Exam 1 Flashcards
neural induction occurs during what stage of embryogenesis
Gastrulation- formation of three distinct germ layers
what pole forms future epidermis/neural tissue? future gut?
Epidermis/neural- animal pole
gut- vegetal pole
invagination of blastopore results in formation of what?
Notochord- mesodermal inducer of neural tissue, later plays a role in dorsal-ventral patterning
the dorsal lip of the blastopore is referred to as _______ what does it do if transplanted to a blastula that already has one?
“The organizer,” forms a second nervous system- a siamese tadpole results. Without an organizer, a blastula forms a blob w no nervous system
Was the second neural tube/nervous system in Spemann’s Organizer transplantation experiment INDUCED or CARRIED OVER? proof (Staining Organizer experiment)?
it was INDUCED- Transplant a STAINED organizer to the ventral side of a blastula, and the newly formed NOTOCHORD will be stained, but the newly formed NEURAL TUBE will NOT- notochord caused cells to form into neural tube
an animal cap isolated in the PREgastrula stage becomes what kind of tissue? how about in the GASTRULA STAGE?
PRE- Epidermis
GASTRULA- Neural tissue
In PREgastrula, notochord has not yet formed to induce neural tissue formation
If you isolate animal cap in PREgastrula stage with dorsal lip intact, what tissue is formed?
Neural tissue- dorsal lip (mesoderm, future notochord) carries the inducing information necessary
Why does isolating the animal cap and jumbling the cells result in epidermis after short term dissociation period, but form neural tissue after long term dissociation (left in solution for a while before plating) period?
because the repressor (BMP) for neural growth dissociated or denatured after a certain period of time
BMP + Ectoderm results in formation of what tissue
Epidermal
BMP + Ectoderm + _______ results in formation of neural tissue?
Noggin/Chordin
Exposing a gastrula to UV radiation results in? Addn of what (two different things can- one is endogenous, one is just added by experimenter) corrects this?
Ventralized embryo. No nervous system. Addn of Li, or Noggin protein (from dorsal lip (“Organizer”)) induces dorsalization/formation of nervous system
How does noggin induce neural tissue formation?
comes from dorsal lip, binds to BMP. Blocks its typical ligand activity of binding to TGF-Beta cell receptors (BMP+TGF-Beta receptor inhibits neural induction).
A truncated Activin (member of TGF-beta family) receptor added to a cell membrane causes what tissue type to form?
neural tissue. Adding a nonfunctional receptor of a mesodermal inducer (in ectoderm the activin would cause epidermis formation though)- dont get too hung up
Is neural fate of ectoderm default or induced? I.e. does BMP inhibit INDUCTION or change a default fate? Proof?
dissociated ectodermal cells alone (NO BMP) form neural tissue.
Dissociated ectodermal cells + BMP form epidermis, so BMP changes a default fate
animal cap alone forms?
Animal cap + noggin, follistatin, or chordin forms?
animal cap + noggin, follistatin, or chordin + excess BMP forms?
epidermis
Neural tissue
epidermis
noggin, chordin, follistatin are secreted from where to cause neural induction?
dorsal lip (future notochord)
transcription factor released from TGF-beta receptor that BMP induces
SMAD
Shh is a ligand that binds to _____, which signals _____ (another transmembrane protein) to release the transcription factor ____
Shh is a ligand that binds to PATCHED, which signals SMOOTHENED (another transmembrane protein) to release the transcription factor Gli1
Drosophila (INVERTEBRATE) gastrulation is on the ______ (D or V) surface of gastrula?
VENTRAL- neurectoderm forms on ventral side in invertebrates
Drosophila:
_____ Promotes production of mesoderm and neural ectoderm by preventing DPP from binding its receptor. Gradient = High concentration in ventral and low concentration in dorsal
Sog
Drosophila: protein that has a Dorsalizing effect- high concentration on dorsal side, low in ventral, what tissue formation or inhibition results
Dpp- inhibits formation of neural ectoderm and mesoderm (dont forget gastrulation is on ventral surface in drosophila)
Drosophila: protein that has a ventralizing effect- high concentration in ventral side, low in dorsal
Dorsal protein (dont forget gastrulation is on ventral surface in drosophila)
what protein family inhibits neurectoderm induction
TGF-Beta. Inhibitors of TGF-B family induce neurectoderm
BMP (TGF-B) + Noggin, Chordin, Follistatin (inhibitor) = neurectoderm in amphibians
Dpp (TGF-B) + Sog (inhibitor) = neurectoderm in drosophila
what are proteins called that establish polarity in the drosophila embryo by holding on to maternal mrna
anchor proteins
what is the first morphogen maternal effect lethal in drosophila, which pole is it supposed to come from (anterior or posterior)
bicoid, anterior
a bicoid deficient mutant will develop what phenotype
an abdomen between two tails
adding bicoid RNA to the center of a bicoid mutant embryo will result in what
a head developing in the center with two thorax, one or two abdomen, and two tails
adding bicoid RNA to the posterior of a wild type embryo will result in what
two heads developing on either side, no tail
A high concentration of caudal in the maternal gradient results in the development of what?
