It’s easy to be overwhelmed when learning about all that goes on during development. Then, you learn about the regularity and geometry seen throughout development (and biology in general) and that anxiety is washed away. I love seeing regular patterns and shapes throughout the biological world, and today’s image is a nice example of precision during development.
During development of a frog’s skin, there are two layers of cells. The top layer is made of cells that secrete mucus, and the bottom layer is made of cells that have cilia, or small hair-like projections. During skin development, these two layers intercalate and the resulting organization of mucus-secreting and cilia-containing cells is precise and predictable. A recent paper identified a role for a receptor protein called dystroglycan (Dg for short) in skin development. Dg is a critical receptor of basement membranes, which are regions that underlie tissues to provide signals and mechanical support. According to Sirour and colleagues, Dg gene expression is found in the bottom layer of cells in the developing skin of frog embryos. Loss of Dg function results in the disruption of skin development, specifically cell intercalation, cell-cell adhesion, and organization of the underlying matrix. As seen in the images above, the skin of control frog embryos have a precise flower-like arrangement of cells—a cilia-containing cell is surrounded by mucus-secreting cells (top). When Dg levels were reduced (bottom), that organization is disrupted.
Sirour, C., Hidalgo, M., Bello, V., Buisson, N., Darribere, T., & Moreau, N. (2011). Dystroglycan is involved in skin morphogenesis downstream of the Notch signaling pathway Molecular Biology of the Cell, 22 (16), 2957-2969 DOI: 10.1091/mbc.E11-01-0074
I like to imagine that actin and microtubules duked it out one day over which was more important. Actin let microtubules have the mitotic spindle, as long as actin could have the leading edge. So, imagine how ticked off microtubules were to learn that actin was discovered a few years ago to play an important role in Golgi organization, a task long-associated with microtubules. Zoinks!
The Golgi apparatus is a ribbon-like network of membrane stacks that process and sort various material synthesized by the cell. Its organization near the nucleus of the cell is long-known to be dependent on the microtubule cytoskeleton, and a recent paper describes new results on how important the actin cytoskeleton is in Golgi organization, too. Zilberman and colleagues have shown that an actin polymerizing protein called mDia1 and its activator, RhoA, affects the organization of the Golgi network. Specifically, when active forms of either of these proteins were introduced into cells, the Golgi network dispersed over an area much larger than in normal cells. In the images above, the Golgi network (red) covers a larger area in cells with an active form of mDia1 (bottom) than in normal cells (top). The actin network is in green.
Zilberman, Y., Alieva, N., Miserey-Lenkei, S., Lichtenstein, A., Kam, Z., Sabanay, H., & Bershadsky, A. (2011). Involvement of the Rho-mDia1 pathway in the regulation of Golgi complex architecture and dynamics Molecular Biology of the Cell, 22 (16), 2900-2911 DOI: 10.1091/mbc.E11-01-0007
There are some images that just stick with you. They might be beautiful, fascinating, or terrifying. For example, I’ll never forget when my former labmates told me to Google pictures of a teratoma. Seriously, don’t do it…wait, you just did, didn’t you? Unless you are a C. elegans worm, you won’t find today’s images terrifying…instead, you are likely to be utterly fascinated.
C. elegans are small 1mm-long roundworms that are used extensively in biology research. When the head of one of these worms is touched, its immediate response is to quickly back away from the touch. A recent paper describes how a fungus may have shaped the evolution of this behavior. Maguire and colleagues found that a predacious fungus called D. doedycoides capture larval stage worms by forming rings that constrict the worm passes through. There is a delay between when the fungus senses a worm passing through its ring and when it constricts to trap the worm. During this delay, the worm’s touch response can trigger the worm to quickly back out of the trap. However, there are some worms with mutations in its touch response—these worms are caught more efficiently by the fungus. Images above are electron micrographs of larval stage worms caught by the constricting rings of the fungus (left) and close-up images of the fungus’ rings before (top) and after (bottom) they are constricted.
BONUS!! Check out the authors’ video abstract, which includes movies of this predator-prey interaction, here.
I bet you think you’re pretty good at wearing the many proverbial hats in your life. I bet you can align a laser, walk your dog, change a diaper, and play in your awesome band of cell biologists. Well, integrins will put your hat-wearing to shame! Integrins are very important proteins (VIPs!) that play huge roles in adhesion, signaling, polarity, cell migration, cell division, and differentiation. Today’s image is from a paper describing new data on integrin trafficking.
Integrins are membrane proteins that interact with the environment outside of the cell to regulate cell adhesion and signaling. As part of the cell’s plasma membrane, integrins are constantly being brought into the cell and recycled back to the cell surface. Understanding this process is important—the way that integrins are recycled back to the cell’s surface (or not) can dramatically affect a cell’s ability to move, adhere to other cells, divide, and invade (in the case of cells in a tumor). A recent paper by Mai and colleagues describes a protein called RASA1 in regulating integrin recycling back to the membrane. RASA1 binds to integrin on a site where another protein called Rab21 also binds. So, these two proteins compete—Rab21 bound to integrin prevents its recycling back to the cell surface, while RASA1 binding allows integrin to traffic back to the surface. In the images above, when levels of RASA1 were reduced (bottom), cells were able to migrate more efficiently to close a “wound” scratched across a layer of cells, as compared to control cells (top). Images on the left show the wound shortly after it was created, while images on the right are four hours later.
