Lecture 7
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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?

    <p>Siamois and Twin genes</p> Signup and view all the answers

    What is the function of the Goosecoid gene?

    <p>It codes for a transcription factor.</p> Signup and view all the answers

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

    <p>Organizer of the embryo</p> Signup and view all the answers

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

    <p>Gray crescent region</p> Signup and view all the answers

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

    <p>Establishment of the dorsal-ventral axis.</p> Signup and view all the answers

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

    <p>To specify the location of cells relative to the body axis</p> Signup and view all the answers

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

    <p>The depletion of cytoplasm at the site of sperm entry</p> Signup and view all the answers

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

    <p>Central axis</p> Signup and view all the answers

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

    <p>Gray crescent region</p> Signup and view all the answers

    What is the role of molecular cues in pattern formation?

    <p>To establish the body axes</p> Signup and view all the answers

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

    <p>The formation of the gray crescent region</p> Signup and view all the answers

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

    <p>Molecules that specify dorsal fate</p> Signup and view all the answers

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

    <p>It specifies the dorsal side of the embryo</p> Signup and view all the answers

    What is the result of the inhibition of BMP4 activity?

    <p>Dorsal development can proceed</p> Signup and view all the answers

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

    <p>Goosecoid</p> Signup and view all the answers

    What is the role of the AVE in the embryo?

    <p>All of the above</p> Signup and view all the answers

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

    <p>Specifying the segment identity of tissues within the embryo</p> Signup and view all the answers

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

    <p>Caudal dysgenesis</p> Signup and view all the answers

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

    <p>Inducing the expression of Nodal and Lefty2</p> Signup and view all the answers

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

    <p>Snail</p> Signup and view all the answers

    What is the role of the node in the embryo?

    <p>Maintaining the expression of the nodal gene</p> Signup and view all the answers

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

    <p>Specifying the segment identity of tissues within the embryo</p> Signup and view all the answers

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

    <p>Inhibition of BMP4 activity</p> Signup and view all the answers

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

    <p>Providing spatial information within the embryo</p> Signup and view all the answers

    What occurs during cytoplasmic rearrangements in an amphbian oocyte?

    <p>Cytoplasm moves towards the site of sperm entry</p> Signup and view all the answers

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

    <p>It marks the future dorsal side of the embryo</p> Signup and view all the answers

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

    <p>Dorso-ventral axis</p> Signup and view all the answers

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

    <p>Gray crescent region</p> Signup and view all the answers

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

    <p>Molecules specifying dorsal fate</p> Signup and view all the answers

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

    <p>Creation of the gray crescent region</p> Signup and view all the answers

    What is the role of molecular cues in pattern formation?

    <p>Establishing the body axes</p> Signup and view all the answers

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

    <p>To regulate the activity of other genes</p> Signup and view all the answers

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

    <p>It determines the dorsal side of the embryo</p> Signup and view all the answers

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

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

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

    <p>It translocates into the nuclei of cells and regulates gene expression</p> Signup and view all the answers

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

    <p>They activate the Goosecoid gene, which regulates the chordamesoderm cells</p> Signup and view all the answers

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

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

    What is the significance of the organizer in the embryo?

    <p>It is the core of the mesoderm and the dorsal lip of the blastopore</p> Signup and view all the answers

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

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

    What is the result of the inhibition of BMP4 activity?

    <p>Favors dorsalization</p> Signup and view all the answers

    What is the role of the node in the embryo?

    <p>Organizing center for the embryo</p> Signup and view all the answers

    What is the function of the AVE in the embryo?

    <p>Specifies the neural pattern by inhibiting primitive streak formation anteriorly</p> Signup and view all the answers

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

    <p>Results in caudal dysgenesis</p> Signup and view all the answers

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

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

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

    <p>Specifies segment identity of tissues within the embryo</p> Signup and view all the answers

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

    <p>Favors dorsalization</p> Signup and view all the answers

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

    <p>Snail</p> Signup and view all the answers

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

    <p>Involved in the formation of the primitive streak</p> Signup and view all the answers

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

    <p>Inhibits the activity of BMP4</p> Signup and view all the answers

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

    <p>To establish the body axes</p> Signup and view all the answers

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

    <p>Mass movement of cytoplasm towards the point of sperm entry</p> Signup and view all the answers

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

    <p>Dorso-ventral axis</p> Signup and view all the answers

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

    <p>Formation of the gray crescent region</p> Signup and view all the answers

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

    <p>Molecules specifying dorsal fate</p> Signup and view all the answers

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

    <p>It specifies the dorsal side of the embryo</p> Signup and view all the answers

    What is the role of molecular cues in pattern formation?

    <p>To provide positional information</p> Signup and view all the answers

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

    <p>Mass movement of cytoplasm towards the point of sperm entry</p> Signup and view all the answers

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

    <p>To regulate the expression of other genes</p> Signup and view all the answers

    Where does beta-catenin accumulate in the embryo?

    <p>In the gray crescent region</p> Signup and view all the answers

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

    <p>The activation of genes involved in establishing the dorsal side</p> Signup and view all the answers

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

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

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

    <p>The organizer</p> Signup and view all the answers

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

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

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

    <p>It determines the location of the dorsal lip of the blastopore</p> Signup and view all the answers

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

    <p>The activation of genes involved in establishing the dorsal side</p> Signup and view all the answers

    What is the outcome when BMF4 is inhibited?

    <p>Dorsal development is favored</p> Signup and view all the answers

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

    <p>To organize the embryo and specify the anterior pattern</p> Signup and view all the answers

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

    <p>To maintain the node and induce regional specificity in the forebrain and midbrain</p> Signup and view all the answers

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

    <p>To control the body plan along the cranio-caudal axis</p> Signup and view all the answers

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

    <p>Caudal dysgenesis</p> Signup and view all the answers

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

    <p>To activate the expression of Nodal and Lefty2</p> Signup and view all the answers

    What is the function of the PITX2 gene?

    <p>To control the formation of the left-right body axis</p> Signup and view all the answers

    What is the role of the node in the embryo?

    <p>To induce the formation of the primitive streak</p> Signup and view all the answers

    What is the outcome when the Goosecoid gene is activated?

    <p>Dorsal development is favored</p> Signup and view all the answers

    What is the function of the Lefty1 gene?

    <p>To prevent left-sided signals from crossing over to the right side</p> 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.

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