April 29, 2010

Epithelial cells form sheets that line cavities and structures. Their organization and structure are polarized, allowing transport of material from one side of the cell to the other. Earlier this year, investigators reported that galectin-3 plays a role in the establishment of epithelial polarity, possibly through its effects on centrosomes, the primary microtubule-organizing centers. Images above show mammalian cells allowed to grow into a polarized epithelial layer. A protein that is typically on the apical side of the cells (top, green) is mislocalized in cells with lower levels of galectin-3 (bottom). DNA is in blue.

Reference: Annett Koch, Francoise Poirier, Ralf Jacob, and Delphine Delacour. Authors’ Molecular Biology of the Cell paper can be found here.

April 26, 2010

Many proteins undergo modifications posttranslationally, meaning after a protein is synthesized. One example is arginylation, which is used to modify many proteins, including actin. A recent paper has looked at the effects of arginylation on the actin cytoskeleton, and found that arginylation is important for actin filament polymerization, actin network structure, and interaction with proteins that regulate actin. Image above shows the leading edges of crawling cells—wild-type (top) compared to arginylation-defective (bottom).

Reference: Sougata Saha, Maureen M. Mundia, Fangliang Zhang, Ryan W. Demers, Farida Korobova, Tatyana Svitkina, Alex A. Perieteanu, John F. Dawson, and Anna Kashina. Authors’ Molecular Biology of the Cell paper can be found here.

April 22, 2010

During development, polarity proteins play an important role by positioning cells and their machinery in the proper orientation. A recent paper asked how a well-studied set of polarity proteins functions in the oocyte of the fruit fly Drosophila. Image above shows an egg chamber, with microtubules in red and DNA in blue.

Reference: Pierre Fichelson, Marlène Jagut, Sophie Lepanse, Jean-Antoine Lepesant and Jean-René Huynh, 2010. Development: 137, 815-824. doi: 10.1242/dev.045013. Adapted with permission by Development. Paper can be found here.

April 19, 2010

During development, cells must differentiate into specific types. This process was understood for many years to be an irreversible event, yet recent papers have challenged this idea. In one paper, researchers have been able to convert fibroblasts into neurons by expressing a specific set of genes. Image above shows these induced neuronal cells, only a few days after they started out as fibroblasts.

Reference: Thomas Vierbuchen, Austin Ostermeier, Zhiping P. Pang, Yuko Kokubu, Thomas C. Südhof, and Marius Wernig. Adapted by permission from Macmillan Publishers Ltd: Nature 463, 1035-1041, copyright 2010. Paper can be found here.

April 15, 2010

The pancreas is made of several different types of cells, and these different types are all derived from the same set of progenitor cells during development. A recent paper investigated the role of a protein named Sel1 in the development of the pancreas, and reported that Sel1 is important for the growth and differentiation of the progenitor cells. Image is of early pancreas cells in the mouse, showing Sel1 (red) and Sox9 (green), used as a marker for pancreatic progenitor cells.

Reference: Shuai Li, Adam B Francisco, Robert J Munroe, John C Schimenti and Qiaoming Long. Authors’ BMC Developmental Biology paper can be found here.

April 12, 2010

Endocytosis is the uptake of material into a cell in membrane-bound vesicles. The material is trafficked through different vesicles, depending on whether it will be degraded or recycled back to the surface of the cell. A recent paper identified a new player in this process called Ema, which is found on some late endosomal vesicles and plays a role in the maturation of these vesicles. Image shows Ema (green) and Rab5 (purple), an early endosomal protein.

Reference: Sungsu Kim, Yogesh P. Wairkar, Richard W. Daniels, and Aaron DiAntonio, 2010. Originally published in Journal of Cell Biology. doi: 10.1083/jcb.200911126. Paper can be found here.

April 8, 2010

The separation of duplicated chromosomes during mitosis was widely believed to be a random process. However, a group was recently able to distinguish the different DNA strands and regions on the chromosomes, and show the non-random segregation of chromosomes in colon epithelial cells. Image shows mouse chromosomes with these different labels.

Reference: Ester Falconer, Elizabeth A. Chavez, Alexander Henderson, Steven S. S. Poon, Steven McKinney, Lindsay Brown, David G. Huntsman & Peter M. Lansdorp. Adapted by permission from Macmillan Publishers Ltd: Nature 463, 93-97, copyright 2010. Paper can be found here.

April 5, 2010

Morphogenesis is the arrangement of cells into tissue during development, and often requires complex coordination of several different cellular processes. A recent paper shows the coordination of endocytosis, the uptake of material into a cell, with contraction of the actin-myosin network, in order to drive cell shape changes. Image is of bottle cells in the embryo of the frog, Xenopus laevis, with microtubules in green and newly internalized vesicles in red.

Reference: Jen-Yi Lee and Richard M. Harland. Current Biology 20, 253-258. ©2010 Elsevier Ltd All rights reserved. Paper can be found here.

April 1, 2010

Cell migration is a dynamic and highly coordinated process. A recent paper assigned a role for an unconventional myosin, named MYO18A, in cell migration. Images above show colocalization of this actin motor (green), with PAK2 (red), which is part of a complex that regulates the assembly of adhesion sites seen in motile cells. The colocalization is at lamellipodia and membrane ruffles, which are membrane protrusion structures important for cell motility.

Reference: Rae-Mann Hsu, Ming-Hung Tsai, Ya-Ju Hsieh, Ping-Chiang Lyu, and Jau-Song Yu. Authors’ Molecular Biology of the Cell paper can be found here.