BB Lecture 3 Embryology and Neurulation

Question 1

What is otx2?

Answer 1

A transcription factor that is essential for the formation of all ANTERIOR neural structures

Question 2

What happens to a otx2 -/- mutant?

Answer 2

No head development!

Question 3

Pax6

Answer 3

A-P for forebrain; induced by fibroblast growth factor (FGF); represses emx2

Question 4

Emx2

Answer 4

A-P for forebrain; induced by FGF; represses pax6

Question 5

Hox genes

Answer 5

A-P for whole embryo; determines rhombomere identity in hindbrain

Question 6

Shh

Answer 6

dorsal ventral axis

Question 7

bmp

Answer 7

dorsal ventral axis polarity. BLOCKING BMP allows ectodermal cells to assume neuronal identity

Question 8

totipotent

Answer 8

cells that can differentiate into anything from all three germ layers as well as extraembryonic tissues

Question 9

pluripotent

Answer 9

a cell that differentiates to cells from 3 germ layers but NOT extra embryonic tissue

Question 10

multipotent

Answer 10

progenitor cells that can give rise to cells from multipled but LIMITED number of lineages (think myeloid progenitor cells)

Question 11

robo-3

Answer 11

example of receptor at growth cone that decides where axons grow; robo-3 mutant in humans = person can’t abduct their eyes

Question 12

Sperry’s Frog

Answer 12

after lesion AND misplacement (rotation of frogs eye) axons grow back to where they were before originally, suggesting that the receptors on the axons induce growth towards same spots

Question 13

EphrinA

Answer 13

repellant for axon guidance (posterior tectum)

Question 14

EphBs

Answer 14

attractant for axon guidance (anterior tectum)

Question 15

neurotrophins

Answer 15

signals secreted by target molecule/organ that allows neurons to survive; limited amount so only limited amount of neurons survive

Question 16

how many neurons are made in embryo?

Answer 16

much more than what actually survives

Question 17

what is the significance of there being a limited quanity of neurotrophin secreted by target organs/cells?

Answer 17

The fittest neurons outcompete other neurons for those neurotrophins in order to survive

Question 18

What happens if you alter the pax6-emx2 ratio?

Answer 18

abnormal development of A-P FOREBRAIN

Question 19

Rhombomere

Answer 19

9 rhombomeres in all; formed in hindbrain; gives rise to cranial nerves (since hindbrain is brain stem); controlled by hox genes

Question 20

What happens to neural tube in Shh mutant?

Answer 20

No differentiation or maldevelopment of midline structures

Question 21

Lack of hox genes in zebrafish

Answer 21

No cranial nerve differentiation (remember hox genes help differentiate rhombomeres)

Question 22

inside-out maturation of cortex

Answer 22

Refers to the phenomenon of how EXCITATORY neurons are made (newest cells migrate closer to pia via radial glia, and older cells remain at bottom of ventricle)

Question 23

Where are inhibitory interneurons made?

Answer 23

generated in the ventral telencephalon and migrate to the cortex

Question 24

How do you get Lissencephaly?

Answer 24

You get the mutation of the Lis1 gene which is responsible for cortical formation of neurons; leads to smooth brain

Question 25

What happens when you get a dcx (doublecortin) mutant?

Answer 25

double cortex problem (double layering of the cortex) a problem with neuronal migration and development in the cortical areas

Question 26

Holoprosencephaly

Answer 26

Defect of forebrain development due to inhibition of pax6 and aberrant expression of shh…basically A-P and D-V patterning; cyclopia