Tail, caudal is a posterior determinant
four maternal gene products in drosophila that determine A-P patterning
What inhibits what? what activates what?
Be Hungry, No Constipation
Bicoid and Hunchback, anterior (bicoid activates hunchback expression)
Nanos and Caudal, Posterior
Nanos inhibits hunchback and bicoid inhibits caudal
Be Hungry, No Constipation
When youre hungry, you put food in the head, when you are not constipated, you are pooping out of the tail
what gives rise to what? gene cascade
Gap genes, segment polarity genes, pair rule genes, maternal morphogens
what two genes give rise to hox genes?
chronological order:
Maternal morphogen -> gap genes -> pair rule genes -> segment polarity genes
gap genes and pair rule genes give rise to Hox genes
gap gene (Kruppel) spatial pattern is specified by what maternal gene? what would happen if this maternal genes gradient were extended two times past the normal? What would have caused that?
Hunchback defines kruppel expression. If the hunchback gradient were extended 2x (by 2x overexpression of bicoid which activates it) then kruppel expression would be pushed posterior by extra hunchback expression- kruppel expression is activated by a medium concentration of hunchback and repressed by too high concentration of hunchback. Makes a perfect line
what does kruppel (gap gene) expression look like in a bicoid mutant that can still express hunchback
Kruppel is not activated in a straight line anymore but rather by the entire anterior half of the embryo
kruppel expression is activated by a medium concentration of hunchback and repressed by too high concentration of hunchback. since bicoid is not there to activate hunchback, we only observe a medium expression throughout the anterior half of the embryo
genes that specify segment identity
Hox
sharpening of rhombomere boundaries depends on the segments alternating their expression of which gene family?
Ephrin. One segment expresses ephrinB, the next expresses Ephrin A, and so on. They then do the bidirectional repulsion to make a sharp boundary between segments
important organizing segment in the hindbrain what does it separate
isthmus separates metencephalon and mesencephalon
Isthmus separates what two gene expressions that are mutually repressive so they create a solid line. Which one confers development of mesencephalon and which development of metencephalon
what would happen if one of the genes were knocked out
otx2 is the mesencephalon gene, gbx2 is the metencephalon. KO of otx2 leads to loss of forebrain structures, KO of Gbx2 leads to loss of structures derived from R1-3
in the development of midbrain and hindbrain. Isthmus produces Otx2 for mesencephalon dev and Gbx2 for metencephalon dev. What respective gene products do these two promote
gbx2 promotes FGF-8
otx2 promotes Wnt-1
donating a quail isthmus to the brain of a developing chicken results in what
development of a second midbrain-hindbrain. Ectopic cerebellum and midbrain at location of placement
genes that play a role in forebrain patterning. anterior vs posterior
anterior, Pax6
Posterior, Emx2. Same mutually repressive gradient
boundaries of hindbrain: what is the main anterior determinant gene product (i.e. what tells hox genes where to be expressed)?
FGF8
mesoderm structures adjacent to hindbrain that create a rostral-caudal gradient of retinoic acid
somite
what is the interaction between Cyp26 and Retinoic acid? where does this interaction take place and what gradient does it establish
in the hindbrain, Retinoic acid (steroid released from somites that triggers Hox gene expression in cells with RA receptors)
generates a Caudal-Rostral gradient (more concentrated in the posterior hindbrain than the anterior). Cyp26 is an enzyme that degrades RA, and there is more released in the anterior hindbrain than the posterior.
Retinoic acid relationship with Hox genes. (hint: remember that Hox genes are organized numerically on the genome
Retinoic acid causes the transcription of Hox genes in cells that have retinoic acid receptors, the number of different Hox genes (say 1 through 4 compared to 1 through 6) is determined by the amount of Retinoic acid available for uptake. The more concentrated the retinoic acid, the more hox genes there are transcribed
RA experiment- what does DEAB do?
