title: P2X7 receptors mediate innate phagocytosis by human neural precursor cells and neuroblasts.
abstract: During early human neurogenesis there is overproduction of neuroblasts and neurons accompanied by widespread programmed cell death (PCD). While it is understood that CD68(+) microglia and astrocytes mediate phagocytosis during target-dependent PCD, little is known of the cell identity or the scavenger molecules used to remove apoptotic corpses during the earliest stages of human neurogenesis. Using a combination of multiple-marker immunohistochemical staining, functional blocking antibodies and antagonists, we showed that human neural precursor cells (hNPCs) and neuroblasts express functional P2X7 receptors. Furthermore, using live-cell imaging, flow cytometry, phagocytic assays, and siRNA knockdown, we showed that in a serum-free environment, doublecortin(+) (DCX) neuroblasts and hNPCs can clear apoptotic cells by innate phagocytosis mediated via P2X7. We found that both P2X7(high) DCX(low) hNPCs and P2X7(high) DCX(high) neuroblasts, derived from primary cultures of human fetal telencephalon, phagocytosed targets including latex beads, apoptotic ReNcells, and apoptotic hNPC/neuroblasts. Pretreatment of neuroblasts and hNPCs with 1 mM adenosine triphosphate (ATP), 100 µM OxATP (P2X7 antagonist), or siRNA knockdown of P2X7 inhibited phagocytosis of these targets. Our results show that P2X7 functions as a scavenger receptor under serum-free conditions resembling those in early neurogenesis. This is the first demonstration that hNPCs and neuroblasts may participate in clearance of apoptotic corpses during pre target-dependent neurogenesis and mediate phagocytosis using P2X7 as a scavenger receptor.
authors.affiliation: Discipline of Anatomy and Histology, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Bosch Institute, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Lovelace
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Gu
authors.forename: Steven S
authors.initials: SS
authors.lastname: Eamegdool
authors.forename: Michael W
authors.initials: MW
authors.lastname: Weible
authors.forename: James S
authors.initials: JS
authors.lastname: Wiley
authors.forename: David G
authors.initials: DG
authors.lastname: Allen
authors.forename: Tailoi
authors.initials: T
authors.lastname: Chan-Ling
mesh_terms: D017209:Apoptosis / Q000502:physiology; D002478:Cells, Cultured; D005333:Fetus / Q000166:cytology / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism*; D010587:Phagocytosis / Q000502:physiology*; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000378:metabolism*; D013687:Telencephalon / Q000166:cytology / Q000378:metabolism*
chemical_list: D058486:Receptors, Purinergic P2X7
keywords: Apoptosis; Neural stem cells; Neurogenesis; P2X7; Programmed cell death; Purinoceptor