The mechanism of regulation of ovarian maturation by red pigment concentrating hormone in the mud crab Scylla paramamosain

Dec 19, 2015Animal reproduction science

How Red Pigment Concentrating Hormone Controls Egg Development in Mud Crabs

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Abstract

Sp-RPCH is a 660 base pair peptide associated with ovarian maturation in the mud crab Scylla paramamosain.

The open reading frame of Sp-RPCH encodes a precursor expected to produce a signal peptide and a mature red pigment concentrating hormone.
Gene expression of Sp-RPCH was found in the eyestalk ganglia, brain, and thoracic ganglia, with levels increasing during ovarian maturation stages.
Synthetic RPCH induced a calcium current in brain neurons and increased the mean oocyte diameter in ovarian tissues when co-cultured with nervous tissues.
Crabs treated with RPCH showed higher gonad-somatic index, hepatopancreas-somatic index, and vitellogenin gene expression compared to controls.
The findings suggest that RPCH may regulate ovarian maturation through factors released from nervous tissues that promote vitellogenesis.

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In this study a full-length cDNA (Sp-RPCH) was cloned from the eyestalk ganglia of the mud crab Scylla paramamosain. Sp-RPCH is 660 base pairs in length and its open reading frame encodes a precursor that is predicted to be processed into a 25-residue signal peptide, a mature red pigment concentrating hormone (RPCH, an octapeptide), and a 75-residue precursor-related peptide. Phylogenetic analysis indicates that it clusters with other crustacean RPCHs and belongs to the adipokinetic hormone/RPCH peptide superfamily. Sp-RPCH gene expression was detected, using an end-point polymerase chain reaction (PCR), not only in the eyestalk ganglia but also in the brain and thoracic ganglia. Quantified using a real-time PCR, Sp-RPCH gene expression levels in the three tissues fluctuated along a cycle of ovarian maturation, with the levels progressively increased from stages I to IV, after which the expression levels decreased (although they remained significantly higher than stage I levels) when the ovary reached the mature stage (stage V). It was demonstrated using a patch clamp analysis that synthetic RPCH was able to evoke a Ca(2+) current in dissociated brain neurons and synthetic RPCH significantly increased the mean oocyte diameter of the ovarian tissues co-cultured with the eyestalk ganglia, brain, or thoracic ganglia; the stimulatory effect of RPCH was absent when the nervous tissues were not included in the ovarian incubation. Animals administrated with RPCH had significantly higher levels of gonad-somatic index, hepatopancreas-somatic index, and vitellogenin gene expression, when compared to control animals receiving a saline injection. The combined results clearly show that RPCH is involved in ovarian maturation in the mud crab; the stimulatory effects of RPCH are likely mediated by its actions on the release from the nervous tissues of factor(s) that directly regulate vitellogenesis in the ovary and hepatopancreas.

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The mechanism of regulation of ovarian maturation by red pigment concentrating hormone in the mud crab Scylla paramamosain

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