9. glial cells II Flashcards
(15 cards)
What are radial glia considered in the context of neurogenesis?
Common progenitors for both neurons and glial cells
This concept revisits the traditional understanding of glial cells and their role in brain development.
Which two key neurogenic sites are identified in the adult brain?
- Dentate gyrus of the hippocampus
- Subventricular zone near lateral ventricles
Neurons migrate from these sites to the olfactory bulb.
What properties do adult neural stem cells in the dentate gyrus share?
Radial glia-like properties
These stem cells can generate both neurons and astrocytes.
How does the neurogenic capacity of adult neural stem cells change with age?
It diminishes; stem cells lose proliferative ability and convert into astrocytes
This highlights the age-related decline in neurogenesis.
What recent research findings are noted regarding adult brain cells?
They can be reprogrammed to different cell types by manipulating transcription factors
This challenges previous notions of cell type permanence.
What is the true nature of microglia?
Macrophages residing in the brain
They are part of the brain’s immune response.
What percentage of brain immune cells do microglia represent?
About 78%
Other immune-capable cell populations are also present in the brain.
List the types of brain-associated macrophages.
- Microglia (in brain parenchyma)
- Perivascular macrophages (associated with blood vessels)
- Choroid plexus macrophages
- Meningeal macrophages
These macrophages play various roles in brain immunity.
What is the traditional view of microglia’s origin, and what is the modern understanding?
Traditional view: Enter the brain postnatally from circulation; Modern understanding: Originate from the yolk sac
This shifts the perspective on microglial development.
When do erythromyeloid progenitors from the yolk sac enter the developing brain?
- Around embryonic day 7-8 in mice
- Around week 5-6 post-conception in humans
This timing is crucial for understanding microglial development.
What happens to the blood-brain barrier around embryonic day 12?
It closes, preventing further cell entry
This is significant for the development of microglia.
What stages are involved in microglia development?
- Myeloid progenitors (MPs) from yolk sac
- Pre-macrophages/A1 cells (intrinsic program)
- Mature microglia (environment-instructed, influenced by IL-34 and TGF-β)
These stages illustrate the transition from progenitors to fully functional microglia.
What factors contribute to microglia heterogeneity?
- Brain region
- Age
- Disease state
These factors create distinct profiles of microglia.
What is noted about microglia density throughout life?
It remains consistent despite aging
This balance is maintained through proliferation and apoptosis.
What does long-term imaging reveal about microglia?
Continuous turnover; many cells die and are replaced by new ones over 30 days
This highlights the dynamic nature of microglial populations.
