomeres (green) and centromeres (red) showing the same bridge geometry as in MEFs. Stars indicate significance in two tailed Student's t-test *P<0.05, **P<0.005, ***P<0.0005