Myelination Flashcards
Spatially, how does myelination progress during development?
Following the rostral-caudal axis: spinal cord-hindbrain-midbrain-forebrain.
When does myelination start and end?
Starts at the third trimester of gestation and ends late into adulthood.
Myelinating glia in the CNS are _____.
Myelinating glia in the PNS are _____.
Oligodendrocytes
Schwann cells
True or false: all axons of the nervous system are myelinated.
False.
Where are Schwann cells originating from? How are they differentiated?
Originating from the neural crest cells. Their fate is determined by the axons with which they associate.
True or false: Schwann cells’ development is driven solely by extrinsic cues (ligands).
False: intrinsic signals (transcription factors) also influence their development.
What population of ventral neural progenitor cells produces at first motor neurons and then oligodendrocytes later in dev.?
Neural progenitor cells expressing TFs olig1 and olig2 (pNM progenitors).
What signal is regulating the expression of Olig1 and Olig2?
Shh.
Oligodendroyctes or Schwann cells can myelinate many axons?
Oligodendrocytes.
When glial cells wrap axons, older myelin layers are found outside or inside?
Outside: layers are forming interiorly.
Why is it that myelin is so compact around an axon?
Cytoplasmic material is pushed to the outside end of the cell (toothpaste analogy).
What is the paranodal region?
Axon segment following a node of Ranvier on which myelin layers anchor.
What differentiates a major dense line from a double intraperiod line?
A major dense line is composed of two juxtaposed cytoplasmic sides of the plasma membrane (cytoplasm is pushed away). A double intraperiod line is formed by the juxtaposition of two external faces of membrane.
What are the myelin basic protein and proteolipid protein respectively sustaining?
MBP stabilize the major dense lines.
PLP stabilize the intraperiod lines of CNS.
Protein zeo is found in exclusively in _____.
Schwann cells.
Protein zero has both extracellular and intracellular domains. What are the domains used for?
Intracellular: formation of major dense lines.
Extracellular: homophilic cell adhesion molecule promoting formation of intraperiod lines.
In mice of shiverer phenotype, myelin of CNS is strongly affected. However, myelin of the PNS is almost intact. Why is that?
Proteins 0 compensate for the loss of MBPs in the PNS.
What phenotype does arise from the loss of function of the MBP gene? From the PLP gene?
MBP gene deletion: shiverer.
PLP gene deletion: jimpy.
Where do voltage-gated ion channels cluster along an axon?
At nodes of Ranvier.
What is particular about the intracellular morphology of paranode regions?
They contain intracellular barriers that help make ions available for polarization at nodes of Ranvier.
