early development of the nervous system

Question 1

what are the 3 layers formed during gastrulation?

Answer 1

ectoderm, mesoderm, endoderm

Question 2

when does gasturalation start and when does neurulation occur?

Answer 2

@7 days

neurulation occurs at the same time as gastrulation

Question 3

what is the primitive streak?

Answer 3

it defines the midline ( starts in the posterior and proceeds anteriorly

Question 4

what happens by the end of gastrulation?

Answer 4

the midline of of the embryo is defined by the formation of the notochord.

this is critical for the formation of all tissue including the CNS.

Question 5

what is the first event in neurogensis?

Answer 5

the formation of neural ectoderm which is induced by the defined midline ( notochord formation)

Question 6

what is the notochord formed of?

Answer 6

mesoderm and is a transient structure which is completely replaced by the neuroplate in humans

Question 7

if ectoderm is exposed to bone morphogenic proteins (BMPs) then they become___________

Answer 7

epidermis

Question 8

if ectoderm exposed to noggin/chordin (( and follistatin) all produced in the notochord) then it becomes____________

Answer 8

neuroectoderm

Question 9

noggin and chordin inhibit_____________

Answer 9

bone morphogenic proteins (BMPs)

thus in the absence of BMPs ectodermal precursor cells will become neurons

Question 10

bone morphogenic proteins (BMPs) come from ?

Answer 10

mesoderm

Question 11

BM binds to ____________ and ___________ that is transported to the nucleus to mediate transcription.

Answer 11

receptor kinases and a SMAD complex

Question 12

Besides inhibition of BMP, inhibition of what other signaling promotes stem cell commitment to neural cells?

Answer 12

inhibition of:

1. Nodal signaling
2. Wnt signaling

Question 13

stimulation of ________,____________, and ___________ induce neural stem cell formation

Answer 13

retinoid acid (RA)
fibroblast growth factor (FGF)
insulin-like growth factor (IGF)

Question 14

why is it that when separated ( a petri dish for e.g.) from the other layers ( mess and endo -derm) does ectoderm form neurons but when intact it forms epidermis?

Answer 14

because BMPs needed to form epidermis comes from mesoderm.

Question 15

what does fibroblast growth factor (FGF) do?

Answer 15

it stimulates production of nogin which in turn inhibits BMP and leads to neural induction.

Question 16

what cells make up the neural tube?

Answer 16

neural stem cells

Question 17

after neural induction what happens to the neural plate?

Answer 17

the lateral margins of the neural plate fold inward to form the neural tube.

Question 18

the floor plate and roof plate of the neural tube are key for_______

Answer 18

signaling

Question 19

the central nervous system is a ( think shape)____________

Answer 19

a tube

Question 20

_____________, particularly _____________ is important for the closure of the neural tube.

Answer 20

b-complex vitamins, especially folic acid

Question 21

what is anencephaly?

Answer 21

lack of fore brain

Question 22

what does the neural crest give rise to?

Answer 22

peripheral nervous system, cartilage, bone, connective tissue, pigment cells, and sympathy-adrenal cells

Question 23

what are some neural tube closure defect?

Answer 23

spina bifida ( most common)- failure of posterior end of the neural tube to close

anacephaly and holoprosencephaly ( both typically deadly)

Question 24

formation of the neural plate and neural groove are _________dependent

Answer 24

sonic hedgehog dependent

Question 25

sonic hedgehog is expressed____________

Answer 25

is expressed only in the notochord and fore plate

Question 26

the ventral signal ( motor) is?

Answer 26

sonic hedgehog (Shh)

Question 27

the dorsal signal ( sensory) is?

Answer 27

TGF betas ( mainly BMP)

Question 28

Sonic Hedgehog absence in the roof plate produces _______

Answer 28

dorsal-ventral polarity ) see pg 42

Question 29

describe Sonic hedgehog signaling (Shh)

Answer 29

Shh binds to patched protein which relieves Patched protein dependent inhibition of smoothened thus changes the identity of the cell (cell fate).

Question 30

what does smoothened do?

Answer 30

smoothened activates the Gii class zinc finger transcription factors

Question 31

what does Gli do?

Answer 31

Gli induces transcription and leads to a ventral (motor neuron) cell fates.

