Immunohistochemical study of the distribution of calcium binding proteins in the brain of a chondrostean (Acipenser baeri)

Abstract

Chondrosteans represent an ancient lineage in ray-finned bony fishes and hence in jawed vertebrates. This immunohistochemical study in the brain of the Siberian sturgeon reports the neuronal distribution of three cytosolic calcium-binding proteins: calbindin-D28k (CB), calretinin (CR), and parvalbumin (PV). CB and CR are widely expressed in different neuron subsets distributed throughout the sturgeon brain. Studies using double immunofluorescence reveal a wide co-distribution of CB and CR in the brain nuclei but scarce co-localization at cellular level. In the forebrain, CR- and CB-immunoreactive (ir) populations were observed in the olfactory bulbs, in pallial and subpallial telencephalic areas, and in some diencephalic nuclei. CR-ir cells were also observed in the posterior tubercle and CB-ir cells in the preglomerular complex. At midbrain and hindbrain basal levels, CB-ir and CR-ir cell bodies were mainly distributed in periventricular areas. In the cerebellum, CB and CR cells were co-localized in some granular cell subsets in laterodorsal and dorsolateral regions, and in some Purkinje-like cells. CB-ir and CR-ir fibers were mainly observed in the olfactory bulbs, hypothalamus, and habenula, and in fiber tracts that coursed in the optic tectum and through the mesencephalic and rhombencephalic basal areas. With regard to PV, the sturgeon brain showed a rather limited distribution of PV-ir perikarya and fibers. Thus, CR, CB, and PV allowed the identification of subpopulations of neurons not distinguished on the basis of cytoarchitecture alone, which provided a better understanding of the anatomical organization of the sturgeon brain. These results reveal numerous shared features with teleosts, but also important differences.

Immunohistochemical distribution of calretinin and calbindin (D‐28k) in the brain of the cladistian Polypterus senegalus

“…Regional segregation of primary olfactory projections expressing these markers has also been reported in zebrafish (Gayoso et al, 2011;Baubrach et al, 2012), and restricted distribution of CR-ir projections in the olfactory bulb was also shown in the Siberian sturgeon (Graña et al, 2012). Segregation of CB-ir glomerular projections in the olfactory bulb has been observed in the Siberian sturgeon (Graña et al, 2012) and the African lungfish (Gonz alez et al, 2010), but not in teleosts and the Senegal bichir. Together, these results in the Senegal bichir suggest that segregation of olfactory bulb projections of main ORN types has appeared early in fish lineages.…”

“…The present results reveal CR immunoreaction in some ORNs of the olfactory mucosa in Polypterus senegalus, which showed a clear zonal distribution near the basis in all lamellae, and most of these neurons probably bear cilia (ciliary ORNs). Expression of CR-ir in ORNs has also been reported in the river lamprey (Pombal et al, 2002), the Siberian sturgeon (Graña et al, 2012), and some teleosts (Porteros et al, 1997;Díaz-Regueira and Anad on, 2000;Castro et al, 2006a;Castro et al, 2008;Gayoso et al, 2011). In trout and zebrafish, most of the CR-ir ORNs were ciliary cells, but occasionally microvillous CRir neurons were demonstrated in the zebrafish (Gayoso et al, 2011).…”

“…The CB antibody has also been previously characterized by western blot in the Siberian sturgeon (Huesa et al, 2002), and lungfishes (Morona et al, 2011b). Although some variability among species was observed (Pochet et al, 1991), both CB and CR show close molecular weights and their primary structures appear to be highly conserved (Rogers et al, 1990;Andressen et al, 1993;Graña et al, 2012). Early western blot analyses with antibodies raised against calbindinD28k revealed a single protein band for CB in teleosts Pasteels et al, 1987), and two bands of close molecular weight in mammals, birds, reptiles, and amphibians .…”

“…In the external cell layer, CB-ir cells were sparsely distributed with CR-ir cells but these populations do not show colocalization. The presence of both CR-ir and CB-ir cells in the olfactory bulb granule cell layer has been reported in the Siberian sturgeon (Graña et al, 2012), which also shows CB-ir mitral-like cells. CR-ir cells in the olfactory bulb of gar (Lepisosteus platyrhincus; holosteans) show a similar distribution (Northcutt, 2009).…”

“…THir, CB-ir, and CR-ir immunoreactive cells were also reported in the granule cell layer of sturgeons (Piñuela and Northcutt, 2007;Adrio et al, 2002;Graña et al, 2012). Olfactory bulb connections were studied in Polypterus by Nauta and Fink-Heimer techniques (Braford and Northcutt, 1974) and also with neuronal tracers (Holmes and Northcutt, 2003) showing mitral cells located within the external cellular layer that project mainly to the ipsilateral dorsal subdivision of P1 (P1d).…”