Flashcards

BIOL 303

Zhining Sui Inglês 165 flashcards

Flashcards do conjunto (165)

1Advantage of frog as modelhuge egg --> large embryo
2Pigmented end Non pigmented endPigmented end: animal pole
Non pigmented end: vegetal pole
3position of dorsal mesoderm of frog reasonopposite to sperm entry site
4dorsal tip of frogspemann's organizer
5initial position of dorsalizing factorsvegetal pole
gray crescent
6transplant spemann organizor to the ventral regionaxis duplication
ectoderm: epidermis --> neural tissues (notochord)
7zygotic transcription of frog starts alate-blastula
8cortical rotationfrog
formation of gray crescent
the cytoplasm remains at the same place but the cortex rotates about 30°towards sperm entry
91st division of frog embryooboth blastomeres have the dorsalizing factors --> each can develop to an embryo
10frog: yolk is located at which polevegetal pole
11frog: function of blastocoel1) Permits cell migration during Gastrulation by providing space
2) Prevents the cells above it from interacting prematurely with the cells beneath it.
12fate map of frog Dorsal mesoderm Ventral mesoderm Intermediate mesodermDorsal mesoderm: notochord
Ventral mesoderm: blood, kidney, heart
Intermediate mesoderm: somites
13dorsal mesoderm vs blastopore vs dorsal lipdorsal mesoderm --> blastopore --> dorsal lip right above the blastopore
14frog: properties of the organizer1) The ability to become dorsal mesoderm
2) The ability to dorsalize surrounding mesoderm
3) The ability to dorsalize the surrounding ectoderm into neural ectoderm
4) The ability to initiate the movements of Gastrulation (form a secondary blastopore)
15frog blastula: equatorial cells animal cap vegetal capequatorial cells --> mesoderm
animal cap --> ectoderm
vegetal cap --> ectoderm
16culture animal cap cells of frogepidermis (undifferentiated ectoderm)
17culture vegetal cap cells of frogfrom endoderm
18culture dorsal equatorial cells of frogdorsal mesoderm and neural tissues
19culture ventral equatorial cells of frogventral mesoderm and epidermis
20Recombine the animal cap and the vegetal regioninduction of both dorsal and ventral mesoderm
Mesoderm is induced from the ectoderm (animal) by the signals from the endoderm (vegetal)
21Nieuwkoop center1. the dorsalmost vegetal cells of the blastula, which are capable of inducing the organizer
(frog)
2. The Nieuwkoop center is created by the cytoplasmic rotation that occurs during fertilization
3. created by the synergy of the activation of β-catenin dorsally and the activation of the TGF-β signal vegetally.
22frog mesodermal induction factors involved?1. Vg1 = TGF-beta; Localized at the vegetal pole; vg1+animal cap --> mesoderm
2. VegT: Expressed in the vegetal region in the endoderm
23when is dorsal mesoderm specified?right at fertilization
24frog 1. Dorsal vegetal cells + animal cap cells --> ? 2. ventral vegetal cells + animal cap cell --> ?1. muscle + notochord
2. blood and associated tissues
25effects of UV light on cortical rotation of frogUV breaks the various molecules involved in cortical rotation
Increasingly lose dorsal-anterior structures as the UV increases
261. Put dorsal vegetal cell in the normal recipient --> ? 2. Put dorsal vegetal cell in the UV-irradiated recipient --> ?1. axis duplication
2. rescue the formation of embryo; replace the cortical rotation by the dorsal vegetal endoderm
27Nieuwkoop center vs spanmman's organizerNieuwkoop center is an endodermal cell
Organizer is dorsal mesoderm
28establish of DV axis in frog1. cortical rotation: activation of the canonoical Wnt pathway: On the dorsal side of the embryo, β-catenin should be stable and accumulated, since GSK-3 is not able to degrade it;
In the ventral portion of the embryo, GSK-3 should initiate the degradation of β-catenin; Dsh initially localized at the vegetal pore, after cortical rotation, they are translated dorsally
2. TGF-beta + beta-catenin --> Nieuwkoop center:
TGF-beta --> Smad2;
