FIG. 1.—

Volcano plot of the significance level of the expression difference between neurons and endothelia cells versus the mean difference in gene expression levels. Each dot represents one gene probe set. The y axis shows negative log₁₀ transformed P values obtained from gene by gene two-sided t-tests (e.g., 4 is equal to a P value of 10⁻⁴). Blue circles indicate the probe sets with enriched expression in neurons and red circles indicate enriched expression in endothelial cells. A gene is called enriched expressed, if it shows a statistically significant expression difference between the two cell types (P ≤ 0.05).