Galanin-like immunoreactivity in the sea cucumber Holothuria glaberrima

Abstract

Galanin, a neuropeptide of 29 amino acids originally purified from porcine small intestine, has been found in most vertebrate groups, where it is present in both the central and peripheral nervous systems. In this study, galanin-like immunoreactivity was detected in an invertebrate, the sea cucumber Holothuria glaberrima. In this organism, fibers and cells expressing galanin-like immunoreactivity were found in the enteric nerve plexuses of the esophagus, and large and small intestine, particularly in the serosal layer. Immunoreactivity was also found in the ectoneural portion of the radial nerve and in nervous elements within the body wall. Preabsorbtion tests indicated that the observed immunoreactivity was not due to cross-reactivity of the antibody with other peptides also found in the intestinal plexuses. The immunoreactivity to galanin was quantified in various tissues using radioimmunoassay and partially characterized with high performance liquid chromatography. These results show that although the holothurian peptide shows common immunological determinants with porcine galanin, it differs with regard to certain biochemical properties.

Novel markers identify nervous system components of the holothurian nervous system

“…1A–B). The nervous system in these organs has been thoroughly described in previous studies by our group (Diaz-Balzac et al 2010a; Diaz-Balzac et al 2010b; Diaz-Balzac et al 2007; Diaz-Miranda et al 1995; Diaz-Miranda et al 1996) and thus provides an excellent starting point for comparison of the immunoreactivity observed with the new markers.…”

“…Such a broad range of immunoreactivity is not surprising in view that other markers of the holothurian nervous system have shown similar ranges. These include the immunoreactivity against the neuropeptides galanin and GFSKLYFamide (Diaz-Miranda et al 1995; Diaz-Miranda et al 1996), the calcium-binding protein calbindin (Diaz-Balzac et al 2012), and immunoreactivity to the antibody RN1 that recognizes a yet undetermined neural-specific epitope (Diaz-Balzac et al 2007). …”

“…This is best observed by their immunoreactivity within the radial nerve cord, particularly the large group of anti-pax6 immunoreactive fibers that was observed in the two apical central regions that are not observed with anti-GFSKLYFamide. Similarly, anti-nurr1 is the first marker that appears to preferentially identify cells of the hyponeural component over those of the ectoneural component, contrary to anti-galanin, which preferentially identify cells and fibers of the ectoneural component (Diaz-Miranda et al 1996). This is particularly surprising in view of the fact that in vertebrates, Nurr1 function has been associated with the catecholaminergic neurotransmitter system (Zetterstrom et al 1997), but previous studies from our group have shown that the holothurian catecholaminergic system is present within the ectoneural component of the radial nerve cord (Diaz-Balzac et al 2010b).…”

“…Most of these are antibodies against neuropeptides or other neurotransmitter systems that recognize subpopulations of neurons or nerve fibers (Cottrell and Pentreath 1970; Diaz-Miranda et al 1995; Diaz-Miranda et al 1996; Elphick et al 1995; Inoue et al 2002; Newman and Thorndyke 1994; Newman et al 1995). More recently, other markers have been obtained by our group that recognize neuronal cells and fibers of the sea cucumber Holothuria glaberrima .…”

A START-domain-containing protein is a novel marker of nervous system components of the sea cucumber Holothuria glaberrima

“…To tackle this problem, the search and characterization of new markers capable of identifying neurons and plexi that form the echinoderm nervous system components are needed. Our lab and those of others have identified various antibody markers for cells and fibers (Diaz-Miranda et al 1995a,b, 1996, Diaz-Balzac et al 2010, 2012, 2014, 2016). In general, the markers fall into two large categories; the first being those antibodies that recognize what are supposed to be the echinoderm homologs of the antigens recognized by the antibodies in other animal species.…”