Lecture 7

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Questions and Answers

What is the function of VegT and Vg1 molecules?

They participate in establishing the cordo mesodermal cells.

They are anchors for cell adhesion molecules.

They are involved in the grey crescent region.

They regulate the activity of other genes. (correct)

What is the key component in the molecular mechanism of dorsal-ventral axis specification?

TGF-Beta

Goosecoid

Beta-catenin (correct)

VegT

What is the function of the Beta-catenin-Trf-3 complex?

It is involved in cell adhesion.

It regulates the expression of other genes. (correct)

It is an anchor for cell adhesion molecules.

It participates in the formation of the chordamesoderm cells.

What genes are activated by the B-Catenin-Tcf-3 complex?

Siamois and Twin genes Signup and view all the answers

What is the function of the Goosecoid gene?

It codes for a transcription factor. Signup and view all the answers

What is the term for the core of the mesoderm and the dorsal lip of the blastopore?

Organizer of the embryo Signup and view all the answers

What is the region where beta-catenin accumulates in the embryo?

Gray crescent region Signup and view all the answers

What is the result of the expression of the Siamois and Twin genes?

Establishment of the dorsal-ventral axis. Signup and view all the answers

What is the primary function of positional information in an embryo?

To specify the location of cells relative to the body axis Signup and view all the answers

What is the result of cytoplasmic rearrangements during fertilization in an amphibian oocyte?

The depletion of cytoplasm at the site of sperm entry Signup and view all the answers

What type of axis is established by the concentration of molecules at the vegetal pole?

Central axis Signup and view all the answers

What is the name of the region that forms opposite the site of sperm entry during fertilization?

Gray crescent region Signup and view all the answers

What is the role of molecular cues in pattern formation?

To establish the body axes Signup and view all the answers

What is the outcome of the mass movement of cytoplasm towards the point of sperm entry?

The formation of the gray crescent region Signup and view all the answers

Which molecules are dragged along with the cytoplasm during cytoplasmic rearrangements?

Molecules that specify dorsal fate Signup and view all the answers

What is the significance of the gray crescent region in establishing the body plan?

It specifies the dorsal side of the embryo Signup and view all the answers

What is the result of the inhibition of BMP4 activity?

Dorsal development can proceed Signup and view all the answers

Which gene is responsible for establishing the cranial end of the embryo?

Goosecoid Signup and view all the answers

What is the role of the AVE in the embryo?

All of the above Signup and view all the answers

What is the function of the HOX genes in the embryo?

Specifying the segment identity of tissues within the embryo Signup and view all the answers

What is the result of the misregulation of the Brachyury gene?

Caudal dysgenesis Signup and view all the answers

What is the role of FGF8 in establishing the left-right body axis?

Inducing the expression of Nodal and Lefty2 Signup and view all the answers

Which gene is responsible for establishing right-sidedness in the embryo?

Snail Signup and view all the answers

What is the role of the node in the embryo?

Maintaining the expression of the nodal gene Signup and view all the answers

What is the function of the HOX genes in the development of the cranial-caudal axis?

Specifying the segment identity of tissues within the embryo Signup and view all the answers

What is the result of the activation of the Goosecoid gene?

Inhibition of BMP4 activity Signup and view all the answers

What is the primary function of positional information in an embryo?

Providing spatial information within the embryo Signup and view all the answers

What occurs during cytoplasmic rearrangements in an amphbian oocyte?

Cytoplasm moves towards the site of sperm entry Signup and view all the answers

What is the significance of the gray crescent region in establishing the body plan?

It marks the future dorsal side of the embryo Signup and view all the answers

What type of axis is established by the concentration of molecules at the vegetal pole?

Dorso-ventral axis Signup and view all the answers

What is the name of the region that forms opposite the site of sperm entry during fertilization?

Gray crescent region Signup and view all the answers

What molecules are dragged along with the cytoplasm during cytoplasmic rearrangements?

Molecules specifying dorsal fate Signup and view all the answers

What is the outcome of the mass movement of cytoplasm towards the point of sperm entry?

Creation of the gray crescent region Signup and view all the answers

What is the role of molecular cues in pattern formation?

Establishing the body axes Signup and view all the answers

What is the primary function of transcription factors such as VegT and Vg1?

To regulate the activity of other genes Signup and view all the answers

What is the significance of the gray crescent region in the embryo?

It determines the dorsal side of the embryo Signup and view all the answers

What is the role of beta-catenin in establishing the dorsal-ventral axis?

It regulates the expression of genes involved in establishing the dorsal side Signup and view all the answers

What is the function of the Beta-catenin-Trf-3 complex?

