Neurodevelopment (Part 1)

Question 1

What is the rough sequence of stages in neuronal development?

Answer 1

• cell proliferation and migration,
• axon outgrowth,
• cell death,
• synapse formation,
• myelination,
• and synapse elimination with stabilization.

Question 2

Regarding embryogenesis, where does the nervous system arise from?

Answer 2

Ectoderm

Question 3

Which protein plays an important role in the formation of the neural plate?

Answer 3

Bone Morphogenic protein

Question 4

How does Bone Morphogenic protein play an important role in the formation of the neural plate?

Answer 4

• During early vertebrate neurogenesis, ectodermal cells are under the influence of BMP that surpresses neural differentiation and promotes the formation of epidermal tissue.
• Diffusible signaling proteins from Hensen’s Node, such as Chordin and Noggin, block the action of BMP and allow for a selection of ectodermal cells to form the neural plate.

Question 5

What are the roles of the proteins Chordin and Noggin

Answer 5

• Diffusible signaling proteins from Hensen’s Node,

- block the action of BMP and allow for a selection of ectodermal cells to form the neural plate.

Question 6

The cells of the neural plate ___, so the infolding to form a tube is caused by changes in the shapes of the cells of the neural ectoderm—___at their apices and___ at their bases.

Answer 6

• do not divide
• pinching
• expanding

Question 7

A failure of the tube to close rostrally leads to ___.

Answer 7

-anencephaly (―no brain)

Question 8

Failure of the tube to close caudally leads to ___.

Answer 8

-spina bifida (part of the meninges or spinal cord protrudes through the spinal column)

Question 9

___ dramatically reduces the incidence of spina bifida.

Answer 9

Folic acid

Question 10

Cells of the neural tube and neural crest (which pinches off from the margins of the neural groove as it closes to become the neural tube) divide and become ___ and ___ as development proceeds.

Answer 10

• neurons

- glia

Question 11

Unlike the rest of the vertebrate brain, the ___ has a conspicuously segmented structure

Answer 11

-hindbrain (rhombencephalon)

Question 12

The role of ___ genes in the development of the segmented organization of a structure

Answer 12

homeobox

Question 13

Several genes have been identified whose pattern of expression at early stages in development correlates with the segmental boundaries of the hindbrain. Some of these genes, (given weird names such as ___, ___, ___ ) play a role in establishing the pattern of segmentally repeated and compartmentalized regions.

Answer 13

• kreisler
• Krox-20
• Eph

Question 14

Which family of genes appear to direct the fate of cells within a segment?

Answer 14

Hox family of genes

Question 15

The Hox genes are similar to homeotic regulator genes in what model?

Answer 15

Drosophila

Question 16

What is the significance of the homeobox?

Answer 16

• Homeobox is a conserved stretch of DNA within homeotic genes.
• they encode a sequence of amino acids that recognize and bind to specific DNA sequences in a series of subordinate genes.

Question 17

Patients with genetic abnormalities of emx, a homeobox gene in humans, develop what?

Answer 17

Shizencephaly (deep crevices in the cortex)

Question 18

Patients with genetic abnormalities of otx, a homeobox gene in humans, develop what?

Answer 18

Epilepsy

Question 19

Retinoic acid is produced where?

Answer 19

Hensen’s node

Question 20

Why is retinoic acid important in Hox gene expression?

Answer 20

• In part determines the pattern of Hox gene expression.
• Diffusion of retinoic acid from Henson’s node establishes a gradient along the short length of the embryo that contributes to the orderly anterior-posterior sequence of Hox gene expression in the hindbrain.