Tissue Repair

Question 1

What are the sources of signals in the developing mammalian midbrain?

Answer 1

Notochord (Shh)
Isthmic organiser (Fgf8)

Question 2

Which structures are at the dorso and ventral ends of the developing brain respectively?

Answer 2

Dorso: Roof plate
Ventral: Floor plate

Question 3

Which end are the motor neurons at?

Answer 3

Ventral: by the floor plate

Question 4

Where is Shh secreted in the midbrain?

Answer 4

By the floor plate and notochord, results in a gradient across the dorso ventral axis

Question 5

How does the Shh signalling pathway work in the midbrain cells?

Answer 5

-Shh binds to Ptch1 in the membrane and pulls it out the way
-This causes SMO to move in ti that spot in the membrane
-This has the effect of changing GLI from an inhibitor to an activator and causes target genes translation

Question 6

How are the genes activated by Shh changed for different cell types?

Answer 6

The high-low concentration gradient. Also affects the strength of activation

Question 7

At what concentration of Shh is GLI activated?

Answer 7

High

Question 8

Where do dopaminergic neurons form?

Answer 8

Close to the floor plate

Question 9

What gene product is required for dopamine synthesis in DA neurons?

Answer 9

Tyrosine Hydroxylase

Question 10

What genes are expressed in floor plate progenitors and DA neurons which have left the floor plate?

Answer 10

Msx1/2 : FP progenitors
Nurr1 : DA neurons
Lmx1a : Both

Question 11

How can low threshold activated gene products be excluded from certain cell types?

Answer 11

Inhibitors

Question 12

Which part of the brain is tyrosine hydroxylase activated in?

Answer 12

Midbrain

Question 13

What is the definition of an organiser?

Answer 13

A group of cells which transmit signals to influence the developmental fate of nearby cells (paracrine signalling?)

Question 14

What are the morphogen gradients present in the midbrain development?

Answer 14

Anterior-Posterior Low-High Wnt
Dorso-Ventral Low-High Shh
Anterior-Posterior Fgf8 produced from isthmic organiser below the midbrain

Question 15

Which morphogen does the Isthmic organiser produce?

Answer 15

Fgf8

Question 16

What do the different brain development morphogen signals instruct?

Answer 16

High Shh instructs Ventral tissue
Fgf8+Medium Wnt instructs midbrain tissue
Fgf8+High Wnt signalling instructs Hindbrain tissue

Question 17

What causes Parkinson’s?

Answer 17

Dying back of DA neurons

Question 18

What part of the brain are the dopamine terminals located?

Answer 18

The Striatum, split into the Caudate and Putamen

Question 19

What is a method of reintroducing DA neurons?

Answer 19

Transplantation of stem cell derived tissue

Question 20

Where is the pigment Neuromelanin located?

Answer 20

The Substantia Nigra

Question 21

What are the possible issues with using foetal embryonic stem cell tissue?

Answer 21

Ethical issues
Poor and unpredictable supply of tissue
Poor quality and heterogeneity of tissue

Question 22

What can be used as a source of stem cells?

Answer 22

Embryonic stem cells from blastocysts
Induced pluripotent stem cells from adult blood or skin cells (iPSCs)

Question 23

How are pluripotent stem cells induced to differentiate into Midbrain tissue?

Answer 23

Dual Smad inhibition to inhibit BMP and Activin/TGFbeta signalling pathways
Induced differentiation with appropriate factors (eg Shh)

Question 24

In what state can stem cell derived tissue be transplanted into the brain?

Answer 24

DA neuron progenitor can be transplanted. Not fully differentiated ones

Question 25

What is the process for making Midbrain floor plate tissue in vitro?

Answer 25

-Dual Smad inhibition, produces anterior ventral tissue
-High Shh activation, produces Ventral tissue
-Medium Wnt signal, Caudal tissue
-Timed Fgf8b signal, produces Midbrain tissue

Question 26

Where are the DA neuron cell bodies located in the striatum?

Answer 26

The core

Question 27

How do the implanted DA neurons avoid innervating the cortex?

Answer 27

They partner with their natural partner neurons which are only present in tissues that they should be innervating.