Characterization of telomeres of BM cells from wildtype and G3 mTerc^−/− B6 animals by telomere restriction fragment, Q-FISH, and flow-FISH analysis.

(A) Telomere length estimation by telomere restriction fragments in pools of primary BM cells from 3 wildtype and 3 G3 mTerc^−/− B6 animals used for transplants into irradiated hosts. The telomere restriction fragments were separated by pulse-field gel electrophoresis, blotted, and hybridized to a P³²-labeled TTAGGG probe. Note the presence of low–molecular weigth TRFs in the G3 mTerc^−/− cells, which correspond to telomeres of 20 kb to fewer than 6 kb. (B) The same cells were hybridized with a flourescent PNA probe to measure telomere length by flow-FISH. Results are expressed as the mean ± SD of 3 different animals. (C) Telomere length distribution of primary and transplanted BM metaphase cells as determined by Q-FISH with the use of a telomeric PNA-Cy3 probe. The G3 mTerc^−/− cells showed a lower telomere flourescence and a change in size distribution toward shorter telomeres. Ten metaphases obtained from a pool of BM cells from 3 different animals were analyzed. A telomere fluorescent unit (TFU) corresponds to 1 kb telomeric DNA.