Development of the NS

Question 1

gastrulation

Answer 1

single-layered blastula reorganised to multilayered gastrula, 4,000+ cels
in frogs blastula with ectoderm(skin), mesoderm and endoderm, cells move to mesoderm now under ectoderm at top (see diagram in notes)

Question 2

blastula

Answer 2

hollow sphere of cells with ectoderm, mesoderm, endoderm, during early stage of embryonic development

Question 3

Neuralation

Answer 3

after gastrulation, folding in vertebrates to form neural plate to neural tube

Question 4

chicken neural tube closure vs human

Answer 4

chicken is zipper from anterior to posterior so slower at back-end
human not zipper but happens in phases (looks like a vag lol)

Question 5

human neural tube closure (3 weeks old)

Answer 5

1 - spinal cord
2 - brain
3 - front (near face)
4 - back skull
5 - posterior end (near butt)

Question 6

3 defective neural tube closure in humans

Answer 6

anencephaly
encephalocele
meningomyelocele (spina bifida)

Question 7

anencephaly

Answer 7

number 2 brain doesn’t close so aborted or don’t live long

Question 8

encephalocele

Answer 8

number 2 - parts of brain protrude outside skull in sac of skin
usually live, mental disability varies
if number 4 (back of skull) then don’t live

Question 9

meningomyelocele

Answer 9

spina bifida

Question 10

spina bifida

folic acid relation

Answer 10

most common
number 5 (near butt)
80-90% survive
varying disability (paralysis, bowel, bladder control, hydrocephalus, learning)

altered folate metabolism from env. or genetics so affect cytoskeleton

Question 11

hydrocephalus

Answer 11

CSF accumulates

Question 12

human neural tube structure (embryo)

Answer 12

3 sections of primary brain vesicles - forebrain, midbrain, hindbrain
5 chambers of secondary brain vesicles - cerebrum, thalamus/hypoth/epithalamus., midbrain, pons, cerebellum, medulla oblongata

Question 13

what is compartmentalisation of neural tube controlled by?

Answer 13

TFs like Hox, Krox20, Otx, Emx2

Question 14

neural fate of ectoderm

Answer 14

becomes neuroectoderm which is diff from the rest

but needs mesoderm (in vertebrates) for signalling

Question 15

BMPs

Answer 15

bone morphogenic protein

stops ectoderm becoming neuroectoderm

Question 16

Lateral inhibition

Answer 16

cells compete to adopt neural fate
all proneural neuroectoderm cells are competent to become neurones but not all do
all cells have Notch receptor and Delta ligand

Question 17

Notch

Delta

Answer 17

receptor, all vertebrates, glial/skin cells, expressed in neural plate

ligand, all vertebrate neurones, expressed in neural plate

Question 18

Drosophila evidence of lateral inhibition

Answer 18

regulation of how much delta controlled by Acheate-scute - suppression or enhancement
suppressor-of-hairless switch on enhancer-of-split so switch off achaete-scute
delta gets upper hand so acheate-scute wins
this happens in vertebrates too but diff genes (neurogenin and neuro D)

Question 19

brainbow

Answer 19

genetic technique shows diff coloured types of neurones (thousands of neurones not just 4 main unipolar/bipolar/pseudouni/multi

Question 20

asymmetric division of neuroblasts

Answer 20

1. components in cell start to move - realignment of metaphase plate so have apical and basal of cell
2. Numb protein on basal part - so when divide daughter cell has Numb, stem cell is without Numb
   Baz/Pins/Insc apical so only in neuroblasts
3. 2ndary ganglion is diff to 1st GMC (ganglion mother cell) - diff things inside each time so age and change competency (what it can become)

Question 21

invariant lineage

Answer 21

diff embryos have same cells so follow division of specific cells (invertebrates)

Question 22

vertebrates development

Answer 22

almost same as invertebrate development
most similar is retina development (progenitor change TF profile, change competency)
determined by timing of division - neuroblasts divide near surface of neural tube then climb radial glia and migrate to cortex then sideways and change TF depending on where end up
position depends on time

Question 23

neuronal diversity mediated by…

and explain

Answer 23

chemical gradients

in neural tube, signalling molecules (not TF) like BMP in dorsal and Sonic Hedgehog in ventral tell neurones what to become (diffuse dorsal to ventral)

Question 24

neuronal diversity dorsal and ventral

Answer 24

dorsal (top) - PNS (neural crest cells) and sensory neurones
roof plate in middle of dorsal tip - conc in BMP

ventral (bottom) - motor neurones, V1 and V2 interneurones
floor plate in middle of ventral - conc in Sonic Hedgehog

gradients define what type of motor/inter (conc decreases as move away)

all happens while neural tube forming

Question 25

anterior-posterior patterning (front to back)

Answer 25

Hox genes in vertebrates pattern neural tube (brain and spinal cord)

Question 26

combinatorial code of TFs to specify individual neurones

Answer 26

codes pretty much same, few TFs make difference to identity of neurones
code homologous in all animals
code driven by TF profile from neuroblasts/patterning molecules/Hox from diff env.

Question 27

spina bifida and folic acid

Answer 27

risk in pregnancy from diet - changes methylation status of proteins and DNA so change gene expression

take up folic acid in diet and forms 5-MeTHF (required to make methionine)

vitamin B12 required for metabolism so makes methionine for methylation

without folate, homocysteine builds up and affects development of fetus

can get rid of it but not if genetics altered, affect cadherins and cytoskeleton