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