Neural tube and crest Flashcards
Neurulation
Formation of the neural tube
Primary neurulation
The process of the neural plate transforming into the neural tube
Secondary neurulation
The process that forms the posterior portion of the neural tube by the coalescence of mesenchyme cells into a solid cord
Junctional Neurulation
When primary and secondary neurulation meed and primary transitions to secondary
What three ectodermal derivatives are produced by neurulation?
- Surface ectoderm
- Neural crest
- Neural tube
Medial Hinge Point
Cells at midline anchored to notochord
Forms by SHH
Dorsal Lateral Hinge Point
Has apical constriction
Forms when Noggin inhibits BMP
Notochord
Transient mesodermal rod that patterns nervous system
Signals SHH to activate MHP and inhibit Noggin
Surface Ectoderm
BMP expressed, inhibits DLHP and MHP
E-cadherin
Expressed in ectoderm
N-cadherin
As neurulation begins, neural tissue is induced and expresses N-cad
Filopodia
The tips of the neuro folds extend filopodia across the opening
Environmental impact
Current hypothesis is that environmental factors can modify the epigenome, leading to transcriptional variation
Folic Acid
Vitamin B9, Key facor in neural tube closure.
Explain why there is great phenotypic variation in the class of human malformations known as neural tube defects
NTDs and multifactorial with more than 300 genes that could be effected
Anencephaly
Failure to close the anterior of the neural tube forebrain (closure 2)
Skull vault doesn’t close
Spina bifida
Failure of neural tube closure at closure 5
Craniorachischisis
Usually miscarriage
Neurocristopathies
Developmental disorders of neural crest cells.
Neural crest cells
- vertebrates
- arise from dorsal neural tube
- give rise to multipotent progenitors
- Transient in early embryo
NCC EMT
EMT is promoted by differential gene expression
NCC specification
Medium Wnt and low BMP signaling in the gradient specify cell fate
NCC Snail
Snail represses Sox2, and N-cad at the top of the cell. Snail also inhibits Cad-6B from being expressed outside of the top of the tube
NCC Cad-6b
aids wnt and BMP to determine pre migratory NCCs
Contact inhibion
Sends NCCs off laterally
Neural crest “highways”
Environmental cues that send NCCs to their target tissues
Cranial NCCs
Neck and cranial nerves, jaw bone, face cartilage
Trunk NCC
Glial cells and melanocytes
Ganglia travel ventrally and transmit touch/pain to the spinal chord
Melanocytes travel dorsolaterally and create pigment cells
Cardiac NCCs
Creates the septum that separates the pulmonary artery and the aorta
Vagal/Sacral NCCS
Migrate and populate the gut
Enteric nervous system
-GDNF is released by developing gut
-GDNF + GRFa bind to Ret on NCCs
- migration to gut
Somite
Mesodermal segments of vertebrate embryos that become the vertebral column
Hirschprung’s Disease
the nerves in the large intestine don’t form properly
How Eph/Ephrin guide NCC migration
NCCs migrate ventrolaterally through the anterior half of the somite
-ephrin is present posteriorly
-Ephrin ligands in the posterior connect with the Eph receptor in the NCC membrane and cause a repulsive interaction
