CNS/PNS boundary transgression by central glia in the absence of Schwann cells or Krox20/Egr2 function.
CNS/PNS interfaces constitute cell boundaries, because they delimit territories with different neuronal and glial contents. Despite their potential interest in regenerative medicine, the mechanisms restricting oligodendrocytes and astrocytes to the CNS and Schwann cells to the PNS in mammals are not known. To investigate the involvement of peripheral glia and myelin in the maintenance of the CNS/PNS boundary, we have first made use of different mouse mutants. We show that depletion of Schwann cells and boundary cap cells or inactivation of Krox20/Egr2, a master regulatory gene for myelination in Schwann cells, results in transgression of the CNS/PNS boundary by astrocytes and oligodendrocytes and in myelination of nerve root axons by oligodendrocytes. In contrast, such migration does not occur with the Trembler(J) mutation, which prevents PNS myelination without affecting Krox20 expression. Altogether, these data suggest that maintenance of the CNS/PNS boundary requires a Krox20 function separable from myelination control. Finally, we have analyzed a human patient affected by a congenital amyelinating neuropathy, associated with the absence of the KROX20 protein in Schwann cells. In this case, the nerve roots were also invaded by oligodendrocytes and astrocytes. This indicates that transgression of the CNS/PNS boundary by central glia can occur in pathological situations in humans and suggests that the underlying mechanisms are common with the mouse.
Coulpier
Fanny
F
Plate-forme Transcriptome and Developmental Biology Section, Inserm, Unité 1024, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8197, Institut de Biologie de l'Ecole Normale Supérieure, 75230 Paris, France.
Decker
Laurence
L
Funalot
Benoît
B
Vallat
Jean-Michel
JM
Garcia-Bragado
Federico
F
Charnay
Patrick
P
Topilko
Piotr
P
D000818:Animals; D001253:Astrocytes / Q000502:physiology / Q000648:ultrastructure; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D002465:Cell Movement / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology* / Q000648:ultrastructure; D051767:Early Growth Response Protein 2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007223:Infant; D051379:Mice; D008822:Mice, Transgenic; D009186:Myelin Sheath / Q000502:physiology / Q000648:ultrastructure; D009457:Neuroglia / Q000502:physiology* / Q000648:ultrastructure; D009836:Oligodendroglia / Q000502:physiology / Q000648:ultrastructure; D017933:Peripheral Nervous System / Q000502:physiology* / Q000648:ultrastructure; D010523:Peripheral Nervous System Diseases / Q000378:metabolism / Q000473:pathology; D012583:Schwann Cells / Q000502:physiology / Q000648:ultrastructure; D013126:Spinal Nerve Roots / Q000502:physiology / Q000648:ultrastructure
C497326:EGR2 protein, human; D051767:Early Growth Response Protein 2; C497327:Egr2 protein, mouse