Prof Ian Johnston

Prof Ian Johnston

Emeritus Professor

Researcher profile



Research areas

Genomic and physiological approaches are being used to investigate muscle growth and adaptation in teleost fish. Skeletal muscle fibres are produced during the embryonic, larval and adult stages of the lifecycle. The genetic mechanisms controlling the production of muscle fibres and their subsequent hypertrophy are being studied. Several novel myogenic genes have been discovered and their functions characterised using in vivo and in vitro using primary muscle cultures. Using various models involving body size evolution and temperature adaptation I have shown strong selection for fibre size optimization, with consequences for the life-time production of muscle fibres. Universal scaling laws affecting muscle dimensions and energy metabolism can therefore successfully explain variations in fibre number and fine scale evolutionary patterns of myogenesis between populations and species. Salmonid fish have undergone two whole genome duplications relative to their common ancestor with tetrapods resulting in up to 8 copies (paralogues) of some genes. The role of gene paralogues in the signaling pathways regulating growth is being studied. Other research interests include the molecular mechanisms underlying seasonal temperature acclimation in fish and the consequences for muscle power output and swimming performance. Embryonic stress in zebrafish was shown to have persistent affects on thermal acclimation and myogenesis that persisted to adulthood, even after fish were raised from hatching at a common temperature. The mechanisms are currently under investigation at the genomic, tissue and whole animal levels.

Selected publications


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