Competitive long-term repopulating ability of G3 mTerc^−/− B6 BM cells.

Groups of 10 irradiated recipient mice were inoculated with different proportions (1:1 and 10:1) of G3 mTerc^−/− B6 versus wild type BM cells; 2 × 10⁵ wildtype cells were inoculated in all animals, and the number of mTerc^−/−cells was 2 × 10⁵ and 2 × 10⁶ in the 2 groups, respectively. The wild type and mTerc^−/− BM cell suspensions were a pool of cells from 4 different animals. Recipients were killed at 90 (all groups), 145 (1:1 group), and 200 days (10:1 group) after transplantation, and the competitive repopulating ability of the test populations was evaluated by hybridization of BM and spleen (Sp) DNA with a neo^r-specific probe (which has replaced the mTerc gene in the mTerc^−/− mice). Signal intensity was analyzed by densitometer by means of the ImageQuant program (Amersham Biosciences, Sunnyvale, CA). A titration of mixtures of different proportions of mTerc^−/−-to-wild type splenic DNA is shown in the bottom of the Figure; this was used to quantitate the densitometric analysis of the autoradiography. Hybridization with a fragment of the GAPDH monocopy gene was carried out to correct DNA loading in the dot blot membranes; the corresponding control for GAPDH hybridization is shown in the bottom panel. Each sample in the dot blot represents a transplanted individual. Data are represented as the percentage of reconstitution by G3 mTerc^−/− B6 BM cells.