Reissner’s Fibre Proteins and p73 Variations in the Cerebrospinal Fluid and Subcommissural Organ of Hydrocephalic Rat

Abstract

Reissner's fibre (RF) is formed by the polymerization of the glycoprotein secreted by the subcommissural organ (SCO). The SCO also secretes soluble glycoprotein into the cerebrospinal fluid (CSF); variations in RF and SCO have been reported in hydrocephalus. On the other hand, hydrocephalus and other brain alterations have been described in p73 mutant mice. The p73 belongs to the tumour suppressor p53 protein family and has two isoforms: the TAp73 with apoptotic activity and DeltaNp73 with anti-apoptotic function. Moreover, the TAp73 isoform is glycosylated and secreted into the CSF. In the present work, we analysed the variations in RF and p73 proteins in the CSF and SCO of spontaneously hydrocephalic rats. Brains from control rats and spontaneously hydrocephalic rats of 12 months of age were used. The SCO sections were immunohistochemically processed with anti-TAp73 and anti-Reissner fibre (AFRU). The spontaneous hydrocephalus presents a decrease in the AFRU immunoreactive material in the SCO and an absence of RF. The anti-TAp73 was also present, slightly decreased, in the hydrocephalic SCO. AFRU and p73 bands were also detected in the CSF by western blot and six AFRU and p73 protein bands of a similar molecular weight were found in the CSF of the control rats. The number of AFRU and p73 bands was lower in the hydrocephalic rats than in the control rats. In conclusion, hydrocephalus produces a decrease in the secretions of the SCO and an absence of RF and a decrease in p73 and RF proteins in the CSF.

A Review of Cerebrospinal Fluid Circulation and the Pathogenesis of Congenital Hydrocephalus

“…In hydrocephalus rats, a reduction in RF and p73 protein levels, as well as decreased SCO secretion, has been observed in the CSF. Additionally, the presence of antibodies against p73 protein and RF has been detected in both SCO and ependymal cells [ 113 , 114 ]. Overall, malformations in the SCO and disruptions in SCO-spondin secretion have been closely associated with the development of aqueductal stenosis-induced hydrocephalus.…”

The Enigmatic Reissner’s Fiber and the Origin of Chordates

“…All three organs (IO, FC, and SCO) are located at the M-D junction in the different species (as said, prosomer P1), either in the floor plate (IO, FC) or in the roof plate (SCO). In recent years, several genes have been found to control SCO development and RF production (as well as the development of other organs too), including Pax6, SOX3, L1-CAM, and apoptosis-related genes ( Estivill-Torrús et al, 2001 ; Ramos et al, 2004 ; Carmona-Calero et al, 2009 ; Lee et al, 2012 ; Matsumoto et al, 2020 ; Yang et al, 2021 ). It is possible that the expression of genes involved in IO (or FO) differentiation in the floor plate of the M-D junction became co-opted in the roof plate during the origin of vertebrates, for reasons yet unknown.…”

Early Regressive Development of the Subcommissural Organ of Two Human Fetuses with Non-Communicating Hydrocephalus

“…The regression and atrophies of the SCO occur after birth, and the SCO disappears entirely after age 30. The SCO functions are related to the circulation and composition of the CSF, as it secretes glycoprotein into the CSF, where a fraction condenses and forms the Reissner’s fiber (RF), while the other fraction stays soluble in the CSF [ 7 , 8 , 11 , 12 ]. SCO cells have also been described as having a unique feature as secretory but immature neuroepithelial cells in adult mouse brains [ 13 ].…”