beta-catenin --> Siamois;
smad2+Siamois --> Organizer proteins: Chordin, Noggin, Goosecoid
29add activated GSK-3 to frogblocks axis formation
30Frog 1. Inject beta-catenin to the UV-radiated embryo 2. Injection of exogenous β-catenin into the ventral side of the embryo 3. activation of Wnt1. rescue of axis
2. secondary axis
3. generate axis
31first zygotic gene in frogSiamois
32beta-catenin cascade in Nieuwkoop centerBeta-catenin binds to the TCF3 proteins --> activates the expression of siamois
33proteins in organizer of froggoosecoid
noggin
chordin
follistatin
34frog: 1. remove goosecoid 2.Inject goosecoid in a UV-irradiated embryo1. loss of dorsal mesoderm
2. rescue axis specification
35frog: BMP is localized inthroughout the embryo but not in the dorsal mesoderm
361. BMP 4 was injected into Xenopus eggs 2. overexpression of a dominant negative BMP4 receptor1. all the mesoderm
of the embryo became ventrolateral mesoderm and no dorsal mesoderm
was formed
2. the formation of two dorsal axes. ie, it results in excess dorsal mesoderm
37the default state of frog embryodorsal since BMP4 is needed to induce ventral mesoderm
38Frog 1. culture animal cap 2. Take animal cap and dissociate it into single cells (not in contact with each other) 3. animal cap + noggin 4. animal cap + Dn BMP receptor1. epidermis
2. neural tissue --> default state is neural
3. neural tissue
4. neural tissue --> BMP is an epidermal inducer
39frog: BMP depletedwhole blob of neural tissue
40frog: 1. neural induced tissue in the anterior region transplanted into the blastocoel cavity 2. neural induced tissue in the most posterior region transplanted into the blastocoel cavity1. neural tissue will form head
2. neural tissue will form tail
--> The neural tissue has already been given anterior and posterior identities in the late gastrula
41frog: 1. transplant organizer form early gastrula to the ventral side 2. transplant organizer form late gastrula to the ventral side1. total duplication of axis (head + trunk + tail)
2. only get induction of a tail (loss the ability to induce head and trunk)
42frog: signals involved in AP axis1. head inducing molecules:
cerberus: Expressed in the endomesodermal cells; overexpression --> Get 3 heads being formed
Frzb and Dickkopf: Expressed in the endomesodermal beneath the head; overexpression --> get one huge head
Frzb: secreted by the anterior region of the organizer; inhibit Wnt signaling by binding to Xwnt8
2. Xwnt8: inhibits neural induction; ventralizing the mesoderm and preventing anterior head formation in the ectoderm.
3. inhibition of Wnt --> induce head structure --> Beta-catenin/wnt signalling specify posterior neural tissue
43frog: 1. inhibits Xwnt8 --> ? 2. Inhibit BMP --> ?1. produce anterior neural tissue (head region)
2. form posterior neural tissue (trunk region)
44Frog: overexpression of FrzbWnt signaling fails to occur, and the embryos lack posterior structures, becoming solely head
45frog: highest concentration of beta-catenin in ?dorsal posterior region
46two gradients involved in frog1. a dorsal gradient of “neuralizing” activity
The neuralizing activity came from the organizer and induced the ectoderm to be neural.
Chordin, Noggin and the other molecules
2. a caudal gradient of posteriorizing (“mesodermalizing”) activity
The posteriorizing activity originated in the posterior of the embryo and weakened anteriorly.
eFGF, retinoic acid, and Wnt3a
47caudalization of neural tissue of frog: 1. ectoderm + Noggin 2. Ectoderm + noggin + FGF1. Anterior Neural Tissue --> Anterior is default state
2. Posterior Neural Tissue
48frog AP neural patterning model1. BMP inhibitors from organizer tissue (chordin, noggin and follistatin from dorsal mesoderm and pharyngeal mesendoderm) block the formation of epidermis, ventrolateral mesoderm, and ventrolateral endoderm.
2. Wnt inhibitors in the most anterior end of the organizer (pharyngeal mesendoderm) allow the induction of head structures.
