Neurogenesis and Migration

Question 1

Lissencephaly means ___________.

Answer 1

smooth brain (i.e., a brain without sulci)

Question 2

Post-mitotic cells must ___________ a radial glia to __________. Any defect in the genes that encode for this can result in lissencephaly.

Answer 2

adhere to; migrate to the more superficial layers of the cortex

Question 3

Reelin is involved in ___________.

Answer 3

migration in the cortex and the cerebellum

Question 4

What cells secrete reelin?

Answer 4

Cajal-Retzius cells

Question 5

__________ have a more severe phenotype of lissencephaly / double-cortex syndrome.

Answer 5

Males (because it is X-linked)

Question 6

List three genes that, if disrupted, can lead to defects in cortical migration.

Answer 6

Reelin and LCH (getting off of the radial glia)
Filamin (getting on)
DCX and Lis1 (staying on the radial glia)

Question 7

What is LCH?

Answer 7

Lissencephaly with cerebellar hypoplasia; a protein involved in getting off of the radial glia

Question 8

What area of the nervous system has the opposite pattern of cortical migration (that is, opposite to the inside-out pattern)?

Answer 8

The retina; in the retina, the neurons migrate outside-in (with the distal-most cells migrating first)

Question 9

What are neurotrophins?

Answer 9

Proteins that stimulate the growth of neurons – such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, glia-derived neurotrophic factor (GDNF), and NT-4

Question 10

To what type of receptors do neurotrophins bind?

Answer 10

Tropomyosin-related kinase (Trk)

Question 11

Almost ________ percent of the Cajal-Retzius cells die during development.

Answer 11

100

Question 12

Growth cones have ________ with a dense population of ___________.

Answer 12

filopodia; receptors

Question 13

CAMs are _________. They work independently of calcium.

Answer 13

cell-adhesion molecules

Question 14

Cytokines directing axonal migration can be repulsive or attractive depending on ______________.

Answer 14

the receptor it binds

Question 15

In patients with a defective filamin protein, _________ cells accumulate in the ventricular zone.

Answer 15

differentiated (because the filamin protein helps differentiated cells migrate outward)

Question 16

Mutations in LIS1 will produce ___________.

Answer 16

lissencephaly with epilepsy and mental retardation

Question 17

Neurons born at the same time tend to ____________.

Answer 17

end up in the same layer

Question 18

Cell death in most neurodegenerative diseases occurs by _____________.

Answer 18

apoptosis

Question 19

What is the neurotrophic factor hypothesis?

Answer 19

The idea that neuron targets produce limited amounts of neurotrophic factors so that only the closest neuron will make a connection

Question 20

Netrins can be _______ or __________.

Answer 20

attractive; repulsive

Question 21

Semaphorins are always ____________.

Answer 21

repulsive

Question 22

Cadherins, CAMs, laminin, and proteoglycans are usually __________ signals.

Answer 22

attractive

Question 23

CNS oligodendrocytes express __________, thought to play a role in preventing axon growth.

Answer 23

Nogo

Question 24

What neurogenic pattern is typical of autism spectrum disorders?

Answer 24

A brain small at birth followed by an abnormally high rate of growth resulting in disproportionately high content of white matter

Question 25

In the CNS, myelination is first observed at the end of the ___________.

Answer 25

first trimester

Question 26

How are GABA channels different in embryonic development?

Answer 26

The E(Cl) is less negative, so GABA channels actually depolarize the cell membrane during development!