Binding of an antibody against a noncompact myelin protein to presumptive glial cells in the visual system of the crab Ucides cordatus

Abstract

Glial cells, in both vertebrate and invertebrate nervous systems, provide an essential environment for developmental, supportive, and physiological functions. However, information on glial cells themselves and on glial cell markers, with the exception of those of Drosophila and other insects, is not abundant in invertebrate organisms. A common ultrastructural feature of invertebrate nervous systems is that layers of glial cell cytoplasm-rich processes ensheath axons and neuronal and glial somata. In the present study, we have examined the binding of a monoclonal antibody to 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) in the compound eye and optic lobe of the crab Ucides cordatus using both light and electron microscopy. CNPase is a noncompact myelin protein that is a phenotypic marker of oligodendroglial and Schwann cells, is apparently involved in the ensheathment step prior to myelin compaction, and is also expressed by the potentially myelinating olfactory ensheathing glia. CNPase has raised much interest, first by virtue of its unusual enzymatic activity and more recently by its membrane-skeletal features and possible involvement in migration or expansion of membranes. We have found CNPase-like immunoreactivity in most cells of the compound eye basement membrane and both in optic cartridges of the synaptic layer and cells of the outer sublayer of the lamina ganglionaris. The results suggest that in the crab visual system some, but not all, glial cells, including some adaxonal glia, may express the noncompact myelin protein CNPase or a related protein.

Glial fibrillary acidic protein (GFAP)‐like immunoreactivity in the visual system of the crab Ucides cordatus (Crustacea, Decapoda)

“…In Drosophila melanogaster, just beneath the basement membrane, the pigmented subretinal glia, also called fenestrated glia in insects, ensheaths the incoming axon bundles of photoreceptors and in the lamina neuropil there are at least two types of glial cells (Kretzschmar and Pflugfelder, 2002). At this point, it is worthwhile noting that since vertebrate and invertebrate glial cells share typical functions, among them, metabolic interactions and axons ensheathment, the GFAP labeling shown in this paper and the CNPase labeling demonstrated in a previous paper (Da Silva et al, 2003) may be related to these different functions performed by different glial cell categories.…”

“…In addition, since the labeling pattern is different from that observed in the same structures of this species when the antibody against CNPase was used (Da Silva et al, 2000;Da Silva et al, 2003), it seems that they do not label the same glial cells. This means that maybe different labels can be used to help classify glial cells in crustaceans, a task that has not been very simple to perform.…”

“…For histological localization of these structures, see the schematic diagram depicted in Fig. 1 in Da Silva et al (2003). In the retina, GFAP-like positive cell processes were detected as evident lines along the ommatidia.…”

“…The molecule 2′, 3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), a non-compact myelin protein that is a phenotypic marker of vertebrate oligodendroglial and Schwann cells and that, due to its membrane-skeletal features, is possibly involved in migration or expansion of membranes (Braun et al, 1988;Dyer and Benjamins, 1989), is one of them. A CNPase-like immunoreactivity has been recently detected by our group in the visual system of the crab Ucides cordatus, suggesting that it may be used as a phenotypic marker for some types of glial cells, at least in the crab (Da Silva et al, 2003).…”

“…However, proteins similar to mammalian neurofilament proteins have been found in some crustaceans (Weaver and Viancour, 1991;Corrêa, 2002), and GFAP-like proteins have been recognized in two silkmoth species (Kumar et al, 1996). Therefore, the proposal of this study was to detect and locate GFAP-like positive structures in the optic lobe of the crab Ucides cordatus, a common species of mangrove forests of the Western Atlantic coast (Coelho and Ramos, 1972), whose visual system has been used as a good model for studies of nervous structures in crustaceans Da Silva et al, 2001;Da Silva et al, 2003).…”