Figure 1. New A-T mouse models expressing clinically related PTCs.
(A) The Atm gene locus was targeted by homologous recombination of a targeting vector containing a modified NorCOMM cassette in intron one and the corresponding A-T PTC mutation in exon 3 to create the targeted AtmR35X and AtmQ35X ES cell lines. Following germline transmission of these alleles in mice, the floxed NorCOMM cassette was removed by Cre-excision in vivo to produce the final AtmR35X and AtmQ35X mouse lines. (B) Genotyping of A-T mouse models. PCR agarose gel of mouse DNA shows 151 bp wild-type (+) allele band and 241 bp Cre-excised targeted allele band. (C) ATM levels were examined using immunoblot analyses of the spleen due to its high expression density in this tissue. Exemplar blots illustrate a gene dose effect of ATM protein expression in samples harvested from wild-type (+), heterozygous (R35X/+, Q35X/+), and homozygous AtmR35X/R35X (R35X) and AtmQ35X/Q35X (Q35X) mice as indicated. (D) Breeding scheme schematic for double mutant and control mice for this study. (E) AtmR35X/R35X; Aptx−/− mice develop an ataxia that at late stages results in a severe loss of motor coordination and ability to ambulate (see Videos 1–4). Abbreviations for panel 1: hβA-human beta Actin promotor; ∆TK1-delta TK1, inactivated Thymidine Kinase 1; (T2A)-self-cleaving peptide sequence; Neo-Neomycin gene; PGKpA-Phosphoglycerate kinase poly A tail; loxP-recombination elements are shown as a blue triangle; orientation of the Gateway attB recombination elements is shown by an orange arrow; orientation of the genotyping (F) and (R) primers is shown by green and blue arrows, respectively; and engineered PTC sites are shown in exon 3 by a red circle. A-T, Ataxia Telangiectasia; ATM, A-T mutated; PTC, premature termination codon.