lec08_diand_kul

lec08_diand_kul - In ovo time-lapse analysis after dorsal...

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In ovo time-lapse analysis after dorsal neural tube ablation shows rerouting of chick hindbrain neural crest Paul Kulesa, Marianne Bronner-Fraser and Scott Fraser (2000) Presented by Diandra Lucia
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Background Neural crest cells emerge from neural tube and migrate away to form structures such as sensory ganglia, motor neurons, and others Guiding mechanism: – Signals from neural tube? – Signals from other emigrating neural crest cells? – Environmental signals? – Combination? – Are cells pre-specified to migrate to a specific location and become a particular structure? (Hox gene expression patterns)
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Background Previous experiments suggest there are multiple guiding mechanisms – Different migratory paths/speeds, frequent path changes To examine importance of potential cues, normal migratory behavior had to be disrupted – Ablating subpopulations of premigratory hindbrain neural crest cells before stage 9 – when the regulative ability of neural tube declines - resulted in normal facial structures • neural tube is still developing; it regenerates and reforms neural crest – Ablating subpopulations of hindbrain neural crest cells after stage 9 still resulted in relatively normal embryos • Why?
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Background Ablating after stage 9: neural crest cells rostral and/or caudal to ablation deviate from migratory paths to fill in for ablated tissue How/why does this happen?
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Main Questions • What are the cell trajectories and migration behaviors of non-ablated neural crest cells in ablated embryos? • Where and when do the cell trajectory deviations take place?
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Methods • To answer these questions, they needed to be able to watch the activity of the neural tube and neural crest cells after ablation • They fluorescently labeled cells and used time- lapse recording and a computer program to track cell migration and see specific cell movements In ovo ( in vivo ) rather than in vitro , which was a limitation of previous experiments
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Methods Cut a “window” into chick egg at 7-9 somite stage Injected DiI to visualize cells in the hindbrain neural tube just before the first somite pair Acrylic ring fixed into shell to serve as a window Microscope continually watched cell movements and this was recorded Made incisions in neural tube using a glass needle – Took out dorsal sections of tube in several different places, using rhombomeres as guideposts
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r7 neural crest cells deviate rostrally in r5-r6 ablations Source: Kulesa, P., M. Bronner - Fraser, and S. Fraser. "In Ovo Time- Lapse Analysis After Dorsal Neural Tube Ablation Shows Rerouting of Chick Hindbrain Neural Crest." Development 127 (2000): 2843 - 2852. Courtesy of The Company of Biologists. Used with permission. Figure 1 – dorsal view
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This note was uploaded on 11/11/2011 for the course BIO 7.344 taught by Professor Bobsauer during the Spring '08 term at MIT.

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lec08_diand_kul - In ovo time-lapse analysis after dorsal...

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