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Monday, March 26

  1. page Creating Body Plans edited ... Patterning is another important aspect of development that is controlled by cell signaling. So…
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    Patterning is another important aspect of development that is controlled by cell signaling. Sonic Hedgehog signaling controls patterning of the endoderm, mesoderm and ectoderm, and patterning of overlaying nervous tissue. The notochord sends the sonic hedgehog signal in an outwards wave to all of the surrounding cells. Sonic hedgehog signaling tells the midline cells of an organism to be one type of cell, and then various cells extending away from the midline are determined to be different types depending on how much of the hedgehog signal they receive due to their proximity to the signal. This ensures symmetry in an organism as well. When this signaling doesn’t happen, deformities such as cyclopia may occur, as shown in the master genes section of this page. Sonic hedgehog proteins are involved with just about all multi-cellular animals’ patterning, and is most complicated in vertebrates. (4)
    {http://ars.sciencedirect.com/content/image/1-s2.0-S0960982295001552-gr3.jpg} Midline of an organism (5)
    Sonic hedgehog proteins are involved primarily in pattern formation, particularly in differentiating the dorsal side of the organism from the ventral side. Gene expression patterns are changed when hedgehog signaling acts on undifferentiated cell types to turn them into particular cells. The sonic hedgehog gene is used by just about every organ system at some point in development. There are also two other very similar hedgehog signaling pathways - the Indian hedgehog signal and the desert hedgehog signal. Because hedgehog signaling is involved in determining cell types, it acts in the precursors of tissues to differentiate those cells. (4)
    Hedgehog signaling begins with a binding of the hedgehog ligand to a protein receptor called the Ptc. The Ptc receptor is an inhibitor of a protein called Smo, downstream of which there is a multi-protein complex called the Hedgehog signaling complex (HSC), which is made of several kinases. When Smo is inactivated, a protein called Ci undergoes cleavage which inhibits transcription, but when Smo is activated, the cleavage of Ci does not occur and transcription of hedgehog genes is induced. In either case, Ci enters the nucleus of the cell, but only when it does not undergo cleavage is transcription induced. In vertebrates there are 3 hedgehog genes, 2 Ptc genes, and 3 Ci genes, called Gli 1-3. Gli-1 and Gli-2 are transcriptional activators, whereas Gli-3 is a transcriptional repressor. (6)
    {http://www.abcam.com/ps/cms/Images/Hedgehog_Pathway1.jpg} Hedgehog signaling pathway (6)

    (1) __http://www.nature.com/scitable/topicpage/cell-signaling-14047077__ - a good website for an overview of cell signaling
    (2) __http://www.nature.com/scitable/topicpage/ephs-ephrins-and-bidirectional-signaling-14403965__ - an in-depth walkthrough of eph-ephrin signaling
    ...
    (4) http://www.learner.org/courses/biology/units/gendev/experts/incardona.html#top - overview of hedgehog signaling
    (5) http://www.cell.com/current-biology/retrieve/pii/S0960982295001552 - image of midline in cells
    (6) http://www.abcam.com/index.html?pageconfig=resource&rid=10858&pid=10039 - explanation of hedgehog signaling pathway
    Master GenesMaster Genes
    Homeobox genes are genes that contain homeoboxes, which are short sequences of DNA that contain a protein homeodomain (binds to DNA) and help regulate the expression of other genes. Homeobox genes may be homeotic, which generally control the identity of body parts.
    (view changes)
    7:22 am
  2. page Creating Body Plans edited ... (3)__ http://www.nature.com/scitable/topicpage/the-ephs-and-ephrins-hardwire-the-nervous-14403…
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    (3)__ http://www.nature.com/scitable/topicpage/the-ephs-and-ephrins-hardwire-the-nervous-14403478__ - discussion of eph-ephrin signaling's effect on the nervous system
    (4) http://www.learner.org/courses/biology/units/gendev/experts/incardona.html#top - overview of hedgehog signaling
    (5) http://www.cell.com/current-biology/retrieve/pii/S0960982295001552 - image of midline in cells
    Master GenesMaster Genes
    Homeobox genes are genes that contain homeoboxes, which are short sequences of DNA that contain a protein homeodomain (binds to DNA) and help regulate the expression of other genes. Homeobox genes may be homeotic, which generally control the identity of body parts.
    (view changes)
    7:05 am
  3. page Creating Body Plans edited ... Ephs and ephrins control most of the development of the nervous system, determining how neuron…
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    Ephs and ephrins control most of the development of the nervous system, determining how neurons wire together and axon guidance. Axons must grow great distances across the body sometimes, so the Eph-ephrin signaling pathway must be extremely precise. At the end of developing axonal profusions are growth cones, and below is a video showing the effects of Eph-ephrin signaling on the growth cones. (3)
    http://vision.ucsf.edu/sretavan/sretavancollapse.html__ - a video of growth cone collapse and retraction
    Patterning is another important aspect of development that is controlled by cell signaling. Sonic Hedgehog signaling controls patterning of the endoderm, mesoderm and ectoderm, and patterning of overlaying nervous tissue. The notochord sends the sonic hedgehog signal in an outwards wave to all of the surrounding cells. Sonic hedgehog signaling tells the midline cells of an organism to be one type of cell, and then various cells extending away from the midline are determined to be different types depending on how much of the hedgehog signal they receive due to their proximity to the signal. This ensures symmetry in an organism as well. When this signaling doesn’t happen, deformities such as cyclopia may occur, as shown in the master genes section of this page. Sonic hedgehog proteins are involved with just about all multi-cellular animals’ patterning, and is most complicated in vertebrates. (4)
    {http://ars.sciencedirect.com/content/image/1-s2.0-S0960982295001552-gr3.jpg} Midline of an organism (5)

