Prof.Placzec

Question 1

What is medulloblastoma and what does it lead to?

Answer 1

• Type of cancer
  -Tumour in cerebellum
• Affects coordinated motion

Question 2

What is the role of a developmental neurobiologist?

Answer 2

Try and categorise neurons by working out how they are born from earlier cells looking at pre-cursors and genes and molecules affecting differentiation

Question 3

What is a blastocyst?

Answer 3

Ball of cells

Question 4

What happens to the blastocyst between weeks 3 and 4 of embryonic development?

Answer 4

Turned in to something with recognisable shape with the anterior portion eventually forming the brain and the posterior portion forming the spinal cord

Question 5

What can be seen at weeks 4-5 of embryonic development?

Answer 5

Early brain and spinal cord cells

Question 6

What is the solution to it being unethical to study embryonic development in humans?

Answer 6

• Studying on other vertebrates such as mice
• Processes essential to life such as sensory detection and breathing and are conserved throughout vertebrate evolution so its generalisable

Question 7

What is a multipotent cell

Answer 7

Capable of giving rise to every cell + entirety of nervous system

Question 8

What is the cell differentiation journey?

Answer 8

• Progressive process with successive proliferation changes
  1. Induction (multipotent cells)
  2. Regionalisation ( Pre-cursor cells)
  3. Differentiation (One final neural fate)

Question 9

What mediates the first break in symmetry
(multipotent cells->regionalisation)

Answer 9

Extrinsic signals

Question 10

What are transcription factors?

Answer 10

Proteins made by the cell that act within the cell to upregulate the expression of other genes within the cell (intrinsic signal e.g.)

Question 11

What is lost as you go through differentiation?

Answer 11

Potency

Question 12

What are characteristics of Neural-like stem cells (multipotent)?

Answer 12

Express genes that regulate multipotent state
E.g. slow cell cycle/ stopping differentiation

Question 13

What are characteristics of pre-cursor/progenitor cells?

Answer 13

Express genes that regulate faster cell cycle
Code for proteins that direct particular differentiation paths

Question 14

What are characteristics of commited, differentiated cells?

Answer 14

Express genes that regulate cell cycle
Enable terminal differentiation

Question 15

How are extrinsic signals received by early embryonic cells?

Answer 15

An ‘undecided’ early cell receives chemical signals from a neighbour, they alter the receiving cell
The receiving cell has to have the receptor for this chemical signal in order to change

Question 16

How are intrinsic signals used in embryonic cells?

Answer 16

• Later on during differentiation
• Intrinsic information is already in the cell and can provide a ‘memory’ and ‘instruction’ for further fate specification
• Transcription factors

Question 17

Give the analogy for a loss of function study

Answer 17

A girl wants to be x when she grows up, will she still become x if you remove etc. her teachers or her family or her friends (one by one)

Question 18

Give the analogy for a gain of function study

Answer 18

Replacing/adding so for example if it was the teachers that influenced the girl to become x, if we take the teachers and put them in a school teaching another girl, will she want to become x as well

Question 19

What are the two ways to conduct a loss of function study?

Answer 19

Background: Cell A produces a protein (an extrinsic signal) which morphs Cell B into Cell E

1. Ablate cell A (which produces protein x), If B stays as B and does not become cell E, conclude that cell A required to cause cell E fate
2. Prevent protein x through ‘mopping it up’, ‘degrading it’ or knocking out the gene which encodes for it. If B stays as B then the protein x is required for the change to cell E

Question 20

What are the 4 ways to conduct a gain of function study?

Answer 20

Background: Cell C is further from Cell A and would not normally respond to the signal to change into cell E despite it having the complementary receptors
1. Take cell A from donor and put it in unusual location so proteins can reach cell C
2. Soak bead in protein X and transplant bead next to cell C to observe change to Cell E
3. Put the gene that encodes for protein X in another cell near to cell C
4. Add receptors for protein X to a cell with no receptors, observe to see if its the protein X signalling pathway responsible for change to Cell E

Question 21

What are Ectoderm cells?

Answer 21

• One of the three germ layers
• The cells will proliferate and give rise to either the neural stem cells or epidermal cells
• Requires a Bone Morphogenetic Signalling Pathway to do so (BMP)

Question 22

Describe the BMP signalling pathway

Answer 22

1. Bone morphogenetic proteins are secreted signals
2. When they bind their receptors (BMPR), they trigger a signal transduction cascade in the responding cell including second messengers
3. As a result, Smad proteins in the cytosplasm are phosphorylated, enter the nucleus and act as ‘transcription factors’ that alter the gene expression

Question 23

Where did our understanding of neural induction come from and how is it different to human neural induction?

Answer 23

• Came from amphibians
• They have a ‘sphere’ in terms of germ layers and we have a flat set of germ layers essentially as if the sphere was squashed

Question 24

What are the three germ layers?

Answer 24

Ectoderm, Mesoderm, Endoderm
These three sub populations will always be arrayed in the same spatial context

Question 25

What are Dorsal mesoderm cells or 'organiser cells'

Answer 25

- A group of cells on one side of the mesoderm - Produce Chordin, Noggin and Follystatin which block the BMP pathway

Question 26

What is an organiser cell referred to as in a human?

