MCDB 423 Lecture 8: Lecture 8

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Molecular, Cellular and Developmental Biology
MCDB 423
John Kuwada

Lecture 8 Slide 1 How do we know cells are migrating? We can look at structures of the cell in the developing brain Using EM, he noted that there were cells that looked like they were hugging the radial process The long cell is called a radial glia -Glia means a cell that isn’t a neuron Now we know that the cell is translocating up the fiber to move Slide 2 This is a classic way to label a cell and to visualize it over long periods of time -Use a virus to manipulate it’s DNA -If we can get a virus to get GFP to a cell or small population of cells, then we can follow those cells over time In this method, the viruses used targeted dividing cells specifically -So this is an engineered virus that has just the machinery to infect only one cell Here we have an example of a stem cell that was labeled Slide 3 This is an example of patches of cells that can be labeled of a developing mouse brain with a low tier (amount) of virus You could give a higher resolution to the experiment if you use not just one virus but package your virus from a library of different viral genomes that have slightly different sizes of DNA in them So take a biopsy of a piece of cell and using PCR, check what viral tag it had -If there are multiple viral tags, that would mean multiple viruses gave rise to this -But if there’s only one viral tag, that would mean that all these cells were derived from one stem cell This helps trace relationships between different cells in the brain Slide 4 Each virus made has a slightly different length of DNA inside So we have a library of viruses with different tags, infect with low tier in the embryonic rat and then process the brain several days later Slide 5 Here, there are individual cells that are expressing GFP that was labeled by the virus -So these cells are cells that derive from a virally infected cells -You see some have the same tags Now we can infer from these individual labeled cells which once could have came from the same progenitor cells Answer: B -The bottom gel is showing the DNA tags and it’s shown that 1 and 4 have the same tag while 2 and 5 have the same sequence -1 and 4 are also in discrete region of the brain so cells from the same progenitor had to move from the mother cell to different places ------------- Answers to the second and third question are both yes We know these cells had virus DNA because they tested positive for LacZ which is a bacterial protein that was put in the virus The molecular tags allowed us to trace the individual lineages of cells -If two cells have the same molecular viral tag, then they are related and came from the same cell slide 6 Answer = d This is an image of a more developed brain since we see more cells were generated A) We can’t infer from this image when they were born; not a birth dating experiment B) We can infer this because we see many cells labeled with the same DNA (for example, number 29) C) Can see that some cells are in different locations from one another We would call the related cells clones because they are genetically related; they arose from a single precursor at one point Slide 7 This is analogues experiment that was done in the spinal cord A virus was injected in one of the neural spheres in the spinal cord -We see multi
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