Statistical analysis
All data are expressed as mean ± SEM. Statistical analyses were
performed using IBM SPSS Statistics 20. Normal distribution was assessed
by Shapiro-Wilk test. Statistical significance was determined according
to sample distribution and homogeneity of variance. Statistical
comparisons between two groups were determined by two-tailed Student’s t
test and Mann-Whitney U test. One-way ANOVA following by Bonferroni’s
post hoc test, two-way ANOVA with simple effect test and Kruskal-Wallis
test with Dunn’s post hoc test were performed for comparisons among
multiple groups. P < 0.05 was considered statistically
significant. The group sizes of the individual experiments were chosen
based on our preliminary experiments. It was shown that the significance
was reached when the number in each group was 3 or 4. In our study,
n =5-8 fulfilled the statistical requirements. The exact statistical
method and exact group size for the individual experiments are shown in
the corresponding figure legends. No samples were excluded from the
analyses.