Figure 1.

(A) Detection of circRNA for miRNA-7 (ciRS-7) in sporadic Alzheimer's disease (AD) and age-matched control hippocampal CA1 [control (C) N = 4; AD (A) N = 6]; the single upper ciRS-7 (~1400 nt) band contains ~70 selectively conserved miRNA-7 binding sites as previously described (Hansen et al., 2013); a lower 28S RNA served as an internal loading control; all samples depleted of rRNA were treated with 50 units of RNaseR prior to electrophoresis RNaseR is a processive, Mg++-dependent hydrolytic exoribonuclease that degrades linear but not circular RNA; see Hansen et al. (2013); predicted circular transcripts consistently resisted an RNaseR challenge; 30 ug total AD and control hippocampal CA1 RNA was separated on agarose gels, transferred and probed with biotinylated or radiolabeled miRNA-7 probes as previously described (Colangelo et al., 2002; Hansen et al., 2013); detection was performed using a nonisotopic BrightStar BioDetect Kit (Ambion, Austin, TX; detection limit ~100 fg) or by standard autoradiography (Lukiw et al., 1992); (B) AD ciRS-7 is significantly reduced to about 0.18-fold of control (con) in a study of 20 control and AD (AD) hippocampal CA1 samples; this implicates loss of miRNA-7 sponge effects, an ambient up-regulation of miRNA-7 (as is observed), and down-regulation of a family of miRNA-7-sensitive mRNAs in the sporadic AD brain; other circRNAs may be involved; there were no significant differences between age for control or AD tissues [mean ± 1 standard deviation (SD) = 75.4 ± 8.3 year vs. 77.5 ± 7.6 year]; all AD cases were for moderate-to-advanced stages of AD; all post-mortem intervals were 2.1 h or less (Colangelo et al., 2002); there were no significant differences in age, ApoE allele status, RNA quality (all RIN values were 8.1–9.0) or yield between the control or AD groups (p > 0.05, ANOVA); a dashed horizontal line at 1.0 indicates homeostatic (control) ciRS-7 levels for ease of comparison; ^*p < 0.001 (ANOVA).