It translocates into the nuclei of cells and regulates gene expression Signup and view all the answers

What is the role of the Siamois and Twin genes in establishing the dorsal-ventral axis?

They activate the Goosecoid gene, which regulates the chordamesoderm cells Signup and view all the answers

What is the function of the Goosecoid gene in establishing the dorsal-ventral axis?

It is a transcription factor involved in regulating the chordamesoderm cells Signup and view all the answers

What is the significance of the organizer in the embryo?

It is the core of the mesoderm and the dorsal lip of the blastopore Signup and view all the answers

What is the role of transcription factors in establishing the body plan of the embryo?

They regulate the expression of genes involved in establishing the body plan and axis specification Signup and view all the answers

What is the result of the inhibition of BMP4 activity?

Favors dorsalization Signup and view all the answers

What is the role of the node in the embryo?

Organizing center for the embryo Signup and view all the answers

What is the function of the AVE in the embryo?

Specifies the neural pattern by inhibiting primitive streak formation anteriorly Signup and view all the answers

What is the result of the misregulation of the Brachyury gene?

Results in caudal dysgenesis Signup and view all the answers

What is the role of FGF8 in establishing the left-right body axis?

Establishes the left-right body axis by inducing the expression of Nodal Signup and view all the answers

What is the function of the HOX genes in the embryo?

Specifies segment identity of tissues within the embryo Signup and view all the answers

What is the result of the activation of the Goosecoid gene?

Favors dorsalization Signup and view all the answers

Which gene is responsible for establishing right-sidedness in the embryo?

Snail Signup and view all the answers

What is the role of the Hensen's node in the embryo?

Involved in the formation of the primitive streak Signup and view all the answers

What is the function of the Cerberus and Lefty factors in the embryo?

Inhibits the activity of BMP4 Signup and view all the answers

What is the primary function of positional information in an embryo?

To establish the body axes Signup and view all the answers

What is the outcome of cytoplasmic rearrangements during fertilization in an amphibian oocyte?

Mass movement of cytoplasm towards the point of sperm entry Signup and view all the answers

What type of axis is established by the concentration of molecules at the vegetal pole?

Dorso-ventral axis Signup and view all the answers

What is the result of the mass movement of cytoplasm towards the point of sperm entry?

Formation of the gray crescent region Signup and view all the answers

What molecules are dragged along with the cytoplasm during cytoplasmic rearrangements?

Molecules specifying dorsal fate Signup and view all the answers

What is the significance of the gray crescent region in establishing the body plan?

It specifies the dorsal side of the embryo Signup and view all the answers

What is the role of molecular cues in pattern formation?

To provide positional information Signup and view all the answers

What is the outcome of cytoplasmic rearrangements in an amphibian oocyte?

Mass movement of cytoplasm towards the point of sperm entry Signup and view all the answers

What is the primary role of transcription factors like VegT and Vg1 in the embryo?

To regulate the expression of other genes Signup and view all the answers

Where does beta-catenin accumulate in the embryo?

In the gray crescent region Signup and view all the answers

What is the result of the interaction between beta-catenin and Tcf-3?

The activation of genes involved in establishing the dorsal side Signup and view all the answers

What is the role of the Goosecoid gene in the chordamesoderm cells?

To regulate the expression of genes involved in establishing the dorsal side Signup and view all the answers

What is the term for the region that forms the dorsal lip of the blastopore?

The organizer Signup and view all the answers

What is the role of Siamois and Twin genes in the embryo?

To regulate the expression of genes involved in establishing the dorsal side Signup and view all the answers

What is the significance of the gray crescent region in the embryo?

It determines the location of the dorsal lip of the blastopore Signup and view all the answers

What is the result of the activation of the Beta-catenin-Tcf-3 complex?

The activation of genes involved in establishing the dorsal side Signup and view all the answers

What is the outcome when BMF4 is inhibited?

Dorsal development is favored Signup and view all the answers

What is the role of the Anterior Visceral Endoderm (AVE)?

To organize the embryo and specify the anterior pattern Signup and view all the answers

What is the function of the gene expressed at the Hensen's node?

To maintain the node and induce regional specificity in the forebrain and midbrain Signup and view all the answers

What is the role of the HOX genes in the embryo?

To control the body plan along the cranio-caudal axis Signup and view all the answers

What is the result of the misregulation of the Brachyury gene?

Caudal dysgenesis Signup and view all the answers

What is the role of FGF8 in establishing the left-right body axis?

To activate the expression of Nodal and Lefty2 Signup and view all the answers

What is the function of the PITX2 gene?

