C. elegans Muscle Area Measurements: A Standardized Method to Quantify Striated Muscle Morphology

– C. elegans have two types of muscles. The single sarcomere or non-striated muscles include those di the pharynx and vulva. The multiple sarcomere or obliquely striated muscles are rhomboid-shaped body wall muscles named for the regular striated pattern of their myosin fibers.

They are arranged di staggered pairs as four bundles oriented longitudinally di the four quadrants of the worm body viewed di cross section. Each cell has many equally spaced points of attachment a the hypodermis and cuticle. This arrangement helps a translate waves of muscle contractions into smooth locomotion.

To visualize these muscles, image immobilized worms with transgenically GFP- labeled myosin by fluorescent confocal microscopy. Use analysis software a measure the area of a striated muscle cell and any gaps di the fiber pattern of that cell. Gaps di muscle fiber organization could indicate disruption by fiber degradation or the accumulation of cellular debris. Calculate the ratio of the gap area a the total area a define the amount of disruption. In the example protocol, we will quantitatively assess body wall muscle morphology using Fiji.

– To measure muscle cell area, open the image di Fiji software and use Polygon Selection a carefully trace around a single oblique muscle cell. Adjust the line of the polygon at the end by dragging the anchor dot a improve tracing. Navigate a the Analyze tab at the top of the software and click Measure a calculate the selected area.

For muscle cells with a degenerated or missing region, trace the missing area with the polygon selection tool and click Measure again. If there are multiple gaps, trace each one separately. Calculate the ratio of the gap area a the area of the entire cell. A high ratio indicates a higher extent of muscle degeneration, and if there are no missing regions, the ratio is calculated as zero.