Poster Presentation 6th Annual Meeting for Australasian Society for Stem Cell Research 2013

P2X7 mediates innate phagocytosis in neuronal progenitor cells (#143)

Michael D Lovelace 1 2 , Ben Gu 3 , Steven Eamegdool 1 2 , James S Wiley 3 , David G Allen 4 , Michael W Weible II 5 , Tailoi Chan-Ling 1 2
  1. Discipline of Anatomy and Histology, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
  2. Bosch Institute, The University of Sydney, Sydney, NSW, Australia
  3. Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
  4. Discipline of Physiology, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
  5. Biomolecular and Physical Sciences, Griffith University, Brisbane, Queensland, Australia

The developing central nervous system (CNS) is characterized by widespread overproduction of cells of all lineages including neurons1-2 , oligodendrocytes2  and astrocytes3 . However, a large proportion of these cells undergo apoptotic suicide before they integrate into neural circuits. Clearance of apoptotic cells is essential in the early development of the central nervous system (CNS) but the receptors mediating this process have not been identified. Recently we have shown a role for the purinergic receptor P2X7 as a scavenger receptor for apoptotic cells in a serum-free, non-inflammatory environment4. Using immunocytochemical staining and functional assays, we demonstrated the presence of functional P2X7 receptor (P2X7R) on the surface of cultured, undifferentiated human neural precursor cells (hNPCs) and immature neurons. These cells were propagated as free-floating neurospheres in culture5  before plating on substrate-coated glass for physiological assay, or enzymatically dissociated for flow cytometric analysis. Commitment of hNPCs to the neuronal lineage was associated with a reduction in P2X7 responsiveness, as assessed by calcium influx experiments. We next identified a population of neuronal precursor cells and immature neurons that highly expressed both P2X7R and the neuron marker doublecortin (DCX). These DCXhigh/P2X7high cells could phagocytose latex beads, apoptotic hNPCs or ReN cells. Preincubation with ATP or a specific P2X7 antagonist resulted in reduced phagocytic uptake of beads or cells by the DCXhigh/P2X7high neuronal precursor cells and immature neurons. This groundbreaking discovery suggests that DCXhigh/P2X7high cells can utilize P2X7R as a scavenger receptor for the clearance of apoptotic cells from the developing CNS.

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  3. Chan-Ling, T., Chu, Y., Baxter, L., Weible, M.W., and Hughes, S. (2009). In vivo characterization of astrocyte precursor cells (APCs) and astrocytes in developing rat retinae: differentiation, proliferation, and apoptosis. Glia 57, 39-53.
  4. Gu, B.J., Saunders, B.M., Petrou, S., and Wiley, J.S. (2011). P2X7 is a scavenger receptor for apoptotic cells in the absence of its ligand extracellular ATP. J. Immunol. 187, 2365-2375.
  5. Weible MW, Chan-Ling, T., (2007) Phenotypic characterization of neural stem cells from human fetal spinal cord: synergistic effect of LIF and BMP4 to generate astrocytes. Glia 55(11), 1156-1168.