Generation of Atmy/y mice and Atm expression. (A) Location of the Atmy mutation and other reported murine Atm mutations; a (14), b (15, 16), and c (13). B, BamHI; H, HindIII; Bg, BglII; Sc, SacI; Xb, XbaI; and Neor, neomycin-resistance gene. (B) Southern blot analysis of Atmy mutation. BamHI-digested DNA is probed with the indicated 3′ probe (A). (C) Northern blot analysis of Atm expression. Total RNA from brain, lymph node, and thymus of wild-type (+/+) and Atmy/y (y/y) mice were probed with an Atm cDNA fragment (Lower) and reprobed with a DNA-PKcs cDNA probe (Upper) to confirm equal RNA loading. (D and E) Western blot analysis of Atm expression in Atmy/y tissues using antibodies raised against the C terminus (D) and N terminus (E) of the ATM protein. The bands at ≈200 kDa and ≈300 kDa are likely nonspecific since they are present in human and murine samples of both genotypes. (F) Kaplan–Meier survival curve of Atmy/y mice (n = 55).