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BIOC19 Animal Developmental Biology > Lecture 11: Ectoderm and Mesoderm Development > Flashcards

Lecture 11: Ectoderm and Mesoderm Development Flashcards

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1
Q

What are the three major derivatives of ectoderm?

A

Surface ectoderm - forms skin

Neural crest - forms periphery of NS

Neural plate/neural tube - forms CNS

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2
Q

What are the three major derivatives of ectoderm?

What does surface ectoderm form?

A

skin

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3
Q

What does neural crest form?

A

periphery of NS

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4
Q

What does the neural plate form?

A

the central nervous system

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5
Q

How is specification accomplished in the ectoderm?

A

Regulating levels of BMP

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6
Q

The epidermis has ______ levels of BMP while the neural plate was _____ levels of BMP

A

High levels = epidermis

Low levels = neural plate

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7
Q

Ectoderm development - Neurulation

What does it consist of?

A

Primary and secondary neurulation

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8
Q

Ectoderm development - Neurulation

Towards the front end

A

Rostral

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9
Q

Ectoderm development - Neurulation

Towards the tail end

A

Caudal

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10
Q

Nervous System Development

Neural tube differentiation into various region of the brain and spinal cord occurs ______

A

simultaneously

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11
Q

Nervous System Development

Neural tube differentiation into various region of the brain and spinal cord occurs simultaneously.

What are the levels that occur at the same time?

A

Cellular level - neuroepithelial stem cells differentiate into numerous types of NEURONS and GLIA

Tissue level - cell populations within neural tube arrange themselves into diff functional regions

Gross anatomical level - neural tube and its lumen bulge and constrict to form brain and spinal cord vesicles

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12
Q

Nervous System Development

Early development of vertebrate brains is ______

A

similar

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13
Q

Nervous System Development

Early development of vertebrate brains is similar.

What happens?

A

Neural folds start closing at the dorsal-most region

This forms the neural tube

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14
Q

NS Development - A-P Axis

In the anterior region (rostral), what happens to the neural tube?

A

It begins to differentiate into distinctive brain regions

Forebrain, midbrain, hindbrain

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15
Q

In nervous system development and forming of the A-P axis, what the neural tube begins to differentiate into distinctive brain regions.

Where does this occur?

What are they and what are they all called?

A

At the anterior (rostral) region

Forebrain
Midbrain
Hindbrain

PRIMARY VESICLES

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16
Q

NS Development - A-P Axis

In the posterior region (caudal), what happens to the neural tube by the time this end closes?

A

Five SECONDARY VESICLES form

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17
Q

What are the 5 secondary vesicles? Where do they form?

A

They form at the caudal region (posterior)

Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
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18
Q

Adult brain structures are derived from _____.

A

secondary vesicles

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19
Q

Adult brain structures are derived from secondary vesicles.

Patterning results in the formation of ______

A

territories

cells within a territory express unique combinations of TFs

specific patterns of differentiation

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20
Q

The A-P patterning of the hindbrain and spinal cord is controlled by what?

A

Hox gene complexes

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21
Q

What is another name for the hindbrain?

A

rhombencephalon

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22
Q

True or False: Polarity is also established along the DV axis of the neural tube.

A

True

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23
Q

Early neural tube is made up of ________

A

progenitor neuroepithelial cells divided into discrete domains

depends on which TF are present

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24
Q

As progenitor domains differentiate further, they eventually give rise to what?

A

specific neuronal cell types

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25
Q

Morphogenetic signals from the notochord induce ________

and overlying epidermis induces _______

A

Morphogenetic signals from the notochord induce ventral pattern and overlying epidermis induces dorsal patterns

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26
Q

Nervous System Development of D-V Axis

Specification initiated by gradient of which two major paracrine factors?

A

Sonic hedgehog (Shh) from the notochord

TGF-beta from dorsal ectoderm

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27
Q

Overlap of _____ and _____ specifies motor neurons

A

Overlap of Pax6 and Nkx6.1 specifies motor neurons

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28
Q

Experiment: Place a second notochord next to the neural tube. What happens?

