Oligodendrocytes and Schwann Cells

Question 1

Oligodendrocytes are found in the … whereas Schwann Cells are found in the …

Answer 1

Oligodendrocytes are found in the CNS whereas Schwann Cells are found in the PNS

Question 2

What is the convergence ratio for myelin from Oligodendrocytes and Schwann cells onto neurones?

Answer 2

• Oligodendrocytes - dunno exactly but many : 1
• Schwann cells - 1:1

Question 3

What are the precursor to Oligodendrocytes called?

Answer 3

OPCs (Oligodendroycte Precursor Cells)

Question 4

What is the name of the common progenitor of oligodendrocytes and fibrous astrocytes?

Answer 4

• O-2A cells

Question 5

Where do Schwann cells originate?

Answer 5

In the neural crest

Question 6

Schwann cells die under normal culture conditions, but survive in which conditions?

Answer 6

In neurone-conditioned medium

Question 7

How are unmyelinated axons arranged?

Answer 7

Unmyelinated axons are arranged into Remak bundles

Question 8

Which factor is essential for both myelination and Remak bundle formation?

Answer 8

• Neuregulin-1 type 3

Question 9

What is Wallerian Degeneration and describe the process of Wallerian Degeneration?

Answer 9

Wallerian Degeneration = the process of degeneration of the axon distal to a site of transection

• Myelin sheaths dissociate from distal axons
• Macrophages remove myelin and axonal debris
• Removal of myelin-associated molecules e.g. MAG which otherwise inhibit axonal growth
• Glial cell proliferation distal to the injury / transection
• Glial cell growth factor secretion → attracts axonal sprouts from the proximal stumps

Question 10

Compare and contrast the event following Wallerian degeneration in peripheral and central nervous systems

Answer 10

Peripheral neuronal axons can regenerate after injury whereas central neuronal axons cannot, due to glial scar

Question 11

Give the name of an astroglial marker

Answer 11

• GFAP (Glial fibrillary acidic protein)

Question 12

Give the name of an oligodendral marker

Answer 12

• Galactocerebroside

Question 13

What was the name of the fluorescent dye used to stain the O-2A progenitors in the experiment where they were transplanted into mice brains?

Answer 13

• Fast-blue

Question 14

How are O-2A precursors induced to proliferate?

Answer 14

• Type-1 astrocytes secreting PDGF which binds PDGF-alpha receptors on the O-2As

Question 15

Which receptor can be used as a marker for oligodendrocyte precursors?

Answer 15

• PDGF-alpha receptors

Question 16

How do neurones stimulate astrocytes and promote myelination?

Answer 16

• Activated neurones release ATP which stimulate astrocytes and promotes LIF which in turn promotes myelination by mature oligodendrocytes

Question 17

Dysmyelination can occur in which groups of disorders and what can they lead to ?

Answer 17

• Leukodystrophies / leukoencephalopathies
• Mental retardation and / or death

Question 18

Give an example of a disease of demyelination

Answer 18

• Multiple Sclerosis

Question 19

Where is the neural crest?

Answer 19

The neural crest (NC) is a highly migratory multipotent cell population that forms at the interface between the neuroepithelium and the prospective epidermis of a developing embryo. Following extensive migration throughout the embryo, NC cells eventually settle to differentiate into multiple cell types, ranging from neurons and glial cells of the peripheral nervous system to pigment cells, fibroblasts to smooth muscle cells, and odontoblasts to adipocytes. NC cells migrate in large numbers and their migration is regulated by multiple mechanisms, including chemotaxis, contact-inhibition of locomotion and cell sorting.

Question 20

Give the name of 6 other factors involved in the development of oligodendrocytes

Answer 20

1. Olig2
2. Neurogenin
3. Sonic Hedgehog
4. Bone Morphogenetic Protein 4
5. Netrin-1
6. Semma3a