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Dev Neuro > Semester One > Flashcards

Semester One Flashcards

1
Q

Cell intrinsic or cell autonomous mechanisms

A

Expression in cell 1 can be controlled by factors in cell 1

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2
Q

Cell extrinsic or cell non autonomous mechanisms

A

Expression in cell 1 can be controlled by factors in cell 2

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3
Q

1) BMP7

2) BMP4. Morphogen

A

1) screw

2) DPP decaplentaplegic

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4
Q

Chordin what does it do and pathway it causes.

A
  • morphogen
  • it prevents BMP binding to its receptor
  • in drosophila it’s called short gastrulation
  • it acts as a sponge in the extra cellular space and catches all the BMP so it cannot reach its receptor on other cells
  • it can also be a competitive inhibitor for the BMP receptor

-if BMP is prevented, a different set of SMADs are phosphorylated
-causing the up regulation of soxD and soxB, which will up regulate neurogenin and the neuroD
This commits the cell to a neural fate.

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5
Q

If a cell receives BMP signalling …
If BMP signalling is blocked…

In drosophila what do cells with DPP become
And what do cells with SOG become

A

It will become an ectoderm skin cell
It will have a neural cell fate

Skin cells
Neural cell

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6
Q

BMP signalling pathway

A
  • BMP binds to its receptor TGFB and triggers the pathway
  • it caused a change in the phosphorylation of SMAD protein so it can now enter the nucleus
  • SMAD will turn on transcription factors
  • these will turn on a second set of transcription factors including LEF1 which will definitely commit cells to their epidermal fate.
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7
Q

D/V expression of chordin

A

In drosophila, SOG is present on the ventral side and will inhibit DPP there and form central neural cells. They have their neural tube on the ventral side

Humans have a dorsal neural tube so will have chordin on the dorsal side.

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8
Q

Double colour in situ hybridisation

A

Two antisense probes that are complementary to the mRNA of interest.

A probe for DPP mRNA and a probe for SOG mRNA will show an image of the cell split down the middle into two colours.

The ventral side will be one colour and show SOG mRNA and the dorsal side will be another colour and show DPP mRNA.

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9
Q

Urbilateria

A

Vertebrates and invertebrates both evolved from a common ancestor.
Invertebrates has a body twist so their NS formed on the bottom.
And vertebrates didn’t and kept their NS on the top/dorsal.

The pattern of signally of BMP/DPP is conserved but they are on opposite sides.

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10
Q

Spina bifida and cause

A

Neural tube doesn’t close

Low folate

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11
Q

Why is proliferation needed

A

More cells means more complex things can occur
During neuralation the plate rolls into a tube and grows because of all the proteins being formed to help with this process

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12
Q

Testing for three germ layers

A

In situ hybridisation
To see the difference in mRNA and transcription factors expressed
They will express different proteins and this can be identified with antibodies.

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13
Q

The organiser / node

A
  • In the mesoderm a specialised set of cells is induced.
  • called the organiser in Xenopus and the Hensens node in chicks and humans
  • they express special transcription factors guscoid and CM1 that produce the morphogens chordin, noggin and follistatin
  • these are BMP antagonists and will cause neural cell fate
  • the morphogens will be secreted from the node in the mesoderm towards the ectoderm to produce the neural plate.
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14
Q

What does the neural plate and it’s edges give rise to

A

All neurons in the body

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15
Q

Noggin

A

BMP antagonist
Binds to BMP receptor as a competitive inhibitor

Causes SOX B and D
Then neurogenin and then neuroD and a neural identity

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16
Q

Xenopus vs humans and chicks

A

Neuralation studies are done on them Hollow ball of cells

Flattened three sheets of cells. The neural plate is on the top.

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17
Q

In situ on the exams.

A

The diagram will show chordin which is in the node.

It will show the other transcription factors around the node because they are turned on in neighbouring cells and not in the node.

It will also show the area which is the neural plate growing and then folding over to form the tube.

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18
Q

What is in the axial mesoderm

And what does it do

A

Anterior endoderm
Prechordal mesoderm
Notochord

They all originate from the self differentiated cells of the node

The organising centre will split into three sections in response to very slight differences in giscoid and CM1 expression.
The cells involute together and do convergent extension forming a very long rod of cells under the midline if the neural plate.

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19
Q

Intercalation

Convergent extension

Ingression

A

Double cell later converges to become a single layer of cells

Ball of cells converges and extends into a long rod of cells.

Cells leave the cell layer and become separate single cells.

