Neural Induction and Cellular Processes during Early Development Flashcards

1
Q

What is a morphogen?

A

Signalling molecule that produces specific molecular/cellular responses based on its concentration

Morphogens influence cell fate in a time and space-dependent manner.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Name three morphogens involved in Anterior-Posterior Nervous System Patterning.

A
  • Retinoic acid (RA)
  • Fibroblast growth factor (FGF)
  • Wnt

These morphogens play critical roles in the development of the nervous system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the morphogens involved in Dorsal-Ventral Nervous System Patterning?

A
  • Bone morphogenic protein (BMP)
  • Noggin
  • Chordin
  • Sonic hedgehog (Shh)

BMP and its antagonists are crucial for establishing the dorsal-ventral axis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are organizers in the context of morphogens?

A

Small groups of cells that release patterning molecules (morphogens)

An example is the notochord, which is the first source of morphogens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What role does the roof plate play in morphogen signaling?

A

Releases TGF-β family, BMPs, dorsalin, retinoic acid (RA), Noggin

The roof plate contributes to the dorsal-ventral patterning of the nervous system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the function of the floorplate?

A

Secretes Sonic Hedgehog (Shh), retinoic acid (RA), Noggin, Chordin

The floorplate is crucial for the ventral patterning of the nervous system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is neurogenesis?

A

Birth of neurons from neural stem cells (NSCs)

Neurogenesis is primarily complete by birth, with exceptions in the SVZ and hippocampus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does the direction of the mitosis plane determine?

A

The type of cell division

The position of the mitotic spindle during mitosis influences whether the division is symmetric or asymmetric.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens during symmetric division?

A

Produces 2 identical cells (e.g., 2 neural epithelial cells or 2 radial glial cells)

This occurs before neurogenesis and contributes to pool expansion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What characterizes asymmetric division?

A

Produces 2 different daughter cells (e.g., 1 radial glial cell + 1 neuron)

This leads to direct neurogenesis where the neuron does not divide again.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is an intermediate progenitor cell (IPC)?

A

Progenitor that gives rise to a neuroblast, which then becomes a neuron

IPCs are not fully differentiated but are crucial in the neurogenesis process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the ‘inside-out’ manner of neuronal migration.

A

Deeper cortical layers are formed before more superficial ones

This pattern is observed during the development of the cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What guidance mechanisms support neuronal migration?

A
  • Radial glial cells (RGCs)
  • ECM proteins (e.g., Reelin, Laminin)
  • Integrin, LIS1, Neuregulin

These factors help neurons migrate to their appropriate layers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the post-natal GABA switch?

A

GABA initially acts as excitatory, then becomes inhibitory upon reaching the cortex

This switch is caused by changes in transporter expression affecting chloride levels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is gliogenesis in the developing brain?

A

The process of forming glial cells, such as astrocytes, oligodendrocytes, and ependymal cells

Gliogenesis starts after neurogenesis and continues after birth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Compare gliogenesis and neurogenesis.

A

Gliogenesis occurs later and is regulated differently than neurogenesis

Signalling and transcription factors determine cell fate in both processes.

17
Q

What is the role of astrocytes in astrogliogenesis?

A

Derived from astrocyte precursors that are influenced by negative proneural bHLHs and positive Notch/Nrg signals

This process is part of gliogenesis.

18
Q

What is myelination?

A

The process of forming a myelin sheath around neurons

Myelination starts soon after an increase in glial cell numbers and is rapid during the first year of life.

19
Q

Which pathways myelinate first during development?

A
  • Sensory pathways
  • Motor pathways
  • Association areas

This sequence reflects the developmental priorities of sensory and motor functions.

20
Q

Neurogenesis genes

A

neg. Notch, pos. bLHLH gene products -> neuronal precursors -> neurons

21
Q

Oligodendrogenesis genes

A

neg. Proneural bHLHs, pos. Olig ½ Nkx2.1 -> oligodendrocyte precursors -> oligodendrocytes

22
Q

“tangential” migration

A

interneurons from the subpallial embryonic region (MGE) undergo this migration to reach their appropriate layers in the cortex

During mid-gestation (week 20, early infancy/pregnancy) and early infancy

Guidance for migration:
- RGCs
- SDF1, Neuregulins

23
Q

RGCs (B cells)

A

generate neuroblasts that migrate in chains into the olfactory bulb, where they differentiate into interneurons

Migratory path = rostral migratory stream (RMS) more anteriorly

Astrocytes, oligodendrocytes and
ependymal cells also derive from RGCs

24
Q

Hox gene expression:

A

divides the CNS into segments. Much of the neural tube (hindbrain, spinal cord) becomes divided into neuromeres (segments).

-Dictated by Homeobox genes
-Organized into 4 clusters
-Temporal AND spatial (A→P)- specific expression
-Contributes to neuronal identity
-Conserved mechanism
-Each segment, cell identity is determined by morphogen concentration and which hox genes are turned on and off

25
Somite
BMPs
26
Guidance for migration:
- RGCs - ECM proteins (e.g. Reelin, Laminin); Integrin, LIS1, Neuregulin
27
Post-natal GABA switch
In the embryonic brain: [Cl-]i is relatively high, Cl- transport dominated by NKCC1 - Depolarizing GABA: guides proliferation, migration and construction/maturation of circuits * Post-natal: Cl-]i decreases, due to increased expression and activity of KCC2 - Hyperpolarizing GABA: fine-tunes circuitry activity (e.g. increase sensitivity to sensory input)
28
neuroblasts and their migratory path
generated by RGCs (B cells), migrate in chains into the olfactory bulb, where they differentiate into interneurons Migratory path = rostral migratory stream (RMS)
29
radial glial cell shape
bipolar
30
order of differentiation
neuroepithelial cell -> radial glial cell -> neuron
31
migratory path of RGC
rostral migratory stream (RMS) more anteriorly