Telomere dynamics in FANCG-deficient human cells. (A) Q-FISH analysis of presenescent IMR90 cells infected with retrovirus encoding FANCG shRNAs or GFP shRNA, at day 10 after infection. Histograms show similar telomere length distribution in GFP shRNA IMR90 cells and FANCG shRNA2 IMR90 cells (top 2 panels). Representative microphotographs (telomeric probe, yellow; DNA, blue) are shown in the bottom 2 panels. (B) Telomere length distribution of early-passage primary fibroblasts (CPD5) obtained from 2 FA-G patients (EUFA 1093-F and EUFA 0636). Note the very homogeneous telomere length and absence of signal-free ends or end-to-end chromosomal fusions. A representative microphotograph of a metaphase from patient EUFA 0636 is shown in the bottom panel.