Neurogenesis and Neural Development Practice Flashcards

Comprehensive practice questions covering neurogenesis, the Spemann-Mangold experiment, BMP signaling gradients, and neural crest induction.

According to the lecture outline, what are the two main regions of the body set aside to form the early nervous system?

The neural plate and the neural crest.

What structure is elaborated from the neural plate to become the Central Nervous System (CNS)?

The neural tube.

Where does the neural crest form in relation to the neural plate?

At the edge of the neural plate.

What part of the nervous system is generated by the neural crest?

The Peripheral Nervous System (PNS).

What three factors characteristically determine the specific type of a neuron?

Position, timing, and origin (either neural tube or neural crest).

What is the result of the expression of specific combinations of transcription factors induced by environmental signals?

The specification of different neuronal cell types.

How do axons and dendrites reach their target cells during development?

Guided by diffusible signals, localized signals, subdivided pathways, and fasciculation.

What final process occurs to refine initial neural connections?

Competition for target cells.

Which two scientists are famous for the 1924 "Organizer" experiment?

Hans Spemann and Hilda Mangold.

The neural plate appears during which life cycle stage of the frog?

The neurula stage (after blastula and gastrula).

Where is the prospective notochord located during gastrulation in relation to the ectoderm?

Directly underneath the developing nervous system (medial ectoderm).

In the frog blastula, what region becomes the Ectoderm?

The Animal region.

In the frog blastula, what region becomes the Endoderm?

The Vegetal region.

In the frog blastula, what region becomes the Mesoderm?

The Marginal zone.

In the Spemann-Mangold experiment, which tissue was transplanted to the ventral side of the host embryo?

Cells from the dorsal blastopore lip.

What was the outcome of transplanting the dorsal blastopore lip to the opposite side of a host embryo?

The induction of a second body axis.

How did lineage tracing with a red marker clarify the role of the transplanted "Organizer" tissue?

It showed the transplanted red cells induced surrounding host tissue to change fate rather than making the whole structure themselves.

The Spemann-Mangold Organizer consists of which specific progenitors?

Notochord progenitors (dorsal mesoderm cells).

What is the natural default fate of ectodermal cells according to the organizer theory?

To become neurons.

Why is the Organizer considered an inhibitor of an inhibitor?

Because it secretes molecules that block $BMP$ activity, which normally represses neural development.

Name the three primary molecules secreted by the Organizer to inhibit $BMP$.

Noggin, Chordin, and Follistatin.

What is the role of Bone Morphogenetic Proteins ($BMPs$) in the ectoderm?

To repress neural development and promote epidermal development.

Which specific $BMP$ proteins are mentioned as being partially redundant in their function during neural induction?

$BMP2$, $BMP4$, and $BMP7$.

What determines if an ectodermal cell becomes epidermis in the default model?

Exposure to high levels of secreted $BMP$ signals and expression of $BMP$ receptors.

What evidence exists regarding animal cap cell dispersal?

If animal cap (ectoderm) cells are dispersed in culture, they develop as neurons instead of epidermis.

If dispersed animal cap cells are cultured with $BMP4$, what fate do they adopt?

Epidermal cells.

How does the distribution of $BMP4$ and its receptor change during gastrulation?

It is everywhere in the blastula but retreats from the prospective neural plate during gastrulation.

What is the phenotype of a mouse double mutant for Noggin and Chordin?

Loss of head and trunk.

What is an animal cap assay?

A technique where ectodermal cells from the top of an early gastrula are sliced out and cultured to observe differentiation.

What neural fate is primarily induced by the Chordin/$BMP4$ system without other influences?

Anterior neural fates (Forebrain).

Name three examples of posteriorizing signals in the developing neural plate.

$FGF8$, Wnt, and Retinoic Acid ($RA$).

How are posteriorizing signals distributed across the neural plate?

They are graded, being high at the tail end and lower at the front.

Describe the "Two-signal model" of neural induction.

First, $BMP$ signaling is repressed to set the neural plate to an anterior default; second, posteriorizing signals transform areas into more posterior fates.

What embryonic region is the source of the neural crest?

The neural plate border.

What happens at the boundary between the prospective neural plate and prospective epidermis?

Neural crest cells are induced.

List four tissues or cell types derived from the neural crest.

