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NEUROSCI 304 > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

Stages of (frog) Development

A
  1. Gametogenesis
  2. Fertilization
  3. Cleavage
  4. Gastrulation
  5. Organogenesis
  6. Larval Stages
  7. Maturity
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2
Q

Blastula forms during …

A

Cleavage

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3
Q

Blastocoel, blastopore, germ layers and body topology form during …

A

Gastrulation

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4
Q

Oocyte Content and Cleavage

A
  • Oocyte size and yolk content depends on the needs of the growing embryo
  • Cleavage pattern is affected by oocyte structure (yoke content)
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5
Q

T or F: amphibians and amniotes show differences in gastrulation and embryo patterning

A

T

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6
Q

Sperm vs. Oocytes

A

Sperm: divide into 4 haploid cells
Oocytes: uneven division of cytoplasm leading to one, large haploid cell that usually has all cytoplasm/material in it

Takeaway: Meiosis between sperm cells and oocytes is different

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7
Q

Why are frog embryos a good model for studying development?

A
  1. Easy to understand in 3D
  2. Produce a lot of eggs
  3. Larger eggs (relatively)
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8
Q

Blastula

A
  • Forms during fertilization
  • Where germ cells are located
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9
Q

Zygote

A

A fertilized egg, containing a full set of chromosomes from each parent

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10
Q

Blastomere

A

Cell that results from division of zygote

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11
Q

Cell divisions are ___________ (complete) but unequal

A

holoblastic

This means the cytoplasm is cut completely

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12
Q

What does the vegetal pole contain? Explain what it is and what it does.

A

The yolk: mixture of proteins, lipids, carbs, and vitamins that support embryonic growth. Inhibits cell division.

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13
Q

T or F: The animal pole divides faster than the vegetal pole, so there are more cells at the animal pole.

A

T

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14
Q

Where is the blastocoel and what does it look like?

A

The blastocoel forms inside the blastula (which forms from the morula), and it is like a liquid-filled center

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15
Q

The 12th Division

A

Up until the 12th division: Embryo is running on maternally derived RNAs. Zygotic genes are not active yet.

After the 12th division: Zygotic genes transcribed and embryo runs on its own genes. This leads to individual variation.

Mechanism for activating zygotic gene transcription involve epigenetic changes that affect chromatin structure.

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16
Q

Important Purposes of Gastrulation. Generally, what happens?

A
  1. Layers
  2. Planes of symmetry

Cells migrate into interior of developing embryo in a process called involution. From this, topological differences emerge.

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17
Q

Explain topologically inside vs. topologically outside

A

Topologically inside is when you cannot come in contact with something from the outside

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18
Q

Phylogenetic Classification: Protostomes vs. Deuterostomes

.. and then Amniotes

A

Protostomes: mouth first
Deuterostomes: mouth second
(Division based on what the first hole gives rise to in gastrulation)

Amniotes have an amniotic sac (i.e., chickens, mice, and humans

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19
Q

Amniotes and their common extra-embryonic membranes

A

Food: Yolk
Waste management: Allantois
Blanket: Amniotic cavity

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20
Q

Chicken vs. Human embryo

A

In humans, the embryo gets nutrients from the mother, replacing the function of the allantois and yolk (even though they are still present)

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21
Q

Amniotes (mammals and birds): similar and different patterns

A

Different early cleavage patterns but similar gastrulation and embryo patterning and overall embryo structure

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22
Q

Where is CNS derived from? Where is PNS derived from?

A

CNS: ectoderm via neurulation (forms neural tube)
PNS: neural crest cells and placodes (ectodermal structures)

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23
Q

Match the animal to the cleavage pattern.

