Oligodendrocytes and Schwann Cells Flashcards
What is the progenitor that gives rise to both astrocytes and oligodendrocytes, and what happens when you inject it into the brain?
O-2A progenitor cells.
In the brain, most of these cells had differentiated into oligodendrocytes, not astrocytes. It is therefore the oligodendrocyte precursor cell (OPC).
O-2A must express which receptor for which key factor?
Platelet derived growth growth factor (PDGF). Experss PDGFR-AA.
Expressed in ventral half of spinal cord.
What are the oligodendrocyte transcription factors?
Olig1
Olig2 (essential)
SHH has a role in inducing the floor plate. What produces SHH, and how does SHH induce the plate?
Notochord produces SHH
SHH travels to ventral region of neural tube, instructs them to produce floor plate.
What happens when floor plate is established?
Cells express SHH, generating neural tube concentration gradient/
Bind Notch-1 receptor on NPCs, inducing Olig2 for OPC specification.
SHH acts in which gradient, and what molecule acts in the opposite direction?
SHH: Ventral to Dorsal gradient
Bone morphogenic protein 4 (BMP4) . (Produced by roof plate, dorsal to ventral.
(SVD, BDV)
What is LIF and what is its role in myelination?
Leukaemia inhibitory factor.
Axon electrical activity releases ATP, causing astrocytes to release LIF. This promotes myelination.
Process of myelin formation?
Oligodendrocyte extends processes, contacts axon.
Leading process tucks under and extends around axon (multiple wraps)
What is a consequence of demyelination during development?
Mental retardation/ Death.
2 distinct actions of myelin biogenesis?
WRAPPING of the leading edge at the inner tongue around the axon, underneath the previously deposited membrane.
Lateral extension of myelin membrane layers, towards nodal regions.
How do oligodendrocyte numbers match that of the axons?
Excess ODs produced, later eliminated by apoptosis.
ODC survival depends on contact wit axons.
competition for axon-dependent survival signals helps adjust ODC numbers to that of the axons needing myelination.
How is an action potential propagated in the PNS?
Sequential changes of local membrane potential caused by local current, which causes opening of nearby Na+ channels.
What is a remak Bundle?
This is a bundle of C fibre axons, grouped together by a non-myelinating schwann cell.
What is a key difference between oligodendrocytes and schwann cell?
ODCs myelinate multiple axons.
1 Schwann cell myelinates 1 axon.
What is the function of neuregulin-1?
Promotes formation and survival of Schwann cells.
Type III is essential for both myelination and remak bundle formation.
It dictates extent of myelination and the decision to myelinate. C fibres express little NRG1- hence less myelination.