RA synthesis inhibitor, so there is less hox being made
RA experiment- what does Cyp26-MO do?
type of RNAi knockdown- environment is unable to degrade RA, so there is more Hox being made
If you wanted to make the same amount of Hox1 as Hox4 (in different cultures) how would you change the amount of RA in Hox1 culture, if they were initially equal?
you would decrease the amount of RA in the Hox1 culture
where can one find the highest concentration of RA in the body?
at the hindbrain-spinal cord border
What is the rostral determinant gradient and the caudal determinant gradient in the SPINAL CORD? What are they regulators of?
FGF8 has highest concentration in caudal spinal cord, RA has highest concentration in rostral spinal cord- regulators of Hox gene expression- motor neuron development
medial motor column nerves do what
motor neurons for muscles of back
hypaxial motor column nerves do what
motor neurons for axial ventral muscles (abdominal, intercostal)
Preganglionic motor column neurons do what?
innvervate sympathetic ganglia
MEDIAL lateral motor column nerves do what?
ventral limb motor neurons
LATERAL lateral motor column nerves do what?
dorsal limb motor neurons
motor neurons exit from ventral or dorsal root
ventral root
the _____ gradient induces differential Hox gene expression in the rostrocaudal axis
FGF
slide 7 patterning II
yes
hox6 expression in the spinal cord specifies what motor neuron identity? Hox9? Hox10?
Hox6- LMC, forelimb (brachial spinal column)
Hox9-PGC, sympathetic chain ganglia (thoracic spinal column)
Hox10- LMC, hindlimb (Lumbar)
Transcription factor that directs LMC dorsal motor neuron differentiation, induces synthesis of retinaldehyde dehydrogenase (needed to make RA), creating a neuronal source of RA, important for distinguishing subdivisions of LMC
FoxP1, induced by Shh and FGF
if you knock out FoxP1, what will be missing in tetrapod development
LMC in spinal cord. no limbs will be innervated
What is born first LMCmed or LMClat motorneurons? what factor induces the fate in the later born neurons?
Retinoic acid from EARLY BORN LMCmed motorneurons induces LMClat fate in late-born motorneurons
what is the dorsalizing factor in spinal cord? ventral?
Shh from notochord is ventralizing, BMP from ectoderm is dorsalizing, produces a further gradient of TGF-Beta family
placing a notochord in a novel place near the spinal cord causes what? removal of any notochord entirely causes what?
novel placement- causes a secondary floor plate and secondary motor neurons to develop
Removal- causes no motor neurons to form at all
do class I or II factors dominate in dorsal-ventral Shh gradient when [Shh] is low? what side is that on?
In dorsal end of gradient, Shh is low, and class I factors dominate. They participate in mutual cross repression with Class II factors that arise from high Shh concentration in ventral spinal cord.
Which is activated by presence of high BMP and which is activated by low BMP (repressed by high)? Lim and Isl. What do they do?
Lim transcription factor is activated by high BMP
Isl transcription factor is activated by low BMP
They specify motorneuron target
ventralizing and dorsalizing neurogenic factor in drosophila (like chordin and BMP)
sog is ventralizing (neurogenic in drosophila- opposite of vertebrates), so it acts like chordin (antagonist of BMP) and dpp is dorsalizing so acts like BMP (ventralizing in vertebrates
ganglion mother cells are the product of the division of ______ and divide to produce ______
product of neuroblasts, divide to produce 2 neurons
bHLH transcription factors are evolutionarily conserved _______ genes
proneural
initially a cluster of cells in drosophila expresses ____ genes
AS-C (achaete Scute Complex)- proneural
what becomes the neuroblast in an achaete-scute mutant fly?
No cells- achaete scute complex is proneural, if there is no AS-C signalling, then there is no neurogenesis
What becomes the neuroblast in a notch-delta mutant?
Every cell in the cluster. Notch-delta is what turns off the achaete scute (proneural) signalling
the cell in the cluster that produces the most ________ becomes the neuroblast?
the cell that produces the most delta becomes the neuroblast because every cell in the complex is already producing notch (receptor) and AS-C (proneural). Whichever cell produces the most DElta DEactivates the other neurogenic cells by binding to notch, in other cells -> binding causes protease to break off a notch fragment -> notch fragment inhibits the AS-C complex enhancer (Enhancer of split). The cell that is producing the most delta continues to produce AS-C.
