The last three SN-PD hubs, ARID4B, MBTD1, and HNRNPA3, have been shown to participate in biological processes associated with neurodegeneration. ARID4B is a chromatin remodeling gene coding for a protein associated with the mSIN3A histone deacetylase (HDAC) complex [98], which participates in neuronal apoptosis and transcriptional signaling in neurodegenerative diseases [99]. MBTD1 is a member of the Polycomb gene family [113], and its protein product binds the Rb- (retinoblastoma-) E2F complex [96], thus contributing to cell cycle progress and apoptosis [97]. Here, MBTD1 is linked to neurodegenerative disease.