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Neuroscience > Developmental Neurobiology > Flashcards

Developmental Neurobiology Flashcards

1
Q

steps to establish a neurone

A
  1. cellular determination
  2. proliferation
  3. cell migration
  4. axon projects out
  5. axon connections to target form
  6. prune unnecessary connections
  7. death of excess neurones
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2
Q

briefly describe development

A
  1. fertilisation
  2. divisions to form 8 cells
  3. blastula forms (ring of cells around blastocoele)
  4. gastrula forms by invagination
    (forms the 3 germ layers)
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3
Q

determination

A

ectoderm cells determined to become neurones by neural induction
-> neural inducer signals from mesoderm

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4
Q

after determination

A

EITHER

differentiate into neurones
OR
remain as neural precursors

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5
Q

what do neural precursors become?

A

neurones
OR
glial cells

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6
Q

what happens to the ectoderm in an embryo (during development)?

A

inhibition process prevents cells becoming neurones

- must be switched off for differentiation

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7
Q

organogenesis

- define

A

= different germ layers become rudimentary organs

via folding, splitting + dense clustering of embryo

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8
Q

organogenesis

  • 1st rudimentary NS organs
  • how do they form?
A

neural tube
neural crest

neurulation
= neural plate folds inwards to form neural tube

the notochord helps to induce the floor plate

as neural tube forms neural crest cells immigrate from dorsal aspect of tube

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9
Q

Xenopus laevis

- experiments

A 
animal cap (ectoderm) transplanted onto second embryo 
-> grew second NS

Spemann organiser (mesoderm)
transplanted
-> forms nervous tissue

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10
Q

Xenopus laevis

- Spemann organiser

A

contains cells releasing neural inducers

e.g. Noggin, Chordin, Follistatin + Cerebrus

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11
Q

fertilisation

A

polarises egg
- animal and vegetal poles

influx of Ca2+ in vegetal pole

  • > diffuses across egg
  • > rapid release of cortical granules
  • > forms fertilisation envelope
  • > blocks polyspermy
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12
Q

cortical rotation

  • what happens
  • what does it form
A

egg membrane rotates in relation to molecules within egg

  • > mixes cytoplasmic determinants
  • > creates dorsal-ventral axis

sperm point of entry determines ventral (entry point) and dorsal (opposite entry)

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13
Q

cortical rotation

- redistributes maternal cytosolic determinants

A

VegT associated with Disheveled at membrane

  • > cortical rotation separates
  • > Dsh interacts with Siamois

Nieuwkoop Centre forms at area of separation

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14
Q

fate mapping the blastula

  • axes formed by?
  • name axes
  • what induces them
A

gradients of signalling molecules

animal-vegetal
(maternal determinants)

dorsal-ventral
(sperm entry + cortical rotation)

anterior-posterior
(Spemann organiser)

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15
Q

organiser transplant experiment

  • what happens
  • what does this show
A

region above blastopore lip transplanted to ventral side of host from EARLY gastrula
-> develops secondary dorsal axis
(evident by secondary neural plate)

this region containing Spemann Organiser is important for inducing NS formation

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16
Q

what do neural crest cells form?

A

PNS
endocrine cells
connective tissue

17
Q

neural tube structure

A

top (anterior)
- brain

bottom (posterior)
- spinal cord

18
Q

ventricular zone of proliferation

A

area within neural tube

gives rise to all neural cells

19
Q

Smad pathway

A

Bone morphogenic proteins
= neural inhibitors

Ectoderm cells have BMP receptors

  • BMP binding -> phosphorylation of Smad-1
  • > activate Smad-1 binds to Smad-4
  • > changes TF expression
  • > inhibits expression of neural genes + activates epidermal genes
  • > induces ectoderm to become epidermis
20
Q

how do neural inducers affect the Smad pathway?

A

neural precursors express inhibitory protein

  • > binds to neural inducers
  • > inhibit BMP binding to receptors and Smad pathway
21
Q

proliferation

A

division of precursors during and after differentiation
-> ends in neuroblasts (these migrate)

results in excess cells in adult NS

  • > not fully determined cells become stem cells
  • > can form progenitor cells
  • > eventually form neuroblasts
22
Q

neural stem cells

  • 2 properties
  • rare set of cells in brain tissue
A

self-renewing
multipotent

single cells divide into neurospheres
-> differentiate into neurones, astrocytes + oligodendrocytes

23
Q

neural stem cell transplants

A

human NSCs transplanted into rat brain:

some differentiate into neurones
-> migrate into brain regions

have appropriate morphology for brain region

incorporated into circuits

24
Q

neuronal tube generates different neuronal and glial cell types

  • where do they arise?
  • cerebral cortex cells
A

arise from ventricular proliferative zone (VPZ) in neuronal tube

migrate to final position along elongated radial glial cells
- early neurones migrate to close sites, later ones to far locations

25
Q

cerebral cortex

  • how many layers?
  • how do they develop?
A

6 layers of neurones

early differentiated cells move to lower regions

later differentiated migrate to top of cortex

26
Q

radial glia

A

span from VPZ to outer surface of neural tube

migrating precursors travel along the axons to final location

27
Q

how to determine birth dates of neurones in a monkey

A
  1. inject radioactive thymidine in short pulse
  2. only cells in S-phase incorporate it into DNA
  3. cells that make terminal division heavily labelled
  4. cells that continue to cycle dilute label
  5. pulse label at various times during development + section brain after birth
28
Q

molecular gradients

- anterior-posterior

A

proteins such as Noggin + Chordin are essential for formation of anterior parts of brain

FGFs

Hox genes

29
Q

molecular gradients

- dorsal-ventral

A

sonic hedgehog
- secreted from notochord

Wnt and BMP
- secreted from ectoderm

30
Q

signalling molecule gradient in neural plate

A

high Wnt, FGFs + RA at posterior end
–> lower at anterior end

leads to different structures forming

31
Q

signalling molecule gradient

- dorsal-ventral axis

A

notochord (ventral) releases sonic hedgehog
- diffuses into neural tube
= forms gradient
-> influences transcription factors and the proteins expressed
-> affects fate of neurones

dorsal side of tube affected more by proteins secreted by ectoderm

32
Q

sonic hedgehog

A

binds to 2-part receptor
(smoothened and patched)

alters gene transcription

33
Q

cell-cell interactions

- lateral inhibition in nervous system

A

notch protein expressed on 1 cell type and delta expressed on another

  • > interact
  • > creates inhibitory signal into cell
  • > inhibition
  • > prevents ectoderm cells differentiating into neuroblasts
34
Q

what can this form of lateral inhibition do in vertebrate nervous systems?

A

stimulate differentiation of neuronal precursors into special cell types
e.g. photoreceptors

Neuroscience (17 decks)

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