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Neural Induction Flashcards

1
Q

What characteristics of zebrafish make it a good model organism for studying developmental biology?

A
  1. genetics are easy to modify
  2. transparent while they develop, so they are easy to image
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2
Q

What characteristics of C. elegans make it a good model organism for studying developmental biology?

A
  1. simple and well-understood
  2. well-characterized nervous system
  3. transparent while they develop, useful for imaging
  4. short life cycle which makes them easy to manipulate genetically
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3
Q

Why are mice used as a common model organism in developmental biology?

A
  1. closely related to humans
  2. good models for disease
  3. easy to perform behavioural experiments on them
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4
Q

Why are Xenopus laevis commonly used to study developmental biology?

A
  1. easy to find in the wild
  2. easy to get gametes from and easy gametes to grow in a dish
  3. have large eggs - optimal for injection and heal quickly
  4. eggs develop externally - easy to harvest
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5
Q

In the blastula stage, why are the cells at the animal pole smaller than the cells at the vegetal pole?

A

Animal pole cells have been cleaved more times

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6
Q

There is very little transcription of different genes in the xenopus embryo until this developmental stage

A

The mid blastula stage

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7
Q

Describe the cleavage of the cells of the xenopus blastula

A

Rapid synchronous cleavage which happens radially

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8
Q

The blastocoel appears at this stage in embryonic development

A

Blastula stage

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9
Q

What is specified by the end of the late blastula stage?

A

3 germ layers

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10
Q

At the end of the late blastula stage, what are the 3 groups of cells present, and what are their cell fates?

A
  1. animal cap cells > ectoderm
  2. marginal cells > mesoderm
  3. vegetal cells > endoderm
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11
Q

What is a key difference in the early development of xenopus and humans?

A

Humans have equivalent structures to amphibians, but we have a flat sheet of cells as opposed to a sphere of cells

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12
Q

Which population of cells slides under the dorsal lip during the cellular reorganization of gastrulation?

A

Animal cells

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13
Q

Why is the generation of asymmetry relevant at the blastula stage?

A

Generation of asymmetry is the basis of later cellular fate determination

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14
Q

The ectoderm later goes on to become these 2 important systems

A

Epidermis
CNS

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15
Q

What is the ultimate cell fate of the cells which make up the blastula mesoderm?

A

Will become muscle and blood cells, among other “middle body” cells

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16
Q

What is the ultimate cell fate of the cells which make up the blastula endoderm?

A

Cells of the gut

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17
Q

Describe neurulation

A

A flat sheet of neural tissue-destined cells fold into the neural tube to establish what will later be the notochord

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18
Q

At what stage is the anterior posterior axis established?

A

Gastrulation

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19
Q

The neural plate stages coincides with this embryonic phase

A

Late gastrulation

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20
Q

Which stages follows gastrulation?

A

Neurula stage

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21
Q

At what stage does the neural-fated tissue go underneath epidermal-fated tissue?

A

Neurula stage (after neural tube formation)

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22
Q

Formation of the neural tube is driven by changes in…

A

Planar cell polarity

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23
Q

What is the medial hinge point (MHP)?

A

The hinge point at which the neural plate folds during formation of the neural tube