3. A gradient of caudalizing factors (eFGF, retinoic acid, and/or Wnt3a) specify the anterior-posterior identity. (concentration highest at the posterior end )
49advantage of zebrafish as a modelvertebrate, short life cycle (19 hours), relatively abundant, its embryo is transparent
50zebrafish: formation of yolk syncytial layerThe individual blastomeres that are in contact with the yolk cell will fuse with the yolk --> give nuclei into the yolk cell --> yolk syncytial layer (yolk filled with nuclei)
51epiblastThe epiblast is derived from the inner cell mass and lies above the hypoblast. The epiblast gives rise to the three primary germ layers (ectoderm, definitive endoderm, and mesoderm) and to the extraembryonic mesoderm of the visceral yolk sac, the allantois, and the amnion.
52zebrafish: formation of mesoderm and endodermIf the cells remain in contact with the ectoderm, they become mesoderm; if they migrate further down close to the syncytial layer, they become endoderm --> ectoderm on the top, mesoderm in the middle, endoderm inside
531st sign of zebrafish gastrulationforming the thickening at the future dorsal mesoderm region -->embryonic shied ( hypoblast by involution or ingression )
54function of embryonic shield- Dorsalize Mesoderm
- Induce Neural Tissue
- Forms Dorsal Mesoderm (notochord)
- Initiates the movements of Gastrulation
55location of beta-catenin in zebrafishno cortical rotation;
in late blastula, nuclear localization of β-catenin is seen in the yolk syncytial layer nuclei beneath the future embryonic shield (future dorsal mesoderm,).
56zebrafish: posteriorize the tissue by ?FGF activity highest at the vegetal pole lowest at the animal pole
57advantage of chick as a modelhuge egg --> big embryo --> Tissue recombination experiment
58where is the chick embryo going to form?blastodisc
59area pellucida area opaca marginal zonearea pellucida: one-cell layer; forms most of the actual embryo
area opaca: the yolk
marginal zone between area pellucida and area opaca
60epiblast in chick embryo formation of primary/secondary hypoblast cells1. a layer of cells of the area pellucida at the surface that will form the endoderm; Other area pellucida cells have delaminated and migrated individually into the subgerminal cavity (yolk region) --> hypoblast islands --> fuse to form a complete sheet of hypoblast cells (primary hypoblast cells)
2. a sheet of cells from the PMZ (distinguished from the other regions of the margin by Koller's sickle, a local thickening) migrates anteriorly to join the primary hypoblast cells, thereby forming the secondary hypoblast
3. The hypoblast does not contribute any cells to the developing embryo
61posterior marginal zonea thickening of cells in the future posterior region. Koller’s sickle is within the PMZ
62formation of primitive streak of chickCells from the epiblast will undergo EMT and they will move inside between the secondary hypoblast and epiblast on top. They start from the posterior region and progress towards the anterior region; This streak is first visible as a thickening of the epiblast at the posterior region of the embryo, just anterior to Koller's sickle
(primitive streak/Hensen's node = organizer = embryonic shield)
migrating cells enter through its dorsal side and move to its ventral side through the opening called primitive groove
63Hensen's nodea thickening of cells at the anterior end of the primitive streak
Dorsal mesoderm (notochord) is formed at the Hensen’s node
64chick don’t have the dorsal/ventral mesoderm the same way as in amphibian and zebrafishAxial mesoderm: the dorsal mesoderm (notochord) that will migrate along the future midline
Axial (=dorsal) --> paraxial --> lateral plate
65formation of endoderm and mesoderm in chickboth at the posterior side;
When the cells move and go through the primitive streak, some of them move deeper down and eventually become the endoder; The endodermal cells that are migrating further down will eventually join the hypoblast along its midline and displace the secondary hypoblast cells to the sides (mosaic of hypoblast and endodermal cells)
66establish AP axis of chick1. As the egg is going down the hen’s fallopian tube, it is rotating in the same direction;
lagging end of the blastoderm --> future posterior region
leading end of the blastoderm --> future anterior region
2. Nuclear beta-catenin is found all around the marginal zone
Vg1 is localized in the posterior marginal zone
3. Koller's sickle
67chick: transplantation of Koller's sickleformation of new axis
68Henson’s Node is specified by the Posterior Marginal Zonethe epiblast and middle layer cells in the anterior portion of Koller's sickle formed Hensen's node and its notochord derivatives;
The posterior portion of Koller's sickle contributes to the posterior portion of the primitive streak;
marginal zone secrets Vg1 and beta-catenin, but the marginal zone cells themselves do not form dorsal mesoderm; it is the anterior end of Koller's sickle!