A

Development of second set of floor plate and motor neurons.

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29
Q

Overall, several signalling gradients determine the differentiation of cells along the AP and DV axis.

Opposing gradients of Retinoic Acid (RA) and Fgf/Wnt (among other signals determine the fate of bipotential

A

neuromesodermal progenitor (NMP) cells

30
Q

The neurons are organized into different regions that arise from the three same basic zones.

What are these zones?

A

Ventricular zone

Intermediate zone

Marginal zone

31
Q

The neurons are organized into different regions that arise from the three same basic zones.

What are the ventricular zone?

A

Layer next to the lumen of the neural tube.

It forms ependyma (epithelial lining of brain and spinal cord cavities)

32
Q

What is the epithelial lining of brain and spinal cord cavities called?

A

ependyma

33
Q

The neurons are organized into different regions that arise from the three same basic zones.

What is the intermediate zone?

A

aka mantle

cells differentiate into both neuronal and glial cells –> forms grey matter

34
Q

What si the intermediate zone also known as?

A

The mantle

35
Q

The neurons are organized into different regions that arise from the three same basic zones.

What is the marginal zone?

A

Neuronal cell-poor regions but enriched in axons

—> forms white matter

36
Q

What forms white matter?

A

The marginal zone - regions that are poor in neuronal cells but rich in axons

37
Q

What forms grey matter?

A

The intermediate zone - where cells differentiate into neuronal and glial cells

38
Q

Why is the neural crest sometimes called the “fourth germ layer”?

A

It gives rise to many cell types

39
Q

What are the 4 major steps of neural crest development?

A
  1. Specification at the border of the neural plate
  2. Localization at the neural fold apex
  3. Delamination at the point of neural tube closure
  4. Migration
40
Q

Neural cell crest delamination and migration is dependent on:

A

Gradients of signalling molecules

Cytoskeletal remodelling

Differential expression of cell adhesion molecules

Positive and negative interactions between signalling molecules

41
Q

Neural cell crest differentiation/commitment will depend on the factors that are present at a given time and location

Name the four kinds of cells.

These cells are committed and act as their respective progenitor cells

A

C = Cartilage/bones

G = Glia

N = Neurons

M = Melanocytes

42
Q

What are the types of neural crest?

A

Cranial (Cephalic) Neural Crest

Cardiac Neural Crest

Trunk Neural Crest

Vagal and Sacral Neural Crest

43
Q

What are the types of neural crest?

What does the Trunk Neural Crest form?

A

Cranial (Cephalic) Neural Crest

Cardiac Neural Crest

Trunk Neural Crest

Vagal and Sacral Neural Crest

Trunk Neural Crest

  • Dorsal root ganglia
  • Adrenal medulla
  • Nerve clusters surrounding the aorta
  • Melanocytes
44
Q

What does the Cranial (Cephalic) Neural Crest form?

A

cranial nerves

bone

cartilage

connective face tissue

45
Q

What does the Cardiac Neural Crest form?

A

septum that separates the pulmonary circulation from aorta

46
Q

What does the Vagal and Sacral Neural Crest form?

A

parasympathetic NS of the gut and digestive system

47
Q

Cranial neural crest cells migrate to produce

Various migratory pathways into the pharyngeal arches (p1-4) form a number of structures

A

cranio-facial structures

i.e.
cranial nerves

bone

cartilage

connective face tissue

48
Q

Mesoderm Development

What are the four major derivatives of mesoderm?

A

Intermediate mesoderm - forms kidneys, gonads

Chordamesoderm - forms notochord

Paraxial mesoderm - forms head, somites

Lateral plate mesoderm - circulatory system, body cavity, limb bones, etc

49
Q

What does the head and somites form from?

A

Paraxial mesoderm

50
Q

What does the chordamesoderm form?