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24
Q

Spina bifida is usually a condition associated with improper…

A

Neural tube closure

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25
How is folic acid thought to be involved in spina bifida?
A lack of dietary folic acid may result in downstream misregulation of factors which are regulated by folic acid, and which are involved in neural tube closure
26
After the neural tube closes, cells of the neural crest...
Delaminate from the dorsal neural tube and migrate elsewhere
27
Neural crest cells eventually give rise to...
The peripheral nervous system (sensory nerves and ganglia)
28
Neural crest cells also give rise to...
Bone, pigment cells, cartilage, connective tissue, endocrine cells
29
Why are cells of the neural crest sometimes referred to as the "4th germ layer"?
Even though the cells give rise to neural tissue, they also give rise to a range of other tissue types
30
What kinds of animals have neural crest cells?
Vertebrates
31
The development of the trigeminal ganglion in humans forms...
Sensory neurons of the face
32
The neural crest eventually gives rise to this part of the nervous system
The PNS
33
The neural tube eventually gives rise to this part of the nervous system
The CNS
34
In early human brain development of the neural tube, there are 3 primary vesicles which can be referred to as...
Forebrain, midbrain, and hindbrain
35
After the 3 vesicle stage of neural tube development, there is further subdivision of the forebrain midbrain and hindbrain into... (5)
Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
36
The telencephalon later gives rise to these adult derivatives in humans
Olfactory lobes, hippocampus, cerebrum
37
The diencephalon later gives rise to these adult derivatives in humans
Optic vesicle, epithalamus, thalamus, hypothalamus
38
The mesencephalon later gives rise to these adult derivatives in humans
Midbrain
39
The metencephalon later gives rise to these adult derivatives in humans
Cerebellum and pons
40
The myelencephalon later gives rise to these adult derivatives in humans
Medulla
41
Dorsal patterning of the neural tube mostly happens through morphogen gradients of...
Shh
42
What is the overall purpose of gastrulation?
Establish the 3 germ layers, tissue becomes regionalized into dorsal-ventral axis
43
Describe involution
A type of cell movement which drives gastrulation, in which cells migrate under the dorsal blastopore lip
44
What does the blastocoel become in a fully developed vertebrate?
Becomes the inner cavity of the gut (does not give rise to a structure, rather, gives rise to a lack of structure)
45
Involution can be initiated due to changes in cell... (2)
Adhesion and morphology
46
Gastrulation begins on the (dorsal/ventral) side of the embryo
Dorsal
47
In deuterostomes, gastrulation begins on the (anterior/posterior) embryo
Posterior
48
The anterior neural tube eventually becomes this part of the CNS
Brain
49
The posterior neural tube eventually becomes this part of the CNS
Spinal cord
50
The yolky endoderm present in the neurula stage will eventually give rise to...
The structures of the gut
51
What is the energy source of a young tadpole in the beginning stages of its life?
Yolky endoderm
52
Describe the motility of a young tadpole while it is living off the yolky endoderm
Will not be motile, sitting around
53
Define a fate map
Map that outlines what a cell or tissue at an early stage of development will eventually become at a later stage of development
54
How could you develop a fate map?
Stain different parts of the embryo with dyes on agar (use landmarks like the dorsal lip) then investigate the location of the dyes at a later stage of development Alternatively: can do genetic fate-mapping now with GFP/fluo dyes
55
Describe the famous experiment which determined when neural and epidermal cell fates are specified. What were the key findings?
Spemann/Mangold experiment: Transplanted presumptive neural ectoderm and attached it to host embryo to see if it could induce formation of a secondary neural plate Early gastrula extraction + transplant: became epidermis (did not induce neural fate) Late gastrula extraction + transplant: became neural tissue Therefore, something must be happening during this phase to induce neural fate
56
How could you design an experiment to test when neural and epidermal cell fates are determined?
Extract different regions of tissue at different stages and try to grow them independently
57
What is the "default state" of the animal cap (dorsal) at the early gastrula stage?
Epidermis
58
What is the default state of the ectodermal tissue, epidermis or neural tissue? Why?
Neural tissue: because ectoderm becomes epidermis with BMP signaling, if tissue is grown in culture without BMP, will become neural
59
Describe where in the embryo the organizer is
In the dorsal mesoderm
60
What is the general role of the organizer?
Secrete BMP antagonists to induce formation of neural tissue
61
The structure responsible for formation of the organizer is called the...
Nieuwkoop centre
62
During the Spemann/Mangold experiments, describe which tissues (donor and host) are exhibiting neural fates and describe why this is important
Donor tissue becomes part of the neural tube, and the surrounding tissue which is also neural is from the host This is important because it demonstrates that it is not just the host tissue becoming neural, the donor tissue is also able to induce neural fates in the surrounding host tissue = must be secreting neural inducing factors
63
If only neural inducing factors are eliminated from an embryo, what is the default state of the dorsal ectoderm?
Epidermis
64
If both neural inducing factors AND BMP are eliminated from an embryo, what is the default state of the dorsal ectoderm?
Neural
65
Describe the theoretical basis of the Smith and Harland 1992 "fishing experiment." What important molecule did they discover?
Used LiCl on xenopus embryos > this results in highly dorsalized embryos = excess of "dorsal genes" Combined mRNAs from dorsalized and wild-type embryos, the like mRNAs will combine to each other and be subtracted, leaving behind the excess genes of the dorsalized embryos Found noggin
66
Describe Occam's razor?
The simplest theory or idea is often the correct one
67
Correlative studies on noggin by Smith and Harland demonstrated that noggin may be a good candidate gene for a neural inducing factor because...
It is expressed in the expected location at the right time
68
Briefly describe how the "odd-skipped" method of in situ hybridization works
mRNA probes are synthesized with DIG groups on them, which upon binding to the target mRNA are capable of catalyzing a reaction with a dark substrate, allowing visualization of the mRNA
69
How does noggin inhibit BMP signaling?
Binds to BMP ligand, sequestering it
70
BMP is a member of this family of signaling molecules
TGF-beta
71
Heterodimers of receptors in the TGF-beta signaling family commonly activate this downstream protein
Smad 2,3, which activates Smad 4 (Smad dimerization)
72
When Smad 2,3 and Smad 4 dimerize, what happens?
The complex is capable of entering the nucleus and can activate or repress transcription
73
BMP activates these downstream signaling molecules
Smad 1,5 and Smad4
74
What is a key source of BMP inhibitors in vertebrate development?
The organizer
75
Signaling from this molecule in this tissue layer helps in formation of the organizer
Beta-catenin from the dorsal endoderm
76
Beta-catenin and this other molecule are secreted from this centre, resulting in formation of the organizer
Wnt from the Nieuwkoop centre
77
Involution is driven by this population of cells
Bottle cells

Biology 467 (20 decks)

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