Neurodevelopment (1)

Question 1

What are the five phases of early neurodevelopment?

Answer 1

1) Neural plate induction
2) Neural proliferation
3) Migration & aggregation
4) Axon growth & synapse formation
5) Neuron death & synapse pruning.

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Question 2

What are the three essential processes in early neurodevelopment besides cell division?

Answer 2

Differentiation: Cells become specialized (e.g., muscle cells, neurons, glial cells).

Migration: Cells move to the right location and align with surrounding cells to form structures.

Connection: Cells establish functional relationships (synapses) with other cells.

Question 3

What are totipotent, pluripotent, multipotent, and unipotent cells?

Answer 3

Totipotent: Can develop into any cell type in the body, including an entire organism (e.g., fertilized egg). Pluripotent: Can develop into most, but not all cell types, giving rise to cells of multiple lineages.
Multipotent: Can develop into different types within a single class (e.g., different blood cells or different types of neurons).
Unipotent: Can develop into only one specific cell type (e.g., a bipolar neuron).

Question 4

What are the main properties of stem cells?

Answer 4

• Self-Renewal: Can divide repeatedly, making one stem cell + one specialized cell.
• Differentiation: Can become different cell types depending on environment and gene expression.

Question 5

How are stem cells used to study brain development?

Answer 5

Can be cultured into different brain cells. Can form 3D brain organoids to study development. Potential use in repairing brain damage.

Question 6

What is the neural plate and when does it form?

Answer 6

A patch of ectoderm that will become the nervous system. Forms around 3 weeks after conception. First major stage of vertebrate neurodevelopment.

Question 7

How is the neural plate induced?

Answer 7

Chemical signals from the mesoderm (“organizer”) instruct ectoderm to form neural tissue. Experimental evidence: Dorsal mesoderm transplanted to ventral ectoderm creates an extra neural plate.

Question 8

How does the neural plate form the neural tube?

Answer 8

The neural plate folds into a neural groove. The lips of the groove fuse to form the neural tube. Inside becomes cerebral ventricles and spinal canal. Errors → neural tube defects.

Question 9

What are the three embryonic cell layers?

Answer 9

Ectoderm: outer layer → becomes nervous system and skin. Mesoderm: middle layer → becomes muscle, bone, and circulatory system. Endoderm: inner layer → becomes internal organs.

Question 10

What is neural proliferation?

Answer 10

The process where cells of the neural tube rapidly increase in number after the neural groove fuses to form the neural tube.

Question 11

What controls the pattern of neural proliferation?

Answer 11

Two organizer areas in the neural tube:
Floor plate – along the ventral midline.
Roof plate – along the dorsal midline. These areas release chemical signals that guide timing, location, and pattern of cell division.

Question 12

What type of stem cells are created during neural proliferation and how do they differentiate?

Answer 12

Almost always radial glial cells.Radial glial cells divide asymmetrically: One daughter cell remains a stem cell. The other becomes a neuron, glia, or other neural cell.

Question 13

What additional role do radial glial cells play besides being stem cells?

Answer 13

They guide migration of newly formed neurons and other cells to their proper locations in the developing nervous system.

Question 14

What happens during neural migration?

Answer 14

Cells born in the ventricular zone move to their target locations. They are immature and lack axons and dendrites. Migration depends on time (when neurons are born) and location (where they go).

Question 15

What are the two main directions of neural migration?

Answer 15

Radial migration: straight outward from the ventricular zone toward the outer wall of the neural tube.

Tangential migration: moves parallel to the walls of the neural tube. Some cells do both.

Question 16

What are the mechanisms of neural migration?

Answer 16

Somal translocation: Cell extends a process, guided by chemicals; the cell body moves along it. Works for radial and tangential migration.

Radial-glia-mediated migration: Cell climbs along a radial glial fiber; allows only radial migration.

Question 17

What is the “inside-out” pattern in cortical migration?

Answer 17

Early cortical cells form deep layers first; later-born cells migrate past them to form superficial layers. Some cells also migrate tangentially.

Question 18

What are neural crest cells?

Answer 18

Neural crest cells are special cells that form on top (dorsal side) of the neural tube when it’s developing in the embryo.

They break off from the neural tube and move to different parts of the body.

Question 19

What is neural aggregation?

Answer 19

After migration, neurons align with others to form nervous system structures.

Question 20

How is neural aggregation mediated?

Answer 20

• Cell-adhesion molecules (CAMs): allow neurons to stick to each other.
• Gap junctions: direct communication channels (via connexins) between adjacent cells.
• Neuron-glia interactions: e.g., microglia help organize neurons.