Molecular Neuro Exam 2

primitive streak

forms at posterior pole of embryo

forms the midline, where newly formed cells migrate inward to form the three germ layers

hensen’s node/primitive node

does not originate the CNS, but is the master organizer that instructs the overlying ectoderm to form it. it is this ectoderm that forms the CNS.

Neural plate

flat, thickened sheet of ectodermal cells that wil develop into neural tube

Neural crest

Derive from edges of neural plate

Migrate dorso-laterally to form sensory neurons and sympathetic neurons, also form cells from other systems (neuroendocrine, skeletal, etc.)

Transplanted progenitors from young to old

Cells travel to a shallower layer (layer 2 and 3) instead of deeper layer (layer 6)

cells lost original layer information, cells are still very plastic

Transplanted progenitors from old to young

Cells travel to a shallower layer (layer 2 and 3) instead of deeper layer (layer 6)

these older cells retained original layer information

Neuroepithelial cells

Symmetric division

Precursor to radial glial

Inside-out gradient

Cells on outer layer are younger

cells on inner layer are older

EMX2 and PAX6

Fgf8 and BMP

In the early post-natal cortex, FGF8 is high
anteriorly and BMP is high posteriorly

state machines

machines that can acquire different states

can change their state in response to specific inputs

in different state can have different functional properties = output

Specific response/function of a cell is influenced by

* Nature of the input or inputs (not all cells face same stimuli)

* Stimuli strength and duration

* The specific signaling determinants in the cell that respond to these stimuli

(not all cells respond in the same way to a given stimuli, if at all...)

both cell-surface receptors and intracellular signaling determinants...

* The specific status of the cell

Allosteric switch

the protein achieves an active conformation in response to stimuli interacting with an allosteric site

examples:

* phosphorylation

* ligand binding

kinase domain of insulin receptor

activated by phosphorylation of its activation loop, that leads to repositioning of the
activation loop to allow binding of peptide substrate.

Modular allosteric switch

Activity regulated by binding to regulatory domain instead of catalytic domain

Tyrosine phosphatase

Modular allosteric switch

Catalytic domain is constitutively active

Two regulatory domains autoinhibit by binding catalytic domain

Binding of tyrosine-phosphorylated ligands to the SH2 domains leads to the release of

the inhibitory binding of SH2 domains, resulting in activation of phosphatase activity.

Protein Kinase A (PKA)

Linear/graded response

Cell detects a range of input levels and produces output that is proportional to the input level

Switch-like response

- Below threshold point, adding input will

lead to a sub-linear increase in output.

- near or at the threshold point, adding

input will lead to a very steep nonlinear

increase in output level

- can be achieved through positive feedback

N-WASP

catalytic domain activates Arp2/3, which induces actin polymerization

multiple inputs: PIP2 AND Cdc42

dual control allows activity to be localized at cell membrane

In Utero Electroporation of Cortical Neuronal Progenitors

Inject DNA into ventricle

electroporation electrodes placed around head

DNA moves towards positive electrode

Demonstrates inside-out manner of cortical development

Dissociated Embryonic Hippocampal Neurons in Culture

Still develop one axons and dendrites, they are just not oriented in a specific direction

BDNF (?) and semaphorin

BDNF may be attractive to axons and deter dendrites

semaphorin is attractive to dendrites and deters axons

Role of Ca2+ in netrin signalling

PKA induces calcium current

high calcium = attraction

low calcium = repulsion

how cAMP self regulates

cAMP activates PKA

PKA phosphorylates and phosphodiesterase

PKAR (regulatory subunit) also binds phosphodiesterase

phosphodiesterase breaks down cAMP

Processive hydrolysis of cAMP by channeling through the PDE8-PKAR complex

PKAR = PKA regulatory subunit

PDE8 = phosphodiesterase 8

inside the rod - how is sensitivity achieved?

Ca2+ enters cell alongside sodium (in the dark)

Ca2+ inhibits cGMP

In extended light, absence of Ca2+ allows for cGMP levels to rise, which reopen ion channels

this ensures that all of the membrane channels don’t close during a given time period

Carvedilol

a b-arrestin-biased agonist for b-AR, has been demonstrated to inhibit the G protein-mediated toxic effect of catecholamines (dopamine; norepinephrine; and epinephrine/adrenalin) and stimulate b-arrestin-mediated cell survival signaling pathways

CRTC1

In basal conditions, is phosphorylated and sequestered in the dendritic spines

Increase in Ca2+ and cAMP leads to dephosphorylation

It then travels to the nucleus and is recruited to the Bdnf promoter by CREB

This promotes neuroplasticity

CBP

“CREB binding protein”

Recruited for transcription by CREB

is also a histone acetyltransferase

NGFI-A

binds to GR gene promoter

recruits CBP, which acetylates histones

in low LG rats, promotor for this gene is highly methylated