Answer 26

Nodes

Question 27

Which of the two fates of the ectoderm cells occurs in the ectoderm cells that are closest to the dorsal mesoderm cells?

Answer 27

Neural stem cells

Question 28

How do Chordin, Noggin and Follystatin work?

Answer 28

- Antagonizers of BMPs - Bind to BMPs or receptors which blocks the pathway - Allow transcriptional profiling in nerual stem cell genes, 'inhibitor of inhibitor is used to create positive effect'

Question 29

Describe the molecular pathway for the decision of ectoderm cells to neural/epidermis

Answer 29

If ectoderm cells see BMPs, Smad proteins are phosphorylated, go into nucleus and bind to target genes allowing the cell to undergo an epidermal fate In the absence of BMP signalling, Chordin, noggin etc. bind to the BMP and they prevent it from binding to its receptor meaning Smad proteins aren't phosphorylated so its inactive, transcription factors such as Sox genes are activated and differentiation into a neural stem cell occurs

Question 30

How does a fate map work?

Answer 30

stick dye into an early embryo, let it develop and see what cells did the early embryo give rise to

Question 31

How was a fate map used to see if its the ectoderm closest to the dorsal mesoderm cells that gives rise to the neural plate?

Answer 31

1. The specialised bit of the mesoderm is morphologically distinct to all the other parts of the sphere 2. Stick a tracer into different sections of the ectoderm (dye) and see where all the cells end up so they could see that the ectoderm cells closest to the dorsal mesoderm cells made up the neural stem cells eventually

Question 32

How was a gain of function experiment used to see if it is the mesoderm cells that are important in adjusting adjacent ectoderm cells to become neural?

Answer 32

1. Two different strains of newts: white newts and dark newts 2. From one white newt (e.g.) specialised mesoderm cells were taken out and transplanted to the other side of the embryo from the dorsal mesoderm in the dark coloured newt 3. This embryo is now developing with two specialised mesoderm regions 4. Two nervous systems were induced!!!! Showing that it is the organiser cells which induce the ectoderm cells to become neural

Question 33

How was a GOF experiment used to see if its the BMP antagonists that are responsible for inducing neural tissue?

Answer 33

1. Specialised mesoderm cells were taken out of an embryo and they were dissociated to single cells and the nucleus was shattered 2. All mRNA from the organiser cell was extracted and reverse transcribed to make cDNA 3. Each of those cDNA one by one was put in the opposite side of the mesoderm and expressed 4. In this way it was identified which mRNAs were coding for a molecule that can induce neural identity 5. The molecules that were able to alter the fate of the overlying ectoderm and tell them to become neural tissue were all antagonists of BMP signalling

Question 34

What was in-situ hybridisation used for in figuring all of this out?

Answer 34

- Used to look at whether proteins are being expressed in the right places you know like is Sox2 being rightfully expressed near the organiser cells or is chordin being expressed at the dorsal mesoderm cells - Can be used to study protein expression over time

Question 35

What is neurulation?

Answer 35

Formulation of neural tube from a flat neural plate

Question 36

What does morphogenesis mean?

Answer 36

Changing shape

Question 37

What happens immediately after the neural plate is induced?

Answer 37

- It grows and elongates in lateral aspects (anterior posterior axis) and rolls into the neural tube in a term called neurulation - The tips fuse, forming a neural tube

Question 38

What is gastrulation?

Answer 38

The process which transforms the embryo from a one-dimensional layer of cells into a multi-layered embryo in which the adult body plan is recognisable

Question 39

What happens during gastrulation and what is it driven by?

Answer 39

- Driven by organiser cells - During gastrulation the germ layers assume their final positions and the anterior, posterior, dorsal and ventral axes become obvious

Question 40

What transcription factors found in the organiser cells are responsible for gastrulation?

Answer 40

- Siamois and goosecoid

Question 41

What does Siamois and Goosecoid do?

Answer 41

- Act within the organiser cells and bind to enhancers and promoters of genes (including BMP antagonists) - Bind to a whole load of genes that direct their next step (dictate their own fate) which is differentiating and undergoing convergent extension

Question 42

What is convergent extension?

Answer 42

Process by which a group of cells ‘squash’ together with nowhere to go meaning a blob of cells turns into a long thin rod of cells

Question 43

What happens when the cells undergo convergent extension?

Answer 43

- More genes are turned on telling the cells to involute and moves under the midline of the induced neural plate

Question 44

What is the 'rod of cells' called

Answer 44

The axial mesoderm

Question 45

What is the axial mesoderm comprised of?

Answer 45

- Leading edge cells - Pre caudal mesoderm cells - Notocord cells

Question 46

What does it mean for the cells if the neural plate is a single cell epithelium?

Answer 46

- That the cells are polarised

Question 47

What does the band of F-actin at the apical domain of the neural plate do?

Answer 47

Pulls tight causing the cells to constrict at the edge causing a change in shape, neural tube formation