Role of Glial Cells Flashcards
What are the PNS Glial cell types?
- Olfactory Ensheathing Cells
- Schwann cells
- Ganglion
- Teloglia
Schwann Cells* Where do Neural Crest Cells come from and form?
- come from mid-posterior trunk region of the neural tube
- NCCs migrating away from ectoderm layer give rise to the sensory and autonomic neurons, and glial cells
Schwann Cells* Describe the development of Schwann cells from neural crest cells.
NCCs —> SCPs (Schwann cell precursors) —> immature SCs —> myelinating or non-myelinating cells ensheathing large and small axons
Schwann Cells* How do you determine a mature Schwann cell?
Bigger axons = myelinated
Smaller axons = to a point, unmyelinated
Schwann cells* Describe the reversible process from immature to mature SCs.
Schwann cells* What factors are involved in Glial lineage differentiation.
Sex determining region Y (SRY), box 10, or SOX10 expressed in NCCs
Schwann Cells* What is the role of Neuroregulin 1 (NRG1)?
Axon-derived survival factor (auto crime = make their own) for SCPs driving proliferation of cells, inhibits neurogenesis
Schwann Cells* Why do Schwann cells have secrete factors and what are important ones for death?
- to support their own survival / not dependant on others
p75 and transforming growth factor β (TGFβ) —> mediate cell death
Schwann Cells* What is the role of KROX20?
- prepares immature SCs for myelination
- balances with either Notch to inhibit or c-Jun to de-differentiation
Myelination* What is the role of myelination?
- provide insulating sheath on neurons to enable saltatory conduction —> increasing speed of action potentials
Myelination* What are some important aspects of myelin? What are some important myelin proteins?
- myelin has high proportion lipid and a lower proportion of protein
Myelin protein 0 (P0) and peripheral myelin protein 22 (PMP22) —> important for initiation and compaction of myelin in PNS
Myelination* What happens when the expressions of P0 and PMP22 are altered?
Gillian-Barré Syndrome:
- Inflammatory disorder of the PNS (some due to antibody response to P0)
- afflicts any age (most common <40yr)
- progression over days to weeks
- 80-90% recover with no lasting effects
- Spontaneous recovery 2-4 weeks after progression
Myelination* What are the 4 stages of Myelination?
- Schwann cells surrounds axon
- Membrane fusion of the plasma membrane in one area
- Layers beginning to form due to Schwann cell cytoplasm rotation
- Layers compact to form a mature sheath and the cytoplasm is squeezed to the outside
Myelination* What is mesaxon?
Spiral double membrane that spirals around the axon
- inner mesaxon (IM) is the origin of the myelin sheet and is continuous with the outer mesaxon (OM)
Myelination* What is the major dense line (MDL)?
- double membrane is formed by apposition of external surfaces that form the MDL
- internal surfaces for the intrapersonal line (IPL)
Myelination* What is the role of Direct Interactions?
Compaction between P0 proteins one opposing external membranes
Myelination* What is the role of Electrostatic Interactions?
Between MBP with the phospholipid internal membrane and interactions with the cytoplasmic tail of P0
Myelination* What is the role of the Internode?
- consists of cytoplasm flies channels spiralling around the paranodal junction of axon
- provides a physical and electrical barrier between voltage-gated Na+ channels
- adhere to axon / each other via adhesion molecules with tight junctions and gap junctions
CNS Myelination* Difference between Oligodendrocytes and Schwann Cells?
Non-Myelination* What are Non-Myelinating Schwann cells (NMSCs)?
NMSCs come from Schwann cell precursors and retain the capacity to myelinate
- ensheath small diameter periopheral axons (Remak cells)
- supports pre-synaptic terminals at neuromuscular junctions (Teloglial cells)
- provide growth and survival factors to the axons and are essential for normal PNS development and function
Non-Myelinating* what is the role of Satellite glial cells (SGCs)?
- SCGs wrap around neuronal cell bodies within the PNS (sensory and sympathetic ganglia)
- SCGs connect to other SGCs via gap junctions, adherents and tight junctions
- SCGs extend to cover cell body, synapses, dendrites, and axons
