Honors Theses

Date of Award


Document Type

Undergraduate Thesis

Degree Name



Mechanical Engineering

Faculty Mentor

Ryan Littlefield


David Nelson, Julia Kar, Joseph Richardson


All striated muscles are composed of small units called sarcomeres [1]. Within each sarcomere, there are thin filaments composed of actin and thick filaments composed of myosin. The thin filaments extend from either end of the thick filament towards the middle of the sarcomere. The lengths of thin filaments are correlated to muscle contraction and force production [1], but it is currently unknown what regulates their lengths. Prior hypotheses based on vertebrate models have focused on a nebulin ruler model [2]. However, nebulin is not present within invertebrate muscles, and this has led to a major gap in the field’s knowledge of length regulation. A proposed model of regulation is that the thin filament length is at least partially affected by the myosin in the thick filament chains [3]. To test this model, I made two strains of transgenic C. elegans roundworms. Both strains had the Tmod-capped pointed ends of the thin filaments tagged with ng-GFP, and one of them also had a headless myo-3 mutation marked with mCh. I imaged the strains with a confocal and Nikon Airyscan microscope to determine whether the targeted muscle proteins were visible. The results of these images and genotyping analysis show that the methods used were successful in making the desired model. The images also indicate that the myosin model of thin filament length regulation warrants further investigation.


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