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One of the three germ layers that will turn into the epidermis and the nervous system.
Middle of the three germ layers that will go on to create muscle, connective tissue, the skeleton, blood, and blood vessels.
One of the three germ layers that will go on to create the gut and the respiratory tract, among other things.
- A ball of cells formed following zygote formation during fertilization
- No cavity is present.
- A hollow sphere of cells formed from the morula.
- Defined from a morula into a blastula upon the formation of the blastocoel.
- Both the blastula and morula will contain cells that are dividing without increasing the overall size of the entire ball of cells.
- The cell-less region of the blastula.
- The first cavity of the organism.
- Caused by an invagination of the blastula at the blastopore.
- It goes from a single layer (more or less) of cells into a trilaminar (three cell layers) structure.
- Second cavity of the gastrula.
- This will develop into the digestive tract/gut.
- The formation of the neural tube.
- The neural plate, part of the ectoderm, will fold into itself (invagination) forming a neural tube, and neural crest cells.
- This happens when signaled on from the notochord.
- The neural tube will go on to form the central nervous system.
Neural crest cells
- Cells formed at the dorsal part of the neural tube
- These will reposition themselves to form the peripheral nervous system.
Part of the mesoderm, but is responsible for driving the induction of epidermis and neural tissue.
- When a cell is instructed to adopt a certain fate or characteristic by signals in its environment.
- Essentially, one cell telling another cell what to do
- The ability of a cell to respond to a signal
- A function of the receptors, signaling molecules, transcription factors, expressed by the cell.
- Cell must want to respond to signal
When a cell is restricted in its developmental potential (to become a specific type of cell).
- When a cell elaborates a specific developmental program (to become a cell type from a precursor cell)
- Cells become different from each other and acquire specific functions and characteristics
What does neural development depend on?
Interactions between environmental cues and genetic factors
- Cell lineages
- Competence to respond to other genetic factors or environmental cues
Whats special about the human (and other species) brain?
Its a highly ordered and complex structure
How are cells of the ectoderm induced to become neural?
What are the milestones in development?
- Cell proliferation/cleavage
Haploid egg and sperm
Zygote goes through series of cleavages
- Cells arranged/specified in the proper positions
- Establishment of the body plan (head vs. toes)
Whats the main problem?
- How do things go from simple to complex
- What are the initial steps in the development of the nervous system?
Real morphological growth starts at what stage?
What is the preferred model for studying early development? Why?
- Xenopus laevis (African clawed frog)
- Embryos are big
What happens during the blastula stage?
Cells differentiate from each other
What happens during gastrula stage?
Movement goes through blastopore into blastocoel
Dent at dorsal lip thatll go into blastocoel
Where is the notochord?
On the dorsal side, right under the neural plate in between the somites
What is the notochord important for?
What two parts does the neural tube split into?
- Rostral- anterior/head
- Caudal- posterior/butt
What does the rostral part of the neural tube lead to?
Formation of the brain
What does the caudal part of the neural tube lead to?
Formation of the spinal cord
What did Spemann and Mangold demonstrate?
Inductive signals are responsible for specifying the nervous system from ectoderm
What happened to early ectoderm if cultured alone, without the dorsal lip?
Became epidermal tissue
What happened to early ectoderm when cultured with the dorsal lip?
Turns into neural tissue
What does DLB stand for?
Dorsal lip of the blastopore
What was the DLB named? Why?
- The organizer
- Transplanted DLB induces host ectoderm to adopt neural fate
What did the early scientists think because of the observations they saw with the dorsal lip and ectoderm? Why were they wrong?
- There had to be some sort of message from the dorsal lip to tell the ectoderm to become neural tissue
- Wasnt exactly telling it to be nervous, it was telling it NOT to be epidermal tissue
What is the animal cap?
Essentially the dorsal part of the blastocyst that is almost completely ectoderm
What experiment was done with the animal cap?
They compared cultured animal cap when it was clumped together, or dissociated
What is a dissociated animal cap?
What happens to the dissociated cells from the animal cap?
Turns into neurons
What happens to intact animal cap?
Turns into epidermal tissue
What did the experiment with the animal caps tell the researchers? Why?
- The default state is neural tissue
- The dissociated cells werent able to efficiently receive any signals when dissociated
- Without any signals, they became neurons
- Meaning, its their default state
What does BMP stand for?
Bone morphogenetic protein
What does BMP bind to?
BMP receptors (BMPRs) ...
What happens when BMP binds to BMPRs?
Sends signaling cascade that induces a cell to NOT become neural tissue, and become epidermal
What is the competing signal for BMP?
Noggin, it binds to BMP
What is noggin?
A BMP antagonist
What happens when noggin binds to BMP?
- Prevents it from binding to BMPRs, kinda makes it a weird shape so it doesnt fit into the receptors
- BMPRs are empty
- No induction to epidermal tissue
- Turns into default neural tissue
What other proteins are similar to noggin?
Where is most BMP secreted?
Where is noggin most secreted?
At DLB (organizer)