L14: drosophila- neurogenesis

what happens after the mesoderm invaginates

neuroectoderm comes to lie ventrally

what side does the neural tube develop in vertebrates

dorsal side

what side does the neural tube develop in drosophila

ventral side

what is BMP/Dpp important for patterning in drosophila

dorsal

what is BMP/Dpp important for patterning in vertebrates

ventral

where is it likely that the D/V inversion took place

lineage leading to chordates/vertebrates

what do cells in drosophila neuroectoderm develop into

some become neurones, some remain ectodermal

what is a proneural cluster

group of equivalent cells, of which a single neuronal cell will be selected

what do achaete/scute genes set up

cluster called proneural genes

what does the notch/delta signalling pathway ensure

single selection from proneural genes

what is delta

transmembrane ligand (can only influence neighbouring cells)

what do achaete scute proteins promote

delta expression

what does a strong notch signal do

downregulates achaete scute

describe the process of lateral inhibition

small differences in delta expression

a strong notch signal downregulates achaete/scute

amplifies difference in achaete/scute

high + continous achaete/scute expression activates neural genes while losing cell reverts to epidermal fate

what happens if the notch signal is blocked

all proneural cluster cells become neurones

what happens if the notch signal is constantly activates

no neurones form from proneural clusters

what happens after selection of a neuroblast

generates a number of neuronal + glial cells in a very stereotypic manner: asymmetric cell division

cell will then drop from epithelium into interior of the embryo

what is the inherent polarity in drosophila epidermis cells

apico-basal polarity

how is apical-basal polarity maintained

localised protein complex made up of bazooka (par3 in mammals), + insc/pins

complex also orients the mitotic spindle which determines plane of division

what 2 cells result from asymetric division of a neuroblast

neuroblast + ganglion mother cell

what does the ganglion mother cell divide into

neurones or glia

where are sensory organs formed from

during pupation from proneural clusters expressing achaete/scute

what is the difference between neuroblast division and sensory organ formation

in neuroblast division: pins on opposite side to numb, occurs in interior of cell

in sensory organ formation: pins on same side as numb, occurs in epithelium. cell receiving numb differentiates as sensory neuron

does asymmetric division also occur in mammals

yes, Par3 asymetric cell division mechanism is also operative