Midterm 1- Excludes Lecture 1,3,5,13 Flashcards
Compartment
boundary restricting movement of cells
Gap gene
a type of gene involved in the development of the segmented embryos of some arthropods. Gap genes are defined by the effect of a mutation in that gene, which causes the loss of contiguous body segments, resembling a gap in the normal body plan
PAL-1
caudal-like transcription factor specifying C and D fates
Holometabolous Development
a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult)
Role of B-catenin in sea urchin development
β-catenin and Otx activate expression of Pmar1 in micromeres
Pmar1 represses HesC, a repressor of micromere fate. Without micromeres there is no vegetal fate
Hox genes
!Specify parasegment! identity through the control of expression domains which work together to give rise to the unique parasegments. It does this through the production of homeobox transcription factors
Cell-autonomously specification
Cell fate develops through the localization of Determinants being asymmetrically distributed in the dividing cell
Methods of Cell fate specification
1)Autonomously
2)Cell-cell interactions
3)Cell-cell interactions through use of morphogens
SKN-1
Disables PAL-1 in the EMS cells, transcription factor specifying EMS fate
APX-1/GLP-1
Homologous to Delta/Notch pathway and signals for ABp cell fate
Relation between Bicoid, Caudaul, Nanos, and hunchback
Nanos prevents translation of hunchback mRNA in the posterior of the embryo and Biccoid prevents the translation of Caudal in the anterior and activates
zygotic hunchback
expression
Relationship between Sog, Dpp, and Tld in forming the Dorsal/ Ventral axis
Sog-Sog binds to Dpp and inactivates it
Dpp- specifies amnioserosa and dorsal ectoderm and only forms when dorsal protein is not present
Tld-cleaves Sog, leading to a peak of Dpp activity in the dorsal most region
Nurse cell
produce (among other things) mRNAs for morphogens for a-p patterning of the embryo. These mRNAs are transported and localized within the oocyte
Three levels of description and Understanding
1)Macroscopic, Descriptive-Focuses on describing the phenomenon instead of explaining it
2)Cellular, “Conceptual”-Describes the steps involved in triggering a phenomenon
3)Molecular- Describes the exact chemicals and genes necessary for an event to occur
Determination
Implies a stable change in the internal state of a cell that cannot be altered usually due to gene expressions
Special properties of C.elegans
- Soil nemotodes composed of 959 cells
- Invarient development
Draw the Bicoid and Nanos effect of Hunchback
Orginally maternal Hunchback is farily evenly spread between the Anterior and posterior but interaction with bicoid greatly increases zygotic hunchback in the anterior with the interaction of nanos disabling zygotic hunchback
Neuroblasts in Drosophila
The nervous system starts to form,
when neuroblasts delaminate from the
ventral ectoderm.
Draw the fate map and appropriate proteins involved in the first 8 cells of C.elegans
Draw the founder cell cleavage pathway with the end tissues formed
Morphogen
a substance involved in pattern formation that forms a gradient and elicits at least two different responses at different thresholds (at the same time)
Nanos localization
Localized to the Posterior Axis
Experiment that corresponds to the three levels of understanding
1)Macroscopic-Observations
2)Cellular-graft or transplant experiment
3)Molecular- gene expression experiments
How is Kruppel regulated by Hunchback
Kruppel is only activated in a specified area where hunchback is in high enough concentration to activate the gene but not high enough concentration to deactivate the gene.
Dorsal/Ventral Axis
Top and Bottom axis
How is bicoid spread throughout the embryo?
bicoid mRNA is localized to the anterior, but
Bicoid protein can diffuse
freely through the syncytium
and forms a gradient
How are EVE strips determined?
generalized activation by bcd and ubiquitous transcription factors combined with localized repression by gap genes. Each of the eight stripe borders of these four stripes is shown to be under the control of a particular gap gene expression domain.
Imaginal Disks
give rise to certain adult structures (wing, leg, eye). They are patterned during embryogenesis
Proteins involved in making the Dorsal Protein
Pipe- begins the pathway by binding to an unknown subtrate
Spatzle-Activates the Toll Receptors
Toll-Triggers the degredation of Cactus
Cactus-Binds to Dorsal and prevents it from entering the Nucleus and altering gene expression
Gastrulation
During gastrulation future endodermal and mesodermal cells move to
the inside of the embryo to form the inner cavities of the body.
