Chapter 53 - Differentiation and Survival of Nerve Cells Flashcards
what are progenitor cells?
- cells that have undergone some level of regeneration
- give rise to new cells
what happens to progenitor cells early in embryonic development?
-most progenitor cells in the ventricular zone of neural tube proliferate rapidly
what are two modes of cell division?
- asymmetric
2. symmetric
what is asymmetric division?
-progenitor produces one differentiated daughter and another daughter that retains its stem cell-like properties
what is symmetric division?
- produce two stem cells
- population of proliferative progenitor cells
what do radial glial cells serve as?
- neural progenitors
- structural scaffolds
what do many radial glial cells differentiate into?
astrocytes
what type of division can radial glial cells undergo?
both asymmetric and self-renewing cell division
are radial glial cells progenitors?
yes
which type of division is most common for early/late development?
early -> symmetric
late -> asymmetric
how is the generation of neurons vs glial cells regulated?
delta-notch signaling
neurons derive from ______ and glia derive from ______ pimarily
neurons -> asymmetric
glia -> symmetric
what is the function of radial glial cells?
- serve as precursors to neurons in the CNS
- provide a scaffold for radial neuronal migration
what is the signaling level of delta/notch initially?
- levels are initially similar in each cell
- signaling strength is equal
what happens when cell A provides a greater delta signal?
-activates more notch signaling on cell B
what does the binding of delta to notch lead to?
-proteolytic cleavage that becomes a transcription factor
what is the result of the transcription factor following the binding a delta to notch?
-inhibits expression of delta
high-notch cells are will become ______ cells
non-neural cells
low-notch cells will become _________ cells
neural cells
what other decision does delta-notch signaling regulate?
-oligodendrocyte vs astrocyte cell fate
what does the activation of notch signaling in glial progenitor cells result in?
- differentiation as astrocytes
- inhibits differentiation as oligodendrocytes
how is layered organization of the cerebral cortex established?
-neurons migrate along radial glial cells
what is the role of radial glial cells in migration?
-act as scaffolds for neurons as they extend to outer layer of the developing cerebral cortex
what happens when neurons approach the pial surface?
-neurons will stop migrating and detach from the radial glial cells
what pattern of migration do cortical cells follow?
-“inside-first outside-last” pattern of migration
what happens in lissencephaly?
-“smooth brain”
-neurons leave the ventricular zone
-fail to complete their migration into cortical plate
-
what happens in a reelin mutation?
- neurons fail to detach from their radial glia scaffolds
- pile up underneath the cortical plate
- inverted arrangement
what is the “hardest” part of the neuron to move along during cell migration?
- nucleus
- like a heavy sac
How is migration possible even with the “difficult” nucleus?
- complex arrangements of microtubules around nucleus orchestrate migration
- nucleus moves in intermittent, stepwise manner
What other types of interactions are involved in neuronal migration along radial glia?
- adhesive interactions between cells
- EX: integrins promote neuronal extension on radial glial cells
What are the three major programs for cell migration?
- radial migration
- tangential migration
- free migration
what is tangential migration?
- central neurons use axonal tracts as their guide
- move laterally then up
what is the evolutionary result of tangential migration?
-increase complexity of neuronal circuits
cortical neurons originate from 2 sources:
- excitatory neurons -> ventricular zone
2. inhibitory -> medial ganglionic eminence
where does the PNS derive from?
neural crest cells
what type of cells are neural crest cells?
-neuroepithelial cells at the boundary of the neural tube and ectoderm
what is free migration?
- migration that does not rely on scaffolding
- requires cell adhesive changes + cytoarchitectural changes
how does free migration work?
- BMP signaling
- BMP triggers molecular changes that convert epithelial cells to mesenchymal state
- causes them to delaminate and express ECM proteases
is the neurotransmitter phenotype of a neuron permanent?
no, it is plastic
what determines the neurotransmitter released by a neuroN?
- transcription factor programs
- intertwined and hardwired with cell fate
what informs cell fate of neurons?
-peripheral targets
what is the default fate for sympathetic neurons?
-noradrenergic
what causes sympathetic neurons to become cholinergic?
-gp130
what are the two types of peripheral nerve cells?
- sympathetic
2. sensory neurons
which is more plastic, sympathetic or sensory?
-sympathetic
what also results in a noradrenergic neuron switching to a cholinergic phenotype?
- secretion of signals from glad cell targets
- transformative effects to direct cholinergic fate
what controls the phenotype of central neuron neurotransmitters?
-helix-loop-helix transcription factors
