Acta Biochim Biophys Sin 2005,37(5): Molecular Cloning and mRNA Profile of Insulin-like Growth Factor Type 1 Receptor in Orange-spotted Grouper, Epinephelus coioides

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ISSN 1672-9145 Acta Biochim Biophys Sin 2005, 37(5): 327–334 CN 31-1940/Q

Molecular Cloning and mRNA Profile of Insulin-like Growth Factor Type 1 Receptor in Orange-spotted Grouper, Epinephelus coioides

Yue-Mei KUANG^#, Wen-Sheng LI^#, and Hao-Ran LIN*

Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals,

Zhongshan University, Guangzhou 510275, China

Abstract 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 a-subunit, and a conserved transmembrane domain and TK domains in its b-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.

Key words orange-spotted grouper (Epinephelus coioides); insulin-like growth factor type 1 receptor; cDNA cloning; mRNA expression

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Received: January 6, 2005 Accepted: March 7, 2005

This work was supported by the grants from the National High Technology Research and Development Program of China (No. 2003AA603410, No. 2003AA603011), the Major State Basic Research Development Program of China (2004CB117402) and the Natural Science Foundation of Guangdong Province (No. 20023002)

^#These two authors contributed equally to this work

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