COL21A1 and Parkinson disease: In addition, four genes associated with neurological disorders were significantly upregulated in hydrogel-cultured cells (NR4A2, Parkinson’s disease; A2M & HMOX1, Alzheimer’s; COL21A1, atypical psychosis) (Safran et al., 2010; Kanazawa et al., 2013; Schipper & Song, 2015).