Lecture 9 - Neurodevelopment: How does central nervous system develop?

Question 1

Eriksson et al., 1998

Where was adult neurogenesis found in humans?

Answer 1

Hippocampus

Question 2

Eriksson et al., 1998

Neurons move from where to where when mature?

Answer 2

Neurons in SGZ (subgranular zone) move to GCL (granule cell layer) when mature

Question 3

Spalding et al., 2005, 2013

How were cells birth dated?

Answer 3

14C levels in the genomic DNA reflects when a cell was born, due to nuclear testing in 1955 raising 14C levels in the atmosphere.

Question 4

Spalding et al., 2005

Which cells were born postnatally and which were not?

Answer 4

Born postnatally - non-neuronal cortical cells

Not - neuronal cortical cells

Question 5

Spalding et al., 2013

Turnover was found in which human neuronal cells?

Answer 5

Hippocampal neuronal cells

Question 6

Spalding et al., 2013

How long does neurogenesis persist in humans?

Does the number of hippocampal neurons change significantly with age?

Answer 6

Neurogenesis persists into at least the fifth decade of life (based on the older subjects)
There is no dramatic decline in hippocampal neurons with age since individuals born longer before 1955 still incorporated similar amounts of 14C levels

Question 7

Spalding et al., 2013

Are hippocampal neurons part of a homogenous or heterogenous group of cells?

Answer 7

Hippocampal neurons are heterogenous as a large subset of neurons are not exchanged postnatally

Question 8

Which part of the embryo do neurons develop from?

Answer 8

Ectoderm

Question 9

How are the neural tube and neural crest formed?

What does the neural crest become?

Answer 9

Neural tube folds to form neural tube and neural crest

Neural crest forms peripheral nervous system

Question 10

What does the neural tube become?

Answer 10

Forebrain, midbrain, and hindbrain

Question 11

How do progenitor neural cells proliferate?

Answer 11

They migrate along radial glial cell, around ventricular zone area to the pial surface, then back to the ventricular surface where they divide into two cells

The newest born neurons are found on the most superficial layer

Question 12

What are the types of cell division for progenitor neural cells?

Answer 12

Symmetrical division - 2 cells similar or equal to each other

Asymetrical division - e.g., neural precursor + radial glial cell

Question 13

How do the gradients of transcription factors control the size of the cortical area?

Answer 13

They result in greater/less development in certain brain regions

Question 14

What are the three phases of pathway formation in the optic chiasm?

Answer 14

Contralateral, ipsilateral, or the other eye

Question 15

How does chemoattraction and chemorepulsion allow pathway formation to the contralateral or ipsilateral optic tract?

Answer 15

Netrin receptors on axon are attracted to the midline. Then, netrin recptors are shut off and robo (slit receptor) causes repulsion from midline

Question 16

How do synapses form at neuromuscular junctions?

Answer 16

Axon contact muscle fibres, releasing agrin molecules which bind to MuSK, which interact with rapsyn, causing ACh receptors to cluster

Question 17

How are CNS synapses formed?

Answer 17

Growing axon comes into contact with filopodium of dendrite to form a synapse

Question 18

How are inputs matched with targets by selective cell death?

Answer 18

Cells that do not manage to synapse undergo apoptosis

Question 19

How does synapse elimination at neuromuscular junctions occur?

Answer 19

Initially, each muscle fiber is innervated by multiple neurons. After maturation, One muscle fiber is innervated by one neuron. This is due to competition for AChRs based on the amount of use of the neurons, resulting in synapse elimination.