Cell lineage of the subcommissural organ secretory ependymocytes: Differentiating role of the environment

SCO-ependymocytes have a secretory activity and a neural innervation relati ng them to neurosecretory nerve cells. To elucidate the cell lineage of the SCO-ependymocytes and emphasize the role of the neural innervation in thei r differentiation, in particular 5-HT innervation, we analyzed the developm ental pattern of expression of several glial and neuronal markers: (1) in t he SCO of mammals possessing (rat, cat) or devoid (mouse, rabbit) of 5-HT i nnervation, (2) in rat 5-HT deafferented SCO, and (3) in rat SCO transplant ed in a foreign environment, the fourth ventricle. The ability of SCO-epend ymocytes to transiently express GFAP during development and express the gli al alpha alpha -enolase confirms the glial lineage of the SCO-ependymocytes . Synthesis of vimentin by SCO-ependymocytes relates them to the classical ependymocytes. The ability of mature SCO-ependymocytes to take up GABA only when they are innervated by 5-HT terminal underlines the role of the neura l environment on the differentiation of these ependymocytes and suggests th at differential maturation of the SCO according to its innervation, may lea d to specific functional specialization of this organ in different species. Microsc. Res. Tech. 52:461-467, 2001. (C) 2001 Wiley-Liss, Inc.