Arborisations Flashcards
what does arbor mean
tree
work of Ramon y Cajal
documented complexity and diversity of dendritic arbors e.g purkinje cells in the cerebellum
desert locust
swarms 1200km^2
robust and predictable response to local stimuli
electrophysiology in desert locusts
electrodes in metathoracic ganglion (sensory neurons terminate) and record responses in: ventral/dorsal tibia, dorsal femur
innervation causes firing (spike noise)
know: interneuron anatomy (produces spatial map)
where is the sensory system of the drosophila
periphery
how to make a tree
neurons need to grow in the same space and repel
repellants form trees (only sister branches repel)
down syndrome cell adhesion molecule (DSCAM)
gene in drosophila and mice
large isoform diversity via alternative splicing (~38000 isoforms)
genomic DNA is multi-exonic - forms mRNA - protein (homophilic binding domain)
self-avoidance - prevents tangles due to repulsive force by homophilic binding
DSCAM mutant
collapsed dendrites (no repelling)
WT: repelling
rescue: sufficient to repair
clustered protocadherins (pcdhs)
in vertebrates
inform neurons of the branches’ identity
self-avoidance requires pcdhgs
CUT
homeodomain protein which regulates branching in drosophila
in class IV - reduces complexity
abrupt (ab)
BTB-zinc finger protein (TF) regulates branching complexity of da neurons (drosophilia)
ab26 mutants
LOF - increased complexity of class I da neurons (simple cells become complex)
class IV - no change in structure
ab26 overexpression in class IV - reduces complexity
terminal selector transcription factors
within post-mitotic neuron
process: regulatory inputs -> terminal selector gene ->terminal gene battery
neuron-type specific gene batteries endow cells with distinct anatomical and functional properties
what do motor neuron dendrites form in drosophila
myotopic maps in the CNS (reflects layout of muscles in the periphery)
what does the adult ventral neural cord contain (drosophila)
(unit for leg control)
539 ascending sensory neurons
1328 descending sensory neurons
MNs
neuroblast (NB)
early vs late born
generates ~50% of leg MNs
early born: lateral to midline
late born: distal to midline
why do dendrites have different morphologies despite trees growing at the same time
midline signalling molecules (act as a repellant)
receptor = Roundabout
Robo mutants
Robo gain of function - repel to lateral edge
robo loss of function - medial territory
Comm gain of function - removes Robo
what are growth cones attracted to
chemoattractants (DCC)
how do class III da neurons orient growth
DSCAM
does self avoidance (DSCAM/pcdh) counter the targetting of dendrites
use ectopic netrin
result: greater distance from cell body and altered morphology
synaptotropic hypothesis
nascent synapses help growth
branches make nascent synapses
pleural muscle motoneuron PMM
PMM are cells in the BS/SC
axons form branching patterns in the abdomen - contraction
molecules required for synapse formation
presynaptic - NRX
postsynaptic - NLG
