Basics Of Brain Development Flashcards
What CNS cells arise from the ectoderm?
Neurons
Astrocytes
Oligodendrocytes
What CNS cells arise from the mesoderm?
Microglia
When does the cortical plate begin to form?
Around 8 weeks post conception
What is the totipotence?
The potential of a cell to create a full being
At what stage do the germ layers arise?
Gastrulation
What are the three germ layers?
Ectoderm
Mesoderm
Endoderm
What is the fate of ectoderm?
Skin or CNS
When does the gastrulation stage take place?
E13 (3 weeks post conception)
Where is the Spemann organiser and what does it do?
In the mesoderm
Involved in induction - changes the fate of cells
What side of the ectoderm becomes skin?
Ventral
What side of the ectoderm becomes brain? (Think of an animal lying prone)
Dorsal
What morphogen induces ectoderm to become skin?
BMP-4
How does the Spemann organiser induce ectoderm to become the neural plate?
Releases morphogens (chordin, noggin) to dorsal ectoderm
These prevent binding to BMP-4
Ectoderm take the default path and become the neural plate
What is the role of sonic hedgehog?
Cells into the brain areas according to gradient
(Telencephalon to hindbrain)
What condition occurs from a homozygous mutation in Sonic hedgehog?
Holoprosencephaly (Cyclopia)
What brain areas are microglia involved in the formation of?
Cerebellum
Corpus callosum
When do microglia move into the brain?
4 post conceptional weeks
Move from the yolk sac into the brain through the blood supply
What is the role of CSF1R?
Signals the microglia to move into the brain
Without this: cerebellar and callosal agenesis
What are the three subdivisions that form from the neural tube?
Forebrain - prosencephalon
Midbrain - mesencephalon
Hindbrain - rhombencephalon
What does the forebrain a
Divide into?
Telencephalon - cortex
Diencephalon - subcortical structures (basal ganglia, thalamus)
What does the rhombencephalon (hindbrain) divide into?
Pons
Cerebellum
Medulla
What conditions arise from the neuropores at the neural tube not closing?
Anencephaly - rostral pore
Spina bifida - caudal pore
How can neural tube defects be prevented?
Folic acid supplements
When does the neural tube close?
Between 21 and 28 days
What does the notch pathway do?
Inhibits proneural genes in a subset of progenitor cells
Progenitor cells become glial cells instead of neurons
Where do excitatory neurons arise from?
Ventricular zone
Migrate towards the cortical (pial) surface
Where do inhibitory neurons arise from?
Ganglionic eminence
Migrate tangentially to pial surface
What are the earliest born neurons in the cortex?
Layer 6
Deepest layer
Neurons arise from the deep to the surface
What gene mutation causes schizencephaly?
EMX2
Disorder of proliferation and onset of migration
What genetic mutation causes lissencephaly?
LIS1
DCX
Disorder of ongoing migration
What genetic mutation causes lissencephaly type 2?
FCMD
Disorder of arrest of migration
What does mutation in reelin affect?
Layering of cortex
How does the number of dendritic spines/synapses differ in Alzheimer’s?
Numbers reduce in line with the time of onset
How does the number of dendritic spines/synapses differ in Autism?
Formation is higher in childhood
Elimination is lower throughout life
How does the number of dendritic spines/synapses differ in Schizophrenia?
Elimination is higher than in normal controls
Timing is in line with onset of disorder
What are the facial features of feral alcohol syndrome?
Small eye openings
Smooth philtrum
Thin upper lip