To control the formation of the left-right body axis Signup and view all the answers

What is the role of the node in the embryo?

To induce the formation of the primitive streak Signup and view all the answers

What is the outcome when the Goosecoid gene is activated?

Dorsal development is favored Signup and view all the answers

What is the function of the Lefty1 gene?

To prevent left-sided signals from crossing over to the right side Signup and view all the answers

Study Notes

Pattern Formation: Establishing Spatial Information

Establishing spatial information in an embryo is equivalent to establishing the body plan, which involves establishing positional information.
Positional information tells embryonic cells where they are supposed to be located relative to the embryo's body axis.
This information is supplied by molecular cues or molecular signals that eventually establish the body axes: dorso-ventral, anterior-posterior, and left-right axes.

Dorsal-Ventral Axis Establishment

During fertilization, there is a cortical reaction, which involves cytoplasmic rearrangement.
This results in a mass movement of cytoplasm towards the point of sperm entry, making the opposite side of the sperm entry devoid of particle granules and cytoplasm.
This area is called the gray crescent region, which is located between the animal and vegetal poles.
Molecules that specify dorsal fate are dragged towards the gray crescent region, marking the cells in this area as the future dorsal side of the embryo.
Examples of these molecules are VegT and Vg1, which are transcription factors that regulate the activity of other genes.

Molecular Mechanism of Dorsal-Ventral Axis Establishment

Beta-catenin accumulates in the gray crescent region, marking the future dorsal side of the embryo.
Beta-catenin with spatio-temporal expression is expressed in blastomeres on the prospective dorsal side.
The prospective dorsal side is marked by the gray crescent region, which determines the location of the dorsal lip of the blastopore.
Beta-catenin-Tcf-3 complex regulates the expression of other genes involved in establishing the ventral and dorsal sides of the embryo.

Anterior-Posterior (A-P) Axis/Cranio-Caudal Axis Formation

In mammals, A-P polarity is specified by Hox genes during gastrulation.
The anterior visceral endoderm (AVE) is an organizing center for the embryo, induced at the distal tip of the embryo.
AVE migrates to the prospective anterior, specifying the neural pattern by inhibiting primitive streak formation anteriorly.
AVE expresses genes coding for transcription factors, such as OTX2, LIM1, and HESX1, and secreted factors, such as Cerberus and Lefty.
These genes interplay to establish the cranial end of the embryo.

Cranio-Caudal (A-P) Axis Patterning

The cranio-caudal axis is established through the somites and vertebrae, which are governed by Hox genes.
Hox genes specify segment identity of tissues within the embryo.
The age of the embryo is based on the number of somites, which can be determined through CRL (Crown-rump length) measurement.

Left-Right Body Axis Formation

The left-right body axis is established by the interplay of genes, including FGF8, Nodal, Lefty2, and PITX2.
FGF8 is secreted by the node and establishes the expression of Nodal.
Nodal and Lefty2 are activated in the lateral plate mesoderm, while Lefty1 is expressed on the left side, ventral aspect of the neural tube.
PITX2 codes for a transcription factor that controls left-sidedness.
SHH (sonic hedgehog) is a repressor of left-sided gene expression on the right.
5HT (serotonin) is broken down by monoamine oxidase on the left side, favoring the activation of FGF8.

Pattern Formation: Establishing Spatial Information

Establishing spatial information in an embryo is equivalent to establishing the body plan, which involves establishing positional information.
Positional information tells embryonic cells where they are supposed to be located relative to the embryo's body axis.
This information is supplied by molecular cues or molecular signals that eventually establish the body axes: dorso-ventral, anterior-posterior, and left-right axes.

Dorsal-Ventral Axis Establishment

During fertilization, there is a cortical reaction, which involves cytoplasmic rearrangement.
This results in a mass movement of cytoplasm towards the point of sperm entry, making the opposite side of the sperm entry devoid of particle granules and cytoplasm.
This area is called the gray crescent region, which is located between the animal and vegetal poles.
Molecules that specify dorsal fate are dragged towards the gray crescent region, marking the cells in this area as the future dorsal side of the embryo.
Examples of these molecules are VegT and Vg1, which are transcription factors that regulate the activity of other genes.

Molecular Mechanism of Dorsal-Ventral Axis Establishment

Beta-catenin accumulates in the gray crescent region, marking the future dorsal side of the embryo.
Beta-catenin with spatio-temporal expression is expressed in blastomeres on the prospective dorsal side.
The prospective dorsal side is marked by the gray crescent region, which determines the location of the dorsal lip of the blastopore.
Beta-catenin-Tcf-3 complex regulates the expression of other genes involved in establishing the ventral and dorsal sides of the embryo.

