The mitotic spindle is composed of microtubules and numerous proteins, all tightly regulated in order to provide the structure and dynamics required for accurate chromosome segregation. TPX2 is a microtubule-associated protein that was recently shown to be transported along microtubules from kinetochores, where microtubules reach chromosomes, to the spindle poles. Image above shows TPX2 (red) transported along microtubules (green) to spindle poles in a normal cell (top), compared to its more even distribution along microtubules when dynein, a microtubule motor, is inhibited (bottom).
Reference: Nan Ma, U. S. Tulu, Nick P. Ferenz, Carey Fagerstrom, Andrew Wilde, and Patricia Wadsworth. Authors’ Molecular Biology of the Cell paper can be found here.
Assembly of the junction between muscle and tendon cells is important for proper development of muscle tissue. A recent study has identified a new player in this process, a gene named slowdown. Developing muscles that lack slowdown have torn muscle fibers, as well as disconnected and broken tendons. The image above shows muscle fibers (red) and tendon cells (blue) in normal (left) and slowdown mutant (right) larvae in the fruit fly Drosophila.
Reference: Eliezer Gilsohn and Talila Volk, 2010. Development: 137, 785-794. doi: 10.1242/dev.043703. Adapted with permission by Development. Paper can be found here.
Microscopists are constantly pushing the limits of what microscopes can show and teach us about cell biology. One group recently used TIRF-based polarization techniques to image events at the plasma membrane during exocytosis. Exocytosis is the fusion of secretory vesicles with the plasma membrane to release their contents outside of the cell. The signal in the image above indicates the submicrometer changes in the curvature of the membrane shortly after the vesicle fuses with it (second image in panel is after fusion; cartoon is interpretation of the images).
Reference: Arun Anantharam, Bibiana Onoa, Robert H. Edwards, Ronald W. Holz, and Daniel Axelrod, 2010. Originally published in Journal of Cell Biology. doi:10.1083/jcb.200908010. Paper can be found here.
During development of an organ or tissue, individual cells must translate positional information into gene expression, which generates changes in tissue morphology. The developing wing in the fruit fly Drosophila is a great model for this, and recent work reveals how one gene is differentially expressed in the wing imaginal disc. The image above shows the symmetrical expression of this gene, optomotor-blind (omb), along the anterior-posterior axis (left-to-right in this image).
Reference: Jie Shen, Christian Dahmann and Gert O Pflugfelder. Authors’ BMC Developmental Biology paper can be found here.
Organization and structure are very important within cells and tissues. A protein in the nematode worm C. elegans called ZYG-12 plays a role in both organization and structure within the organism’s gonad. Image above shows gonads in wild-type (left) and zyg-12 mutant (right) worms—nuclei of mutants are irregularly arranged compared with wild-type.
Reference: Kang Zhou, Melissa M. Rolls, David H. Hall, Christian J. Malone, and Wendy Hanna-Rose, 2009. Originally published in Journal of Cell Biology, doi:10.1083/jcb.200902101. Paper can be found here.