Neuro_Unit 3_Lec2

Question 1

Early Neurulation Time

Answer 1

Coincides with Gastrulation (~18 days)

Question 2

Early Neurulation Purpose

Answer 2

Defines the midline of the embryo and induces the formation of the neural ectoderm.

Question 3

BMP

Answer 3

Growth factors that push the ectoderm towards the epidermal state.

Question 4

Noggin/ chordin/Follistatin

Answer 4

Factors produced by the notochord which inhibit the BMP signal causing the cells to choose the neural fate (can be seen as the default pathway)

Question 5

BMP signaling

Answer 5

1. ) BMP binds to serine kinase receptor
2. ) Receptor activates SMAD
3. ) SMAD mediates transcription

Question 6

FGF

Answer 6

signaling likely preceeds BMP and it critical for neural induction

Question 7

Neural Crest formation

Answer 7

As the neural tube closes the neural crest pinches off and the roof plate forms

Question 8

Neural Crest differentiation

Answer 8

Neural Crest gives rise to:

1. ) Cranial neural crest
2. ) Trunk neural crest
3. ) Vagal and Sacral neural crest
4. ) Cardiac neural crest

Question 9

Dorsal Ventral Patterning

Answer 9

Ventral secretes Shh
Dorsal secretes BMP
(RA and FGF also play a role)

Question 10

Shh signaling

Answer 10

1. ) Shh binds to Patched
2. ) PTC stops inhibiting SMO
3. ) SMO activates the Gli class of zinc finger transcription factors
4. ) Gli induces transcription which leads to ventral (motor neuron) cell fates

Question 11

Absence of Shh signaling (sheep example)

Answer 11

Sheep ate cyclopamine which inhibits Shh
-eye field does not seperate
- nose above eye
Also absence leads to cancers like medulloblastomas and basal cell carcinoma because Shh regulates polarity, cell differentiation and proliferation

Question 12

Anterior/ Posterior Patterning leads to:

Answer 12

1. ) Spinal Cord
2. ) Rhimbencephalon (pons and medulla)
3. ) Mesencephalon (midbrain)
4. ) Prosencephalon (thalamus and retina, forebrain)

Question 13

HOX genes in the posterior CNS patterning

Answer 13

Define segmental differences in the spinal cord, medulla and pons through the action of multiple HOX genes repressing and enhancing each other.

NOT involved in the brain

Question 14

OTX2 knockout mice

Answer 14

completely missing forebrain

Question 15

Ventricular Zone

Answer 15

Thin strip of cells surrounding the CSF- filled ventricles

  -neural stem cells and progenitor cells divide and                          differentiate in this zone to give rise to all the cells in the CNS.

Question 16

Neural Stem Cells

Answer 16

Give rise to all cell types in the nervous system and have unlimited self renewal

Question 17

Progenitor Cell

Answer 17

Can make neurons or glia but not both. Some can self renew for a few generations.

Question 18

Symmetric and Asymmetric cell divisions in CNS development

Answer 18

Early- symmetric- 1 NSC to 2 NSCs
Middle- Asymmetric- 1 NSC to 1 NSC and 1 Neural progenitor
Late- Symmetric- symmetric- 1 NSC to 2 Neural progenitors

Question 19

low/ moderate levels of Notch stimulation by Delta

Answer 19

CONTACT DEPENDENT
1.) Intracellular domain of Notch is cleaved which activates bHLH genes
2.) bHLH activation upregulates Delta
for surrounding cells
3.) Notch gets hyper-activated in surrounding cells, which turns off those cell’s bHLH so they stay in their pluripotent NSC state.

Question 20

Atrogliogenesis

Answer 20

opposite of what causes neurogenesis, happens later on to determine neuron vs glia cell
Atrogliogenesis needs high notch and low bHLH

Question 21

Timing of Neurogenesis vs Gliogenesis

Answer 21

Nuerogenesis- majority generated by the middle of the second trimester
Gliogenesis- majority happens after birth (myelination also continues into your 20s)

Question 22

Cortical development pattern (for projection neurons)

Answer 22

forms inside out due to radial migration

• earliest born are deeper closer to the ventricle
• later cells migrate along radial glia fiber to get where they are going
• leads to a column pattern when looking a cells derived from the same NSC. (form a functional unit in the cortex)

(discovered through thymidine labeling in monkey brains)

Question 23

Reeler mutant

Answer 23

Problem with cortical development pattern. The later cells can’t get by the earlier cells, so the column develops upside down. Leads to Lissencephaly.

Question 24

Interneuron migration

Answer 24

Tangential migration, come up and then dive back down.