Mammal
Chick
Holoblastic
Meroblastic

A

Mammal: holoblastic (complete cleavage)
Chick: meroblastic (incomplete cleavage)

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24
Q

Meroblastic Cleavage

A

Blastomeres are still partially connected (incomplete cleavage)

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25
Q

Zona Pellucida

A
  • Tough ECM shell that covers early embryo
  • Prevents embryo from implanting ectopically
  • Blastula digests and “hatches” from zona pellucida, usually in uterus
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26
Q

Ectoderm, Mesoderm, Endoderm and what they give rise to

A

Ectoderm: nervous system, epidermis, lining of mouth and anus
Mesoderm: dermis, muscle, vasculature, skeleton, gonads, kidneys
Endoderm: stomach, intestine, bladder, lungs

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27
Q

Induction

A

Influencing cell fate through cell-cell interaction

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28
Q

In what direction does chick neurulation proceed and what end develops earlier?

A

Anterior to posterior
The anterior end develops earlier

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29
Q

Neural tube closure in mammals

A
  • Tube “zips up” along the middle from anterior to posterior
  • Neuropores are holes on either end of the tube filled with amniotic fluid and are eventually closed and form a separate compartment
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30
Q

T or F: The brain cannot develop in the presence of amniotic fluid

A

T

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31
Q

Craniorachischisis

A
  • Open brain and spinal cord
  • Incompatible with life
  • Soft tissue doesn’t develop properly - Brain degenerates
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32
Q

Anencephaly

A
  • Failed closure of anterior neuropore
  • Brain protrudes from cranium and then degenerates
  • Inside skull
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33
Q

Spina Bifida

A
  • Failed closure of posterior neuropore
  • Can be covered or exposed
  • Can range from mild to severe
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34
Q

Neural tube defects have been related to ___________ deficiencies.

A

Folate (Vitamin B9)

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35
Q

Match the neuron to the horn.

Sensory neurons
Motor neurons
Dorsal horn
Ventral horn

A

Sensory neurons: dorsal horn
Motor neurons: ventral horn

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36
Q

Neural tube gives rise to

A

CNS (brain, spinal cord) and retina

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37
Q

Neural crest gives rise to

A

PNS (sensory and autonomic neurons, Schwann cells)

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38
Q

Ectodermal placodes give rise to

A

Special sensory structures (olfactory epithelium, vestibular and auditory inner ear)

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39
Q

Placode

A

Specialized portions of ectoderm that thicken and differentiate into neural and non-neural structures (stay in epithelium). Forms just outside developing neural plate

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40
Q

Olfactory system/placodes

A
  • Form along with neural plate
  • Derived from cells that reside at edge of neural tube from same tissue as CNS
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41
Q

Development of olfactory placode

A

Curls in/invaginates and then becomes complex (epithelium filled with neurons)

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42
Q

When does neural cell fate specification happen around?

A

Fertilization

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43
Q

Hans Spemann (1920s) Two-Cell Blastomere Separation

A
  • Zygote has patch of cytoplasm called gray crescent
  • Separated blastomeres containing gray crescent produce normal embryos BUT separated blastomeres without gray crescent led to abnormalities: no dorsal tissues, disorganized ventral belly piece
  • So, it was concluded that cells from the gray crescent form the dorsal lip of the blastopore
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44
Q

Spemann and Mangold (1920s) Dorsal Blastopore Transplantation

A
  • Transplanted dorsal lip of one newt embryo into ventral surface of another (donor was pigmented for detection and newt embryo was albino)
  • Second site of gastrulation and second body axis induced
  • Dorsal lip transplant becomes mesodermal structure called notochord
  • You get conjoined twins with their own nervous systems, d/v axes, and a/p axes
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45
Q

What is “The Organizer?”

A

Dorsal lip of blastopore

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46
Q

The Organizer: has dorsal lip cells that…

A
  1. Initiate gastrulation
  2. Dorsalize central tissues (neural induction: ventral ectoderm to neural ectoderm, ventral mesoderm to dorsal mesoderm/somites)
  3. Define complete body axes (d/v, a/p)
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47
Q

Induction

A

Process by which embryonic cells in one part of the embryo influence the developmental fate of surrounding cells

Plays crucial role in development of neural ectoderm, eyes/lens, heart

48
Q

What organizes The Organizer?

