Signaling pathways inhibited in HD animals included CREB signaling in neurons (FDR < 9 × 10−7; Figure 2), synaptic long-term depression (FDR < 4 × 10−10) and potentiation, synaptogenesis (FDR < 4 × 10−10), tight junction (FDR < 4 × 10−10), endocannabinoid neuronal synapse (FDR < 4 × 10−10), opioid signaling (FDR < 4 × 10−10), neuregulin signaling (FDR < 4 × 10−10), and PPARα/RXRα activation (FDR < 4 × 10−10). This evidence concerns the gene PPARA and Huntington disease.