For instance, dendrites on pyramidal CA1 hippocampal neurons of Ptk2b−/− mice suffer a loss of dendritic spines and PSD-95 clusters; moreover, Pyk2 restoration in the hippocampi of Huntington’s disease model mice, which exhibit low Pyk2, partially rescues this same phenotype [12]. The gene discussed is PTK2B; the disease is Huntington disease.