Correlation with larval body size of mRNA levels of growth hormone, growth hormone receptor I and insulin‐like growth factor I in larval torafugu
Abstract:The full‐length of insulin‐like growth factor (IGF) complementary (c)DNAs encoded by igf‐I and igf‐II from torafugu pufferfish Takifugu rubripes were cloned in the present study. The deduced amino acid sequences of the two genes showed c. 80% identity each with those of Igf‐I and Igf‐II from other teleosts, respectively. Two growth hormone (GH) receptors, ghr1 and ghr2, were also cloned in silico using the T. rubripes Fugu genome database. The transcripts of T. rubripes igf‐I were detected in slow muscle, heart, skin, gill, liver and intestine but not in fast muscle, spleen and testis of adult fish, whereas those of igf‐II were found in all tissues examined. Subsequently, the accumulated messenger (m)RNA levels of igf‐I and igf‐II were investigated in an F2 population derived from a male of an apparent fast‐growing T. rubripes strain and a wild female T. rubripes together with those of other growth‐related genes encoding Gh, Ghr1 and Ghr2, and with those of prolactin (Prl) and leptin (Lep) previously reported. The accumulated mRNA levels of igf‐I, gh and ghr1 were significantly correlated to growth rate at larval stages in the population, but not for those of igf‐II, prl, ghr2 and lep. Although it is unclear whether or not this phenotype is directly related to the heredity of the fast‐growing strain, the findings suggest that the expression of igf‐I, gh and ghr1 is involved in the regulation of growth rate at larval stages in T. rubripes.
Document Type: Regular Paper
Publication date: October 1, 2011