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20
Q

What is above the axial mesoderm

A

Developing forebrain

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21
Q

What shape are axial mesoderm cells

A

Open fan like triangular shape

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22
Q

What is stomodaum

A

Opening of the mouth

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23
Q

Adding a second organiser node to a newt in an ectopic location

A
  • the original organiser will differentiate into the axial mesoderm and will form a neural plate above it.
  • the implanted node will differentiate into a second axial mesoderm and will cause host cells to become a second neural plate.
  • this will give two neural tubes and a twinned organism.
  • the second axial mesoderm cells are from the foreign newt and the second neural tube cells are host newt cells.
  • you can do this in chick and quail too to see which cells are from the implanted quail node.
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24
Q

Discovering BMP antagonists

A

All mRNA was extracted from the organiser

It was reverse transcribed to make cDNA

the cDNA was tested to find the protein that would be able to induce a neural plate

The proteins were discovered and are morphogens

Testing the inhibition of the gene should stop axial mesoderm formation

25
Q

What are the notochord and prechordal mesoderm sat directly underneath

A

The midline of the neural tube

26
Q

What is neuralation driven by

What does the neural plate look like

A

Changes in cell shape

The neural plate is a single row of columnar cells, neuroepithelium.

The cells can change shape because they are polarised. Apical basal polarity

The apical side of the cells has a band of F actin which is contractile. It causes invagination when the actin is pulled.

Folate receptors are expressed on the apical side and folate bonding causes F actin contraction and neuralation.

27
Q

Anterior neural tube gives

Posterior neural tube gives.

A

Forebrain

Hindbrain and spinal cord

28
Q

What arises from the neural plate

A

Brain
Spinal cord
Specialised sensory derivatives

Starts to establish in weeks 3-5

29
Q

Antibody tagging

A

Antibodies complementary to different proteins can be tagged and we can follow their differentiation

30
Q

Forebrain

Midbrain

Hindbrain

A

Telencephalon is lateral ventricle
Diencephalon is third ventricle, neural retina and lens

Mesencephalon is cerebral aqueduct

Metencephalon is is fourth ventricle, pons and cerebellum.
Myelincephalon is medulla

31
Q

Axial mesoderm and which parts give which signals

A

The anterior endoderm and prechordal mesoderm induce anterior neural transcription factors in the neural plate above. To give forebrain like cells.

The notochord will induce posterior neural transcription factors in the neural plate above.

32
Q

Why is the early neural plate anterior in character

A

If we experimentally stop development after only the anterior endoderm and prechordal mesoderm have involuted

We will find that the neural plate is expressing markers like sox2 and other that are confined to the forebrain.

There is no notochord to signal for posterior fate so the whole plate is anterior at that time.

33
Q

The activation transformation model

A

The basis of formation of the forebrain and hindbrain

Where the notochord is involuted and causes the posterior neural cells to have a posterior fate and stop them being anterior.

34
Q

What needs to be inhibited to get anterior neural plate cells.

What are three antagonists of each

A

No BMP or Wnts

Gsc up regulates chordin noggin and follistatin in the anterior endoderm and the prechordal mesoderm. They stop BMP.

Gsc also upregulates cerebrus frisbe and dickopf which inhibit Wnts

So there is low BMP and Wnts in the anterior axial mesoderm

35
Q

When the notochord involutes what will it upregulate

A

Wnt in the posterior axial mesoderm

FGF and retinoic acid are secreted signals which are only found in the posterior axial mesoderm.

36
Q

What is FGF for in the posterior axial mesoderm

A

Maintain the proliferation of cells.

37
Q

What does retinoic acid do

A

It is small so diffuses into cells and binds to cytoplasmic receptors.
They then enter the nucleus and bind to gene promotors and upregulate gene expression.

It is a signal and a regulator.

38
Q

Wolpert french flag

A

Small medium and large concentrations of a regulator will all have different effects.

There are thresholds of concentrations and when reached a different set of events is caused.

39
Q

Hox genes 5

A

Evolutionarily conserved

In drosophila and each is expressed in a specific region along the AP axis.

For every drosophila hox gene a human will have four homologues
If a mutation happens in one of the genes. In humans there are three more to take over.

Hox genes are transcription factors
They are upregulated in response to retinoic acid

40
Q

Homeobox DNA encodes

A

A DNA binding protein domain of 60 amino acids called the homeodomain.

41
Q

Which hox genes are found in which spine segments.

A

Cervical - most 5, some 6

Thoracic - at the top mostly 6 and few five. At the bottom 9

Lumbar - 10 and 9

Sacral - 10 and 11

Caudal - 11

Caudal has the highest amount of retinoic acid.

42
Q

What is turned on at the highest retinoic acid conc and what cell fate does it cause.

And second highest conc

A

Hox 11 and caudal fate.

Both 10 and 11. Causing sacral fate.

43
Q

Hindbrain rhombomeres

Which hox genes and what happens when knock out.

A

Hoxa1 and hoxb1 specify rhombomeres 4 and 5

The knockout missed rhombomere 4 and the facial nerve is missing.