69function fo Hensen's nodeDorsalize Mesoderm
Induce Neural Tissue
Forms Dorsal Mesoderm (notochord)
Initiates the movements of gastrulation
70establish LR axis in chick1. the snail gene is characteristic of the right side of avian embryonic organs
2. Shh is expressed more on the left side than the right side.
3. Activin is expressed more on the right side
4. Cerberus is expressed more on the left side than the right side.
5. Nodal is expressed more on the left side
6. Pitx2 is a TF will tell if it is a right side or left side
71advantage of mouse as modellike human is a mammal
72mouse: 1. Separate 2 blastomeres 2. Separate 4 blastomeres 3. Fuse 2 2-cell embryo1. twins
2. 4 embryos
3. get only one embryo
73mouse: time when Apical-Basal axis is gained8-cell stage
74unique gastrulation processes in mammalstrophectoderm --> placenta
inner cell mass --> primitive endoderm --> yolk sac
75Cell polarity model vs inside-outside model
76mouse: Genes controlling early lineage differentiation1. Oct4 and Nanog: Initially expressed in all cells of early embryo; Subsequently restricted to inner cell mass of blastocyst; Required for normal development of inner cell mass
2. Cdx2: Initially expressed in all cells of early embryo; Subsequently restricted to outer cells of morula; Required to maintain the function of trophectodermal cells
3. Gata6: Initially expressed in a few cells of the inner cell mass; Subsequently restricted to the primitive endoderm; Required to maintain primitive endoderm cells
4. recoprocal repression between Oct4 and Cdx2
77mouse: organ size determinationHippo pathway of the outside cell is not activated
Hippo pathway: Hippo active --> Lats activated: kinase that phosphorylates Yap --> yap are degraded (cannot bind to Tead4 to transcribe trophoblast specifying genes) --> no translation of Cdx2
78embryo implantation: hormones used to 1. changes the uterus from inrefractive to prereceptive stage 2. changes the uterus from the prereceptive stage to receptive stage1. progesterone
2. estrogen
79process of embryo implantationPolar trophectoderm connects the uterus and invades the internal tissue
80mouse nodemouse node = henson's node = organizer = embryo sheid
there is a dorsal (axial) mesoderm forming and migrating to the anterior position and fill the gap between the mesoderm wings
81distal visceral endoderm --> anterior visceral endodermspecific genes only expressed in the distal visceral endoderm
The distal visceral endoderm moves to the future anterior region (anterior visceral endoderm)
82AP axis of mouse1. nodal: Initially in the epiblast, later in the posterior region
2. Wnt3: expressed at the embryonic-extraembryonic junction
As the anterior visceral endoderm moves, the Wnt3 expression is only at the future posterior region
3. Cerberus and Lefty: Initially expression at the distal tip of visceral endoderm, finally in the anterior visceral endoderm
4. Hox genes pattern: increasing number --> more posterior
5. Retinoic acid, wnt3a, fgf8 promotes cdx2 and cdx4, promotes Hox genes
831. knock out Nodal in mouse 2. knock out Wnt31. no mesoderm, no primitive streak
2. no mesoderm, no primitive streak
84interaction between Nodal and Cer1/Lefty1Nodal expressed in the epiblast --> secreted to distal visceral endoderm --> distal VE responses --> cer1 and lefty1 produced in distal VE
cer1 and lefty 1 are secreted and inhibit the nodal in epiblast
85function of 1. Lefty1 2. cerberus 3. dickkopfLefty1 - Nodal Inhibitor
Cerberus - Nodal, BMP and Wnt Inhibitor
Dickkopf -Wnt Inhibitor
86knock out anterior visceral endodermheadless mouse;
mouse node can induce trunk and tail but not head because in order to induce head structure, the anterior visceral endoderm is required
872 organizers of mouseAVE - Required for Head Organization
Node - Required for Trunk and Tail Organization
88mammalian LR axisnodal flow: Node cilia causes a leftward flow; Node crown cells detect Nodal Flow
