MCDB 423 Lecture 7: Lecture 7

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Molecular, Cellular and Developmental Biology
MCDB 423
John Kuwada

Lecture 7 Slide 3 Golgi staining only labels a small number of cells We know the brain is a big mass of tissue but how does the tissue get the complex functions that the brain has? Cajal discovered that the brain is made out of cells and individual cells have unique structures and shapes -They are organized in a very highly orchasted and complex organization and highly specified Individual neurons take on distinct shapes and take on distinct functions and are in distinct functions in the brain A key aspect to making these hypothesis about the brain was the ability to see individual neurons -If you just stain for cells (nuclei, ribosomal organelles, etc.) you see that there is lots of cells A key to understand specific organizations is to see a subset of cells The technique Cajal had was called the Golgi staining technique -It’s a dye which will form a reaction in the cell and fill the cell with a dark color but only happens stocastly (very low efficient; labels only a small amount of cells) -Because of this, you can see individual cells and see what their shapes are From these drawings that he made by looking at individual neuron stains, he inferred that neurons are communicating with each other (another fundamental property of the brain) In the next several lectures, we’ll discuss how we form these structures? Where do we get different neurons? How do neurons get distinct properties in distinct places? Slide 4 Where do neurons come from? We’ll talk about the cortex because this is what we know the most about to answer this question The cortex is a layer of cells on the outside of the brain -Has a basic processing function in the brain -We have layers of cells that are making connections with each other and these connections allow for processing information Cortex is also very large (humans have more cortical neurons than rodents and reptiles for example; we also have more layers in the cortex) Slide 5 Here’s another way to look at neurons in the cortex The golgi stain are showing us the shapes of the cells (left figure) A nissal stain (I think?? Not very important to know) is a stain for specific transcriptional factors that are expressed in a specific pattern Slide 6 Microcephaly is a rare genetically inherited disorder where the feature is less neurons in the brain and a smaller head size -Recently, more cases have been occurring because of the Zika virus slide 7 Answer = c (technically they also come indirectly from embyronic stem cells (as do all parts of the body) but neural stem cells are the immediate presursor cells that give rise to neurons. Neuroblast = neural stem cells Where did neurons come from? Neurons don’t divide; they are differentiated cells in our brain -They develop in the womb and once you have them, that’s it So where do they come from? -The answer is C A) These give rise to everything in our body; so indirectly they give rise to neurons B) IPs are something we can make in vitro C) Neuroblasts is an old fashioned word; a more common term is neural stem cell (can use terms interchangeably) Slide 8 This is a review slide The fertilized egg gives rise to blastocyst which are pluripotent and gives rise to all the other cells in the body During development, we have specialized stem cells that give rise to different things Slide 9 As a review, we talked about the neuroblast and how in the developing grasshopper embryo, you have a bunch of epidermeal cells and 30 neuroblast form after -Each neuroblast gives rise to a specific set of cells -They’ll go through different cell divisions and thus form different types of cells slide 10 Chordin, noggin & follistatin inhibit BMP4 to induce neural fate After gastrulation, we have 3 layers of tissue The neural ectoderm gives rise to the nervous system Slide 11 These cells will take on a neural cell faith and they’ll proliferate and form what will become a neural tube -This tube will give rise to the spinal cord and the brain slide 12 These are images of a neural tube from a chick embryo The lumen will become the ventricular system The cells that are dividing are called neural epithelial cells Epithelial cells have an apical and basal process -A part touches the lumen -The cell body divides and proliferates to give rise to more cells like it This is what the early brain looks like where the neural epithelial cells are proliferating Slide 13 The figures shows example of antero/posterior patterning which you discussed in previous lectures (eg., patterned by Fgf and Wnt morphogens) Ultimately the neural tube will take on patterning (discussed in the previous lecture) -this figure is just showing you the anterior and posterior patterning the neural tube will take -Don’t have to memorize all this stuff slide 14 During this phase, many of the cells are starting to be generated so it is a good place to look where neural stem cells are being ge
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