Week 6 - Neural development

• processes involved in forming a synapse or neuromuscular junction?

  contact between cells

  stabilise contact

  cell adhesion: in neuromuscular junction B2 laminin expressed to maintain connection.

  signalling like neuromuscular junction: receptors expressed on myocyte receive acetylcholine. Motor neuron express agrin which causes receptors to cluster.

  maturation
• Glial cells in CNS and PNS

  CNS: Astrocytes, oligodendrocytes

  PNS: satellite cells and Schwann cells
• Equivalent of white and grey matter in PNS?

  White matter: peripheral nerves(axons and Schwann cells) Grey matter: Ganglia (cell bodies and satellite cells)
• How does neurogenesis switch to gliogenesis?


  Change in expression patterns over time
• What can cause a neuron to undergo apoptosis?

  Absence of survival signal neurotropin
• How do neural crest cells separate and migrate from the dorsal neural tube?

  Epithelial to mesenchymal transition pre ability to bind to ECM then

  delamination (separate from basal lamina): happens after EMT usually but varies depending on the species and region of neural tube
• Different derivatives of neural crest cells at different levels?

  Cranial: connective tissue, neurons, glia, melanocytes

  vagal: cardiac and enteric neural crest, melanocytes, connective tissues

  trunk: dorsal root ganglia (sensory neurons and satellite cells), sympathetic ganglia, Schwann cells, adrenal gland medulla, melanocytes

  sacral: some enteric neurons and parasympathetic ganglia
• How do bones form in cranial neural crest

  Intramembranous ossification
• Most trunk neural crest cells were multipotent, right? how did we know?

  Yes. Brain bow : labelling of individual cells to see how many different cell types they form
• What controls where neuroblasts stop migrating? what pattern this creates in developing cortex?

  Reelin secreted by Cajal-Retzius cells. Inside out pattern
• What cytoskeleton elements for axon extension and guidance?

  Axon extension: microtubules

  Axon guidance: actin filaments/microfilaments. By disassembly or polymerisation or atomyosin contraction (actin filaments only)
• Neuron change

  Allows for complicated axonal path finding (go to midline then after crossed midline be repelled from going back to midline)
• Guidance molecules

  • Slit: ligand (expressed in the middle, guides axon to stay away from midline)
  • Robo: receptor (either side)
• Comm

  Inhibits Robo from expressed on cell surface
• Netrin

  Binds to Frazzled attracting axon to midline
• Increased netrin-frazzled signalling

  Triggers down regulation of Comm by retrograde transport of secretory vesicle
• Robo is not degraded so can be expressed on cell surface
• Growth cone responds to slit repulsion

  Axon stays away from midline
• How do neural crest cells separate and migrate from the dorsal neural tube?

  Inductive signals from surrounding sites like epidermal ectoderm, paraxial mesoderm, node, neural plate.

  Epithelial-to-mesenchymal transition, delamination (separation of neural crest from neural folds) then migration
• Does delaminating always happen after EMT?

  No. Depends on species and region of neural tube
• Defects in neural crest development?

  cranialfacial abnornalities, heart defects, GI disease: Hirschsprung diseade
• Neural crest cells

  • Become different cell types at different levels:
• Cranial neural crest cells

  1. Become melanocytes

  2. Become connective tissue like cartilage and bone of face and neck (through intramembranous ossification)

  3. Become neurons and ganglia
• Vagal neural crest cells

  1. Become cardiac (smooth muscle and connective tissue of heart)

  2. Become enteric neural crest (neurons and glia of enteric nervous system)

  3. Become connective tissues of branchial arches

  4. Become melanocytes
• Trunk neural crest cells

  Become a lot of PNS (dorsal root ganglia: sensory neuronal cell bodies and satellite cells, sympathetic ganglia, Schwann cells, adrenal gland medulla, melanocytes)
• Sacral neural crest cells

  1. Become some enteric neurons in colon

  2. Become parasympathetic ganglia
• what is ganglion?

  neuronal cell bodies and their supporting cells
• What are the two major ways that trunk neural crest migrate?

  underneath epidermal ectoderm (dorsolateral) and ventral (between and through somites)
• Special thing about ventrally migrating trunk neural crest

  Only migrate through anterior half of each somite
• How do growth cones respond to environmental signals?

  Receptors. Different level of expression of a receptor-
• Weaker synapse ones degrade get bigger synapse. what is this process?

  Maturation in forming synapse
• Ventrally between or through somites or dorsolateral which is underneath the skin


  What migration paths do neural crests follow in the trunk
• What interactions do neural crest cells have with each other and ECM?

  Temporary adhesion, Attraction and repulsion