Bio 127 Section III
 Axis Formation
 General background
o A single mRNA added may introduce a second organizer power
causing drastic change.
o Blastula has no axis.
o Doral-Ventral Axis
o Anterior-Posterior Axis
o Left-RT Axis
 Relationships between chick and frog
o Chicken
 Hypoblast- dorsal vegetal cells. Organizer.
 Koller sickleHensen’s nodeprimitive streak
o Frog
 Koller sicklepre-dorsal lip; mesoderm
 Wnt and FGF signals from hypoblast
 Organizer(endodermal cells) secretes noggin and BmP7 and
Dickoeff
 Block BMP, Wnt, and FGF
o Yolk Positioning
 Eggs are rotated rt angle to gravity
o Specification of the chicken anterior-posterior axis
 Complex signals from notochord
 Positional specification by gravity
 Hox genes
o Rostral-Caudal
 Hox genes
o Left-RT
 Nodal expression
 Stem Cells
 General background
o Each system has stem cell niche
o Most cancers arise from regeneration prone cells
o Stem cell-cell that produces one stem cell and one differentiated cell
(asymmetric mitosis)
o Fast divisions occur in bone marrow, gut , and skin
o Slow divisions occur only in stress or repair: heart, and prostate
o 1 trillion cells live in us, 1 out 10 are human
 Terminology
o Totipotent
o Pluripotent
o Multipotent
o Unipotent
 Types of Stem cells
o Inner cell massembryonic stem cell
o Hematopeitic
o Mesenchymal
Bio 127 Section III
o Epidermal
o Gut
o Mammary
o Melanocyte
o Muscle
 Location(niche)
o Bone marrow
 Hematopoietic stem cellsmultipotentmyeloid progenitor
cell
 Control on differentiation
 Bone cell matrix
 Stromal paracrine factors
 Pericyte paracrine factors
 Systemic hormones
 Neuronal signals
 Enzymes
 Wnt
 Angiopoietin
 Stem cell factor
 Delta-Notch
 Integrin
o Mouse tooth
 Balance of positive and negative signals
 FGF3 Vs BMP3
 Activin Vs Follistalin
 Combination of two systems for differentiation and
division
o Drosophila testes
 Hubs cell hold centrioles
 Somaic cells
 Control rate
 Organizer pathway
 Hub cellsunpairedjak-Stat stem cell division
 Stem cell stays bound and diff cell moves away
o Niche Breakdown
 Too much cell differentiation
 Craps out
 Ectoderm
 General background
o GastrulaNervous system
o First organ system made
o 2 major steps
 Formation of neural tube
 Differentiations of neurons
o NC forms PNS
Bio 127 Section III
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o Pregnant women take folic acid
o Stimulation of neural folding begins at the front as hensen node is
migrating back
o Primary and secondary neuralation begins at regression of hensen
node
o Further anterior, more complex
Neuralation
o Primary
 Formation and Folding
 Elevation
 Convergence
 Closure
 3 pts of closure
 Doesn’t form posterior neural tube
 NotochordMHPepiboly from ectodermMHP flattens
causes wedge shape bendsecond hinge dorsolateralfolds
over NC migrates outFolate binding proteine-cadherin
to n-cadherinneural link
o Secondary
 Far posterior
 Epithelialdelaminate to form mesenchymemedullary
chordrecoilless to solid mass of cellapoptosis in middle to
form hollow tubereestablish connectionsform other layer
Three simultaneous levels of development in tube
o Gross anatomy
o Tissue anatomy
o Cell biology
Early human Brain Development
o Primary vesicles: Forebrain, midbrain, hindbrain
o Secondary vesicles: Telencephalon, Diencephalon, mesencephalon,
metacephalon, myelencephalon.
Dorsal-Ventral axis specified by ectoderm and notochord signals
Increase Buldging and increase neurons
Differentiation of neurons in the Brain
o Three types
 Neurons
 Glia
 Astrocytes
 Oligodendrocytes
 Ependymal
o 1 output(axon and neurotransmitter)
o 1-100,000 inputs
o Axon has microspikes for migratory traction
Neuron birthday
o Nucleus location determine cell life cycle
Bio 127 Section III
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Three layers in Spinal Cord
Six layers in Cerebellum
12 layers in Cerebral Cortex
Development of Sensory System
o Cranial ectodermal placodes
 Lens placode
 Olfactory placode
 Optic placode
o lens
o Skin and Hair
 Neural Crest
 General background
o CNS regulation
o Bugging out the neural tube
o Advancement to vertebrates
o Most cells in NC are multipotent pregenitors and determined fate
o Multipotent progenitor not a stem cell
o Specificity in position and determine fate by migratory path
 Cranial NC
o Many potentials (18) ex. Thyroid, thymus gland, tendon
o Endocrine power vs CNS
 Cardiac NC
o Smooth muscles located in large outflow arteries
 After heart is made by mesodermNC cause apoptotic
distruction to smooth muscles in major outflow
arteriesreplace smooth muscles
o NC tissue not prone to cancer or blockage
 Trunk NC
o Two Directions
 Ventralsympathetic and sensory neurons
 Dorsal migrate out and primary source of melanocytes
 Vagosacral NC
o Migrate to form medulla
o Sympathetic interneurons
o Parasympathetic interneurons
 Pre-patterning and Plasticity
 Neural and Axons Specification
 General background
o 100 billion neurons in the adult
 300 billion born
 Race of neuronal and sk muscle connections
 Determined by anterior-posterior position and hox genes leaves neuron
competent to certain interneuron or sk muscle connections
 Co-expression