| Growth in crustaceans involves periodic shedding of the exoskeleton during molting. This process is under the control of two antagonistic hormones. It is stimulated by the molting hormone (ecdysone) and suppressed by the molt-inhibiting hormone (MIH). MIH is produced in the medulla terminalis of the X-organ (MTXO) and stored in the sinus gland of the eyestalk. It regulates molting by inhibiting the production of ecdysone by the Y-organ. Although the detail mechanism of MIH actions is unknown, it has shown that MIH can suppress the production of ecdysone through cyclic nucleotide-dependent pathway in crab and crayfish.Several cDNAs encoding the MIH of crustaceans have been isolated, cloned and characterized by recombinant DNA technology. Both the cDNA and amino acid sequences of the MIH from different crustaceans show a high degree of homology. Moreover, MIH also shares a high degree of homology with other members of Crustacean Hyperglycemic Hormone peptides family (CHH family), such as the Crustacean Hyperglycemic Hormone (CHH), Mandibular Organ-Inhibiting Hormone (MOIH) and Gonad-Inhibiting Hormone (GIH). The mature peptides of these hormones usually consist of 72-78 amino acid residues and have a similar amino acid sequence with six conserved cysteine amino acid residues.The Chinese mitten crab (Eriocheir japonicus sinensis) is of important value in Chinese and overseas markets. The size of the crab was decreased in recent years because of the mixing of crab seedlings from different river systems. This in turn, affected the benefit of crab farms,. Molting is an important step during the growth of crabs. But the hormones regulating the molting of the mitten crabs have not been studied so far. There is no information on the MIH gene, not only its cDNA but also its structure and organization are unknown. Using RT-PCR and inverse PCR technology, complementary DNA and structure organization of MIH gene in the mitten crab were cloned and analyzed respectively. |
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