Bicoid localization
Localized to the anterior axis
Regulative Development
embryos using external signals have the potential to replace missing cells
Bithorax Complex Genes
UBX, abd-A, Abd-B
Lithium treatment of sea urchins
Li treatment of sea urchin embryos causes vegetalisation. This is because Li is known to block the GSK-3 kinase, which negatively
regulates the Wnt/Wg pathway by mediating degradation of the effector β-catenin
Anterior/Posterior Axis
Front and Back axis
Germ Layers and their organs formed
1)Mesoderm-Skeleton, Muscles,kidney,heart, blood
2)Endoderm-Gut,Liver,lungs
3)Ectoderm-Skin, Nervous System
Dorsal Protein
Morphogen which helps define the ventral axis. At high concentrations it activates the twist genes and at low concentrations it activates the dpp gene
Caudal protein
responsible for the formation of abdominal structures
Homeobox transcription factors
Transcription factors recognizing specific DNA sequences and regulate target genes and are coded for by HOX genes
What happens when wingless is lost?
leads to a loss of genes normally expressed in the posterior
part of the segment. The cells adopt an anterior fate and produce denticles
Parasegment
mark the position of boundaries that separate every segment of the Drosophila embryo into anterior and posterior compartments. Each segment is formed through pair-rule and gap gene expression
Vegetal Pole
Half of the sea urchin blastomere which goes on to form the gut and skeletal elements
Antennapedia complex
specifies PS 1-4
Mosaic Development
if development was exclusively controlled by cytoplasmic determinants, the fate of every cell would depend uniquely on itslineage, while its position in the embryo would be totally irrelevant.Thus, in “mosaic embryo” (which is an abstraction)the fate of the cell is governed entirely by its intrinsic characteristics, i.e. cytoplasmic determinants it inherits at cell division.If the
cells are removed from the embryo they should, in principle, develop according to their intrinsic instructions and differentiate into the appropriate part of the embryo even if the rest of the embryo is not there.
Label the Following diagram
A)Nurse cell
B)Oocyte
C)Posterior follicle cell
D)Nucleus
E)Follicle cell
F)Anterior Follicle cell
G)Stalk
Sea urchin blastula fate map
Bithorax complex
specifies PS 5-14
Gastrulation in drosophilla
mesoderm
invaginates on the ventral
side first forming a furrow
and then an internalized
tube.
POP-1
Must be removed form the cell by MOM-2 pathway to allow transcription to occur in the E cell which derives from the EMS cell
Cellularization
creates an individual cell membrane for each nucleus
Pair Rule gene
promote the formation of alternate body segments in Drosophila,A parasegment corresponds to the posterior part of one segment and the anterior part of the following segment ex. eve
Cell-cell signalling specification
a signal received by a cell changes its developmental potential from one fate to a different one either through diffusion of a or direct contact between cells to transmit the signal.
Maternal effect genes for Drosophilla
Bicoid, Nanos, Pipe, and Gurken, and Torso
Relationship between the P2, ABa, ABp, and EMS cell
P2 cell produces the signal form MOM-2 and GLP-1 which MOM-2 will help differentiate EMS into E and MS, while GLP-1 will differentiate ABp from ABa
Describe the location of PAR genes in the embryo of a C.elegans
PAR-3,Par-6 and PKC-3 are localized into the Anterior where as PAR-2 and PAR-1 are localized into the posterior
Draw the flow chart to go from maternal genes to specified cells
Draw the Localization of Pipe, Nanos, Bicoid, and Torso-like in early embryo of drosophilla
Axis formation in sea urchins
Vegetal- Animal is determined during oogenesis and appears to be related to the site of attachment in the ovary (Equivalent to the anterior and posterior in other animals)
Oral-Aboral-first molecular differences appears around the 60 cell stage (equivalent to the dorsal ventral axis)
Example of a maternal gene, gap gene, pair rule gene, segment identity gene, and segment polarity gene
Maternal gene:Biccoid
Gap gene: Kruppel
Pair rule gene: Eve
Segment identity gene:UBX, Abd-a,ABd-b
Segment Polarity gene:Wingless, HH
MEX-5
Localized in the anterior by PAR-1 and Responsible for degrading PIE-1 in the AB cell
Wingless path way
1)Hh interacts with wingless to activate it’s expression
2)wingless binds to frizzled
3)Frizzled binds to axin and GSK-3 complex which has the proteosome that degrades B-cantenin
4)B-cantenin is not degraded and can move to the nucleus to activate genes
How is the Ventral axis determined in Drosophilla?
1)Gurken signalling blocks the synthesis of Pipe on the dorsal side
2)Pipe binds to an unknown substrate triggering a cascade which leads to Spatzle binding Toll. Toll degrades the protein Cactus allowing for Dorsal to be freed and enter the nucleus of the cell. This creates a gradient along the cell. High concentrations leads to the development of the Ventral side.
3) A number of genes are activated or repressed by different concentrations of
Dorsal protein (transcription factor) leading to a series of distinct fates along the
dorso-ventral axis.