A

notochord

51
Q

What do kidneys and gonads form from?

A

intermediate mesoderm

52
Q

What does the lateral plate mesoderm form?

A

circulatory system, body cavity, limb bones etc.

53
Q

What is the developmental process of forming somites from paraxial mesoderm called?

A

somitogenesis

54
Q

Somitogenesis

Initial patterning is called ______ is via Hox genes (thought to work via chromatin remodeling)

A

presomitic mesoderm

55
Q

Somitogenesis

Forms ____ to ____

A

Forms rostral (head) –> caudal (tail)

All skeletal muscles develop from somites (craniofacial muscles are an exception)

Form in all vertebrates but numbers vary between species

56
Q

All skeletal muscles develop from somites.

What is the exception?

A

Craniofacial muscles

57
Q

Somite formation requires
_________

Once the somite is formed, it is surrounded by the ________ cells.

A

mesenchyme-to-epithelial transition (MET)

58
Q

What is the dorsolateral portion of the somites called?

What does it contain?

A

Dermomyotome

contains progenitor cells for skeletal muscle and dermis

59
Q

What are the various ‘zones’ contain progenitor cells for a number of structures called?

What is its function?

A

Sclerotome

maintains segmental arrangement

60
Q

The fate of somite cells depends on the signals received from

A

adjacent tissues

i.e. notochord induces sclerotome

61
Q

Somite formation results from _______ along the embryonic axis resulting in cyclic gene expression.

Involves formation of gradients of a number of factors (e.g. FGF8, WNT3A which then induce other transcription factors)

What is this model called?

A

molecular oscillations (clock)

Clock and Wavefront Model

62
Q

What is the developmental process of forming muscles called?

A

Myogenesis

63
Q

What are the three major phases of myogenesis?

A

Commitment - muscle precurssor cells (myoblasts) become restricted to the myogenic pathway

Differentiation - transcription of skeletal muscle and fiber-specific genes

Maturation - final changes to form muscles fibres

64
Q

Neural tube and notochord promote determination of myotome cells through

A

paracrine factors

i.e. Wnt, Shh which then induce the activation of muscle specific transcription factors such as MyoD, Myf5

65
Q

Once growth factors are used up, myoblasts (mononucleated) exit the cell cycle, align together and fuse to form

A

myotube – multinucleated single large cell

66
Q

Myoblast recognition and alignment occurs only with other myoblasts (e.g. chick and rat myoblasts fuse in vitro not species specific)

Fusion mediated by meltrins (metalloproteinases – proteases that require metal ions to function)

A

induces activation of myogenin – muscle specific regulatory factor that is necessary for differentiation

67
Q

Myotubes mature and organize to form contracting muscle fibers

Myostatin (belongs to TGF-β family) negatively regulates muscle development —> loss-of-function mutation results in muscle hypertrophy (larger fibers) and hyperplasia (more fibers)

Myostatin inhibitors (e.g. Myo-X) are (ab)used in body-building

A

Loss of function of myostatin results in muscle hypertrophy (larger fibers) and hyperplasia (more fibers)

68
Q

What is used in growth and generation of muscles in adults?

A

A population of stem cells/progenitor cells resides along the adult muscle fibers

there are called satellite cells

69
Q

What is the first functional organ in the developing embryo?

Hint: It is critical to the circulatory system

A

The heart!

70
Q

Heart development starts with the formation of _______ and _______

A

primary and secondary heart fields (aka cardiogenic mesoderm)

Heart development starts with
- formation of primary and secondary heart fields (aka cardiogenic mesoderm) at the cardiac crescent stage

  • followed by formation of heart tube that then loops and partitions to form different chambers
71
Q

Heart Cell Differentiation

Heart cell types differentiate from lateral plate mesoderm to form

A

multipotent cardiovascular progenitor cells

which further differentiate into specific cell types based on signals and receptors

BIOC19 Animal Developmental Biology (6 decks)

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