Expression and release patterns of neuropeptides during embryonic development and hatching of the green shore crab, Carcinus maenas

Aug 27, 2004Development (Cambridge, England)

Patterns of Neuropeptide Production and Release During Development and Hatching of the Green Shore Crab

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Abstract

The expression of two neuropeptides, moult-inhibiting hormone (MIH) and crustacean hyperglycaemic hormone (CHH), during late embryonic development is similar to that observed in adults.

MIH represses ecdysteroid synthesis and CHH influences both ecdysteroid synthesis and water uptake during moulting.
Similar expression profiles of MIH and CHH mRNA were found during late embryonic development compared to adults.
Increased levels of CHH were detected in abdominal peripheral neurons, which may play a role in larval hatching and water uptake.
Developmental expression of red pigment-concentrating hormone (RPCH) and pigment-dispersing hormone (PDH) did not align with their gene transcription.
Maternally derived PDH mRNA significantly contributes to the embryo.
High-level expression of RPCH during late embryogenesis is associated with a novel site, the post-commissural organs.

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Crustacean ecdysis is controlled by at least three neuropeptides: moult-inhibiting hormone (MIH), which represses ecdysteroid synthesis; crustacean hyperglycaemic hormone (CHH), which not only influences ecdysteroid synthesis but also water uptake during moulting; and crustacean cardioactive peptide (CCAP), which is involved in stereotyped ecdysis behaviour. During embryonic development, moulting takes place in the egg, but there is little information regarding developmental expression of these neuropeptides during this period or during hatching--an event that is analogous to eclosion in insects. To address this problem, we determined expression profiles of MIH and CHH mRNA by quantitative RT-PCR, together with developmental peptide expression studies [confocal immunocytochemistry (ICC) and radioimmunoassay (RIA)]. Likely homologous events relating to neuropeptide surges of both CHH and CCAP were seen during larval hatching, when compared to the adult moult, and cell-specific copy concentration of both MIH and CHH mRNAs was identical to that of the adult during late embryonic development. We measured parallel mRNA and peptide expression of two neuropeptides (red pigment-concentrating hormone RPCH) and pigment-dispersing hormone (PDH) during development, as these have roles as neuromodulators and as classical neurohormonal roles. For MIH and CHH, gene expression was in accordance with peptide expression, but novel sites of CHH expression were found (abdominal peripheral neurones), the expression and release patterns of which may be related to larval eclosion and water uptake necessary for eggshell rupture and hatching. For RPCH and PDH, gene transcription and peptide expression were not in accordance. A significant contribution of maternally derived (non-translated) PDH mRNA to the embryo was seen, and for RPCH, high-level mRNA and peptide expression during late embryogenesis is related to a long ignored, but potentially important release site--the enigmatic post-commissural organs--which are the most prominent structures expressing RPCH during late embryogenesis.

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Expression and release patterns of neuropeptides during embryonic development and hatching of the green shore crab, Carcinus maenas

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