Xenopus, Lateral Inhibition and Localised Determinants

What are the 3 mechanisms of cell fate determination?

1. Lateral Inhibition
2. Localised Determinants
3. Induction and morphogens

Blastula

The hollow ball of cells marking the end stage of cleavage during early embryonic development

Gastrula

An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.

Vegetal Pole

The portion of the egg where most yolk is concentrated; opposite of animal pole.

Germ layer

one of the 3 layers: endoderm, mesoderm, ectoderm

Neurula

The neurula stage of embryo development begins with the formation of the notochord and the neural tube cells, which are part of the development of a nervous system.

Blastocoel

the fluid-filled cavity of a blastula

Animal Cap

cells from the roof of the blastocoel in the animal hemisphere

6 Principles for Localised Determinants to analyse a system

1. What is being localized in either the cytoplasm/ RNA/ protein
2. When is the determinant localised
3. How is the determinant localized
4. Is the determinant necessary (LoF) AND sufficient (GoF) to impose cell fate
5. How is activation of the determinant regulated
6. Determinant must be a TF - what are the genes it targets?

What type of cells does lateral inhibition affect?

neural cells

What is lateral inhibition?

When a neurons response to a stimulus is inhibited by the excitation of a neighbouring neuron

What signalling pathway is associated with lateral inhibition?

Notch-Delta signalling pathway

What genes are involved in the patterning of the neuroectoderm/ formation of neuroblasts?

* Proneural
* Neurogenic

What is the function of proneural genes in the formation of neuroblasts?

Define the equivalence group

What is the function of neurogenic genes in the formation of neuroblasts?

Selection of neuroblasts from equivalence group

What are examples of proneural genes?

* Scute
* Achaete
* Lethal of scute
* Asense

What complex is associated with proneural genes?

Achaete-Scute Complex

What complex is associated with the neurogenenic genes?

Enhancer of Split Complex

What fate do proneural genes induce?

epi

What transciption factor is associated with proneural genes?

bHLH

What happens to proneural genes in lateral inhibition?

* Neuroblasts express proneural genes
* Expression of Delta
* Delta binds to Notch
* Proneural gene expression is inhibited due to Enhancer of Split
* Prevention of cells becoming NEURAL
* Only 1 cell becomes a Neuroblast

What is the function of neurogenic genes?

Select cells in equivalence group that will become a Neuroblast

What are the 2 fates of neuronal ectodermal cells?

1. Neuroblast
2. Non-neuronal cells

What are some examples of non-neuronal cells?

* Sheath cells
* Cap cells

What cells do neuroblasts form?

Ganglion Mother Cells

What cells do ganglion mother cells form?

Neurons

What type of signalling is responsible for lateral inhibition in neurogenesis?

Notch-Delta SIgnalling

How is the transcription of the delta ligand activated?

By proneural genes

What is an equivalence group?

Set of unspecified cells that have the same developmental potential to fates

How is an equivalence group determined in neurogenesis?

By proneural genes

What are the principles for lateral inhibition? (3)

1. Is a "salt and pepper" pattern produced
2. Is the pattern produced from an 'equivalence group'
3. Is cell fate dependent on Notch-Delta signalling