wiring up in development (dr maloney)

Question 1

what determines the anterior/posterior axis in developement

Answer 1

mRNA gradients

Question 2

steps of differentiation (drosophila fly)

Answer 2

1. mRNA gradients establish ant/post
2. gap genes are expressed based on gradients
3. pair-rule genes (ex. even-skipped) are expressed based on the combination of gap genes
4. results in:
   - segment polarity genes which establish ant/post in individual segments
   - homeobox (Hox) genes which establish the segments/devisions themselves

Question 3

where are inhibitory interneurons formed

Answer 3

ventral forebrain then migrate to cortex

Question 4

where are cortical neurons (pyramidal cells) formed

Answer 4

dorsal forebrain

Question 5

what is the structure/apendage neurons use to find the right place to go

Answer 5

growth cones

Question 6

how fast do growth cones grow/move

Answer 6

up to 8mm a day in humans

Question 7

explain netrin/slip

Answer 7

in spinal chord, netrin is attractive to growth cones and is located on midline. guides neurons to midline where they switch their receptors from netrin to slit, making it so that they dont cross back over the midline

Question 8

how to retinal ganglion cells know where to go (optic chiasm)

Answer 8

rgcs in temporal retina project impsilaterally/dont cross chiasm. they express ephB1 receptors but the chiasm itself releases ephrin B2, stopping the temporal rgcs from crossing chiasm

Question 9

how do retinal ganglion cells know where to go (optic tectum)

Answer 9

use ephrins to establish topographical map:

ephrin A controls ant/post (in optic tectum)
ephrin B controls med/lat (in optic tectum)

Question 10

how do neurons get to be the right shape (4 ways)

Answer 10

1. self-avoidance
2. homotypic avoidance
3. regulation by activity
4. compartments

Question 11

self avoidance (def + explain)

Answer 11

creates bushy, evenly spaced dendrites.

prodocadherans make it so that a neuron’s own dendrites repell eachother

Question 12

homotypic avoidance (def + explain)

Answer 12

in sensory systems (particurally retina)

neurons avoid overlap and taking up the same space by repelling eachother

Question 13

regulation by activity (def + explain)

Answer 13

inputs (often inhibitory) can tell a neuron to prune synapses that dont end up exciting it. + retinal waves in developement

ex. a synapse that is only excitatory during lateral inhibition isnt needed (get rid of it)

Question 14

compartments (regulation) (def + explain)

Answer 14

below the level of axons, signaling molecules exist that compartmentalize dendrites and leads to morphology and striation

Question 15

how do neurons find synaptic partners (5 ways)

Answer 15

1. expressing specific ligands or receptors on specific parts of their dendritic arbors
2. gradients (can express different amounts of receptors/ligands from distal to proximal due to neurotropic factors released from neighboring cells)
3. synaptic pruning
4. synaptic plasticity/learning
5. programmed cell death (apoptosis)