Mai, A., Veltel, S., Pellinen, T., Padzik, A., Coffey, E., Marjomaki, V., & Ivaska, J. (2011). Competitive binding of Rab21 and p120RasGAP to integrins regulates receptor traffic and migration originally published in The Journal of Cell Biology, 194 (2), 291-306 DOI: 10.1083/jcb.201012126
You may live in many places throughout your life, but you have only one hometown. No matter what, your core is deeply affected by where you grew up (for me, that core is made of a fondness for fries covered with gravy, impassioned shouts of Bruuuuuce, and traumatic experiences with a teasing comb and hairspray…yes, that’s New Jersey). Just like us, a tumor is affected by its origin…its growth, malignancy, and responsiveness to treatment are all dependent on where the cancer cells came from. A recent paper tracks tumor growth to determine the origin of a certain type of tumor.
The countless types of cancer each come from different cell types. A tumor’s potential for growth, spreading, and treatment are heavily dependent on the tumor’s cell of origin. Malignant glioma is a deadly type of brain tumor, and a recent paper has determined the cell of origin for this cancer. Lui and colleagues used a technique called MADM (mosaic analysis with double markers) that mimics the genetic mutations seen in gliomas. This technique labels mutant cells green and normal cells red, enabling them to track how and when the mutant cells develop into tumors. These biologists started out with neural stem cells, which were suspected as the cells of origin for gliomas, yet found that cells called oligodendrocyte precursor cells (OPCs) are the cells of origin. The images above show mutant MADM neurons. Left and right images show MADM labeling of mutant (green) and normal (red) cells, while middle image shows the nuclei of cells (blue in merged).
“Our country is just so polarized these days,” I say as I shake my fist, then tell those pesky kids to get off of my lawn. “Polarized” doesn’t have to be a dirty word…in fact, if it weren’t for polarized epithelial cells we’d all be big puddles of cells lacking the ability to digest food, reproduce, circulate blood, or breathe. Today’s image is from a paper describing how septins guide microtubule organization in polarized epithelial cells.
Epithelial cells form sheets that line various organs throughout the body. These epithelial sheets are polarized, meaning the cells are not symmetrically organized. For example, our intestine is lined with a polarized epithelial sheet that must absorb nutrients from the intestine’s cavity in one side of the cell sheet, and then eventually guide those nutrients to blood vessels. A key step in the polarization of a cell is the organization of the microtubule cytoskeleton. Microtubules are organized in a radial array in rounded cells, while the microtubules in polarized epithelial cells are arranged along the lateral borders of the cells and in networks under the apical and basal membranes (top and bottom). A recent paper looks at the role of proteins called septins in guiding microtubule organization during the establishment of polarity. Septins are filamentous proteins known for their roles in cell polarity, but Bowen and colleagues were able to show a functional link between septins and microtubule organization. Specifically, two populations of septins allow microtubule growth, bundling, and capture in different regions of the cell. In the image above, thick septin filaments (left, green in merged) are seen colocalized with microtubules (middle, red in merged) in epithelial cells. Bottom images are higher magnification views of the boxed region.
Bowen, J., Hwang, D., Bai, X., Roy, D., & Spiliotis, E. (2011). Septin GTPases spatially guide microtubule organization and plus end dynamics in polarizing epithelia originally published in The Journal of Cell Biology, 194 (2), 187-197 DOI: 10.1083/jcb.201102076
Most of us are aware and in awe of the images from the Nikon Small World image competition. In case you are not, prepare to experience the world of microscopy in a new way. Check out the Image Galleries for the past few years here.
If you love geeking out over the beauty of cells, you must check out The Cell: An Image Library. It's a site of images, videos, and animations of cells that are contributed by some of the world's best biologists. The Library is hosted by the American Society for Cell Biology, so you know it is a great resource.
Some favorites:
A famously beautiful image of an actin network known to many of us as "the Svitkina image" is here. This image got me excited about actin in a way I wasn't willing to admit for years, especially as a proud lover of microtubules.
A rat intestinal cell absorbing a fatty meal is here. Next time you're tempted to order that delicious Fettuccine Alfredo, maybe this image will convince you to order the salad instead.
A dividing cell in metaphase, using Fluorescence Speckle Microscopy to visualize microtubule dynamics and kinetochores is here. Ah, spindles (contented sigh).
An animation of kinesin walking on a microtubule is here. If you feel moved for interpretive dance, you're not alone...my old labmates have seen my performance of this animation.
HighMag is going to take a few days for a summer break. This will give me an opportunity to reflect on the state of science and magnify my interest in cell biology, with high resolution and a low noise-to-signal ratio. Lastly, I'll put myself in proper alignment so I can properly illuminate the world of cell biology imaging. Get it?! Man, I'm funny.
In the meantime, I'll post a few odds and ends in the cell biology imaging world that should be fun to share. For now, you can sit back and enjoy one of my favorite clips of Ernie. He totally embodies the curiosity that a lot of us had as kids, and maintain today as scientists. So, if you are at the bench and sick of doing 50 minipreps just to find out that your cloning didn't work (again), maybe this will remind you of the romance that drove you to the science world in the first place.
It’s easy to be overwhelmed when learning about all that goes on during development. Then, you learn about the regularity and geometry seen throughout development (and biology in general) and that anxiety is washed away. I love seeing regular patterns and shapes throughout the biological world, and today’s image is a nice example of precision during development.
Sirour, C., Hidalgo, M., Bello, V., Buisson, N., Darribere, T., & Moreau, N. (2011). Dystroglycan is involved in skin morphogenesis downstream of the Notch signaling pathway Molecular Biology of the Cell, 22 (16), 2957-2969 DOI: 10.1091/mbc.E11-01-0074