Dorsal root ganglia, sympathetic ganglia, enteric ganglia, cartilage in the head, and pigment cells.

According to Harrison (1938), what did fate mapping reveal about the neural crest?

It always originates at the precise boundary between the prospective neural plate and the prospective epidermis.

What does it mean for neural crest cells to "delaminate"?

They leave the epithelium to sit on top of the neural tube before dispersing.

Describe the 1990 experiment by Moury and Jacobson using axolotl embryos.

They juxtaposed prospective neural plate and epidermis; neither formed neural crest alone, but together they induced pigmented melanocytes.

Why were melanocytes used as a marker in the axolotl induction experiment?

Melanocytes are derived from the neural crest.

What third tissue is identified in frogs as being vital for driving neural crest fate besides the two ectodermal tissues?

Dorsolateral (lateral plate) mesoderm.

What two signal types combine to specify neural crest cells at the boundary in the frog embryo?

Intermediate $BMP$ signals and Wnt signals.

According to the "Gradient Model," what level of $BMP$ drives epidermis development?

High $BMP$ signaling.

According to the "Gradient Model," what level of $BMP$ drives neural plate development?

Low or No $BMP$ signaling.

What is the "Golden Zone" in the context of neural crest induction?

The region at the neural plate border with intermediate levels of $BMP$ signaling.

In the Liem et al. experiment, what happened when intermediate neural tube explants were treated with $BMP4$/$7$?

They were induced to form neural crest and expressed markers like HNK-1 and Slug.

What did the Liem et al. experiment prove regarding $BMP$ proteins?

That $BMP$ proteins are sufficient to induce neural crest characteristics in neural tissue.

What two molecular markers are commonly used to identify neural crest cells in experiments?

HNK-1 and Slug.

What is the phenotype of the zebrafish Swirl mutant ($BMP2b$)?

The entire ectoderm becomes neural plate because there is essentially no $BMP$ signaling (no intermediate threshold).

How do the Somitabun ($Smad5$) and Snailhouse ($BMP7$) mutants affect the $BMP$ gradient?

They reduce signaling and flatten the gradient, putting a larger portion of the embryo into the "intermediate" range.

What is the consequence of a flattened $BMP$ gradient in Somitabun and Snailhouse mutants?

The embryos generate an unusually large amount of neural crest cells.

What is the source of Wnt signaling required for full neural crest induction?

The underlying lateral plate mesoderm.

Which 2009 paper provided a dissection of the roles and signals in neural crest specification involving Wnt?

Steventon et al.

What is the full title of the textbook by Sanes et al. referenced in the notes?

Development of the Nervous System, $4^{th}$ Edn.

Who are the authors of the 12th edition of "Developmental Biology"?

Barresi and Gilbert.

Which stages in the frog life cycle are focused on for understanding neural plate formation?

The stages between blastula, gastrula, and neurula.

During gastrulation, the "tucking in" cells grow along which axis?

The long axis.

What occurs molecularly when Chordin/$BMP4$ induces the neural plate?

It creates a zone free of $BMP$ signaling.

The term "prospective epidermis" refers to which future tissue?

Skin.

What happened to the pigmentation of albino axolotls in the Moury/Jacobson experiment?

Pigmented melanocytes appeared after interaction with the neural plate.

True or False: According to the notes, prospective neural plate tissue normally forms neural crest on its own.

False (it requires interaction with the epidermis or specific signals).

What is the specific region of mesoderm that lies under the frog neural plate border?

Lateral plate mesoderm.

Which molecule, mentioned as a secreted factor from the organizer, specifically binds to $BMP4$?

Cerberus (and Noggin, Chordin, Follistatin).

What is the "primary axis" in the Spemann-Mangold Organizer experiment?

The axis generated by the host's own dorsal blastopore lip.

What does the abbreviation "CNS" stand for?

Central Nervous System.

What does the abbreviation "PNS" stand for?

Peripheral Nervous System.

In the "Step-wise process" of specification, identity is refined throughout which period?

Throughout development.

How is the embryo described physical shape-wise in chick vs. frog?

Chick embryos are flat sheets of cells, whereas frogs are a ball.

What is the role of glia as defined in the notes?

Support cells.

What is the primary aim of the neural development outline in the lecture?

To understand the principles underlying neural development.