Analysis of cerebro-spinal fluid protein composition in early developmental stages in chick embryos

Foetal cerebro‐spinal fluid (CSF) has a very high protein concentration when compared to adult CSF, and in many species five major protein fractions have been described. However, the protein concentration and composition in CSF during early developmental stages remains largely unknown. Our results show that in the earliest stages (18 to 30 H.H.) of chick development there is a progressive increase in CSF protein concentration until foetal values are attained. In addition, by performing electrophoretic separation and high‐sensitivity silver staining, we were able to identify a total of 21 different protein fractions in the chick embryo CSF. In accordance with the developmental pattern of their concentration, these can be classified as follows: A: high‐concentration fractions which corresponded with the ones described in foetal CSF by other authors; B: low‐concentration fractions which remained stable throughout the period studied; C: low‐concentration fractions which show changes during this period. The evolution and molecular weight of the latter group suggest the possibility of an important biological role. Our data demonstrate that all the CSF protein fractions are present in embryonic serum; this could mean that the specific transport mechanisms in neuroepithelial cells described in the foetal period evolve in very early stages of development. In conclusion, this paper offers an accurate study of the protein composition of chick embryonic CSF, which will help the understanding of the influences on neuroepithelial stem cells during development and, as a result, the appropriate conditions for the in vitro study of embryonic/foetal nervous tissue cells. J. Exp. Zool. 301A:280–289, 2004. © 2004 Wiley‐Liss, Inc.