Gurken
Prevents Synthesis of pipe of the dorsal side. Signal which causes the dorsalization of follicle cells
Draw the distribution for Bicoid,Nanos, Hunchback and Caudal protein gradient in the embryo
Favoured Model organisms and why
1)Chicken- Large embryo, easily accessible
2)Sea Urchins/ Amphibians- Easy to manipulate, large quantity, easy to observe
3)Drosophilla/ Mouse-Small, easy to culture, short generation times, developed genetic tools
Role of Nanos in Anterior/Posterior Axis formation
Nanos prevents the translation of hunchback mRNA in the posterior
Syncytium
Refers to a single cell with multiple nuclei. A syncytium provides the rapid communication and transfer of information to allow cells to function as a coordinated unit
Fate
describes what a cell (group) will develop into
Par and the first division of a C.elegans embryo
PIE-1 moves into the P1 cell right before cell fertilization. After the first division some PIE-1 remains in the AB cell but is degraded
- Occurs due to phosphorylation of MEX-5 by PAR-1 in the posterior end allowing it to travel to the anterior end. There it is dephosphrylated and become trapped in the anterior. MEX-5 Degrades PIE-1
- A similar phosphylation/deposphoryation event occurs to trap PIE-1 in the posterior
Specification
implies a change in the internal state of a cell (group) leading to differentiation into their normal fate, when isolated. Cells can still respond to outside influence and
potentially change their fate.
Draw the Distribution of bicoid,nanos,caudal and hauncback mRNA in the Oocyte
How are the A-P and D-V axis set up in C.elegans
- a-p axis is determined by sperm entry. Entry position becomes the posterior cell
- d-v axis is determined by the tilting of cleavage plane of the AB blastomere due to
oval egg shape
Isolation experiment
Removal of a cell from it’s original location of the blastula to observe weather it will develop normally when separated from the embryo. If develops normally this can tell us that the cell fate is either Specified or Determined
Maternal effect Genes
those genes whose products, RNA or protein, are produced or deposited in the oocyte or are present in the fertilized egg or embryo before expression of zygotic genes is initiated.
Blastomere experiments in sea urchins
Separation experiment- allows for the vegetal and animal to develop into two separate incomplete halves
Recombination experiment- by adding micromeres to the animal half the embryo can fully form
Recombination experiment- by adding micromeres to the side of a blastomere leads to the development of a secondary gut
How is the Dorsal axis formed
Dpp protein is expressed when Dorsal is not present in the cell. Sog protein prevents it from spreading too far from inactivation of Dpp. Tld cleaves Sog in the dorsal most region leading to a clean line of Dpp in the upper regions.
Hemimetabolous Development
Immature forms of these insects are called nymphs and these gradually increase in size and change form
Engrailed function
defines a compartment by establishing a cell-lineage boundary effectively confining cells to one particular parasegment.
Determinants
Cytoplasmic factor (e.g. a protein or RNA) in the egg and in embryonic cells that can be asymmetrically distributed at cell division and so influence how the daughter cells develop.”
Ventralized Embryo
Embryo forms denticle belts on the dorsal and ventral side where normally the would only form on the ventral side
PAR proteins
Act as adapters and kinases in the developing C.elegan leading to the uneven cleavage of cells. proteins become asymmetrically localized before the first cleavage
Understanding gene names and their meanings
dorsal (lower case, italic): gene name
Dorsal (Capitalized, regular): protein name
dorsal (lower case, regular): plain English
Ex. dorsal codes for the Transcription Factor Dorsal
Competence
The ability for a cell to receive and act upon a signal produced by another cell.
Long germ vs Short germ insects
Long germ-late cellularisation simultaneous formation
of all segments
Short germ-early cellularisation sequential formation of
abdominal segments but Expression of gap and pair-rule genes in
short-germ and long germ insects is similar
SYS-1
Binds to POP-1 in the E cell to activate transcription of genes required to form the gut
How is segment polarity obtained in Drosophilla
In between parasegments there are zones that lack denticles. The anterior will contain denticles but the posterior will not. A feedback loop involving Wg and Hh signalling establishes the parasegment border
Notch Signalling pathway
The receptor (Notch) is cleaved
upon ligand binding to Delta.The intracellular domain moves to the nucleus, where it acts as a transcription
factor
MOM-2/MOM-5
Homologous to Wingless/Frizzled. MOM-2 is produced by the P2 cell and activates the MOM-5 receptor to differentiate EMS into E and MS
Pipe
Signal on the ventral side of the drosophilla embryo
Oogenesis
the process by which the female gametes, or ova, are created.
PIE-1
Disables PAL-1 and SKN-1 in the P2 cell line. Acts as a general transcriptional repressor specifying germ cell fate
Role of Bicoid in Anterior/posterior axis formation
1)Anterior, the mRNA is localized to the posterior and diffuses using a syncytium. Forms the Acron, Head, and Thorax
2) Bicoid prevents the translation of caudaul mRNA in the anterior letting it form a gradient along the anterior-posterior axis
3) Biscoid also acts as a transcription factor for hunchback
Animal Pole
Half of the sea urchin blastomere which Form the ectoderm
Cell-Cell Interactions using a Morphogen specification
allows the co-ordinated specification of several different cell fates simultaneously through a Morphogen gradient. Different concentrations of Morphogen induces multiple cell fates
Transplant experiment
Removal of cell from it’s original position on a blastula and transplanting it onto a different segment of a separate embryo and recording what occurs. If the cell develops based on it’s original position on the embryo then it is Determined, if it develops into a cell type that matches the transplant location it is Specified.
