Ahhh…I remember the first time I saw worms under the microscope. I was an undergrad attending my future graduate school’s recruitment weekend, during which a kick-ass scientist showed me beautiful worms with glowing green seam cells down their bodies and matter-of-factly told me that “Worms rock.” I silently agreed with her, and found myself a few months later in that lab and spreading the gospel of the awesome rocking ability of worms. So, whenever I see a worm paper I feel like I’m part of the family…using genetic nomenclature that makes fly biologists roll their eyes (right back at you, sillies) and waxing nostalgic about beers in front of Royce Hall at the big worm meetings. Today, stunning images of worm muscles serve as a great example of the power of worms to show scientists some fascinating biology.
A sarcomere is the basic unit of muscle that contracts and relaxes. The fine balance of the proteins involved in a functional sarcomere is achieved by degradation of damaged proteins and production of new proteins. This balance is tipped during muscle atrophy in humans, caused by disease, disuse, starvation, or old age. The small nematode worm C. elegans has been a great model for muscle development and function, and a recent paper describes how protein degradation in muscle is regulated. Wilson and colleagues found that the sarcomeric protein UNC-89 (obscurin) binds to another protein called MEL-26 in C. elegans. MEL-26 is an adaptor protein that plays an important role in the ubiquitin proteasome system that degrades damaged or old proteins. Mutations in the mel-26 gene cause disorganization of the sarcomere structure, and some of this disorganization is due to an increase in the activity of a microtubule-severing protein called MEI-1 (katanin). These results suggest that normally UNC-89 inhibits the MEL-26 degradation complex toward MEI-1 in muscle. In the images above, adult body wall muscle from C. elegans is stained for UNC-89 (left, purple in merged) and MEL-26 (middle, green in merged). Some MEL-26 is found at the M-line of the sarcomere, where UNC-89 predominantly sits (arrow).
Kristy J. Wilson, Hiroshi Qadota, Paul E. Mains, & Guy M. Benian (2012). UNC-89 (obscurin) binds to MEL-26, a BTB-domain protein, and affects the function of MEI-1 (katanin) in striated muscle of Caenorhabditis elegans Molecular Biology of the Cell, 23 (14), 2623-2634 DOI: 10.1091/mbc.E12-01-0055