Cloning and differential expression of two β‐pigment‐dispersing hormone (β‐PDH) isoforms in the crab Cancer productus: Evidence for authentic β‐PDH as a local neurotransmitter and β‐PDH II as a humoral factor

Abstract

Two beta-pigment-dispersing hormone (beta-PDH) isoforms have been identified in several decapod crustaceans, including the crab Cancer productus, but whether these peptides serve common or distinct physiological roles remains to be elucidated. Here we show that the distribution of beta-PDH-like immunoreactivity in the nervous system of C. productus is similar to that found in other brachyurans, suggesting roles as both a circulating hormone and a locally released transmitter for members of this peptide family. cDNAs encoding NSELINSILGLPKVMNDAamide (authentic beta-PDH; here termed Canpr-beta-PDH I) or NSELINSLLGLSRLMNEAamide [corrected](Canpr-beta-PDH II) were cloned. Double in situ hybridization revealed that these two beta-PDH isoforms are differentially distributed within the eyestalk. For example, in most neurons between the medulla interna (MI) and the medulla terminalis (MT), both isoforms appear present; however, in some neurons in this region, mRNA for only one or the other isoform was detected. Likewise, only prepro-beta-pdh I mRNA was detected in the somata of the lamina ganglionaris (LG) and in the brain. By direct tissue mass spectrometry, only Canpr-beta-PDH II was detected in the neurosecretory sinus gland (SG), whereas Canpr-beta-PDH I was found in all other parts of the eyestalk. Collectively, these data suggest distinct functions for each of the C. productus beta-PDHs; Canpr-beta-PDH II appears to be a neurohormone in the SG, whereas Canpr-beta-PDH I may function as a local transmitter/modulator. Our data support the hypothesis that duplication and subsequent mutation of a common neuropeptide gene may underlie the evolution of two differentially distributed transcripts that serve distinct physiological roles.

Transcriptome and Peptidome Characterisation of the Main Neuropeptides and Peptidic Hormones of a Euphausiid: The Ice Krill, Euphausia crystallorophias

“…These seem to be specific to the Euphausiacea , and are described for the first time in this study. Their expression levels were significantly lower than those for PDHβ [100], [105], [106].…”

“…This peptide possesses a particularly conserved structure within the decapod crustaceans and the importance of its expression and translation indicates one or more major biological functions. Although members of this family have been characterised in numerous species of arthropods, crustaceans and insects, the function, or functions, of these remain largely unknown and are potentially different between species: either neurohormone regulation of pigment movement and/or neurotransmission/modulation [100]. Given that there is clearly a structural relationship between PDH family members and those of PDF in insects, it is possible to infer that there might be homologous functions, in particular, in the modulation of circadian rhythms which are very important in krill.…”

Development of pigment-dispersing hormone-immunoreactive neurons in the American lobster: homology to the insect circadian pacemaker system?

“…In the woodlouse, a group of PDHir somata has been found (group 3 in Nussbaum and Dircksen 1995) that also shares the properties of group C cells and their sisters (as described in the present report) in that their fibres project towards the medulla externa and are the origin of a fibre bundle running towards the medulla terminalis. This latter bundle is also present in adult crayfish and crabs (Mangerich et al 1987; Hsu et al 2008). The neurons in groups A and B (present study) also have counterparts in the adult crustacean eyestalks where they are “located in the X-organ area” (Mangerich et al 1987).…”

“…Many of the immunolabelled structures described in these reports can be found in the developing lobster nervous system at the earliest embryonic stages examined in the present study. Exceptions are the PDHir cells associated with the lamina ganglionaris in adult shore crabs and crayfish (Mangerich et al 1987; Hsu et al 2008), which are not present in lobster embryos but may develop postembryonically. Mangerich and coauthors (1987) have described two clusters of PDHir neurons comprising a total of 30–35 somata that correspond to cell groups C, C’ and C” in the present report, although the number of cells within these clusters is smaller in the embryos that we have examined (about 22).…”

“…In order to localise the sources of PDH and neuronal pathways utilising this peptide, an antiserum raised against synthetic β-PDH (Dircksen et al 1987), which is the most common crustacean PDH (Rao et al 1985), has been used to reconstruct the architecture of PDH-immunoreactive (PDHir) neurons in the adult crustacean nervous system, viz. in crabs and crayfish (Dircksen et al 1987; Mangerich et al 1987; Mangerich and Keller 1988; Nussbaum and Dircksen 1995; Hsu et al 2008). …”