Exam 1 Flashcards
The neural tube derives from _____, while somites derive from ________
Ectoderm, Mesoderm
Neural induction is mediated by _________ secreted from the organizing region
BMP inhibitors
Suppose you deliver a baby and find that axons from two adjacent motor columns in the spinal cord innervate the same ares. You surmise that this is likely due to a mutation in
Homeobox transcription factors
What determines the neurotransmitter phenotype in neurons in the central nervous system and in the periphery?
NT phenotype is hardwired by TFP in the CNS, while target-derived signals in the periphery drive this decision.
Trk receptors are major receptors for trophic factor signaling in neurons. If you were to overexpress Trk receptors in motor neurons during development, what would you predict would change, if anything, in terms of neuronal survival? Why?
Overexpression of Trk receptors should not do anything to NM survival, since its the level of neurotrophic factors secreted by muscle that is the rate limiting step.
Dendritic patterning is accomplished by
Transcription factor programs
Define the six mechanisms through which extracellular cues guide growth cones?
ECM interaction, Cell surface adhesion, Contact inhibition, Axon fasciculation, Chemoattraction, Chemorepulsion
To pattern the developing spinal cord, the floor plate secretes _____ while the roof plate secretes _______
Shh, BMPs
Define the key difference between the transcription factor programs that orchestrate neuronal responses to Shh signaling compared with Hox signaling?
Shh signaling utilizes a combinatorial code of transcription factors to drive cellular differentiation.
In contrast, Hox genes are a hierarchical system in which more posterior (or caudal) Hox genes supercede more anterior (or rostral) Hox genes.
Hox genes are responsible for orchestrating the transcriptional changes necessary for?
Motor neuron subtype and axon guidance
The Barrel Cortex of hte rodents is a somatosensory region that responds to whisker activity. Describe a simple experiment you would use to test the role of activity from a single whisker in the development of the Barrel Cortex. What would you predict would happen and what does this tell you about the role of activity in somatosensory development in the cortex?
I would propose to cut a single whisker in the mouse/rat pup and allow the Barrel Cortex to
develop normally into adolescence. I would sacrifice the animal and measure the barrels in the cortex. I would predict that the barrel that corresponds to the cut whisker would be smaller than normal, and neighboring barrels would be larger (overtake some of this territory). This suggests
that activity is necessary for the barrel to grow and/or be maintained during development.
Describe how Delta and Notch signaling between adjacent precursor cells always leads to
one neuronal precursor and one support cell?
A small imbalance in Delta/Notch signaling between the two cells is established. This promotes a negative feedback loop that amplifies this imbalance through transcriptional network which ultimately leads to greater delta in one cell and greater Notch in the other.
Is neurotransmitter identity similarly “hardwired” or “plastic” between the central and
peripheral nervous systems?
Why might this be the case
Neurotransmitter identity is more hardwired in the CNS, while it is more plastic in the PNS.
There is much more cellular diversity in the PNS with a variety of muscles, glands, and
sensory systems that need to be innervated. Plasticity in neurotransmitter identity provides the PNS with a tool to adjust to this diversity in targets
Which of the following are NOT neurotrophins?
A. NGF
B. DRG
C. BDNF
D. GDNF
E. NT-3
B. DRG
TrkA and P75 signal to modulate the _________ cell death program?
Intrinsic
Name two properties of neuronal dendrites that are hardwired through intrinsic transcription
factor programs
Dendritic morphology/ structure/complexity and dendritic tiling
Name two properties of neuronal dendrites that are influenced by environmental cues?
The complexity of dendritic growth and the formation of axons vs dendrite
True or False: The neurotransmitter phenotype of a neuron plastic.
True
Neurotrophic Factor Hypothesis
A small amount of signal released by synaptic targets and is necessary to inhibit the default program of cell death. Competition by many neurons for the limiting amount of this signal determines which neurons live or die.
True or False. The morphologies of neurons are preserved in dissociated cell culture?
True: Neurons must therefore have intrinsic information about their shape because their patterns in culture are strikingly similar to those in vivo. Strongly suggesting intrinsic TFPs play key roles in determining dendritic arborization and complexity.
What are axonal growth cones?
Dynamic molecular motors driven to grow and search, but can be “guided” by extracellular adhesion and recognition
How is adhesion converted into directional cues in the growth cone?
Changes in the level of intracellular regulatory proteins determine whether the same extrinsic cue attracts or repels the growth cone (CA2+ gradient, cAMP, PKA, protein synthesis for new factors, etc.)
What is the difference between Ephrin and Netrin
Ephrin is a secreted molecule that is involved in axonal guidance (i.e. growth cone). Netrin is thought to act at a distance to either attract (active PKA + cAMP) or repel (PKA inactive) growth cones via directional cues based on intracellular factors.
What areas undergo tangential migration?
Central neurons migrate along glial cells and axons to reach their final settling position.
There are three major programs:
1. Radial migration: central neurons move along radial glial cells
2: Tangential: central neurons use axonal tracts at their guide
3: Free migration: occurs in PNS without 1 or 2