AS-C initially enhances delta levels so technically more AS-C -> more delta -> more AS-C
injecting a cell with ______ turns off proneural genes (AS-C)
Notch ICD
injecting an embryo with proneural bHLH gene NeuroD results in what
an embryo with many ectopic neurons
vertebrate neural precursors proliferate in the _______ zone
ventricular
proliferating neurons are on the ______ surface and postmitotic (mature) neurons are on the _____ surface (basal vs apical)
proliferating- apical
postmitotic- basal
is symmetric division or asymmetric division of neural progenitors more common early in development
symmetric division is more common early in development because a symmetric (vertical) division creates two new progenitors, whereas an asymmetric (“horizontal”) division only produces one new progenitor and one new neuron. want more progenitors to extend neural tube
cell that retains ______ upon asymmetric division remains a progenitor
adherens junction
asymmetric division, basal inheritance of _____ and ____ proteins result in _____ inhibition and neuronal differentiation
Numb and Prox1 are basally inherited (postmitotic neuron fate) proteins that inhibit Notch. Notch can no longer inhibit proneural gene transcription
asymmetric division- apical inheritance of _____ and _____ activate _____ which results in the inhibition of proneural genes and remaining progenitor
apical inheritance (progenitor neuron fate) of mlnsc and par complex proteins results in activation of Notch which inhibits transcription of proneural genes and causes further progenitor proliferation
does the cell cycle of progenitors lengthen or shorten as development progresses? why?
cell cycle lengthens so you don’t over populate the brain
what protein inhibits EF2, preventing S-phase in neural progenitor cells in the eye? phosphorylation of this protein results in s phase genes being transcribed, but mutation in this protein altogether results in s phase genes being transcribed indefinitely. What is this protein called?
Retinoblastoma (Rb) protein
in what cortical layer are excitatory pyramidal, primary neurons derived from dorsal VZ
layer 6, long apical dendrites that extend upward to highest cortical layers
in what cortical layer are callosal, intracortical projection neurons
II and III- communicate within cortex
in what cortical layer are subcortical (corticofugal) projection neurons?
V and VI- communicate outside of cortex
injecting embryos at different E# dates with _____ allows you to track the birthdating of brain cells. when the cells become postmitotic, thats when they are “born”- no more dividing. Where would an E11 born cortical cell be located compared to an E15 cortical cell?
Labeled nucleotides (3H thymidine or BrdU), an E11 born cortical cell will end up in the lower (apical) cortical layers (5 and 6) and an E15 born cortical cell will end up in the higher (basal, more traveled) cortical layers (2 and 3)
what are the first born neurons of the cortex called?
preplate
cortical development, second step (after preplate formation): cortical plate neurons nestle into the middle of the preplate and split it into the ______ and the ______
marginal zone (basal) and subplate (apical)
the _____ is a crucial transient layer that receives THALAMOcortical afferents prior to the generation of their target layer #
subplate, thalamocortical afferents prior to TARGET LAYER IV
cortical genesis- what neurons die postnatally but are critical during embryonic corticogenesis
subplate
what would happen to the fate of a cortical progenitor cell taken from the VZ of an E29 rat and transplanted into the VZ of a P1 rat?
What was likely to become a lower layer (V/VI) cortical neuron in the E29 rat develops into an upper layer (II/III) cortical neuron in the P1 transplant
what would happen to the fate of a cortical progenitor cell taken from the VZ of an E29 rat that is cocultured with other E29 cells in pellet before transfer to the VZ of a P1 rat?
the lower layer (V/VI) fate of the E29 cell will be retained after coculture (maintaining a “younger” fate)
what would happen to the fate of a cortical progenitor cell taken from the VZ of a P1 rat and transplanted to the VZ of an E29 rat?
the upper layer (II/III) “older” fate will be retained from the P1 rat. Older cells become progressively less plastic in their fate.
what is it called when neurons migrate without radial glia by contacting each other and guiding cells along the way? what type of neurons do this?
tangential migration, inhibitory interneurons
what type of neurons utilize radial migration for neural migration?
primary cortical neurons
What type of radial migration is early and faster? like spiderman- neuron retains its pial process, sheds its apical process and is pulled up- INDEPENDENT OF RADIAL GLIA
somal translocation
what type of radial migration happens later in development and is dependent on radial glia- climbs on radial glia
locomotion
when antibody to astrotactin is added to culture of migrating neurons, what happens?
migration stops. astrotactin is a cell surface adhesive molecule that binds to an unknown radial glial ligand. necessary for neural migration
cortical ______ derive from a ventral forebrain structure, the ganglionic eminence. How do they migrate?
cortical inhibitory neurons migrate tangentially from the medial ganglionic eminence
What transcription factors must be expressed for tangential migration of inhibitory interneurons from the medial ganglionic eminence to the neocortex?
