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BISC 407 > Chapter 52 - Patterning the Nervous System > Flashcards

Chapter 52 - Patterning the Nervous System Flashcards

1
Q

what are the 3 germ layers? what do they each develop into?

A
  1. ectoderm -> exoskeleton (skin + CNS)
  2. mesoderm -> organs
  3. endoderm -> inner linings of organs
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2
Q

what CNS precursor becomes regionalized early in embryogenesis?

A

the neural tube

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3
Q

what does the ectoderm give rise to?

A

the neural plate

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4
Q

what is the neural plate a precursor of?

A

the CNS and PNS

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5
Q

what gives rise to the neural plate?

A

the ectoderm

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6
Q

how does the neural tube form?

A
  • the neural plate buckles at its midline

- closure of the dorsal neural folds

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7
Q

what does the neural tube lie over?

A

the notochord

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8
Q

what is the notochord?

A
  • mesodermal tissues

- important organizational role

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9
Q

what does the notochord later become?

A

vertebral column

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10
Q

what is the neural tube flanked by?

A

somites

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11
Q

what are somites?

A
  • mesodemral cells

- give rise to muscle + cartilage

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12
Q

what is the neural tube?

A

-ectodermal tissue that becomes the entire CNS

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13
Q

what is the first major stage of neural tube development?

A

the formation of 3 brain vesicles

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14
Q

why are 3 brain vesicles formed?

A

-differences in rate of the proliferation of cells in the rostral regions of the neural tube

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15
Q

what is the second major stage of neural tube development?

A

-3 brain vesicles elaborate into 5

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16
Q

what drives progressive patterning and subdivision of cells/tissues in the neural tube?

A

-a variety of secreted molecules

17
Q

what is the organizer region?

A

-play an important “instructive” role in early differentiation

18
Q

where does the entire nervous system derive from?

A

-a restricted region of of the ectoderm

19
Q

what choice do ectodermal cells have early in development?

A

-whether to become neural or epidermal cells

20
Q

what happened when Spemann and Mangold transplanted organizer cells? what does this show

A
  • they followed their normal developmental program
  • caused change in fate of the neighboring ventral ectodermal cells of the host embryo
  • nervous system is induced by signals from a highly restricted organizing center
21
Q

What is the default fate of ectodermal cells?

A

-neural differentiation

22
Q

what is preventing ectodermal cells from becoming neural cells?

A

-signals from neighboring ectodermal cells

23
Q

what are BMPs?

A
  • group of growth factors

- play key roles in morphogenetic signaling

24
Q

what do BMPs do in the absence of organizer cells?

A
  • suppress the potential for neural differentiation

- promote epidermal differentiation

25
Q

what do BMP inhibitors do?

A

-block BMP signaling and enable cells to become neurons

26
Q

what are examples of BMP inhibitors?

A
  • noggin
  • chordin
  • follistatin
27
Q

how is the forebrain, midbrain, and hindbrain patterned?

A

signals from the mesoderm and endoderm

28
Q

what is Wnt?

A

-proteins that create a gradient and pattern the mid/hindbrain boundary

29
Q

where do Wnt signals come from?

A

-expressed by paraxial mesoderm

30
Q

where are Wnt inhibitors secreted?

A

-secreted by endoderm

31
Q

where are there more Wnt signaling activity?

A

lower at rostral levels of neural and higher at caudal direction

32
Q

how is the forebrain, midbrain, hindbrain patterning further refined?

A
  • 2 specialized cell groups
    1. zona limitans intrathalamica
    2. isthmic organizer
33
Q

what do zona limitans intrathalamica do?

A

-secret sonic hedgehog

34
Q

what does sonic hedgehog do?

A
  • patterns nearby cells that give rise to nuclei of the thalamus
  • also patterns spinal cord
35
Q

what does the isthmic organizer region do?

A

-secretes FGF signals which work with shh gradients to specify serotonergic and dopaminergic cells

36
Q

how do FGF signals work?

A

-express onto midbrain and hindbrain regions

37
Q

which transcription factors do the midbrain and hindbrain have?

A
  • midbrain (Otx2)

- hindbrain (Gbx2)

38
Q

how does FGF act to pattern/differentiate midbrain/hindbrain?

A
  • cells have already acquired Gbx2 or Otx2 transcriptional fate
  • receive the same FGF signal
  • but signal is interepreted differently

BISC 407 (3 decks)

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