Introduction to neurodevelopment

Question 1

What is the purpose of fate mapping?

Answer 1

To follow cells as they differentiate and mature

Question 2

How is fate mapping carried out?

Answer 2

• Cut out a piece of tissue from the donor embryo
• Remove the same region of tissue from the host
• Stick the cut piece of tissue from the donor into the host
• Donor cells can be identified because they are different - they have a distinctive nucleolus which allows them to be identified

Question 3

Name 2 methods of seeing where expression occurs.

Answer 3

1. In situ hybridization using a complementary nucleic probe
2. Immunohistochemistry using an antibody

Question 4

Describe how to carry out in situ hybridization using a complementary nucleic probe

Answer 4

Using a probe which carries the complementary sequence of RNA; add the probe to the mRNA and label the probe to see where it goes

Question 5

Describe how to carry out immunohistochemistry using an antibody

Answer 5

A cell producing a protein which is not being expressed by adjacent cells can be seeked out by adding the antibody of the protein

Question 6

What is a chimera?

Answer 6

An animal which has more than one genetically-distinct population of cells.

Chimeras arise when cells originating from different fertilised eggs come together to create a single embryo.

Question 7

Explain what a reporter sequence of DNA is

Answer 7

Adding in a piece of DNA which encodes for something which can be seen.

Question 8

How would you create a knock-out mouse?

Answer 8

To knock out a specific gene: create a construct which has that gene mutated. Run an electrical current through the cell membrane to make it more porous and the DNA cells will enter.

Question 9

Explain what the Cre-Lox system does?

Answer 9

Allows knock-out of a gene at a specific place and time.

Put LoxP signals on either side of the gene of interest and cre recombinase will cut out the gene sequence between the two LoxP sites.

Put cre recombinase under the control of the elements of the particular place you want to knock the gene out of.

Example - albumin is expressed only in the liver so put cre recombinase under the control of albumin and it will only knock out partial sequence in the liver.

Question 10

What do RNA polymerases bind to?

Answer 10

Promoters with non-specific transcription factors

Question 11

What do site-specific transcription factors bind to?

Answer 11

Promoters on specific target genes

Question 12

What do co-activators bind to?

Answer 12

Enhancers

Question 13

What do transcription factors + enhancers combine to make?

Answer 13

A complex that can stimulate gene transcriptions

Question 14

What is chromatin?

Answer 14

DNA and asociated proteins

Question 15

How are transcription factors regulated?

Answer 15

• Ligand binds to receptor
• In response to this binding there is a cascade of biochemical reactions in the cytoplasm
• This results in phosphorylation of the ligand and a protein is expressed which enters the nucleus and acts as a transcription factor

Question 16

What happens during neural induction?

Answer 16

Induction is when one tissue (the inducer) causes a change in the development of another tissue (the responder).

In the case of neural induction, the inducing tissue tells the responding issue to adopt a neural fate.

Question 17

What is a specified cell?

Answer 17

A cell or tissue which has some level of information directing it towards its fate.

Question 18

What is cell commitment?

Answer 18

Commitment is a measure of how firmly a developing cell adheres to its specified fate.

Question 19

What is an organiser?

Answer 19

The source of a soluble, neural-inducing factor that could neuralise competent ectoderm

Question 20

What happens when you dissociate ectoderm cells before culturing them and what does this imply?

Answer 20

They differentiate into neurons in the absence of any inducing signals.

This implies that the ectoderm is predisposed to becoming neural.

Question 21

How, if the ectroderm is predisposed to becoming neural, does it differentiate into the epidermis?

Answer 21

Neural inducers block an inhibitory signal that prevents differentiation to neural tissue resulting in the formation of the epidermis

Question 22

What does BMP do?

Answer 22

It is a blocking signal which does not allow differentiation towards becoming neural tissue.

• Increase BMP signal = lose neural fate
• Decrease BMP signal = increase in neural tissue
• BMP signalling can activate both the SMAD pathway and the mitogen-activated protein kinase (MAPK) pathway

Question 23

Name 4 BMP agonists

Answer 23

• Noggin
• Chordin
• Cerberus
• Follistatin

Question 24

What does FGF signalling do?

Answer 24

Activates the mitogen-activated protein kinase (MAPK) pathway.

FGF has a similar effect to BMP antagonism

Question 25

What is caused by Wnt signalling?

Answer 25

Wnt signalling results in β-catenin translocating to the nucleus.

It blocks β-catenin from being degraded and so it travels into the nucleus.

Wnt also blocks response to FGF signalling.

Question 26

What does Wnt do in the lateral part of the neural plate?

Answer 26

Represses neural fate so cells become epidermal