| Abstract No.: | B-B2067 |
| Country: | Canada |
| | |
| Title: | OLIGODENDROGLIAL EXPRESSION OF DCC IS REQUIRED FOR THE ORGANIZATION OF PARANODAL JUNCTIONS IN VIVO.
|
| | |
| Authors/Affiliations: | 1 Sarah-Jane Bull*; 2 Mohammadali Almasieh; 1 Sathyanath Rajasekharan; 2 Barbara Morquette; 2 Adriana Di Polo; 1 Timothy Kennedy;
1 McGill University, Montreal, QC, Canada; 2 Université de Montreal, QC, Canada
|
| | |
| Content: | Objectives: Paranodal axoglial junctions are essential for the segregation of myelinated axons into distinct domains and the efficient conduction of action potentials. We have previously established that netrin-1 and DCC are expressed at paranodal axo-oligodendroglial junctions both in vivo and in vitro. Myelination in the CNS of mice occurs during the first few post-natal weeks. Unfortunately, netrin-1 or dcc null mice die within a few hours after birth, and it is therefore not possible to examine myelin formation in these animals in vivo. Studies carried out in vitro have provided evidence that netrin-1 and DCC are required for the maintenance of normal paranodal axo-oligodendroglial junctions. To determine if netrin signalling is required for the organization of oligodendroglial junctions in vivo, we assessed the capacity of oligodendrocyte precursor cells (OPCs) derived from dcc-/- mice to myelinate retinal ganglion cell axons when transplanted into the eyes of wild-type mice. The axons of retinal ganglion cells are myelinated in the optic nerve, however OPCs do not invade the retina during development and the proximal segment of the axon within the retina remains unmyelinated. Thus the intraretinal segment of the ganglion cell axon provides a unique opportunity to assess the capacity of OPCs transplanted in to the retina to myelinate, in the absence of competition from endogenous OPCs.
Material and Methods: OPCs were purified by shake-off from a mixed glial culture derived from dcc-/- pups and wild-type littermates. Isolated OPCs were injected into the vitreous chamber of 2 month old wild type mice. Eight weeks after transplantation, animals were perfused transcardially with 4% PFA, eyes were enucleated and the retinas dissected. Flat-mounted retinas were immunolabelled and images captured using a Zeiss LSM 510 confocal microscope.
Results: Abundant MBP-positive myelin segments were observed along retinal ganglion cells axons of eyes that received OPCs. Paranodal specializations, visualized by labelling for the paranodal marker caspr, were readily detectable. Quantitative analysis revealed a significant increase in length of the caspr positive domain in retinas myelinated by DCC null OPCs compared to retinas myelinated by wild-type or heterozygotes OPCs.
Conclusion: This finding provides evidence that netrin-1 signalling through DCC is required for normal paranodal organization in the mature CNS in vivo and reveals that paranodal deficiencies are dependent on a cell-autonomous function of DCC in oligodendrocytes.
|
| | |
| Back |
|
