Only four of these compounds were detected in the cisternal CSF of PN30 rats. Eight AFRU-immunoreactive bands were consistently found in CSF samples from rats at E18, E20 and PN1. The presence of these proteins in both, RF and CSF suggests a steady-state RF/CSF equilibrium for these compounds.
Two other compounds (200, 63 kDa) were present in SCO, RF and CSF and may be processed forms.
These may be precursor and/or partially processed forms. Four of the AFRU-immunoreactive compounds present in the SCO (630, 450, 390, 320 kDa) were absent from the RF and CSF. The 630 and 390 kDa compounds of the rat SCO have affinity for concanavalin A but not for wheat germ agglutinin, suggesting that they correspond to precursor forms. With the exception of the 200-kDa compound, all other compounds present in the rat SCO were also present in the mouse SCO. Resultsįive glycoproteins were identified in the rat SCO with apparent molecular weights of 630, 450, 390, 320 and 200 kDa. To analyse RF-glycoproteins, RF was extracted from the central canal of juvenile rats and mice to investigate the CSF-soluble proteins secreted by the SCO, CSF samples were collected from the cisterna magna of rats at different stages of development (from E18 to PN30). In addition, the glycosylated nature of SCO-compounds was analysed by concanavalin A and wheat germ agglutinin binding. The proteins of the SCO secreted into the CSF were studied (i) by injecting specific antibodies into ventricular CSF in vivo (ii) by immunoblots of SCO, RF and CSF samples, using specific antibodies against the SCO secretory proteins (AFRU and anti-P15). The aims of the present investigation were: (i) to identify and partially characterize the SCO-secretory compounds present in the SCO gland itself and in the RF of the Sprague-Dawley rat and non-hydrocephalic hyh mouse, and in the CSF of rat (ii) to make a comparative analysis of the proteins present in these three compartments (iii) to identify the proteins secreted by the SCO into the CSF at different developmental periods. Evidence exists that the SCO also secretes proteins that remain soluble in the CSF. SCO-spondin is the major constituent protein of RF. The subcommissural organ (SCO) is a highly conserved brain gland present throughout the vertebrate phylum it secretes glycoproteins into the cerebrospinal fluid (CSF), where they aggregate to form Reissner's fiber (RF).
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