Intro to developmental neuroscience

Question 1

Induction

Answer 1

signal originating in one tissue that causes another responsive tissue to differentiate into something else

Question 2

Inducer

Answer 2

chemical signalling molecule

short range or long range

Question 3

from stem cell to neuron

Answer 3

competent neural precursor
specified neural precursor
committed neural precursor
differentiation

Question 4

from stem cell to radial glial cell

Answer 4

neuroepithelial cells
early radial glial cell
neuron or late radial glial cell eg astrocyte
can replenish previous pool

Question 5

Model organism example and steps in development

Answer 5

xenopus

egg - blastula - gastrula - neurula

Question 6

2 poles of egg

Answer 6

vegetal - unpigmented, heavy, full of yolk

animal - pigmented

Question 7

Where does grey crescent form?

Answer 7

directly opposite where sperm enters

Question 8

what does grey crescent determine?

Answer 8

d/v axis - ventral = sperm comes in, dorsal = grey crescent

Question 9

what does 1st division do to grey crescent?

Answer 9

splits it in half

Question 10

animal pole cells are?

Answer 10

smaller

Question 11

gastrulation

Answer 11

cells migrate towards inside of embryo through the blastopore to form 3 germ layers

Question 12

ectoderm

Answer 12

CNS, PNS, skin, hair

Question 13

mesoderm

Answer 13

blood, muscle, cartilage, kidneys

Question 14

endoderm

Answer 14

GIT and RT lining, liver, thyroid

Question 15

purse string contraction

Answer 15

in neurulation the flat ectoderm thickens to form a neural plate by contraction and then a hollow neural tube

Question 16

border cells of neural plate become what?

Answer 16

neural crest

Question 17

neural crest cell migration

Answer 17

laterally to form PNS, including spinal ganglia

Question 18

What happens to the notochord?

Answer 18

degenerates and only persists in IV discs

Question 19

contact between notochord and neural tube

Answer 19

physical - allows induction

Question 20

dorsal lip transplantation

Answer 20

Spemannn and Mangold 1924

Question 21

Explain dorsal lip transplantation

Answer 21

dorsal lip of blastopore cut out

transferred to ventral site

Question 22

dorsal lip transplantation control

Answer 22

ventral tissue grafted to ventral position

Question 23

findings from dorsal lip transplantation

Answer 23

active = 2 neural tubes, 2 complete nervous systems without ventral tissues 
control = normal embryo

Question 24

what is the spemann organiser?

Answer 24

dorsal lip of blastopore - able to organise 2nd nervous system

Question 25

organiser potency with time

Answer 25

early donor - complete 2nd axis | late donor - extra tail only

Question 26

vertical and planar movement

Answer 26

vertical - between layers of different tissue, late gastrula | planar - within a single plane (early-late gastrula)

Question 27

early evidence favoured vertical or planar?

Answer 27

vertical

Question 28

who did the exogastrula experiments?

Answer 28

holtfretter in 1933

Question 29

explain exogastrula experiment

Answer 29

high salt concentration planar induction not sufficient for nervous system must have opposed layers

Question 30

Mangold 1933

Answer 30

embryo in neurulation - dissect mesoderm and graft into blastocoele anterior mesoderm - 2nd head posterior mesoderm - 2nd tail

Question 31

vertical induction findings mangold 1933

Answer 31

Vertical induction of ectoderm by mesoderm | mesoderm contains inducers that specify A/P nervous tissue

Question 32

homeobox genes

Answer 32

1983 - genes encoding transcription factors that determine body segmentation highly conserved from flies

Question 33

what are homeobox genes markers for?

Answer 33

A/P position

Question 34

2 homeobox experiments

Answer 34

exogastrula and keller sandwhiches

Question 35

homeobox - exogastrula

Answer 35

label embryos for neural markers N-CAM and xhox3 present in ectoderm next to envaginated mesoderm

Question 36

What lead to a rethink that not only vertical induction was involved?

Answer 36

homeobox genes

Question 37

Keller sandwhiches

Answer 37

2 embryos - cut out identical regions | later them under piece of glass and allow to develop

Question 38

keller sandwhich findings

Answer 38

homeobox genes found in same position in embryo and keller sandwhich no vertical induction

Question 39

Is planar induction enough?

Answer 39

No - no floor plate, no D/V patterning | keller sandwhich - no eyes, anterior structures

Question 40

What is the default state for ectoderm?

Answer 40

neural tissue

Question 41

Evidence for default model

Answer 41

xenopus - animal cap intact tissue = epidermis reaggregate immediately = epidermis delay reaggregation for 1 hour = some neural markers reaggregation delayed >5 hours = neural tissue only

Question 42

neural default model - explain

Answer 42

absence of signal required for neural differentiation | no signal = neural

Question 43

Neural default model reinterprets spemann and mangold

Answer 43

epidermal inducer in ectoderm an receptor - bind epidermal induction spemann organiser produce antagonist - neuronal