Homeostasis of cerebrospinal fluid has a role in early brain development

Embryonic cerebrospinal fluid (E-CSF) is a protein-containing fluid present in brain cavities that plays key roles in neuronal development and function. From the beginning of primary brain neurogenesis, E-CSF composition and homeostasis are precisely tuned by a transient blood–CSF barrier function, which controls protein transport and their relative concentration of within-brain cavities. One of the proteins found in E-CSF is ovalbumin, which is postulated to play a role in nutrition. Here, we address the question of whether neuroepithelial progenitor cells in developing chick embryos use ovalbumin as a highly specific nutritional source of amino acids or alternatively whether they use other amino acid sources, despite the fact that they cannot be transported from blood serum to brain cavities under physiological conditions. Although ovalbumin was not found to be a key protein required for neurogenesis and cell survival, our observations reinforce the crucial role of the embryonic blood–CSF barrier, as its precise regulation of protein transport and E-CSF homeostasis ensures the maximum efficiency of neural development.