Identification of an insulin-like androgenic gland hormone transcript highly expressed in male precociousness of the Chinese mitten crab Eriocheir sinensis

The androgenic gland (AG) hormone is well known as a key peptide to induce masculinization and maintains male characteristic in crustaceans. In this study, a full-length cDNA encoding insulin-like androgenic gland hormone (EsIAG) was identified from the AG of the Chinese mitten crab Eriocheir sinensis. The full length of EsIAG cDNA contains 1,481 nucleotides, which encodes for a deduced protein of 151 amino acid residues. The predicted pre-peptide is composed of a signal peptide of 19 amino acids (aa), A chain of 44 aa, B chain of 31 aa, and C peptide of 57 aa. Moreover, six conserved cysteine residues and a putative N-linked glycosylated site were found in the deduced protein as reported in other crustaceans. Reverse transcription polymerase chain reaction and in situ hybridization analysis showed EsIAG was only expressed in the AG with especially high abundance during the mature stage of testis. Interestingly, a significantly higher expression level of EsIAG was also detected in precocious individuals than that in the normal grown ones, suggesting that the abnormally high expression of EsIAG might contribute to male precociousness in E. sinensis.