Dlx-1/2 distal-less homeobox transcription factors
an early development cortical slice that does not include the medial ganglionic eminence will be lacking what if allowed to proliferate in culture
inhibitory interneurons (GABA) that migrate tangentially from MGE to neocortex
cells with Neuropilin (Nrp) receptors (receive semaphorins) in the medial ganglionic eminence do what and why
migrate tangentially to form the neocortex because sema binding to nrp repulses the cells
what is different in reeler cortex organization of development vs wt
reeler cortex is “Upside down”, the upper layers develop first, migrate as far as they can and then cortex grows inward toward the center of the brain
what two receptors are necessary for Reelin signalling, causing migratory neurons to migrate? what secondary messenger is necessary for signal cascade?
Receptors- VLDLr and ApoER2
Secondary messenger- Dab-1
what genetic system is important for purkinje cell migration in the cerebellum?
Reelin
What is released by early differentiating purkinje cells and promotes proliferation of granule neuron precursors in the EGL? As the postmitotic granule neurons migrate down to the IGL, do they down regulate or up regulate the transcriptional effector (Gli) of this protein?
Shh, downregulated as neurons migrate. If Gli is not downregulated, then medulloblastomal tumors will result
Sensory bristle formation- Division of sensory organ precursor cells, what determines what becomes socket and bristle cells (SOPIIa) and what becomes glial sheath cell and neuron (SOPIIb)?
retaining high notch activity proteins makes the cell into socket and bristle cells (remember notch leads to no neuron), retaining high numb expression leads to glial sheath cells and neurons. think, a numb mutant becomes numb- drosophilas are named weird remember
Sensory bristle formation- does notch inhibit numb or does numb inhibit notch in SOP division
numb inhibits notch
sensory bristle differentiation- a notch mutant sensory organ precursor cell will develop into _______ (type and number)
4 neurons
sensory bristle differentiation- a numb mutant sensory organ precursor cell will develop into ______ (type and number)
4 socket cells
sensory bristle differentiation- what causes SOPIIA cells to become socket cells? what does the other cell become?
Numb protein is not proportionally shared, so it is not able to inhibit notch which causes it to become socket. In BRISTLE cell, retained numb inhibits notch.
sensory bristle differentiation- what causes SOPIIB cells to become neurons? what does the other cell become?
numb expression is disproportionately split, future neuron retains more numb which inhibits notch. future glial sheath cell does not retain enough numb to inhibit its notch, which inhibits neural fate
what drosophila photoreceptor cell shows up first in a cluster to differentiate others
R8
photoreceptor cell differentiation- hedgehog is expressed from what end of the eye disk? what proneural factor does it turn on?
posterior, differentiation of photoreceptor cells occurs in a posterior-anterior wave. spacing accomplished by lateral inhibition from notch signaling. Hh turns on bHLH proneural factor ATONAL
a fly that is lacking ultraviolet sight is lacking sight either due to lack of ___ or ___ gene function(Receptor or ligand)
could be lacking due to boss (bride of sevenless) or sevenless (receptor tyrosine kinase that creates a cascade for the cell to an R7 fate when it binds to boss protein
TF marker for corticospinal motor neurons (layer V) with zinc fingers
Fezf2
a knockout of ______ leads to no spinal cord mn projections from cortical layer V or Corticospinal motorneuron cell bodies in cortical layer V
Fezf2
Fezf2 from cortical layer IV induces the expression of many genes in cortical layer V, but the most important one (for axonal guidanceto the spinal cord) is ____
EphB1- Ephrin binding receptor
produced in what order, neurons, oligodendrocytes, astrocytes
neurons, astrocytes, oligodendrocytes
bHLH TFs that act as genetic switches to control neuronal vs glial production
Olig1 and 2
differentiation 2 slide 12
yes
a neural projection with the + end of a microtubule pointing toward the terminal is a ______
an axon. + end is kinesin, taking things away from cell
after severing an axon, how would you predict which process will become the new axon?
the process that ends up with ALL of the cells kinesin