44
Q

Why is it difficult to study hox genes.

A

Because they have been duplicated over evolution.

So if you knock one out it won’t show anything because there are three more.

It is very expressive to do quadruple knockouts.

45
Q

How midbrain cells are formed.

A

After fore and hindbrain are distinguished, the two groups of cells interact and induce midbrain cells at the boundary.

46
Q

3 primary vesicles into the 5 secondary vesicles

A

Forebrain (prosencephalon) into telencephalon and diencephalon

Midbrain into mesencephalon

Hindbrain (rhombencephalon) into metencephalon and myelincephalon

47
Q

What is in each of the secondary vesicles

A

Telen- olfactory lobes, hippocampus, cerebrum, basal ganglia

Dien- retina, epithalimus, thalamus, hypothalamus

Mesen- midbrain

Meten- cerebellum and pons

Myelin- medulla

48
Q

Single celled organism

Vs multi

A

Responds to light photons
They are transduced by pigment localised to the eyespot
This can trigger movement

They are receptive and responsive
Very basic NS and little complex behaviour

Euglena

Multi has many cells and allows for specialisation and complex behaviour

49
Q

Sponges

A

On bottom of seabed and have an osculum on top of their heads

Water flow into body is regulated by myocytes which are specialised muscle that responds to stretch.
They are thought to have evolved into primordial NS

myocytes are mechanoreceptive and span the outer epithelial ectoderm layer. They are thought to have evolved into the first neurons.

The cells were able to span from the interior to the exterior.
Some neurons evolved to be located beneath the ectoderm eg hydra

50
Q

Hydra

A

Used to think they had a two layered NS
Sensory to motor outputs.

But now they have been found to have neurosecretory cells which secrete peptide hormones. Insulin somatostatin and glucagon

So specialised cells are present in hydras

Hydras have interneurons between sensorys and myocytes and between neurosecretorys and myocytes
They can inhibit or excite and allow complex interactions.

The layout of nerves is net shaped.

51
Q

Worms

And 5 definitions

A

Segmented or not

Flatworms have clustering and organisation of neurons
Shows gangliation- clusters of neurons

Cephalisation- clear head area
Bilateral symmetry
Fasciculation- not just one nerve connected to another. They all come together in big bundles
Commisures- info travels from one side of the midline to the other

This has happened to allow eating to be easier for survival and for communication and movement for catching food and protection.

52
Q

Pharynx

A
  • the most complex arrangement of neurons is around the pharynx of many organisms
  • clusters of neurons begin to pile up on those in the pharynx and rise dorsally to create suprapharyngeal ganglia
  • they release the same neurotransmitters as the brain so are thought to be early brain developments.
  • this explains why the brain is positioned above the mouth.
53
Q

C elegans 7

A

NS has been mapped
302 neurons and 56 glia

Large fascicles called the ventral lateral and dorsal nerve cords.
Lots of ganglia in a nerve ring around the pharynx

It develops from a single cell so we can trace the progeny as it divides.
Most neurons derive from AB cell and have a shared lineage with the hypodermis.

In simple model organisms the skin and nervous cells have the same lineage.

54
Q

Insects

A
  • drosophila have clusters of neurons above the pharynx
  • their NS has fasciculated to form the ventral nerve cord
  • see signs of protocerebrum and eyes and the basic form of complex neurons
  • can see the NS developing in the embryo
  • the neurogenic region is next to the skin region
  • the region moves ventrally during gastrulation
  • delamination forms neuroblasts and they give a neuroblast and a ganglion mother cell which forms neurons and glia.
55
Q

Vertebrates

A

Common body plan
Early NS is similar across the families

Easy to see how it has developed by studying drosophila

Hard to distinguish between embryos chicks and humans.

56
Q

Vertebrates similarities to lower Order animals

A

Sensory and motor systems

Have specialised set of neurons around the pharynx. But in humans it has evolved into the brain.

Above the oral cavity is the ventral region of the forebrain and the hypothalamus develops here.

The hypothalamus is one of the most ancient parts of the vertebrate CNS and does things don’t don’t require conscious thought.

57
Q

Vertebrates different to lower order animals

A

-vertebrate NS arises from a sheet of cells called the neural plate

Chick-one day after fertilisation is when you can see the neural plate

  • bumps in tube help to see future structures
  • the time scale is different in each vertebrate but the events are the same.
  • humans- neural plate forms at two weeks and before this time experiments are allowed.
58
Q

Xenopus

A

Hollow ball of cells

Neurogenic region is next to the ectoderm and it migrates down the ball.

Goes next to the mesoderm and involutes during gastrulation

Neural cells do not delaminate they stay in the neural plate.

Dev Neuro (7 decks)

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