A

The oocyte

  • Gray crescent is positioned opposite the point of sperm entry through rotation of oocyte cytoplasm
49
Q

B-catenin

A

Transcription factor that initiates dorsal fate

Stabilized in dorsal embryo by protein complex

Acts as dorsal signal (dorsal lip -> notochord -> mesoderm)

50
Q

Nodal

A

Protein secreted from vegetal cells that induces mesoderm to form in neighboring cells by interacting with cells just above them

51
Q

B-catenin and nodal signaling overlap in ______________

A

The Organizer

52
Q

What is the blastocoel doing when nodal is at work?

A

Preventing nodal from affecting the ectoderm

53
Q

Cells become what before gastrulation?

A

Mesoderm

Dorsal mesoderm is where gastrulation begins

54
Q

What about changes in ectodermal cell fate?

A

The newly formed dorsal mesoderm may interact with the ectoderm, leading it to form the nervous system

55
Q

Spemann (1918) Ectodermal Transplant in Early vs. Late Gastrula

A

EARLY:
1. Remove ectoderm (that would become nervous system)
2. Transplant to region that would become ventral epidermis
Result: transplanted ectoderm became epidermis, so dorsal ectoderm takes on identity of final transplant location

LATE:
^ Same procedure as above
Result: transplanted ectoderm becomes nervous system, so dorsal ectoderm restricted to nervous system during gastrulation

56
Q

Ectoderm and its induction

A

Ectoderm no induction = epidermis
Ectoderm induction = neural
Ectoderm single cells = neural

Takeaway: Neural cell fate is the default

57
Q

BMP4

A
  • Produced by ectodermal cells onto each other
  • Acts on TGFB receptors to inhibit neural differentiation/neural fate (they become epidermis)
58
Q

noggin, follistatin, and chordin

A
  • BMP inhibitors released by newly formed dorsal mesoderm
  • Disrupt BMP4 signaling in overlying ectoderm, which becomes neural plate
59
Q

Prosencephalon and its vesicles

A

Forebrain (most anterior)
1. Telencephalon
2. Diencephalon

60
Q

Mesencephalon and its vesicles

A

Midbrain
1. Mesencephalon

61
Q

Rhombencephalon and its vesicles

A

Hindbrain (most posterior)
1. Metencephalon
2. Myelencephalon

62
Q

T or F: Drosophila’s body plan is defined in the embryo (early on in development)

A

T

63
Q

AP patterning in flies: A? P?

A

A: bicoid
P: nanos
These are RNAs unequally deposited into the oocyte by the mother

64
Q

Bicoid and nanos

A
  • Locally translated after fertilization
  • Are morphogens that form opposing concentration gradients
65
Q

Morphogen

A

Protein that is non-uniformly distributed and acts in a concentration-dependent manner to determine cell identity

65
Q

Bicoid LOF vs. GOF

A

LOF: two tails
GOF: two heads

66
Q

Bicoid and nanos and the subsequent cascade

A

Bicoid and nanos set up a cascade of TFs that further divides the embryo into increasingly smaller segments with well-defined borders

67
Q

The types of genes in the bicoid-nanos cascade

A

Maternal polarity
Gap genes
Pair-rule genes
Segmented polarity genes
Homeotic/Hox genes

68
Q

Hox genes

A
  • Encode TFs
  • Turn on/off other genes to define identity of fly segments
  • Found in clustered arrays
69
Q

Colinearity

A

Spatial expression matches genomic location. Anterior-posterior follows 3’-5’ arrangement of genes in cluster

70
Q

Specific Hox genes and what they do

A

Ubx: in 3rd thoracic segment, deletion converts T3 to T2 and duplication of T2 makes 2 sets of wings
Antp: expressed in T2 and T3
abd-A: not expressed in T2 nor T3

