Gastrulation and Neural Ectoderm Patterning in Zebrafish

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Questions and Answers

Which signaling proteins family is involved in a wide variety of processes, most noticeably in normal development?

  • Cyp26
  • Retinoic acid
  • Wnts
  • FGF (correct)

What kind of factors are Wnts in the context of embryonic development?

  • Suppressors of cell motility
  • Activators of diverse signaling cascades (correct)
  • Inhibitors of differentiation
  • Stabilizers of anterior gene expression

Which enzyme regulates the coordinated regulation of the anterior-posterior axis in zebrafish, specifically in the neural ectoderm patterning?

  • Cyp26
  • RA receptor
  • FGF
  • Retinoic acid 4-hydroxylase (correct)

What is retinoic acid's role as a morphogen in cell regulation?

<p>Regulating cell properties based on its concentration (C)</p> Signup and view all the answers

Where is the gene encoding the enzyme cyp26, which is pivotal in zebrafish's neural ectoderm patterning, expressed?

<p>Anterior end of the embryo (C)</p> Signup and view all the answers

Which factor plays a key role in regulating cell properties dependent on its concentration during embryonic development?

<p>Retinoic acid 4-hydroxylase (A)</p> Signup and view all the answers

What is the role of retinoic acid-4-hydroxylase in hindbrain development?

<p>Prevents the accumulation of retinoic acid at the anterior side (C)</p> Signup and view all the answers

How do FGFs and Wnts reciprocate the inhibition by retinoic acid-4-hydroxylase?

<p>Inhibit the expression of cyp26 gene (A)</p> Signup and view all the answers

What role do NODAL signaling and Pitx2 transcription factor play in zebrafish left-right axis development?

<p>Control left-right asymmetry in zebrafish cells (C)</p> Signup and view all the answers

How is the left-right asymmetry controlled in zebrafish embryos?

<p>Via a transient fluid-filled organ called Kupffer’s vesicle (A)</p> Signup and view all the answers

What happens when ciliary function is blocked in zebrafish embryos?

<p>Results in abnormal left-right axis formation (C)</p> Signup and view all the answers

How does reciprocal inhibition create a border between posterior and anterior gene expression zones?

<p>By mutual inhibition between FGFs and Wnts (B)</p> Signup and view all the answers

What is responsible for imparting dorsal-ventral patterning to the developing neural tube in the text?

<p>Shh (C)</p> Signup and view all the answers

Which major phase in AP patterning involves the formation of muscles tissue blocks called somites in the vertebrate embryo?

<p>Elaboration phase (B)</p> Signup and view all the answers

Where is the part of a very important signaling center called the organizer first specified in zebrafish?

<p>Dorsal side near the equator (D)</p> Signup and view all the answers

During which phase does the initiation phase occur in zebrafish in relation to gastrulation?

<p>Before gastrulation (B)</p> Signup and view all the answers

Which molecule is NOT mentioned as being involved in AP patterning in the text?

<p>Morphogen (C)</p> Signup and view all the answers

Which process involves cells migrating towards the animal pole where the brain forms?

<p>Gastrulation (B)</p> Signup and view all the answers

Flashcards

Gastrulation and AP Axis Formation

The most posterior cells of the embryo move towards the vegetal pole, forming the tailbud, and the animal-vegetal pole establishes the AP axis.

Patterning of Neural Ectoderm

The regulation of neural ectoderm patterning along the AP axis in zebrafish involves the interplay of different signaling molecules.

Retinoic Acid as a Morphogen

Retinoic acid (RA) acts as a morphogen, influencing cell properties based on its concentration.

Retinoic Acid-4-Hydroxylase (cyp26)

Enzyme that degrades retinoic acid, preventing accumulation of RA and blocking posterior gene expression in the embryo.

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Shh's Role in Dorsal-Ventral Patterning

Shh, secreted from the notochord, plays a critical role in dorsal-ventral patterning of the developing neural tube.

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Evolutionary Significance of AP Axis

The AP axis is the first embryonic axis to evolve, allowing animals the ability to move forward.

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AP Axis in Bilaterians

Corresponds to the head-tail axis in bilaterians.

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Mechanisms of AP Axis Formation

Animals use various mechanisms during early development to establish the AP axis.

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Phases of AP Patterning

AP patterning in the vertebrate embryo is divided into two phases: initiation and elaboration.

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Initiation Phase in Zebrafish

The initiation phase of AP patterning in zebrafish occurs before gastrulation.

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Left-Right Axis Formation

The series of embryonic events that create left and right distinction include axial rotation direction, individual organ formation, and organ placement.

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Left-Right Asymmetry in Vertebrates

Vertebrates have asymmetric development, resulting in the heart being located on the left side.

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NODAL and Pitx2 in Asymmetry

NODAL signaling and the Pitx2 transcription factor play a role in conveying left-right asymmetry information.

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Study Notes

Gastrulation and AP Axis Formation

  • The most posterior cells migrate towards the vegetal pole, forming the tailbud, and the AP axis aligns with the animal-vegetal pole by the end of gastrulation.
  • The patterning of neural ectoderm along the AP axis in zebrafish involves the interplay of FGF, Wnts, and retinoic acid.

Regulation of AP Axis

  • Retinoic acid (RA) acts as a morphogen, regulating cell properties depending on its concentration:
    • Cells receiving low RA express anterior genes
    • Cells receiving high RA express posterior genes
    • Cells receiving intermediate RA express genes characteristic of cells between anterior and posterior regions
  • Retinoic acid-4-hydroxylase (cyp26) degrades RA and is expressed at the anterior end of the embryo, preventing accumulation of RA and blocking posterior gene expression.

Dorsal-Ventral Patterning

  • Shh secreted from the notochord imparts dorsal-ventral patterning to the developing neural tube.

Anterior-Posterior Axis

  • The AP axis is the first embryonic axis to arise in evolution, allowing animals to move unidirectionally.
  • In modern bilaterians, the AP axis corresponds to the head-tail axis.
  • Different animals use various mechanisms to create this axis in the early embryo.

AP Axis Formation in Zebrafish

  • AP patterning in the vertebrate embryo can be divided into two phases:
    • Initiation phase: embryo divided into head and body
    • Elaboration phase: body forms towards the posterior end, forming the trunk and tail
  • In zebrafish, the initiation phase occurs prior to gastrulation, and the different territories of the final body plan can be roughly mapped onto the embryo.

Left-Right Axis Formation

  • The series of embryonic development that distinguish the left and right sides of the embryo include:
    • Direction of axial rotation
    • Morphogenesis of individual organs
    • Organ placement
  • In vertebrates, the left and right sides develop differently, with the heart on the left side in fish.
  • NODAL signaling and the Pitx2 transcription factor provide left-right asymmetry information to cells on the left side of the body.

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