Development

Question 1

Radial Unit Hypothesis

Answer 1

• Radial glial cells expand radially spanning from ventricle to pial surface.
• According to this hypothesis, the key function of radial glia is to provide scaffolding and guide the migration of neurons in the developing brain by forming “ontogenetic columns” in the cortex

Question 2

Intermediate Progenitor Cells

Answer 2

• Intermediate progenitor cells are daughter cells of radial glial cells.
• When the radial glial cell divides, the daughter cell (intermediate progenitor cell) migrates to the subventricular zone and they divide again.

Question 3

What is the mistake in the radial unit hypothesis?

Answer 3

Radial glial cells are not only fibers that neurons travel on, but they are actually neural stem cells.

Question 4

Ventricular Zone

Answer 4

Contains radial glial cells

Question 5

Radial Glial Cell

Answer 5

Radial glial cells are neural stem cells - they make neurons and glial cells, initially astrocytes and then oligodendrocytes.

Question 6

Subventricular Zone (SVZ)X

Answer 6

Subventricular Zone (SVZ) is a separate layer of intermediate progenitor cells apart from the original progenitor ventricular zone (VZ).

Question 7

Outer Subventricular Zone

Answer 7

Additional to the ventricular zone and subventricular zones found in rats, humans have a separate layer called the outer subventricular zone(OSVZ)

Question 8

Outer Ventricular Zone becomes the largest during the second half of neurogenesis.
(TRUE or FALSE)

Answer 8

TRUE

Question 9

Mitotic Somatic Translocation (MST)

Answer 9

Mitotic somatic Translocation refers to the peculiar jump of neural progenitor cells of OSVZ just before cell division.

Question 10

In mouse mitotic somatic translocation jump is longer than MST in the human brain.
(TRUE or FALSE)

Answer 10

FALSE

In mouse, mitotic translocation is shorter than in the human brain.

Question 11

Outer Subventricular Zone Radial Glial Cells (oRGs)

Answer 11

• They are a new type of stem cells, not only found but enriched in human brains.
• oRG cells show a peculiar jump just before cell division

Question 12

oRGs (Outer Subventricular Zone Radial Glial Cells) are not found in other mammals.
(TRUE or FALSE)

Answer 12

FALSE

• oRGs like cells are also found in other mammals but less.

Question 13

IP transit amplifying cells

Answer 13

• Migrating daughter cells of the oRGs
• IP transit-amplifying cells divide more than once unlike intermediate progenitor cells in mouse
• They rapidly increase the overall number of neurons

Question 14

Astrocytes and oligodendrocytes

Answer 14

Outer radial glial cells turn into astrocytes and oligodendrocytes AFTER the phase of neuronal production

Question 15

The difference between folded (gyrencephalic) and smooth (lissencephalic) brains stems from the presence of OSVZ.
(TRUE or FALSE)

Answer 15

FALSE
• smooth (lissencephalic) and folded (gyrencephalic) brains can be found within the same class in highly related species; this doesn’t seem to be tied to the presence of the OSVZ
• Having outer subventricular zone radial glial cells does not mean that you are going to have a folded cortex, so folding is not about presence of OSVZ!

Question 16

Genes that are unique to oRG cells fell into some categories:

Answer 16

• Growth factors
• Extracellular proteins
• self-renewal pathways
• mTOR signaling which has been linked to autism

Question 17

Human cortical development is more diverse in terms of ___.

Answer 17

• Progenitor types

Also more diverse in terms of NUMBER and DIVERSITY of neurons they produce

Question 18

What can be told about the difference between developing the human cortex and rodents?

Answer 18

Early human cortical development is highly similar to rodents; in later stages, however, the OSVZ emerges as a separate zone of proliferation

Question 19

What does contribute to cortical growth and expansion particularly in the upper layers?

Answer 19

Outer radial glia (oRGs)

Question 20

The outer radial glia cell is particularly abundant in the developing human brain, forming _____.

Answer 20

Outer subventricular zone

Question 21

Around this week, radial glial cells reach into the OSVZ and oRGs extend from the OSVZ to the pial surface, this also coincides with the formation of layer 4.

Answer 21

16.5

Question 22

In primates, lower layers are derived from ___ (1) cells, and upper layers from ____ (2) cells.

Answer 22

1. Radial Glia
2. oRGs
   Other mammals (rodents, carnivores) do not seem to have this distinction.

Question 23

Cell density in upper layers (above layer 4) is not higher in primates compared to other mammals.
(TRUE or FALSE)

Answer 23

FALSE

• Upper layers are more cell dense in primates than in other species.