Microglia proliferation is controlled by P2X7 receptors in a Pannexin-1-independent manner during early embryonic spinal cord invasion.
Microglia are known to invade the mammalian spinal cord (SC) at an early embryonic stage. While the mechanisms underlying this early colonization of the nervous system are still unknown, we recently found that it is associated, at least partially, with the ability of microglia to proliferate at the onset of motoneuron developmental cell death and of synaptogenesis in mouse embryo (E13.5). In vitro studies have shown that the proliferation and activation of adult microglia can be influenced by the purinergic ionotropic receptor P2X7 via a coupling with Pannexin-1. By performing patch-clamp recordings in situ using a whole-mouse embryonic SC preparation, we show here that embryonic microglia already express functional P2X7R. P2X7R activation evoked a biphasic current in embryonic microglia, which is supposed to reflect large plasma membrane pore opening. However, although embryonic microglia express pannexin-1, this biphasic current was still recorded in microglia of pannexin-1 knock-out embryos, indicating that it rather reflected P2X7R intrinsic pore dilatation. More important, we found that proliferation of embryonic SC microglia, but not their activation state, depends almost entirely on P2X7R by comparing wild-type and P2X7R-/- embryos. Absence of P2X7R led also to a decrease in microglia density. Pannexin-1-/- embryos did not exhibit any difference in microglial proliferation, showing that the control of embryonic microglial proliferation by P2X7R does not depend on pannexin-1 expression. These results reveal a developmental role of P2X7R by controlling embryonic SC microglia proliferation at a critical developmental state in the SC of mouse embryos.
Institut National de la Santé et de la Recherche Médicale, U952, Université Pierre et Marie Curie, Paris, Ile de France, France.
Chiara
C
Rigato
Nina
N
Swinnen
Roeland
R
Buckinx
Isabelle
I
Couillin
Jean-Marie
JM
Mangin
Jean-Michel
JM
Rigo
Pascal
P
Legendre
Hervé
H
Le Corronc
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D015703:Antigens, CD; C504120:CEACAM8 protein, human; D000073883:CX3C Chemokine Receptor 1; D015815:Cell Adhesion Molecules; D017630:Connexins; C471885:Cx3cr1 protein, mouse; D004791:Enzyme Inhibitors; D058851:GPI-Linked Proteins; D019394:Ki-67 Antigen; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; D058911:Purinergic P2X Receptor Agonists; D058920:Purinergic P2X Receptor Antagonists; D012333:RNA, Messenger; D019707:Receptors, Chemokine; D058486:Receptors, Purinergic P2X7; D012394:Rosaniline Dyes; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D053148:Caspase 3; C004692:coomassie Brilliant Blue; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid