Cellular Basis of Neurogenesis

Question 1

neurogenesis

Answer 1

a process by which a neural stem cell/neural progenitors generate neurons

Question 2

neural tube formation

Answer 2

neuroepithelial cells move from the apical and basal neural tube (where the ECM is)
N-cadherin is the main component of the cadherin junctions

Question 3

interkinetic nuclear migration

Answer 3

occurs in the cell cycle
nucleus moves up (to basal) and down (apical)

Question 4

what are the types of progenitors

Answer 4

radial glia
neuroepithelial cells

Question 5

neuroepithelial cells

Answer 5

adopt a RG shape when the neuronal layer forms at the basal surface of the neuroepithelium. Progenitors remains at the apical surface
neurons occupy the basal surface (mantle zone) - GFP labelled
progenitors occupy the apical surface (ventricular zone) - RFP labelled

Question 6

division types

Answer 6

symmetrical (8n) - forms 2 daughter cells of similar fates - forms neurons
asymmetrical (3n+1p) progenitor forms progenitor and 1 neuron
indirect neurogenesis asymmetrical (4n+2p) most efficient, progenitor selfs renews, intermediate progenitors expand the neural pool

Question 7

Timelapse

Noctor et al., 2004

Answer 7

in vivo imaging of single cells labelled by lentivirus/DNA constructs expressing slice cultures of the mammalian brain
apical progenitors divide asymmetrically to form progenitors and neurons

Question 8

basal radial glia

Answer 8

have no apical attachments, only basal attachments
found in higher mammals (humans/ferrets/apes)
divide asymmetrically for growth and gyrification

Question 9

role of wnt

Answer 9

induces & orients asymmetrical cell fates
extrinsic factor

Question 10

Wnt experiment

Habib et al., 2013

Answer 10

wnt proteins are immobolised onto beads
mouse embryonic stem cells grown on a culture dish and are co-cultured with the wnt beads
one distal cell ended up further away from wnt bead, other daughter cell in contact with bead (proximal) inhibited B-catenin

Question 11

intrinsic factors (drosophila)

Answer 11

1) asymmetrical segregation of cell fate determinants e.g. prospero-GFP
2) perpendicualr alignment of mitotic spindle with molecular cresent
3) sensory organ precursor (SOP) cells divide with cleavages parallel to the molecular cresent that lead to asymmetrical inheritance of cell

form P2a/P2b cell fates

Question 12

numb

Answer 12

cell fate determinant - needed for progenitor cell maintenance and stops precocious neurogenesis
appears concentrated at the apical end
undergoes oblique cleavage
numb can be asymmetrical inherited

Question 13

numb mutant

Petersen et al., 2002

Answer 13

too many neurons (thicker mantle layer)
fewer progenitors

Question 14

where is numb localised

Answer 14

localised to cadherin rich adherens junctions between progenitors

Question 15

KO of N-cadherin in mice

Zhang et al., 2010

Answer 15

KO conducted via NCad shRNA
increases population of Tbr1+ neurons
decreases progenitor population

Question 16

benefits of zebrafish

Answer 16

transparent
tiny
fast development

Question 17

perpendicular vs oblique division

Answer 17

perpendicular division - forms 2 progenitors
oblique division - cells loses apical contact - neuron , cell with apical contact - progenitor

Question 18

Par3 overexpression

Alexandre et al., 2010

Answer 18

Par3 is an apical polarity protein
co-expression of Par3 in ZO-1 and aPKC
par3 is asymmetrically and symmetrically inherited
neuron inherits par3 domain

Question 19

notch-delta signalling pathway

Answer 19

delta (sending cell) binds to the notch receptor (in receiving cell)
notch intracellular domain is cleaved and activates transcription of genes
cells which activate N-D pathway become progenitors (difficult to become neuron)

Question 20

repressing and overexpressing delta in chick retina

Henrique et al., 1997

Answer 20

overexpress dominant negative Delta - overproduces neurons and inhibits progenitor fates
ectopic delta eliminates neurons - if many cells forced to express delta, activate notch on its neighbours and prevents neuron formation

Question 21

role of mindbomb

Answer 21

tags delta
ubiquitin ligase
exposes cleavage site and allows delta to be cleavaged
localisation depends on Par3 function

Question 22

weak and strong notch-delta signalling

Answer 22

progenitors which receive delta signals from neighbouring cells - weak
progenitors which receive delta signals from only its descendants (intralineage) - strong signals

Question 23

transplanting mutant progenitors in zebrafish embryo brain

Dong et al., 2012

Answer 23

cannot deliver delta activation of notch R
mutant cells express dla morpholino (MO) - reduces delta translation

results: no progenitors near the apical surface (lack of RFP), lack of cells undergoing asymmetric division