Chapter 13 Part 3: CNS Patterning Flashcards
in the anterior region, the neural tube balloons into three primary vesicles:
1) proscephalon: forebrain 2) mesencepahlon: midbrain 3) rhombencephalon: pons, medulla, cerebellum.
the forebrain becomes ____ and ____
telencephalon (forms cerebral hemispheres) and diencephalon (optic vesicles)
the rhombencephalon develops little swellings called ____, which divide the entire rhombencephalon into smaller sections. Within each ____, the cells can freely mix, but they do not mix with cells in other segments.
the rhombencephalon develops little swellings called RHOMBOMERE, which divide the entire rhombencephalon into smaller sections. Within each RHOMBOMERE, the cells can freely mix, but they do not mix with cells in other segments.
T/F; rhombomeres associate with each other.
false. Within each RHOMBOMERE, the cells can freely mix, but they do not mix with cells in other segments. They each express different transcription factors which promote neural differentiation.
the ___ ___ cells in each rhombo mere will form ganglia, which are:
the neural crest cells (recall: anterior region of neural tube has neural crest cells right near the face that touches the ectoderm, which delaminate and later form the peripheral nervous system). the NC cells in each rhombomere will form ganglia, which are clusters of neuronal cell bodies whose axons form a nerve.
in the spinal cord, the ___ region is where neurons receive input from sensory neurons, and the ___ region is where motor neurons reside. middle regions contain interneurons that relay infor between the sensroy and moto neurons.
in the spinal cord, the DORSAL region is where neurons receive input from sensory neurons, and the VENTRAL region is where motor neurons reside. middle regions contain interneurons that relay infor between the sensroy and moto neurons.
CNS patterning: dorsal-ventral cells arise from ____ cells located beside ventricles that develop along the anterior-posterior axis
arise from progenitor cells. Each progenitor domain can be defined by its expression of specific transcription factors, which specify progeny to differentiate into different neuronal and glial classes that make up the CNS.
Dorsal ventral axis:
the ventral pattern is imposed by the ____, whereas the dorsal pattern is unduced by the ____.
the ventral pattern is imposed by the notochord, whereas the dorsal pattern is unduced by the OVERLYING EPIDERMIS.
the ventral pattern is imposed by the notochord, whereas the dorsal pattern is unduced by the OVERLYING EPIDERMIS. what is the main opposing gradient responsible for dorsal-ventral axis formation? explain
SHH and TGFbeta (nodal) factor. The notochord secretes high concentrations of SHH (this was also used for proper hinge formation), and the epidermis (dorsal ectoderm) secretes high concentrations of TGFbeta (nodal)
Dorsal-Ventral axis continued:
- SHH from the notochord induces the ___ ___ ___ cells to become the ____ ___ of the neural tube. What does SHH-exposed cells give rise to? What is the secondary signalling center that’s created due to SHH from notochord?
SHH from the notochord induces the MEDIAL HINGE POINTS cells to become the FLOOR PLATE of the neural tube.
Secondary signalling center: once the floor plate forms, it also secretes SHH, which acts as a “double dose” of SHH in the ventral region of the neural tube. Cells exposed to most SHH ie the most ventral crest cells becomes V3 neurons and motor neurons. Lower Shh produces more dorsal progenitor populations.
dorsal ventral axis of CNS continued
dorsal ectoderm secretes large amounts of TGFBeta proteins like ___, ___, ___, and ___ (like nodal). These also create a seconday signalling center, and makes the dorsal neural plate cells to form a ___ ___, making them also release TGFbeta proteins (like nodal).
dorsal ectoderm secretes large amounts of TGFBeta proteins like BMP4, BMP7, DORSALIN, and ACTIVIN (like nodal). These also create a seconday signalling center, and makes the dorsal neural plate cells to form a ROOF PLATE, making them also release TGFbeta proteins (like nodal).
BMP4 released from the roof plate cells of the neural tibe, causes a cascade of TGFbeta proteins to be released in neighboring cells.
cells differentially express trnascription factors based on their _____ from a morphogen (either SHH or TGFbeta) as well as the amount of ___ they are exposed to the morphogen.
cells differentially express trnascription factors based on their distance from a morphogen (either SHH or TGFbeta) as well as the amount of time they are exposed to the morphogen.
Cells near the neural tube’s floorplate with high SHH express ___ and ___ to form vetnral interneurons.
Cells a little more dorsal ( a little less SHH, slightly more TgFB) produce ___ and ___ to make motor neurons.
cells even more dorsal only express ___ to make V1 and V2 interneurons
cells in the most dorsal aspect only express ____ to make dorsal progenitors
Cells near the neural tube’s floorplate with high SHH express NKX6-1 and NKX6-2 to form vetnral interneurons.
Cells a little more dorsal ( a little less SHH, slightly more TgFB) produce PAX6 and OLIG2 to make motor neurons.
cells even more dorsal only express PAX 6 to make V1 and V2 interneurons
cells in the most dorsal aspect only express PAX 7 to make dorsal progenitors
Nkx2.2 inhibits ____ to allow for intense specification of cells that might be right beside each other.
Olig2.
in the rostral (anterior) region, ___ acid in the somatic mesoderm counters the effect of fgf8. What does this allow?
in the rostral (anterior) region, RETINOIC acid in the somatic mesoderm counters the effect of fgf8.
- this antagonistic RA/fgf8-wnt gradients provides a pathway along the rostral-caudal (anterior-posterior axis) that establishes a road to NMP maturation
Converging axis patterning:
NMP cells are born in the ____ and enters the ____ by undergoing secondary neurulation.
NMPS that enter the neural ____ become ____ ___ cells and respond to both SHH and BMP signals by becomeing floor or roof plate cells.
NMP cells are born in the TAILBUD and enters the MESENCHYME by undergoing secondary neurulation (MESENCHYME-EPITHELIAL TRANSITION).
NMPS that enter the neural MESENCHYME become PRONEURAL PROGENITOR cells and respond to both SHH and BMP signals by becomeing floor or roof plate cells.
as the tailbud extends, the PREneural NMP cells move further from the ___-___ signalling which usually maintain them, and become more affected by ____in the anterior/rostral end, making them respond to signals of ___/___, becoming ___ ___ cells, subsequently allowing for dorsal-lateral axis patterning to occur.
as the tailbud extends, the PREneural NMP cells move further from the fgf8-wnt signalling which usually maintain them, and become more affected by RA in the anterior/rostral end, making them respond to signals of SHH/TGFbeta, becoming proneural progenitor cells, subsequently allowing for dorsal-lateral axis patterning to occur.
these proneural progenitor cells then interacts with Pax7/Nkx1/2 etc depending on TGFbeta/SHH concentrations, allows for dorsoventral axis patterning to occur.
