HDAC4 and Huntington disease: Indeed: (1) stimulation of the p38 signaling pathways contributes to neuronal cell death (Xia et al., 1995); (2) Sp1 knockdown improves survival in cellular and animal models of Huntington's disease (Qiu et al., 2006) or after PCB exposure (Formisano et al., 2015c); (3) inactivation of HDAC4 by small interfering RNA reduced neuronal cell death to potassium withdrawal (Bolger and Yao, 2005) or after OGD (Yuan et al., 2016); (4) BDNF treatment concurrent with Aβ1–42 exposure prevented neuron death (Nagahara et al., 2009).