Molecular cloning and mRNA profile of insulin-like growth factor type 1 receptor in orange-spotted grouper, Epinephelus coioides.
The insulin-like growth factor type 1 receptor (IGF-IR) belongs to the tyrosine kinase (TK) receptor family. Besides being mitogenic, IGF-IR plays a crucial role in cell survival, transformation and maintenance of the malignant phenotype. In this study, we cloned the cDNA from the hypothalamus of the orange-spotted grouper (Epinephelus coioides) using reverse transcription PCR (RT-PCR) and the rapid amplification of cDNA ends (RACE) method. The deduced amino acid sequence showed that the receptor comprises 1413 amino acid residues. It contains cysteine-rich domains in its alpha-subunit, and a conserved transmembrane domain and TK domains in its beta-subunit. Comparison of the amino acid sequence with those of other species showed that the grouper IGF-IR shares 90.2%, 89.6%, 71.9% and 72% similarity with the IGF-IR of the Japanese flounder, turbot, zebrafish-a and zebrafish-b, respectively. When compared with its mammalian homologue, grouper IGF-IR contains a large insertion at its C-terminus. Phylogenetic analysis has revealed that the grouper IGF-IR belongs to the b-type IGF-IRs and has a higher similarity with flounder and turbot IGF-IR, and a lower similarity (<70%) with human, mouse and avian IGF-IR. Grouper IGF-IR transcripts were detected in the brain, peripheral tissues, embryos and early development larvae by semi-quantitative RT-PCR assay. It was observed that IGF-IR mRNA expression was greater in the brain than in peripheral tissues. The level of IGF-IR mRNA expression was much higher in retina, gonad, skeletal muscle and gill tissues than in liver, heart and thymus tissues. The expression of IGF-IR can be visualized as a ubiquitous signal in unfertilized eggs, embryos and early development larvae. The distribution pattern of IGF-IR mRNA in grouper development suggests that IGF-IR plays an important role in the embryo and early larval development stages.
Kuang
Yue-Mei
YM
Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, Zhongshan University, Guangzhou 510275, China.
Li
Wen-Sheng
WS
Lin
Hao-Ran
HR
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular / Q000379:methods; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005399:Fishes / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012333:RNA, Messenger / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D012333:RNA, Messenger; D011994:Recombinant Proteins; D017526:Receptor, IGF Type 1