In a talk about midbodies while I was in graduate school, a fellow worm biologist* once endearingly described the midbody as a little “turd”. This talk signaled to me that 1) midbodies are totally fascinating, and 2) I can still have my third-grader sense of humor, giggle at the word “turd” AND be a biologist at the same time. Today’s stunning image is from a paper describing a thorough analysis of midbody assembly and maturation.
At the end of cytokinesis, the two resulting daughter cells are separated at the site of the midbody. This structure is derived from the midzone, which is a zone of overlapping microtubules that assembles between the separating chromosomes during anaphase. The midbody is made of this microtubule bundle as well as proteins involved in cytoskeletal regulation and membrane trafficking, and is very compact. In fact, the center of the midbody is so tightly packed that antibodies cannot reach the proteins, in turn preventing immunofluorescent imaging. A recent paper describes how known midbody proteins are rearranged and regulated as the structure assembles and matures. Hu and colleagues found that the proteins from the midzone/midbody fall into three different subgroups that localize to different regions, each subgroup likely having a different function in the mature midbody. In the images above, the proteins CENPE (red) and RacGAP1 (blue) colocalize at the midzone during anaphase (left). After that, the localization of the proteins changes (middle, left)—CENPE flanks RacGAP1 at midbodies starting from furrow ingression in cytokinesis.
Hu, C., Coughlin, M., & Mitchison, T. (2012). Midbody assembly and its regulation during cytokinesis Molecular Biology of the Cell, 23 (6), 1024-1034 DOI: 10.1091/mbc.E11-08-0721