leftward nodel flow induces Nodal, Lefty2
89Pronephros vs mesonephrosPronephros: blood filtration units that are developing and eventually linked to the nephric duct (non functional, eventually go apoptosis, transient)
10 day: generate mesonephros (non functional, part of it will be maintained and be taken over by the developing gonad)
90Mullerian duct vs Wolffian duct (Nephric duct)Mullerian duct --> oviduct and uterus
Nephric duct = Wolffian duct
Gonad is undifferentiated  bipotential gonad
91Differentiation of human gonads male determination factor female determination factor1. Cells start to proliferate in the genital ridge to form the gonad, no germ cells --> Mullerian duct forms,
germ cell move into the developing gonad
Testis: Complicated testis cords are linked to the Wolffian duct
2. Male determination factor: SRY (without specificity) and Sox9 (with specificity)
3. Female determination factor:
Dax: expressed in the same cells as SRY; antagonize the function of SRY and Sox9
Wnt4: on the autosomal genes; activates Dax1 expression
92mammal Primordial germ cells precursors form atthe base of the primitive streak
931. X Y + 2 copy of Sox9 2. XX + 2 copies of Sox9 3. XX + 3 copies of Sox9 4. X Y + 1 copy of Sox91. male
2. female
3. male
4. female
941. XX Lacking Wnt 4 2. XY Extra copy of Wnt 4 3. XY extra copy of Dax1. male
2. female
3. female
95X:A (drosophila sex determination)Genes on the X chromosome are more highly expressed than on the autosome
homodimerization of X genes --> make a functional TF that leads to expression of sxl
heterodimerization (one from X one from A) --> repressor --> sxl not activated
Sxl acts as splicing factor to remove male exon from transcript
Transformer is a splicing factor that affect the splicing of female doublesex
96what portion of embryo forms CNSonly central dorsal portion of ectoderm --> neutral tube --> entire control nervous system (CNS)
97Mechanical forces driving neurulationapical constriction of medial hinge point: cuboid morphology --> wedge-like
98effect of 1. colchicine 2. cytochalasin B in neurulation1. colchicine prevents the thickening of neural plate by disrupting microtubules --> inhibits the formation neural tube --> thickening is microtubule dependent
2. cytochalasin B disrupts the actin cytoskeleton --> block formation of neural furrow
99in neurulation, reason for Separation of surface ectoderm and the neural tubeSurface ectoderm expresses E-cadherin; neural tube expresses N-cadherin
100AP axis of nervous system1. Forebrain, midbrain, hindbrain
2. Otx/Otd specifies forebrain and midbrain
3. Gbx2 specifies hindbrain
101Mutant Otxloss of forebrain and midbrain
102why the cells in each rhombomere do not mix with cells of other compartments (hindbrain)After compartmentation, the descent cell do not go into neighboring compartment since they express different cell surface proteins
r3 and r5 express EphA4; r2, r4, r6 express EphrinB2
EphrinB2 is the ligand of EphA4 --> binding can induce
1. a repulsive response
if try to migrate to the neighboring compartment, it will be prevented by the repulsion
2. cleavage of Ephrin B2 from cell surface
103What makes the compartments of hindbrain different?different rhombomeres express different hox genes --> specifies the identity
104DV axis of neurulation1. Floor plate: ventral most structure
Roof plate: dorsal most structure
2. Specification of ventral cell fate by sonic hedgehog (shh)
Notochord produces Shh which then stimulates floor plate to produce Shh --> concentration highest in the ventral region, lowest in the dorsal region
3. BMP4 and BMP7
Before neurulation, it prevents the neural development; After neural tube formed, it no longer prevents the neural cell fate
BMP induces roof plate to express TGF-beta family proteins, BMP4, BMP7 and activin --> establish a gradient highest in the dorsal
105Symmetric/asymmetric division of neuroepithelial cellsCell division always occur in the lumen side
