Bi- and uniciliated ependymal cells define continuous floor-plate-derived tanycytic territories

Abstract

Multiciliated ependymal (E1) cells line the brain ventricles and are essential for brain homeostasis. We previously identified in the lateral ventricles a rare ependymal subpopulation (E2) with only two cilia and unique basal bodies. Here we show that E2 cells form a distinct biciliated epithelium extending along the ventral third into the fourth ventricle. In the third ventricle floor, apical profiles with only primary cilia define an additional uniciliated (E3) epithelium. E2 and E3 cells' ultrastructure, marker expression and basal processes indicate that they correspond to subtypes of tanycytes. Using sonic hedgehog lineage tracing, we show that the third and fourth ventricle E2 and E3 epithelia originate from the anterior floor plate. E2 and E3 cells complete their differentiation 2–3 weeks after birth, suggesting a link to postnatal maturation. These data reveal discrete bands of E2 and E3 cells that may relay information from the CSF to underlying neural circuits along the ventral midline.

Tanycytes: A rich morphological history to underpin future molecular and physiological investigations

“…This question is controversial. Scanning 221 and transmission 7,9,62,222 electron microscopy, and in block immunocytochemistry, have shown that some tanycytes are endowed with a single 9+0 cilium, similar to those reported for the NSC present in the sub- Glutamate is known to be neurotoxic at elevated concentrations and plays an important role in brain injury following acute and chronic brain insults. Therefore, the BBB is impermeable to glutamate, even at high concentrations.…”

“…62 The cilia occupied the lumen of a deep invagination of the plasma membrane. Some cells were seen to project one or two 9+2 cilia.…”

“…These cells would correspond to bi-ciliated α-tanycytes visualised via block immunofluorescence. 62 The cilia occupied the lumen of a deep invagination of the plasma membrane. The space around the cilium was 30 nm in width.…”

“…The basal body has an elaborated structure. 62 No cilia roots are present, suggesting that these cilia are not motile. The well in which the cilium is immersed would allow putative receptors localised in the cilium membrane to be exposed to CSF signals for a longer time.…”

How the Ciliary Membrane Is Organized Inside-Out to Communicate Outside-In

“…This diversity is perhaps nowhere on more prominent display than in C. elegans. In addition to the single cilia that are similar to those found on most mammalian cells, C. elegans neurons (e.g., ADF and ADL neurons) can possess pairs of cilia, at least superficially similar to the paired cilia found on mammalian tanycytes [14–17]. Even more impressively, other C. elegans neurons possess cilia with elaborate membrane extensions that have been compared to wings (AWA, AWB, AWC neurons), bags (BAG) or flaps (FLP).…”