Human Adult Glial Progenitors Are Transcriptionally Distinct from Their Fetal Counterparts [scRNA-seq]

Glial progenitor cells (GPCs), the primary source of oligodendrocytes and astrocytes in the human CNS, emerge during the 2nd trimester of human development and subsequently colonize the brain, where a pool remains throughout adulthood. While fetal GPCs are highly migratory and proliferative, there is evidence that their capacities diminish throughout aging or as a result of demyelination-induced exhaustion, thus compromising their ability to mobilize, remyelinate, and self-renew. To investigate this mechanism, we first utilized bulk and scRNA-Sequencing to characterize the human fetal GPC pool and leveraged these data to elucidate transcriptional discrepancies in adult human GPCs. This revealed age-induced transcriptional shifts towards loss of proliferative competency and the potential onset of senescence. Further, we inferred adult networks of direct repressive transcription factor activity that may drive functional decline during GPC aging. Finally, we coupled these data with miRNA profiling of both populations to establish both upstream and parallel arms of repression that may stifle the functional aptitude of aged GPCs. These identified upstream regulators may be ideal therapeutic targets toward rejuvenating GPCs crippled by mitotic exhaustion or aging. Human brain samples were obtained under approved Institutional Review Board protocols from consenting patients at Strong Memorial Hospital at the University of Rochester. Brain tissue was obtained from normal GW 18-24 cortical and/or VZ/SVZ dissections or adult white matter/cortex epileptic resections (18,19, and 27 years old for mRNA, 8, 20, 43, and 54 years old for miRNA). Fetal GPC acquisition, dissociation and immunomagnetic sorting of A2B5+/PSA-NCAM- cells were as described (Windrem et al., 2004). GPCs were isolated from dissociated tissue using a dual immunomagnetic sorting strategy: depleting mouse anti-PSA-NCAM+ (Millipore, DSHB) cells, using microbead tagged rat anti-mouse IgM (Miltenyi Biotech), then selecting A2B5+ (clone 105; ATCC, Manassas, VA) cells from the PSA-NCAM- pool, as described (Windrem et al., 2004; Windrem et al., 2008). After sorting, cells were maintained for 1-14 days in DMEM-F12/N1 with 10 ng/ml bFGF and 20 ng/ml PDGF-AA. Alternatively CD140a/PDGFRA-defined GPCs were isolated and sorted using MACS as described (Sim et al., 2011b), yielding an enriched population of CD140+ glial progenitor cells.