Sternopygus macrurus electric organ transcriptome and cell size exhibit insensitivity to short-term electrical inactivity

• Published in: Journal of physiology, Paris Vol. 110; no. 3; pp. 233 - 244
• Main Authors: Güth, Robert, Pinch, Matthew, Samanta, Manoj P., Chaidez, Alexander, Unguez, Graciela A.
• Format: Journal Article
• Language: English
• Published: France Elsevier Ltd 01.10.2016
• Subjects: Animals; Cell Size; Cell size regulation; Contractile gene expression; Electric organ; Electric Organ - cytology; Electric Organ - physiology; Electrical inactivity; Gymnotiformes - genetics; Gymnotiformes - physiology; Muscle transcriptome; Spinal cord transection; Transcriptome; ST; Spinal cord transection; Cell size regulation; Muscle transcriptome; Contractile gene expression; Electric organ; Electrical inactivity; EO
• ISSN: 0928-4257; 1769-7115
• DOI: 10.1016/j.jphysparis.2016.11.005

[Display omitted] •Spinal cord transection has minimal effect on sarcomeric gene expression.•Electrical inactivity caused a transient upregulation of proteolytic mechanisms.•Electrocyte size did not change after spinal cord transection.•Electrocyte-“specific” genes were unaffected by short-term electrical inactivity. Electrical activity is an important regulator of cellular function and gene expression in electrically excitable cell types. In the weakly electric teleost fish Sternopygus macrurus, electrocytes, i.e., the current-producing cells of the electric organ, derive from a striated muscle lineage. Mature electrocytes are larger than muscle fibers, do not contain sarcomeres, and are driven continuously at frequencies higher than those exerted on muscle cells. Previous work showed that the removal of electrical activity by spinal cord transection (ST) for two and five weeks led to an upregulation of some sarcomeric proteins and a decrease in electrocyte size. To test whether changes in gene transcription preceded these phenotypic changes, we determined the sensitivity of electrocyte gene expression to electrical inactivity periods of two and five days after ST. Whole tissue gene expression profiles using deep RNA sequencing showed minimal alterations in the levels of myogenic transcription factor and sarcomeric transcripts after either ST period. Moreover, while analysis of differentially expressed genes showed a transient upregulation of genes associated with proteolytic mechanisms at two days and an increase in mRNA levels of cytoskeletal genes at five days after electrical silencing, electrocyte size was not affected. Electrical inactivity also resulted in the downregulation of genes that were classified into enriched clusters associated with functions of axon migration and synapse structure. Overall, these data demonstrate that unlike tissues in the myogenic lineage in other vertebrate species, regulation of gene transcription and cell size in the muscle-like electrocytes of S. macrurus is highly insensitive to short-term electrical inactivity. Moreover, together with data obtained from control and long-term ST studies, the present data suggest that neural input might influence post-transcriptional processes to affect the mature electrocyte phenotype.