PDE1A and Alzheimer disease: Notably, the transcriptome profiles of the AD-up-regulated oligodendrocyte subpopulations o1 and o2 were characterized by enriched expression of HSPA1A (a heat shock protein), NEAT1 (a nuclear noncoding RNA), and PDE1A (which encodes phosphodiesterase 1A) (SI Appendix, Fig. S5 I and J); this expression pattern resembles that of remyelinating oligodendrocytes in patients with multiple sclerosis (22).