symmetric: Cleavage plane is perpendicular to outer surface
1 stem cell --> 2 stem cells
Asymmetric: Cleavage plane is parallel to outer surface
1 stem cell --> 1 stem cells + 1 neuron
106factor involved in Symmetric Divison of Neuroepithelial Stem CellsLis-1 binds to microtubules or dynein motors
mutant Lis-1 --> Cleavage plane mis-oriented --> apoptosis -->
Decrease of neurons in brain
107factor involved in Asymmetric Divison of Neuroepithelial Stem CellsPar-3: cytoskeletal regulator
Daughter stem cell contains Par-3
Daughter neuron does not contain Par-3
With Par3 --> high Notch signal --> stem cell
Without Par3 --> low Notch signal --> neuron
108Nervous system: monolayer --> multilayerventricular zone --> preplate --> cortical plate (gray matter)
Born earlier  occupying region closest to the lumen side
Later born neurons  migrate and pass through the plates that have be establish
109factors leading the migration of neurons to the cortical plate (Glia guidance1. Radial glia located in the ventricular zone, projecting long process to the outer surface
2. Cajal-Retzius cells located at the most superfacial region
produce Reelin which promote the formation of radial glia and promote migration
110knock out Reelin in nervous systeminverted cortical plate (cannot pass through preplate)
111cell fate of neural crest cellsneural crest cells give rise to peripheral nervous ystem
112When the neural crest cells are located in the original position, they are tightly associate with each other. Why?N-cadherin
to migrate: EMT (downregulates N-cadherin)
113Dorsal root ganglia: a cluster of sensory neurons Melanocyte: pigment cell that gives skin color Ventral root Schwann cells: peripheral glial cells that insulate the peripheral axons Adrenal medulla: produce epinephrineDorsal root ganglia: cluster of sensory neurons
Melanocyte: pigment cell that gives skin color
Ventral root Schwann cells: peripheral glial cells
that insulate the peripheral axons
Adrenal medulla: produce epinephrine
114Migration of trunk neural crest cellsPath 1: dorsal-lateral migration
migrate over the surface of dermomyotome; Eventually enter epidermis, become melanocyte
Path 2: ventral migration
Enter the sclerotome
If stay in the sclerotome, give rise to dorsal root ganglia
If exit the sclerotome, give rise to sympathetic neurons, adrenal medulla and schwann cells
115Molecules that promote and direct the migration of neural crest cells1. Attractive signals:
-Extracellular matrix (ECM) proteins (e.g. fibronectin, laminin, collagen): provide the substrate/route for the migration of neural crest
-Secreted proteins such as BMP from adrenal cortical precursor cells, and stem cell factor (SCF) from dermal cells.
2. Repulsive signals from the posterior portion of the somite: Semaphorin 3F is only expressed
in the posterior half of somites
Neural crest cells expressing neuropilin-2, the binding of semaphorin 3F to its receptor neuropilin-2 on neural crest cell surface initiates a repulsive response.
116pathway selection (axon guidance)growth cone
axonal bundles formed by early neurons
The projecting axon may encounter the pre-exists axonal bundles. It will associate with the bundle if both the bundle and the axon contains N-cadherin. The bundle is used as the substrate/rail for long distance migration
117midline crossing of commissural axonsCommissural neuron vs Ipsilateral neurons
Cues from midline cells:
-Netrin (attractive)
-Shh (attractive)
-Slit (repulsive)
Their receptors on axons
-Dcc/Unc40 (Netrin receptor)
-Boc (Shh receptor)
-Robo 1 and Robo 2 (Slit receptor)
Expression of the Robo3 gene can generate two alternatively spliced forms Robo3.1 and Robo3.2 that differ only in the cytoplasmic domain sequence.
-Before crossing, contralateral axons only produce Robo3.1, which inhibits Robo1 and Robo2 (no repulsion), allowing DCC-mediated attraction.
Robo3.2 is produced after crossing, no longer inhibit Robo1/2, Robo3.2 is also a repulsive receptor.