Question 32

what can absence of Shh result in?

Answer 32

holoprosencephaly - forebrain does not form and Dorsal ventral pattern is disrupted. cancers like: medulloblastomas, and basal cell carcinoma cyclopia- one eye ( seen in humans and in sheep ( sheep ate cyclopamine and Shh antagonist))

Question 33

what does Shh regulate?

Answer 33

polarity and proliferation

Question 34

in addition to BMPs and Shh pathways ______ and _________play a key role in dorsal ventral pattenrning

Answer 34

retionic acid ( RA) and fibroblastic growth factor (FGF)

Question 35

what are Hox genes?

Answer 35

transcription factors critical for body plan ( patterning): really only for the hindbrain, research is going on to figure out what goes on in the forebrain

Question 36

what is symmetric differentiation?

Answer 36

differentiation into 2 neurons or 2 neuronal stem cells

Question 37

what is asymmetric differentiation?

Answer 37

differentiation into a neuron and a different neuronal stem cell

Question 38

where do nerve stem cells proliferate and differentiate?

Answer 38

in the ventricular zone ( which surrounds the CSF-filled ventricles)

Question 39

inhibition of notch gives rise to?

Answer 39

neurons

Question 40

what cells have a lot of notch?

Answer 40

neurostem cells which inhibits pro neural genes and keeps it in a pleuripotent state and down regulates delta

Question 41

what do pro neural genes do?

Answer 41

they inhibit differentiation of glia

Question 42

why does the brain get bigger after birth?

Answer 42

brain gets bigger because of continuing connections made after birth and myelination

Question 43

what does anterior posterior patterning lead to?

Answer 43

spinal cord, rhombencephalon ( future pons and medulla), mesencephalon- future midbrain, prosencephalon ( future thalamus and retina, and future forebrain

Question 44

how do hox genes work?

Answer 44

by repressing and enhancing each other to create unique patterns of gene expression in each segment

Question 45

neural progenitors give rise to?

Answer 45

neurons and glia

Question 46

in early development how to neural stem cells divide?

Answer 46

symmetrically

Question 47

as development continues how doe neural stem cells divide ?

Answer 47

asymmetrically

Question 48

late in development how do neural stem cells divide?

Answer 48

symmetrically but giving rise toe 2 neural precursors thus neural stem cells disappear

Question 49

how do neural precursor cells divide?

Answer 49

symmetrically and asymmetrically

Question 50

neurogensis proceeds ____________

Answer 50

gliogenesis

Question 51

vitamin A excess or to little vitamin A, or drug abuse lead to?

Answer 51

birth (neural) defects

Question 52

cells made earlier are closer to the ________ and cells made later are closer to the ______

Answer 52

ventricular surface pial surface

Question 53

where are projection neurons made?

Answer 53

the ventricular zone

Question 54

what is lissencephaly?

Answer 54

failure of gyri ( or fold ) formation

Question 55

where are interneurons made?

Answer 55

in the lateral or medial ganglionic eminence along the ventricular zone

Question 56

what path do interneurons take?

Answer 56

the tangential path for migration through the CSF. they migrate based on where the projection neurons went.

Question 57

when does neurogenesis in humans end?

Answer 57

by the end of the middle of the second trimester ( 19 weeks)

Question 58

when does gliogenesis end in humans?

Answer 58

sometime after birth ( to about 20 years old)

Question 59

when is primary neurulation complete?

Answer 59

within the first 3 weeks of pregnancy

Question 60

how does the cortex form?

Answer 60

in an inside out manner the first layer formed is closest to the ventricular zone

Question 61

what do radial gill cells do?

Answer 61

they rise to neurons and provide scaffolding on which they can migrate to their appropriate destination ( see pg 68)

Question 62

what does a mutation in the extracellular matrix protein reel in do?

Answer 62

results in a disruption of radial migration and causes earliest neurons to be on the outer surface rather than the inner surface near the ventricular zone.

Question 63

what are Mash1 and DLX1 and DLX2 involved in?

Answer 63

interneuron tangential migration

Question 64

describe how notch and Bhlh signaling resulate neural stem cell differentiation

Answer 64

see board (fill in later)