The primers for PCR were as follows: Fli-1 exon
IX/forward primer (positions 1156–1180), GACCAACGGGGAGTTCAAAATGACG; Fli-1 exon IX/reverse primer (positions 1441–1465), GGAGGATGGGTGAGACGGGACAAAG; and Pol II/reverse primer, GGAAGTAGCCGTTATTAGTGGAGAGG. Caspase inhibitor DNA was isolated from tail snips (4-week old mice) using a QIAamp Tissue kit (Qiagen, Santa Clarita, CA, USA). PCR conditions were one cycle at 94°C for 10 min followed by 35 cycles at 94°C for 1 min, 68°C for 1 min and 72°C for 1 min. A 309-base pairs (bp) fragment indicates the presence of the WT allele, and a 406-bp fragment is amplified from the mutated allele. BM cells were prepared for FISH using standard techniques. Briefly, cells were cultured overnight in Chang bone marrow culture (BMC) media (Irvine Scientific, Santa Ana, CA, USA), supplemented with penicillin and streptomycin. Then ethidium bromide (Sigma, St Louis, MO, USA) was added to the culture at a concentration of 10 µg/ml and the cells were incubated for 45 min. Next, colcemid (Invitrogen/Gibco, Akt inhibitor Grand Island, NY, USA) was
added to the culture at 0·1 µg/ml and incubated for an additional 40 min. Red blood cells were disrupted in hypotonic solution buffer (0·075 M KCl). Cells were then fixed in methanol acetic acid solution at the ratio of 5 : 2. Cells were suspended in fixation buffer at 1 × 107 cells/ml. A drop of each sample was placed on a microscope slide. After air-drying, slides were then dehydrated with ethanol. Next, slides were denatured at 65°C in denaturing solution [0·6× standard saline sodium citrate (SSC) and 70% formamide]. Slides were then quenched in 70% ice-cold ethanol and dehydrated again in ethanol. BM cells were then hybridized to Thymidylate synthase cyanine 3 (Cy3)-labelled mouse X-chromosome paint and fluorescein isothiocyanate (FITC)-labelled mouse Y-chromosome paint in hybridization solution (Cambio, Cambridge, UK) overnight
at 37°C. Slides were then washed in Stringency Wash solution (50% formamide and 0·5 × SSC) at 45°C for 5 min. After washing twice with SSC at 45°C, the slides were incubated with wash detergent solution (4 × SSC, 0·05% Tween-20) for 4 min at 45°C, and mounted with Gelmount (Biomedia, Foster City, CA, USA) containing 125 ng/ml 4,6-diamidino-2-phenylindole (DAPI; Invitrogen-Molecular Probes, Carlsbad, CA, USA). Finally, slides were examined using a Leica epifluorescent microscope with standard epifluorescence filters for FITC, Cy3 and DAPI (Leica, Bannockburn, IL, USA). Two hundred cells were counted from each sample. Mice were placed in metabolic cages for 24-h urine collection every 4 weeks, beginning at the 12 weeks of age after BM transplantation. Antibiotics (ampicillin and gentamicin from Invitrogen and chloramphenicol from Sigma) were added in collection tubes to inhibit bacterial growth. Urinary albumin excretion was determined by enzyme-linked immunosorbent assay (ELISA) as described previously .