Robo1 and 2 inhibits DCC --> no attraction
118Neuronal target selection Nasal TemporalRetinal ganglion cells
Nasal  posterior
Temporal  anterior
repulsive response: growth cone has surface EphA, target cell has ephrin
119Synapse formation and refinement at neuromuscular junctionNerve terminal produces Agrin;
Agrin induces post-synaptic differentiation (muscle site): clustering of AChR
Muscle produces Gbb (fly)
Gbb induces presynaptic differentiation: accumulation of synaptic vesicles at nerve terminal
120one-to-one connction between motor axon and muscle fiberHigh neural activity  more Gdnf produced by muscle fiber  maintain this connection
121vertebrate limb field is determined byHox genes
122PD of vertebrate limb: remove apical ectodermal ridgeearlier AER is removed  more distal structure lost
FGF4,8
123PD of vertebrate limb: Progress zoneFGF4,8 stimulates the cell proliferation in progress zone
124AP of vertebrate limb: zone of polarizing activityMesodermal cells located at posterior margin of a limb bud
high Shh --> high Gli3 in ZPA
125DV of vertebrate limbWnt7a in ectodermal cells specifies dorsal structures: induce dorsal mesodermal cells to express Lmx1b
Engrailed prevents the expression of Wnt-7a in the ventral ectoderm.
126external organs of insects are formed from ?imaginal discs
127AP of insect wingHh(Shh) is in posterior compartment
Dpp is expressed in the anterior border cells
engrailed induces Hh, Hh functions as short range morphogen  induce anterior border cells expressing Dpp, Dpp is long range morphogen
128DV of insect wingApterous is only expressed in the dorsal compartment
Wingless: expressed in both border cells; important for the outgrowth of wings
Serrate
-Vestigial: a master selector gene for wing development
Vestigial expressed in all wing cells, vestigial integrates different signals via different enhancers in its control regions
129PD of insect wingImaginal disc: concentric ring-like structures since they are folded epithelium
Depending on the position of rings, innermost ring  most distal structure
Peripheral rings  most proximal structure
130insect leg has no DV compartment AP similar to wingsDorsal border cells  Dpp  specify dorsal A-P formation
Ventral border cells  wingless  specify ventral A-P formation
131accretionary growthGrowth by accretion: bones, cartilage
1322 Intracellular pathways in the control of tissue growthTOR pathway: Growth factor activates the Tor pathway --> larger cell size
Hippo pathway: negative regulation of growth
Hpo  phosphorylation of Wts  phosphorylation of Yki  degradation
133Cholaons and Mystatinlimit tissue sizes
134Hormones and growth factors in the control of overall body sizePituitary secreted Growth Hormone --> IGF-1
135Hormonal control of insect metamorphosisJH (Juvenile hormone) binds to its nuclear receptor Met to prevent metamorphosis
20E (active Ecdysone by oxidation ) binds to its nuclear receptor ECR to promote metamorphosis
Pairs of neurons in brain produce PTTH  stimulate prothoracic gland to produce ecdysone  circulation of ecdysone make it oxidized
Remove corpus allatum  no JH  precocious metamorphosis
136Morphallaxis vs. epimorphosisMorphallaxis: a smaller individual
epimorphosis: growth of the missing parts
137processes in amphibian limb regenerationRemove distal limb  the surrounding epidermis move towards and cover the wound surface
Nerve innervation
Regenerating limb has the apical epithelial cap
Blastema (similar to progress zone): dedifferentiated cells located beneath AEC
138factors required to convert myotube to myoblastCleavage of BMP4/7 by Thrombin
139nervous control in amphibian limb regenerationAG
Prod1
Retinoic acid
Decreasing concentration of retinoic acid from proximal to distal
Decreasing concentration of prod1 from proximal to distal
Retinoic acid gradient induces prod1 gradient
Prod1 as AG receptor promote proliferation
Prod1 specify positional value
140Calorie restrictionIncrease in the activity of SIR2 (or sirtuin) (silent information regulator)
-descrease in insulin signaling
-decrease in the expression of cell death genes
-increase in stress resistance, etc.
