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Unformatted text preview: so the hope is one day we can identify the birth and life span of every cell every Can’t do it yet in more Can’t complex organisms • • Neurogenesis and Cell Fates
nematode, • C. elegans, a nematode, has 987 cells (302 neurons) the mitotic history of every neuron is known the 2. Cell Migration
Cells • Cells migration, movement of progeny cell away from ventricular zone to their final destination destination Cells • Cells to not migrate at random… they travel along a particular type of glia cell (radial glial cells) cell 2. Cell Migration • Radial glial cells act as a series of guide wires • Newly formed cells creep along these radial glia • Cell adhesion molecules guide cell migration 3. Cell Differentiation • Many different types of neurons 3. Cell Differentiation
Migrating • Migrating cells are not differentiated (no neuronal phenotype) phenotype) When cells reach destination When genes that make neuronal proteins are expressed proteins Cells differentiate into those Cells appropriate for brain region (e.g., motor neurons in ventral horn, sensory neurons in dorsal horn) neurons • • 3. Cell Differentiation
Purkinje • Purkinje cells develop like this even if they are removed and put in a dish. Thus, the development is independent of neighboring cells (called cell-autonomous) cell-autonomous 3. Cell Differentiation
Some • Some cells will only develop into the appropriate cell if they get a specific signal from a neighboring cell from The neighboring cell usually The secretes a chemical that changes the gene expression and the phenotype of the developing cell… this is called induction called Thus, there are cases where Thus, cell-cell interactions are necessary for the development of some neural systems systems • • 3. Cell Differentiation
This • This is the case with the development of motor neurons neurons Chick spinal cord Notochord (green) lies Notochord beneath the spinal cord...
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- Winter '08