Chapter 53 - Differentiation and Survival of Nerve Cells

Question 1

what are progenitor cells?

Answer 1

• cells that have undergone some level of regeneration

- give rise to new cells

Question 2

what happens to progenitor cells early in embryonic development?

Answer 2

-most progenitor cells in the ventricular zone of neural tube proliferate rapidly

Question 3

what are two modes of cell division?

Answer 3

1. asymmetric

2. symmetric

Question 4

what is asymmetric division?

Answer 4

-progenitor produces one differentiated daughter and another daughter that retains its stem cell-like properties

Question 5

what is symmetric division?

Answer 5

• produce two stem cells

- population of proliferative progenitor cells

Question 6

what do radial glial cells serve as?

Answer 6

• neural progenitors

- structural scaffolds

Question 7

what do many radial glial cells differentiate into?

Answer 7

astrocytes

Question 8

what type of division can radial glial cells undergo?

Answer 8

both asymmetric and self-renewing cell division

Question 9

are radial glial cells progenitors?

Answer 9

yes

Question 10

which type of division is most common for early/late development?

Answer 10

early -> symmetric

late -> asymmetric

Question 11

how is the generation of neurons vs glial cells regulated?

Answer 11

delta-notch signaling

Question 12

neurons derive from ______ and glia derive from ______ pimarily

Answer 12

neurons -> asymmetric

glia -> symmetric

Question 13

what is the function of radial glial cells?

Answer 13

• serve as precursors to neurons in the CNS

- provide a scaffold for radial neuronal migration

Question 14

what is the signaling level of delta/notch initially?

Answer 14

• levels are initially similar in each cell

- signaling strength is equal

Question 15

what happens when cell A provides a greater delta signal?

Answer 15

-activates more notch signaling on cell B

Question 16

what does the binding of delta to notch lead to?

Answer 16

-proteolytic cleavage that becomes a transcription factor

Question 17

what is the result of the transcription factor following the binding a delta to notch?

Answer 17

-inhibits expression of delta

Question 18

high-notch cells are will become ______ cells

Answer 18

non-neural cells

Question 19

low-notch cells will become _________ cells

Answer 19

neural cells

Question 20

what other decision does delta-notch signaling regulate?

Answer 20

-oligodendrocyte vs astrocyte cell fate

Question 21

what does the activation of notch signaling in glial progenitor cells result in?

Answer 21

• differentiation as astrocytes

- inhibits differentiation as oligodendrocytes

Question 22

how is layered organization of the cerebral cortex established?

Answer 22

-neurons migrate along radial glial cells

Question 23

what is the role of radial glial cells in migration?

Answer 23

-act as scaffolds for neurons as they extend to outer layer of the developing cerebral cortex

Question 24

what happens when neurons approach the pial surface?

Answer 24

-neurons will stop migrating and detach from the radial glial cells

Question 25

what pattern of migration do cortical cells follow?

Answer 25

-"inside-first outside-last" pattern of migration

Question 26

what happens in lissencephaly?

Answer 26

-"smooth brain" -neurons leave the ventricular zone -fail to complete their migration into cortical plate -

Question 27

what happens in a reelin mutation?

Answer 27

- neurons fail to detach from their radial glia scaffolds - pile up underneath the cortical plate - inverted arrangement

Question 28

what is the "hardest" part of the neuron to move along during cell migration?

Answer 28

- nucleus | - like a heavy sac

Question 29

How is migration possible even with the "difficult" nucleus?

Answer 29

- complex arrangements of microtubules around nucleus orchestrate migration - nucleus moves in intermittent, stepwise manner

Question 30

What other types of interactions are involved in neuronal migration along radial glia?

Answer 30

- adhesive interactions between cells | - EX: integrins promote neuronal extension on radial glial cells

Question 31

What are the three major programs for cell migration?

Answer 31

1. radial migration 2. tangential migration 3. free migration

Question 32

what is tangential migration?

Answer 32

- central neurons use axonal tracts as their guide | - move laterally then up

Question 33

what is the evolutionary result of tangential migration?

Answer 33

-increase complexity of neuronal circuits

Question 34

cortical neurons originate from 2 sources:

Answer 34

1. excitatory neurons -> ventricular zone | 2. inhibitory -> medial ganglionic eminence

Question 35

where does the PNS derive from?

Answer 35

neural crest cells

Question 36

what type of cells are neural crest cells?

Answer 36

-neuroepithelial cells at the boundary of the neural tube and ectoderm

Question 37

what is free migration?

Answer 37

- migration that does not rely on scaffolding | - requires cell adhesive changes + cytoarchitectural changes

Question 38

how does free migration work?

Answer 38

- BMP signaling - BMP triggers molecular changes that convert epithelial cells to mesenchymal state - causes them to delaminate and express ECM proteases

Question 39

is the neurotransmitter phenotype of a neuron permanent?

Answer 39

no, it is plastic

Question 40

what determines the neurotransmitter released by a neuroN?

Answer 40

- transcription factor programs | - intertwined and hardwired with cell fate

Question 41

what informs cell fate of neurons?

Answer 41

-peripheral targets

Question 42

what is the default fate for sympathetic neurons?

Answer 42

-noradrenergic

Question 43

what causes sympathetic neurons to become cholinergic?

Answer 43

-gp130

Question 44

what are the two types of peripheral nerve cells?

Answer 44

1. sympathetic | 2. sensory neurons

Question 45

which is more plastic, sympathetic or sensory?

Answer 45

-sympathetic

Question 46

what also results in a noradrenergic neuron switching to a cholinergic phenotype?

Answer 46

- secretion of signals from glad cell targets | - transformative effects to direct cholinergic fate

Question 47

what controls the phenotype of central neuron neurotransmitters?

Answer 47

-helix-loop-helix transcription factors