Decrease insulin reasonably (not too much)  increases Foxo  increase lifespan
141Overexpression of superoxide dismutase and catalase in fliesROS decreases  lifespan increases  fertility decreases
142Indy mutation/Indy mutation Indy wt/Indy mutationIndy mutation/Indy mutation  lethal
Indy wt/Indy mutation  extended lifespan
Indy optimizes the metabolic activity  both longevity and fertility at old ages
1431. remove suspensor 2. detach suspensor and reattach it1. embryo dies since suspender feeds the growing embryo
2. embryo won't die
144when is the 1st radial pattern and 1st AB established?1st AB: Octant 8-cell
1st radial pattern: Dermatogen (outside is epidermis)
145globular stageearly: all the radial patterns established
late: organizer cell that sends signals to the hypophysis
146only cell in the suspensor that contributes to the embryohypophysis formed in the early globular stage
defines RAM + root cap
147mutant monopterous (MP)missing hypocotyl and root (only have the shoot)
148factors involved at heart stage1. MP: Needed for root + hypocotyl; Transcription factor; MP responds to the presence of auxin
2. GN: Needed for apical-basal patterning; Encodes ARF-GEF; Involved in vesicle trafficking + protein secretion; Involved in auxin based patterning by determining location of auxin;
Determines polar location of PIN family of auxin efflux carriers
3. Wox genes: functional redundancy; Expression pattern predicts embryo pattern
149mutant gnom (gn)big ball of cell --> don't get any AB patterning nor radial patterning
150AB axis of plantapical: WOX2 --> HD-ZIP
Basal: WOX9 --> PLT
hypophysis: WRKY2-WOX8/9
151Location of PIN proteinbasal cell surfaces, organizer cell and hypophysis
152movement of Auxin
153Axin establish of hypophysisauxin --> activate MP in basal cell --> activate TMO7 --> TMO7 tranlocates into hypophysis through plasodesmata
TMO7 + other proteins (like auxin response factor 9 –ARF9) are directly activated by auxin specify hyophysis fate which subsequently specifies RAM
1542 models of organization of SAM1. Tunica-corpus model: three distinct cell layers
epidermis (L1) + cortex (L2) = Tunica maintained as distinct cell layers by anticlinal cell divisions (perpendicular to the cell surface)
Corpus (L3): random cell division
2. Apical Zonation Model
155factors involved in SAM establishment1. Wushel (Wus) – WOX transcription factor;
located in the organizer center (right underneath the stem cell pool);
Involved in conferring stem cell fate on overlying cells of SAM proper
2.Shoot meristemless (STM) – HOX transcription factor;
Expressed throughout the central zone;
Activates biosynthesis of cytokinin (CK) through upregulation of IPT gene;
3. Clavata 1, 2, & 3 (CLV1-3):
CLV1, CLV2 - Recepoter kinases
CLV3 - ligand
4. Coryne (COR) - receptor kinases
156knock out WUSstem cell get depleted, no SAM
157STM mutant + cytokininSAM rescues
158why STM is excluded from cells undergoing organogenesis?STM is repressed in the peripheral zone by the TFs ASYMMETRIC LEAVES 1 & 2 (AS1 & 2)
Creation of auxin maxima in the leaf primordia, i.e. peripheral zone (mediated by localization of PIN proteins)
Auxin accumulation is repressed by the meristem itself
Auxin drives organogenesis
159mutant apetala1 (AP1)/leafy (LFY)just get leaves, no flowers or floral organs
160vegetative to reproductiveFT protein is made in the leaves; Transported through the phloem to shoot apex
FT binds to FD in the shoot apex
FT-FD activates the SOC1 gene
SOC1 acts with FT-FD to activate floral meristem identity genes (AP1/LFY)
161Floral Organ identity in ArabidopsisABC model
A: required for sepals and pedals (AP1, AP2)
B: Required for petal and stamen production (AP3, PI)
C: Required for stamen and carpel production (AG)
162Class A mutantenlarged carpel and stamen, no sepals, no pedals
163mutant Bhave sepals and a big carpel, no pedals, no stamen
164Universal BC model
165Sepallata genes (SEP1-4)Needed to make floral organs in the first place;
MADS box genes;
Work in tetramers with A, B, and C MADS box genes;