Figure 4

Soluble neuritin peptide prevents neuritic atrophy in neurons from Tg2576 mice. (a) mRNA levels of neuritin are depicted from the hippocampi of 6-month-old Tg2576 and WT mice after the normalization to those of the WT littermates (WT, 1±0.0201 versus Tg2576, 0.8340±0.0177, n=5 mice, respectively). (b) The experimental scheme for neuritin peptide treatment and imaging. (c) Representative images of eGFP-expressing hippocampal neurons prepared from Tg2576 or their WT littermate mice after treatment of recombinant neuritin peptide (150 ng/ml^{16, 27, 42}) or vehicle (PBS as Control). Scale bar, 50 μm. (d) Sholl analyses are performed to measure dendritic branch crossings with the designated distanced circles from the soma. Statistical significance between WT-Control versus Tg2576-Control is expressed as *P<0.05, **P<0.01, ***P<0.001, whereas the comparison between Tg2576-Control versus Tg2576-Neuritin is expressed as ^‡P<0.05, ^‡‡P<0.01. (e) Total number of crossings until the marginal branch, ~120 μm is depicted for each group. WT-Control, 286.8±11.3 versus WT-Neuritin, 320.4±11.1 versus Tg2576-Control, 182.3±16.6 versus Tg2576-Neuritin, 253.3±14.1, n=11 neurons, respectively. (f) Representative images of eGFP-labeled dendrites of Tg2576 and WT neurons after treatment of recombinant neuritin or vehicle (PBS as Control) are presented. Scale bar, 10 μm. (g) Total number of spines per 10 μm from each group. WT-Control, 8.69±0.37 versus WT-Neuritin, 8.78±0.33 versus Tg2576-Control, 5.48±0.37 versus Tg2576-Neuritin, 8.68±0.46, n=11 neurons, respectively. Multiple comparisons using post hoc Bonferroni test after ANOVA reveals a marked decrease in total number of crossings (e) and spine numbers (g) from Tg2576 neurons compared with those from other groups. Statistical significance is expressed as **P<0.01 and ***P<0.001