71
Q

Hox Code Hypothesis

A

The identity of a segment can be determined by a unique combination of TFs that are expressed in that cell

72
Q

T or F: Effects of gene mutations are typically more subtle than in flies

A

T

73
Q

T or F: Hox genes are duplicated in multiple clusters in mammals

A

T

74
Q

Homolog vs. Paralog vs. Ortholog

A

Homolog: gene that looks like another gene (related to common ancestor gene)
Paralog: Homologs in same organism
Ortholog: Homologue in another species

75
Q

A/P patterning in mammals?

A

Wnt (high in posterior end)
Early gradient of Wnt parses ectoderm into different domains

76
Q

Wnt-B catenin pathway

A
  1. Wnt activates frizzled and LRP5/6
  2. Protein complex with B-catenin is recruited to receptor complex
  3. B-catenin released and translocated to nucleus
  4. B-catenin binds to TCF to form activating TF
    Ultimately: regulates gene expression.
77
Q

Segmentation of the rhombencephalon (hindbrain)

A

8 rhombomeres each giving ice to unique set of neurons and brain regions (unique combination Hox genes). Transient segments in developing rhombencephalon

78
Q

What happens when you delete a Hox gene in rhombomere segments?

A

Facial motor neurons (normal) to trigeminal-like motor neurons

79
Q

D/V patterning

A

Also determined by morphogens (gradient of identity)
Recall: dorsal sensory, ventral motor

80
Q

Notochord

A
  • Transient structure made of axial mesoderm (chordamesoderm), so presence defines chordates
  • Induces ectoderm to become neural tube
  • Morphogen source of Sonic Hedgehog protein to specify ventral neural tube
  • Forms central part of invertebrate discs of spinal column in adult vertebrates
81
Q

Morphogens and their 3 characteristics

A
  1. Emanate from a source
  2. Diffuse to form non-uniform distribution
  3. Induce concentration-specific changes in gene expression
    Cells closer to morphogen have more of a response
82
Q

T or F: You don’t need multiple morphogens to give rise to multiple cellular identities–it can be achieved with different concentrations of the same morphogen

A

T

83
Q

BMP and Shh

A

BMP: dorsal to ventral. Roof plate; these cells can now secrete BMP.
Shh: ventral to dorsal. Floor plate; these cells can now secrete Shh.

84
Q

Shh and other developmental mechanisms

A
  1. AP axis of limbs
  2. Split prosencephalon into left and right hemispheres (affects facial development)
85
Q

Holoprosencephaly

A

Failure of prosencephalon to form 2 distinct hemispheres (genesis of corpus callous to cyclopia)

86
Q

BMP: MAP Kinase and SMAD pathways

A

BMP receptor gets phosphorylated and activates pathways to affect gene expression

87
Q

TF Cross-Repression

A

Expression of one TF inhibits the transcription of another (Olig2 represses Nkx22 and vice versa)
- Happens in single cells (conversion occurs in “winner takes all” process)
- Initial gradient of expression give sharp boundary

88
Q

Pia

A

Innermost meningeal layer

89
Q

Neuroepithelial cells

A
  • Rapidly dividing multipoint stem cells
  • Give rise to more neuroepithelial cells
  • Give rise to radial glia
90
Q

Totipotent, pluripotent, and multipotent stem cells

A

Totipotent: cells in extra embryonic membranes, early cell type, can become anything
Pluripotent: cells in embryo proper, give rise to any cell in embryo proper
Multipotent: give rise to several cells types (neurons and glia arise from radial glia)

91
Q

Neural progenitor cells

A

Limited capacity to divide and restricted to becoming on of a few cells types. Not self-renewing.

