Transcript Neural Crest Cells and Axonal Specificity

Neural Crest Cells and
Axonal Specificity
Neural Crest
► Where
is the neural
crest located and why
is this region so
important?
Neural Crest
► What
factors are
important in the
specification of neural
crest?
Neural Crest
► What
are the four domains and their
derivatives?
 cranial
►cartilage,
bone, cranial neurons, glia, connective
tissue of face
 trunk
►dorsal
root ganglia – sensory neurons, sympathetic
ganglia, adrenal medulla, nerves around aorta,
melanocytes
Neural Crest
► What
are the four domains and their
derivatives?
 vagal and sacral
►parasympathetic
ganglia of gut
 cardiac
►melanocytes,
neurons, cartilage, connective tissue,
wall of large arteries, septum between aorta &
pulmonary artery
Neural Crest
Trunk Neural Crest
► What
are the two migration pathways of trunk
neural crest cells?
Trunk Neural Crest
► What
initiates the migration of these cells?
 transformed from epithelial to mesenchymal
cells
►presence
of Wnt, FGF, and BMP’s induces formation
of Slug and Rho B proteins
 slug – dissociation of tight junctions, loss of N-cadherin
 Rho B – promotes actin polymerization into microfilaments
Trunk Neural Crest
► How
do migratory cells know the route to
travel?
 proteins that promote or impede migration
found in extracellular matrix
►promote – fibronectin, laminin, tenascin
 thrombospondin – found in anterior part of sclerotome
►impede – ephrin proteins
 found in posterior part of sclerotome
 stem cell factor promotes proliferation of neural
crest that enter skin
Trunk Neural Crest
► What
cells?
is meant by the pluripotency of these
► What
determines how a specific cell will
differentiate?
► Are
all neural crest pluripotent?
Cranial Neural Crest
► What
is a major distinction between cranial
and trunk neural crest?
 cranial can form bone and cartilage in addition
to neurons, melanocytes and glial cells
Cranial Neural Crest
► cranial
neural crest
migrate ventrally from
rhombomeres of
hindbrain
Cranial Neural Crest
► What
is involved in
intramembranous
ossification?
Cranial Neural Crest
► What
are the cranial
placodes?
Cranial Neural Crest
► Placodes
are induced
to form by neighboring
tissue
Cranial Neural Crest
► What
happens during the “second wave” of
migration?
 crest cells migrate dorsally to form glial cells
 glial cells provide tracks to guide neurons from
placodes to hindbrain
Cardiac Neural Crest
Neuronal Specification
► First
decision
 neuron or epidermis
► Second
decision
 type of neuron
►sensory
►motor
►interneurons
► Third
decision
 target of neuron
Neuronal Specification
► What
determines the specification of the
type of neuron?
 position of neuronal precursor within neural
tube
 when it forms (birthday)
Neuronal Specification
► What
determines target of motor neuron?
 a-p specification
►hox
genes from hindbrain through spinal cord and
head genes (Otx) in brain regulate
 in a given region – cell layer
►age
of cell – last division
►Lim genes – transcription factors
► Targets
are specified before axons extend
into periphery
Neuronal Specification
Pattern Generation
► How
does a neuronal axon “know” how to
travel to a given area and make specific
connections?
► Appears
to involve three steps:
 pathway selection
 target selection
 address selection
Pattern Generation
► What
role does the
substrate play in
directing the
pathway of axons?
Pattern Generation
► Are
there other
molecules known to
direct the migration
of axons?
Pattern Generation
► What
is the function of
neurotrophins?
Pattern Generation
► What
is involved in the formation of a synapse?
Pattern Generation
► What
is the role of
neurotropic factors in
the survival of
neurons?
Pattern Generation
► What
is known about
the migration of retinal
ganglion axons?
Pattern Generation
► How
do axons
distinguish between
different regions of
optic tectum?