Neurodevelopment (Part 3)

Question 1

Sonic hedgehog protein is synthesized by what?

Answer 1

Notochord

Question 2

The floor plate cells and motoneurons are induced by what?

Answer 2

Sonic hedgehog protein

Question 3

Development along the dorsal-ventral axis of the embryo is under the influence of what?

Answer 3

Sonic hedgehog gene

Question 4

Besides the spinal motoneurons, sonic hedgehog induces formation of what other ventrally located groups of neurons in other parts of the neuraxis?

Answer 4

• Serotoninergic neurons (in anterior hindbrain)
• Dopaminergic neurons (in posterior midbrain)
• Oculomotor neurons (in anterior midbrain)

Question 5

The general rule appears to be that the repertoire of responses available to a multipotent precursor cell within a region of the developing nervous system is first restricted according to its anterior-posterior position, for example by ____ gene expression, and then further restricted according to dorso-ventral position by midline signals such as ____.

Answer 5

• Hox

- Sonic Hedgehog

Question 6

Once cells become neurons, they stop dividing and migrate along _____ to the external or pial surface, thus younger neurons typically migrate past the older ones.

Answer 6

-Radial glia (which are briefly lived and die during development)

Question 7

Radial glia persist in the adult retina as ____ and cerebellum as _____.

Answer 7

• Muller cells

- Bergman glia

Question 8

All neurons in the brain are born before birth except..

Answer 8

• Some granule cells in the cerebellum, which can go on multiplying into the second year
• Olfactory neurons

Question 9

Dividing cells migrate ___

Answer 9

Radially

Question 10

A single progeniter may give rise to both…

Answer 10

Neurons and glia

Question 11

In cortex and other regions of the developing brain, the migration of neurons is dependent on ____.

Answer 11

Radial glial cells

Question 12

The proteins mediating neuronal migration along radial glial cells include the neural glycoprotein _____ and specific isoforms of the extracellular matrix adhesion molecule receptor ____.

Answer 12

• Astrotactin

- Integrin

Question 13

The product of the reeler gene is…

Answer 13

A large extracellular matrix glycoprotein called reelin.

Question 14

Reelin is expressed where?

Answer 14

In Cajal-Retzius cells in the marginal zone of the cortex.

Question 15

What is the functional significance of Reelin?

Answer 15

It is the signal that tells neurons to get off the glial monorail and take up their final position in the cortex.

Question 16

What is expressed in neurons that migrate through regions of the CNS in which there are no radial glial cells?

Answer 16

Gonadotropin-releasing hormone (GnRH)

• migrates INTO the CNS.

Question 17

Where do GnRH cells travel?

Answer 17

Move from olfactory pit, an ectodermal derivative (placode) that gives rise to the nasal epithelium, into the hypothalamus along a previously est. axon tract.

Question 18

In the peripheral nervous system, ____ cells migrate along pathways that lack both axon tracts and organized glial structures.

Answer 18

Neural crest

Question 19

What is Kallmann’s syndrome?

Answer 19

Occurs in male patients in whom the migration of neural crest cells fail during development resulting in the malformation of the olfactory placode. Result: no sense of smell; fail to mature sexually.

Question 20

Cells of the neural crest migrate along pathways marked by ____ and other key components of the extracellular matrix

Answer 20

Laminin