Differential regulation of hepatopancreatic vitellogenin (VTG) gene expression by two putative molt-inhibiting hormones (MIH1/2) in Pacific white shrimp (Litopenaeus vannamei)

Dec 3, 2014Peptides

Different effects of two molting-inhibiting hormones on egg yolk protein gene activity in Pacific white shrimp

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Abstract

Only LivMIH2 significantly increased VTG mRNA expression in both in vitro and in vivo experiments.

Molt-inhibiting hormone (MIH) is part of a peptide family that regulates crucial processes in crustaceans.
Phylogenetic analysis indicates no significant differentiation between MIH and vitellogenesis-inhibiting hormone (VIH).
Recombinant LivMIH1 did not affect VTG mRNA expression in either primary cell culture or in vivo tests.
In contrast, LivMIH2 significantly stimulated VTG gene expression and promoted ovary maturation.
The findings suggest that LivMIH2 may play a role in both molting and vitellogenesis in Pacific white shrimp.

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Molt-inhibiting hormone (MIH), a peptide member of the crustacean hyperglycemic hormone (CHH) family, is commonly considered as a negative regulator during the molt cycle in crustaceans. Phylogenetic analysis of CHH family peptides in penaeidae shrimps suggested that there is no significant differentiation between MIH and vitellogenesis-inhibiting hormone (VIH, another peptide member of CHH family), by far the most potent negative regulator of crustacean vitellogenesis known. Thus, MIH may also play a role in regulating vitellogenesis. In this study, two previously reported putative MIHs (LivMIH1 and LivMIH2) in the Pacific white shrimp (Litopenaeus vannamei) were expressed in Escherichia coli, purified by immobilized metal ion affinity chromatography (IMAC) and further confirmed by western blot. Regulation of vitellogenin (VTG) mRNA expression by recombinant LivMIH1 and LivMIH2 challenge was performed by both in vitro hepatopancreatic primary cells culture and in vivo injection approaches. In in vitro primary culture of shrimp hepatopancreatic cells, only LivMIH2 but not LivMIH1 administration could improve the mRNA expression of VTG. In in vivo injection experiments, similarly, only LivMIH2 but not LivMIH1 could stimulate hepatopancreatic VTG gene expression and induce ovary maturation. Our study may provide evidence for one isoform of MIH (MIH2 in L. vannamei) may serve as one of the mediators of the physiological progress of molting and vitellogenesis. Our study may also give new insight in CHH family peptides regulating reproduction in crustaceans, in particular penaeidae shrimps.

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Differential regulation of hepatopancreatic vitellogenin (VTG) gene expression by two putative molt-inhibiting hormones (MIH1/2) in Pacific white shrimp (Litopenaeus vannamei)

Abstract

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