92
Q

Neuroblast

A

No longer dividing cell and differentiates into neuron

93
Q

Nuclear migration in neural tube directionality

A

Apical to basal

94
Q

Stem cell mitosis in neuroepithelium

A

Go to apical surface to divide and then come back up to basal surface

95
Q

Symmetric vs asymmetric division of cells in neuroepithelium

A

Self-renew stem cells vs. give rise to other cell types (neuroblasts)

Asymmetric inheritance of par protein complex

96
Q

Radial glia can give rise to

A

Neuroblasts, intermediate progenitors, glia through symmetric and asymmetric divisions

Radial glia are transient cell type

97
Q

Processes of a glial cell

A

Highway for daughter cells to migrate

98
Q

Intermediate Progenitors

A

Migrate up to subventricular zone (SVZ), resulting daughter cells become neurons and intermediate progenitors

Intermediate progenitors greatly amplify the number of neurons that can be produced by radial glia

99
Q

Cortical plate

A

Developing cortex

100
Q

T or F: The cortex is built for inside out

A

T

101
Q

Building cortex with early and late born neurons

A

Early born neurons migrate to cortical plate and start differentiating. Late born neurons migrate past them into superficial layers. Think: inside first, outside last

102
Q

Type 1/Classical Lissencephalies (smooth brain, less cortex)

A

Mutations in several genes that impact neuronal migration/microtubule function

Symptoms: hypotonia, seizures, mental disability, often fatal. Relatively rare.

103
Q

Proneural genes vs Hes genes

A

Proneural: trigger neuronal and inhibit stem cell identity
Hes genes: promote stem cell and inhibit neuronal identity

104
Q

Notch Pathway in radial glial cells

A

Ligand: delta
Receptor: notch
1. Binding of delta to notch activates He’s genes (stem cell fate promotion)
2. Hes turns off pro neural genes
3. Proneural genes turn on delta expression

105
Q

What happens to cortex size if you inhibit Notch in radial glia?

A

Cortex gets smaller because you make all neurons early and don’t invest in the future by creating stem cells that can alter give rise to more neurons). Without notch, you can’t reinforce radial glial cells, so you just get neuroblasts.

106
Q

NOTCH2NL Deletion

A

Deletion: microcephaly
Duplication: macrocephaly

Overtime, NOTCH2NL was repaired to correct a disrupted gene, and we now have an extra copy that changed cortical development in modern humans

107
Q

Neural Crest and the cells there

A

Cells at neural plate border undergo an epithelial-to-mesenchymal transition–this process is called delamination (neural tube folds over)

108
Q

Head vs. Trunk neural crest

A

Head: Sensory neurons, Schwann Cells, Melanocytes, Bone & Cartilage
Trunk: Autonomic neurons (sympathetic and parasympathetic), Sensory neurons Schwann cells, Melanocytes, Adrenal Medullary cells

109
Q

Post vs Pre ganglionic cells

A

Post: cell bodies in ganglion (neural crest)
Pre: projections to periphery from spinal cord (neural tube)

110
Q

Parasympathetic vs Sympathetic neurons and their derivations

A

Para: vagal and sacral neural crest
Sympathetic: trunk neural crest

111
Q

LeDouarin’s Quail-Chick Chimeras

A

Trunk neural crest placed in head became cholinergic and head neural crest placed in trunk became adrenergic

Takeaway: transplanted neural crest took on identity of new position (potential to become other things)

112
Q

Fate of neural crest cells is strongly influenced by

A

Environment (e.g., chemical cues)

113
Q

Dorsolateral pathway vs ventral pathway

A

Dorsal: melanoctyes
Ventral: Schwann cells, sensory, autonomic neurons, adrenal medullary cells

114
Q

Adrenal medulla

A

A modified postganglionic sympathetic ganglion

Ventrally migrating sympathy-adrenal neural crest cells become sympathetic and adrenal chromatin cells (driven by local glucocorticoids from develop adrenal cortex)

NEUROSCI 304 (2 decks)

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