Gene Expression of GH/IGF Axis Components and Myogenic Regulatory Factors in Juvenile Rainbow Trout (Oncorhynchus mykiss Walb) under the Influence of Continuous Lighting

Gene expression levels of myogenic regulatory factors (MRF, myf5, myog, myod1, myod2), myosin heavy and light chains (myhc, mlc-2), myostatin, and GH/IGF axis components (ghr1, ghr2, igf1, igf2, igfr1a, igfbp2a) were studied in the muscles and liver of a rainbow trout (Oncorhynchus mykiss Walb) farmed under conditions of continuous (24-h) lighting with night feeding to assess the impact of such a rearing regimen on growth regulation in this valuable commercial species. The introduction of a new rearing protocol into rainbow trout aquaculture (implemented in the Republic of North Ossetia-Alania) affected the gene expression of MRFs (myf5, myog, myod2) and muscle proteins (myhc, mlc2), as well as GH/IGF axis components in muscles (igf2, ghr2) and the liver (ghr1). Fish reared under continuous light demonstrated higher expression levels of myf5, myhc and mlc-2 genes compared to those raised under natural lighting, which also corresponded to their growth rates. The different patterns of changes in the expression of igf2, ghr1 and ghr2 genes in the muscles and liver in response to the introduction of continuous lighting were found. By November, individuals from both control and experimental groups showed an increase in the expression of igf1, igf2, igfr1a, ghr2, igfbp2a genes in the liver, as well as igfr1a and mstn1a genes in muscles, which was consistent with an increase in their relative growth rates. The results indicate differences in myogenesis regulation depending on lighting conditions.