July 14, 2011

Do you spend your photon budget wisely? This is a question that a recent paper asks, and answers back with a new technique that produces images that will blow your socks off. Once you put your socks back on, check out today’s image.

Cellular imaging is a constantly evolving field made of biologists on a never-ending quest for higher resolution of structures and faster image acquisition of a living cell. There are several challenges to these demands. For example, cells are not pancake-thin. Current techniques use illumination that leads to background noise in an image due to excited out-of-focus light. In addition, these techniques can cause phototoxic effects on cells, and can photobleach the fluorescent tags used to mark structures. Biologists have addressed these problems by using plane-illumination microscopy, which uses a separate excitation lens positioned orthogonally to the detection objective lens, leading to a more confined excitation of the focal plane. Planchon and colleagues recently improved this technique by using thinner sheets of light to illuminate the sample. The images produced using this Bessel beam plane illumination are remarkable, and allow for very fast 3D imaging of living cells. Images above show filopodia on a HeLa cell (left column), and the membrane ruffles on a kidney cell (right group of images). Purple arrowheads point to vacuole formation by macropinocytosis.

BONUS!! For a movie of the filopodia in the image above, click here. For a movie of the membrane ruffles and vacuole formation, click here. For many other knock-your-socks-off movies, click here.

Planchon, T., Gao, L., Milkie, D., Davidson, M., Galbraith, J., Galbraith, C., & Betzig, E. (2011). Rapid three-dimensional isotropic imaging of living cells using Bessel beam plane illumination Nature Methods, 8 (5), 417-423 DOI: 10.1038/nmeth.1586
Adapted by permission from Macmillan Publishers Ltd, copyright 2011

February 21, 2011

Cell migration is a complicated process, and the ease of genetic manipulation in the fruit fly Drosophila makes it an ideal organism for investigating the genes involved. Add some great live imaging to the mix, and you are a big step closer to understanding cell migration.

Border cells are a cluster of migratory cells in the fly egg chamber that are required for proper fertilization of the egg and early patterning of the embryo. This group of 6-10 cells collectively moves to one end of the egg chamber, where the oocyte resides. A recent paper looks at how these cells move collectively by responding to the different guidance cues. These guidance cues affect the formation, size, and productivity of cell extensions that are crucial for migration. Images above show border cells (green) in the egg chamber (left, white line shows the track of one cell during migration). Higher magnification images of the cell cluster (right) show the more streamlined shape of the cluster during the faster early phase of migration, compared with the late phase.

BONUS!! For a verrrrry cool movie of border cell migration, click here. For many great more movies from this paper, click here.

Poukkula, M., Cliffe, A., Changede, R., & Rorth, P. (2011). Cell behaviors regulated by guidance cues in collective migration of border cells originally published in The Journal of Cell Biology, 192 (3), 513-524 DOI: 10.1083/jcb.201010003

December 9, 2010

Some of the most striking and informative images aren’t of cells or organisms, but are computer-generated representations of what is going on in cells or organisms. These computer-generated images come from the use of two-photon microscopy, a powerful technique that allows for imaging of tissue that’s buried deep in a living organism.

Zebrafish is a freshwater fish that serves as a great model organism to cell and developmental biologists. During development, cells undergo dramatic reorganization during formation of the central nervous system, a process called neurulation. A recent paper describes the interaction between two proteins, called Protocadherin-19 and N-cadherin, and how these two proteins regulate cell movements during neurulation. These proteins together regulate cell-cell adhesion at a time when cells converge together to form a midline seam in the neural plate, a key feature of brain development. Images above are cell trajectories taken from time-lapse series of zebrafish embryos undergoing neurulation. The trajectories of cells in a normal embryo (top left) show a convergence of cells to the midline and a general movement of cells in one direction. Cells showed compromised movement in embryos with low levels of either protocadherin-19 (top, right), N-cadherin (bottom, left), or both (bottom, right).

BONUS!! Cool movies of two-photon image sequences can be found here.

Biswas, S., Emond, M., & Jontes, J. (2010). Protocadherin-19 and N-cadherin interact to control cell movements during anterior neurulation Originally published in The Journal of Cell Biology, 191 (5), 1029-1041 DOI: 10.1083/jcb.201007008

September 16, 2010

The endoplasmic reticulum (ER) is a very large organelle made up of continuous membrane tubules and sheets, where membrane-bound and secreted proteins are made and sorted. The ER is very dynamic, with membrane constantly rearranging, and does so with the help of microtubules. A recent paper looks at ER dynamics and through the use of live imaging shows ER sliding along a population of microtubules that are stabilized by acetylation modifications. Image above shows typical ER dynamics—the ER at the first time point is in green, and the ER at 30 seconds later is in red. The yellow arrow shows a region where the ER did not move, while the white arrow shows a sliding event.Reference: Jonathan R. Friedman, Brant M. Webster, David N. Mastronarde, Kristen J. Verhey, and Gia K. Voeltz, 2010. Originally published in Journal of Cell Bioloy. doi: 10.1083/jcb.200911024. Paper can be found here.

BONUS! Cool movie of above image can be found here.