BDNF mRNA levels showed a tendency to decrease in HD patients with respect to controls and preHD samples after normalisation to the mRNA of the housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), although this difference was not statistically significant (P>0.05 by Kruskal-Wallis test followed by Dunn's multiple comparison test; Fig. 3A). The gene discussed is GAPDH; the disease is Huntington disease.