NEU 335 Exam 2

What’s the difference between a blastula and a gastrula?

A blastula is a hollow ball of cells that came from several cell divisions from the zygote.

A gastrula is a blastula that underwent gastrulation, meaning the hollow ball of cells folded in on itself, forming 3 distinct tissue source layers.

Where does the neural plate originate?

The neural plate develops from a group of cells in the ectoderm of the gastrula

What is neurulation?

neurulation is the process of the neural plate folding into a tube to form the neural tube, which will become the CNS

What are Neural Crest Cells?

Cells that originate in the ectoderm and differentiate into neurons with cell bodies in the PNS (e.g. DRG)

What are the 3 primary vesicles of the neural tube?

1. Prosencephalon (forebrain)

2. Mesencephalon (midbrain)

3. Rhombencephalon (hindbrain)

Into what other structures does the prosencephalon develop?

1. Telencephalon (forms as 2 vesicles), which will make up your cerebral hemispheres

2. Diencephalon (engulfed by the telencephalon)

What are optic vesicles?

Extensions of the diencephalon, which develop into your retina, making them part of the CNS

What do the cavities within the 3 primary vesicles of the neural tube develop into?

The cavities of the 3 primary vesicles develop into the adult ventricle system

What important structures develop from the telencephalon?

• Cerebral cortex (2 hemispheres)

• thalamus

• corpus callosum

• basal ganglia

• hippocampus

• amygdala

What important structures develop from the diencephalon?

• hypothalamus

What occurs when a zebra fish embryo has 2 DLB

The fish will develop 2 CNS

Suppose a chunk of ectodermal tissue is placed in a petri dish. Into what types of cells will these ectodermal cells differentiate?

Since the tissue remains intact, these cells will differentiate into epidermal skin cells

Suppose a chunk of ectodermal cells is placed in a petri dish. Into what types of cells will these ectodermal cells differentiate?

Since each cell is separated from each other, they will differentiate into neural cells

What happens when single ectodermal cells receive BMP

the ectodermal cells turn into epidermal skin cells

Consider the experiment where ectodermal tissue receives BMP inhibitors, resulting in the development of only neural cells. In this case, is BMP signaling necessary or sufficient for epidermal skin cell fate?

BMP signaling is necessary for epidermal skin cell fate

Consider the experiment where ectodermal cells are treated with BMP, resulting in the development of only epidermal skin cells. In this case, is BMP signaling necessary or sufficient for epidermal skin cell fate?

BMP signaling is sufficient for epidermal skin cell fate

T/F do all ectodermal cells secrete and sense BMP?

True! Even dissociated ectodermal cells secrete + sense BMP, but the BMP concentration is too low among dissociated cells that it’s not enough for them to differentiate into epidermal skin cells

Which structure releases BMP inhibitors?

Dorsal Lip of the Blastopore (DLB)

What do cells further away from the DLB differentiate into?

Into epidermal skin cells because BMP inhibition gradient is too low for BMP signaling to be significantly impaired

T/F BMP signaling represses neural fate?

True

T/F BMP inhibition derepresses neural fate?

True

What is the distinction between dorsal and ventral ectodermal cells?

Dorsal ectodermal cells differentiate into neural cells because they’re closer to the DLB

Ventral ectodermal cells differentiate into epidermal skin cells because they’re further away from the DLB

What might happen to ectodermal cells in a mutant embryo lacking all BMP inhibitors? What are the consequences on CNS development?

Dorsal ectodermal cells would become epidermal (skin) cells instead of neural cells —> no neural plate —> no CNS

What is a morphogen?

a signaling molecule secreted from a locus, forming a concentration gradient that influences the fate of cells

How does BMP signaling directly influence the differentiation of ectodermal cells into skin cells?

After BMP binds to an ectodermal cell, it activates a transcription factor pathway that leads to the expression of certain genes to make the ectodermal cell more skin-like

What is the function of a TF?

amplify OR inhibit transcription of a gene

Which embryonic structures releases SHH, and describe the SHH gradient produced?

SHH secreted from the floor plate and notochord —> high SHH ventral concentration

What types of cells to precursor cells closer to the neural plate + notochord differentiate into?

Motor Neurons

What is the relationship between FGF8, PAX6, EMX2 in the forebrain?

FGF8 = morphogen that’s secreted rostrally

Pax6 = TF that’s highly expressed anteriorly

Emx2 = TF that’s highly expressed rostrally

What types of structures do pax6 and emx2 activity contribute to?

Pax6 = motor cortex and somatosensory cortex
Emx2 = auditory and visual cortex

What would the cortex of an emx2 knock-out mutant look like?

• Expansion of anterior structures (motor + somatosensory cortices)

• Reduction of posterior structures (auditory + visual cortices)

What would the cortex of a pax6 knock-out mutant look like?

• Reduction of anterior structures (motor + somatosensory cortices)

• Expansion of posterior structures (auditory + visual cortices)

Where would we expect visual cortex to develop if the FGF8 gradient was reversed along the rostral-caudal axis?

Anteriorly

What are the 2 BMP inhibitors covered in class?

Noggin + Chordin

What morphogens and TF’s are important for cortical development?

FGF8 + pax6, emx2

What is cell proliferation and where does it occur?

Cell proliferation is the process of cell growth + division, which occurs in the 3 primary vesicles of the neural tube

What are radial glial cells (RGCs)

Precursor cells that give rise to ALL the neurons in the cerebral cortex

Describe the interkinetic nuclear migration performed by radial glial cells

1.