Ontogenetical development of the chick and duck subcommissural organ

Abstract

The ontogenetical development of the subcommissural organ (SCO) was investigated in chick embryos collected daily from the 1st to the 21st day in incubation. Some duck embryos, and adult chickens and ducks were also studied. Immunocytochemistry using an anti-Reissner's fiber (RF) serum as the primary antibody was the principal method used. In the chick embryos the events occurring at different days of incubation were: day 3 morphologically undifferentiated cells in the dorsal diencephalon displayed immunoreactive material (IRM); days 4 to 6 immunoreactive cells proliferated, formed a multilayered structure and developed processes which traversed the growing posterior commissure and ended at the brain surface; day 7 blood vessels penetrated the SCO, scarce hypendymal cells appeared, the first signs of ventricular release of IRM were noticed, appearance of IRM bound to cells of the floor of the Sylvius aqueduct; day 7 to 10 the number of apical granules and amount of extracellular IRM increased progressively; day 11 RF was observed along the Sylvian aqueduct, day 12 RF was present in the lumbar spinal cord; day 13 IRM on the aqueductal floor disappeared; days 10 to 21 hypendymal cells proliferated, developed processes and migrated dorsally, ependymal processes elongated and their endings covered the external limiting membrane. In adult specimens the ependymal cells lacked basal processes and the external membrane was contacted by hypendymal cells. the duck SCO appears to follow a similar pattern of development.

Polarized expression of integrin β1 in diencephalic roof plate during chick development, a possible receptor for SCO‐spondin

“…On the other hand, following immunoelectron microscopy in the adult rat brain, Losecke et al (1984) also found AFRU-immunoreactive material within the intercellular spaces between the basal processes but no signal was observed in the endothelial cells of the capillaries. Of interest, Schoebitz et al (1986) described the presence of AFRU-immunoreactive material in the basal processes of chick embryos incubated for 5 days as well as in the adult stage, but the methodology used in this study did not discriminate whether this material was inside these processes or aggregated on the surface. Together with the aforementioned evidence, our immunohistochemichal data support the idea that the extracellular localization of SCOspondin allows the interaction of this protein with axons of the PC.…”

“…The cells of the SCO are formed by a main body, contacting the cerebrospinal fluid by the apical region, and basal processes that cross the posterior commissure and contact with the meningeal basal membrane (Schoebitz et al, 1986). Figure 3 depicts a scanning electron microscopy analysis performed in HH34 chick dorsal diencephalon showing the close proximity between basal processes of SCO cells with axons of the PC.…”

Subdivisions of chick diencephalic roof plate: Implication in the formation of the posterior commissure

“…From HH37 onward, SCO-spondin is apically secreted to the cerebrospinal fluid, where it remains attached to the apical domain of SCO cells forming a layer with different degrees of aggregation and finally forms a highly ordered fibrillar structure known as the Reissner fiber (RF; Schoebitz et al, 1986). The RF grows caudally along the brain aqueduct, the fourth ventricle and the whole length of the central canal of the spinal cord (Rodriguez et al, 1992(Rodriguez et al, , 1998.…”

“…SCO is composed of radial glial cells with their apical domain facing the third ventricle and, hence, contacting the cerebrospinal fluid, whereas their basal domains extend prolongations that cross the nerve bundles of the PC and are attached to the pial membrane (Caprile et al, 2009). (2) In the chick, SCO differentiation occurs at HH17-18, concomitantly with the presence of the pioneer axons of the PC (Schoebitz et al, 1986;Didier et al, 2007;Caprile et al, 2009). (3) Mutations in genes that regulate the development of prosomere 1 display a wide range of abnormalities in the development of the SCO that are highly similar to the phenotypes observed in the PC (Schwarz et al, 1999;Estivil-Torrus et al, 2001;Fernandez-Llebrez et al, 2004;Ramos et al, 2004).…”

Monoclonal Antibodies as Probes for the Analysis of the Secretory Ependymal Differentiation in the Subcommissural Organ of the Chick Embryo

“…The SCO shows a rem ark able phylogenetic and structural constancy in all chordate classes [8,9] appearing very early during ontogene sis [10][11][12][13][14]. We decided to investigate some molecular characteristics of this organ.…”