PMC

Effect of ST on muscle fiber type distribution in S. macrurus. Average type I muscle fiber distribution in myomeres 3 and 4 from control and spinal transected fish ventral muscle (n = 3 each) was determined as the average ratio of total cross-sectional area from type I muscle fibers to the total area of all muscle cells from four myomeres (i.e., L3, R3, L4, R4). Bars represent means ± SD for each sample.

Effect of ST on cross-sectional area of muscle fiber types in S. macrurus. Minimum Feret diameter measurements were obtained for type I (A) and type II (B) muscle fibers from control and 5-day ST fish (n = 3 each) and used to calculate cross-sectional area, which was then normalized against total tail area to account for small differences in fish size. The number of fibers analyzed for each sample is indicated in parentheses. Data are represented as box plots with each open circle representing a single fiber measurement and “X” indicating the mean cross-sectional area for each fish.

Fiber types in the ventral muscle of S. macrurus. Tissue cross section showing the ventral musculature of a tail from a control fish immunolabeled with an antibody against type I sarcomeric myosin heavy chain (green). Left (L) and right (R) myomeres are numbered in increasing order along the ventral-to-dorsal axis. Morphological and fiber type distribution analyses were performed bilaterally on myomeres 3 and 4 from tails of control and ST fish (n = 3 each). Scale bar, 1,000 μm.

Heat map of transcript abundance ratios of muscle transcription factor and sarcomeric genes between control and ST fish. Normalized transcript abundance ratios were determined for 2-day ST/control and 5-day ST/control muscle samples and the log₂-transformed ratios were visualized as heat maps using the “heatmap.2” function in the “gplots” package in R for muscle transcription factors (A) and sarcomere genes (B). Transcription factors were ordered by the fiber type specificity of their target genes, whereas sarcomere genes were sorted by expression pattern using the default row clustering method in the “heatmap.2” function. Genes flagged as differentially expressed by DESeq2 are indicated by including the unadjusted P value overlaying the appropriate color cell.