Anterior-Posterior (A-P) Axis/Cranio-Caudal Axis Formation

In mammals, A-P polarity is specified by Hox genes during gastrulation.
The anterior visceral endoderm (AVE) is an organizing center for the embryo, induced at the distal tip of the embryo.
AVE migrates to the prospective anterior, specifying the neural pattern by inhibiting primitive streak formation anteriorly.
AVE expresses genes coding for transcription factors, such as OTX2, LIM1, and HESX1, and secreted factors, such as Cerberus and Lefty.
These genes interplay to establish the cranial end of the embryo.

Cranio-Caudal (A-P) Axis Patterning

The cranio-caudal axis is established through the somites and vertebrae, which are governed by Hox genes.
Hox genes specify segment identity of tissues within the embryo.
The age of the embryo is based on the number of somites, which can be determined through CRL (Crown-rump length) measurement.

Left-Right Body Axis Formation

The left-right body axis is established by the interplay of genes, including FGF8, Nodal, Lefty2, and PITX2.
FGF8 is secreted by the node and establishes the expression of Nodal.
Nodal and Lefty2 are activated in the lateral plate mesoderm, while Lefty1 is expressed on the left side, ventral aspect of the neural tube.
PITX2 codes for a transcription factor that controls left-sidedness.
SHH (sonic hedgehog) is a repressor of left-sided gene expression on the right.
5HT (serotonin) is broken down by monoamine oxidase on the left side, favoring the activation of FGF8.

Pattern Formation: Establishing Spatial Information

Establishing spatial information in an embryo is equivalent to establishing the body plan, which involves establishing positional information.
Positional information tells embryonic cells where they are supposed to be located relative to the embryo's body axis.
This information is supplied by molecular cues or molecular signals that eventually establish the body axes: dorso-ventral, anterior-posterior, and left-right axes.

Dorsal-Ventral Axis Establishment

During fertilization, there is a cortical reaction, which involves cytoplasmic rearrangement.
This results in a mass movement of cytoplasm towards the point of sperm entry, making the opposite side of the sperm entry devoid of particle granules and cytoplasm.
This area is called the gray crescent region, which is located between the animal and vegetal poles.
Molecules that specify dorsal fate are dragged towards the gray crescent region, marking the cells in this area as the future dorsal side of the embryo.
Examples of these molecules are VegT and Vg1, which are transcription factors that regulate the activity of other genes.

Molecular Mechanism of Dorsal-Ventral Axis Establishment

Beta-catenin accumulates in the gray crescent region, marking the future dorsal side of the embryo.
Beta-catenin with spatio-temporal expression is expressed in blastomeres on the prospective dorsal side.
The prospective dorsal side is marked by the gray crescent region, which determines the location of the dorsal lip of the blastopore.
Beta-catenin-Tcf-3 complex regulates the expression of other genes involved in establishing the ventral and dorsal sides of the embryo.

Anterior-Posterior (A-P) Axis/Cranio-Caudal Axis Formation

In mammals, A-P polarity is specified by Hox genes during gastrulation.
The anterior visceral endoderm (AVE) is an organizing center for the embryo, induced at the distal tip of the embryo.
AVE migrates to the prospective anterior, specifying the neural pattern by inhibiting primitive streak formation anteriorly.
AVE expresses genes coding for transcription factors, such as OTX2, LIM1, and HESX1, and secreted factors, such as Cerberus and Lefty.
These genes interplay to establish the cranial end of the embryo.

Cranio-Caudal (A-P) Axis Patterning

The cranio-caudal axis is established through the somites and vertebrae, which are governed by Hox genes.
Hox genes specify segment identity of tissues within the embryo.
The age of the embryo is based on the number of somites, which can be determined through CRL (Crown-rump length) measurement.

Left-Right Body Axis Formation

The left-right body axis is established by the interplay of genes, including FGF8, Nodal, Lefty2, and PITX2.
FGF8 is secreted by the node and establishes the expression of Nodal.
Nodal and Lefty2 are activated in the lateral plate mesoderm, while Lefty1 is expressed on the left side, ventral aspect of the neural tube.
PITX2 codes for a transcription factor that controls left-sidedness.
SHH (sonic hedgehog) is a repressor of left-sided gene expression on the right.
5HT (serotonin) is broken down by monoamine oxidase on the left side, favoring the activation of FGF8.

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Learn about the process of establishing spatial information within an embryo, including positional information and molecular cues.