    (1) __http://www.nature.com/scitable/topicpage/cell-signaling-14047077__ - a good website for an overview of cell signaling
    (2) __http://www.nature.com/scitable/topicpage/ephs-ephrins-and-bidirectional-signaling-14403965__ - an in-depth walkthrough of eph-ephrin signaling
    (3)__ http://www.nature.com/scitable/topicpage/the-ephs-and-ephrins-hardwire-the-nervous-14403478__ - discussion of eph-ephrin signaling's effect on the nervous system
    (4) http://www.learner.org/courses/biology/units/gendev/experts/incardona.html#top - overview of hedgehog signaling
    Master GenesMaster Genes
    Homeobox genes are genes that contain homeoboxes, which are short sequences of DNA that contain a protein homeodomain (binds to DNA) and help regulate the expression of other genes. Homeobox genes may be homeotic, which generally control the identity of body parts.
    (view changes)
    7:02 am

Sunday, March 25

  1. page Creating Body Plans edited By: Niki Striar, Rachel Fyler, and Julie Henry {CreatingBodyPlansfinalcopy1.pptx} {Creating Body…
    By: Niki Striar, Rachel Fyler, and Julie Henry
    {CreatingBodyPlansfinalcopy1.pptx} {Creating Body Plans Test.docx}
    Cell Signaling Master Genes Early Embryonic Development
    Cell SignalingCell Signaling
    (view changes)
    11:14 pm
  2. page Creating Body Plans edited ... HHMI Embryonic Developement Video {Untitled.png} http://www.drze.de/in-focus/figures/zygote.g…
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    HHMI Embryonic Developement Video
    {Untitled.png} http://www.drze.de/in-focus/figures/zygote.gif/image_preview
    Early embryonic development occurs during the first 1 to 12 days after fertilization. The steps of early embryonic development can be broken down into 6 stages (1): fertilization, cleavage, early blastocyst, beginning of implantation, completion of implantation, and primitive streak. Fertilization begins with the initial ejaculation of male gamete, sperm into the receptacle of the female, and ends with a single celled, diploid organism (1). Cleavage of the zygote begins as a single cell division into two cells and commences the start of many other divisions. Every 20 hours new blastomeres, newly divided cells, are formed. The zygote becomes a morula once around 16 blastomeres have been formed. When the embryo changes its shape from a round shape to a mulberry shape, the process is called compaction (3) During the early blastocyst stage, the morula travels to the uterus. This occurs after approximately 4 days. Once in the uterus, a blastocele cavity forms in the middle of the morula, caused by continued cell division. Within the cavity, embryoblast cells, the cells that will in time form the animal (4), begin to form into a flattened and compact structure. Outside of the cavity, trophoblast cells form, which will in time form the placenta. The embryo is now considered a blastocyst. During the beginning of implantation the blastocyst outgrows its zona pellucida shell, leaving the trophoblast cells exposed and able to secrete an enzyme that will break down the uterine lining enough for the blastocyst to implant itself. To help maintain health of the uterus, human chorionic gonadotrophin is secreted by the trophoblast, helping to keep the uterine lining rich with blood. The uterus is full of newly formed blood capillaries, stimulated by the egg about six days prior, and allow continuous blood circulation between the blastocyst and mother (4). Towards the completion of implantation, the placenta around the blastocyst begins to form when the trophoblast cells have broken down enough of the uterine lining to create pools of blood and induce new capillary growth. At this point in time, the inner cell mass begins to separate into two cell layers: epiblast and the hypoblast. The epiblast will become the embryo and the hypoblast will become the yolk sac (4). During the primitive streak phase, the blastocyst becomes fully engulfed by the placenta, which further secures the embryo to the uterine wall. Blood vessels appear in the placenta, connecting to the uterus. The embryo attaches to the developing placenta via a stock that will eventually become the umbilical cord. A “primitive streak” forms between the epiblast and hypoblast layers in the embryonic disk, showing the gasturation, or separation and migration of cells from the outer layer, towards the embryonic disk, ultimately forming a third layer. These layers are called the endoderm, mesoderm, and ectoderm layers (4). The ectoderm is the top layer of the embryonic disk. It will become skin, hair, ear, nose, mouth, anus, tooth enamel, pituitary and mammary glands, as well as the nervous system. The mesoderm (middle) will become the muscles, bones, lymphatic system, blood cells, lungs, heart and reproductive system, as well as the spleen and excretory system. The endoderm will become the lining of lungs, tongue, tonsils, urethra, bladder, and digestive tract (4).
    {4.png} a depiction of the 3 embryo layers
    1) http://www.visembryo.com/baby - A great site that gives pictures for each stage of embryonic development
    2) http://www.vivo.colostate.edu/hbooks/pathphys/reprod/fert/index.html - a good site for detailed information on the ‘players’ in the reproduction process
    3) http://www.hhmi.org/biointeractive/ - this site is the home to a good video that summarizes in a simplistic manner the early stages of embryonic growth

    (view changes)
    10:50 pm
  3. file 4.png uploaded
    10:49 pm
  4. page Creating Body Plans edited By: Niki Striar, Rachel Fyler, and Julie Henry CreatingBodyPlansfinalcopy1.pptx {CreatingBodyPla…
    By: Niki Striar, Rachel Fyler, and Julie Henry
    CreatingBodyPlansfinalcopy1.pptx{CreatingBodyPlansfinalcopy1.pptx}
    Cell Signaling Master Genes Early Embryonic Development
    Cell SignalingCell Signaling
    ...
    Early Embryonic Development
    Early Embryonic Development
    HHMI Embryonic Developement Video
    {Untitled.png} http://www.drze.de/in-focus/figures/zygote.gif/image_preview

    (view changes)
    9:41 pm
  5. file Untitled.png uploaded
    9:40 pm

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