Paper4InClassQ&A

Names of people in your group _____________________________ Lab TA______ Discuss these questions with your group, and write down your answers on this sheet. Turn this in at the end of class for your groups 5 points. We will pick a group from each side to respond to each question. 2. (1) In Figure 2, panels M-V, what additional information is provided about the identity of the neural crest cells Whats the point of looking at two different stages of development (E9.5 and E10.5) now looking at another marker, ngn-2sensory neurons only (cad-6 is expressed in all neurons). At the earlier stage, E9.5, you can see the onset of migration of the neural crest cellsand it appears there are more ngn-expressing cells undergoing migration in the mutant. At higher magnification, you can see that there are ngn cells in the DRG in the control (where they should be), but also in additional places in the mutant, and that the mutant has lots of neuroD cells, but no autonomic cells. 3. (1) Explain whats being shown in Figure 3, panels G-N This part of the figure shows that NCSCs incubated in culture for several days lose expression of the stem cell marker sox10. In normal cells, only a small proportion become sensory neurons (brn-3), but in the mutant cells (stabilized b catenin), all cells become brn-3--ie, all are sensory neurons. For some reason not explained, complete differentiation is delayed, since staining with NF is lower in mutant cells than in normal. By 75 hours in culture, the cells are completely differentiated. Im not sure why it takes the mutant cells longer to differentiate, or if its even important. 4. (1) Explain the effects of different growth factors on the fates of neural crest cells, as described in the right-hand column of page 1022 (and supplementary table S2). What do the authors conclude from this data This data just supplements the data shown in Figure 4, although the supplementary table S2 does not exactly match the numbers presented in the text of the article. Essentially, different growth factors increase the proportions of different kinds of neurons that differentiate. BMP2 makes 90 of the cells become autonomic, while 79 of clones subjected to Wnt-1 made sensory neurons (some also made glia).TGF-b treatment makes the cells differentiate into smooth muscle. Also interesting to note is that without growth factors, the NCSCs make primarily mixed clones of autonomic neurons and glia. Questions for Team WEST Paper Discussion 4 MCDB 4650 Names of people in your group ______________________________ Lab TA______ Discuss these questions with your group, and write down your answers on this sheet. Turn this in at the end of class for your groups 5 points. We will pick a group from each side to respond to each question. (1) What does the data in Figure 3, panels A-F, show, and what conclusions can be made from this data Panels A,B,D and E show the relative number of stem cells in wt and mutants (A,B) and the relative number of dividing cells (Dapi marks all cells, BRDU only the dividing cells). The migration index is described in the supplementary MMas best as I can tell, they let NCSC grow in culture for 20 h, then measured how large of an area the cells covered. The migration index is the same for both conditions, as is the number of dividing cells, suggesting that the number of cells being produced by the NCSC is the same in both conditions, and that they still have the same migratory potential. What is the goal of the experiments presented in Figure 4 What do the authors conclude In this experiment, the authors are giving NCSCs different factors (or no factors), and then measuring what proportion of cells differentiate into sensory neurons. They also show that Wnt1 is what is actually activating b-catenin normally (wnt1 makes cells differentiate into sensory neurons if the cells are b-catenin-/-, the cells cannot respond to wnt1). They also show that other factors, like bmps and tgf-b induce different fates (autonomic or muscle like fate). Lastly, they demonstrate that individual NCSC are not stimulated to proliferate more by addition of Wnt1, but rather just stimulated to differentiate into sensory neurons.