bis_104_pq_11_ans_fall_08

bis_104_pq_11_ans_fall_08 - BIS 104 Practice Question 11...

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BIS 104 Practice Question 11 11. Mukouyama et. al. use the erbB3 mutant, a mouse strain that lacks Schwann cells, to demonstrate that Schwann cells are required for arterial differentiation and blood vessel-nerve alignment. What is the function of the signaling molecule Neuregulin-1? Neurugulin-1 is a signaling factor produced by neurons. It acts on the erbB3 co-receptor on Schwann cells. This interaction is required for the development and survival of Schwann cells. How is the marker known as BFABP (brain fatty acid binding protein) used in these erbB3 studies? BFAP is a protein that is produced only by differentiated Schwann cells and therefore, can be used as a marker to identify them. Fluorescently labeled antibodies against BFABP are used to verify the presence of Schwann cells in normal tissue and their absence in the skin tissue in erbB3 mutant mice. Why was it important in these studies to show that erbB3 is not normally expressed in endothelial cells as they differentiate? It must be remembered that in the erbB3 mutant strain of mice, the erbB3 gene is defective in all cells of all tissues, not just in the Schwann cells. So the failure of arteriogenesis in erbB3 mice could also be explained if endothelial cells themselves need to express the erbB3 gene for their normal differentiation. 12. Mukouyama et al. claim to have experimental evidence that VEGF is expressed in nerves at a relatively higher level than in surrounding mesenchymal tissue. Describe the experiment and the results they obtained that tend to that support this claim. EXPERIMENT: See fig. 6 color panels A, B, & C. 1. Skin samples from E14.5 mouse limbs were stained with fluoresently labeled antibodies directed against VEGF(red) and against neurons (green - TuJ1 marker for tubulin). 2. Stained samples were examined by double immunofluorescence confocal microscopy. 3. The staining pattern of the two markers was compared.
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RESULTS: VEGF is expressed in nerves at a relatively higher level than in surrounding mesenchymal tissue, as seen from the intensity of fluorescence from the two markers . 13. a)What does the Semaphorin3A (Sema3A) gene code for in normal (wild type) mice? The Sema3A gene codes for an axon guidance factor (neuregulin) b) What do the peripheral sensory nerves in the limb skin of Sema3A mutant mice look like. That is, how are they different from PSNs in wild type mice? The pattern of PSN outgrowth is disorganized. The nerves appear more fasciculated and less finely branched than normal. c) How is the immunostaining pattern of arterial endothelial cell markers, such as CX40 and NP1, affected by the Sema3A mutation? The arterial cell markers follow the pattern of the disorganized nerves in the mutant. That is, the arteries are still aligned with the disorganized mutant nerves. d)
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This note was uploaded on 04/03/2010 for the course NPB 105 taught by Professor Fuller during the Spring '10 term at UC Davis.

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bis_104_pq_11_ans_fall_08 - BIS 104 Practice Question 11...

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