Tanycyte

Tanycytes are special ependymal cells found in the third ventricle of the brain, and on the floor of the fourth ventricle and have processes extending deep into the hypothalamus. It is possible that their function is to transfer chemical signals from the cerebrospinal fluid to the central nervous system. Tanycytes are special ependymal cells found in the third ventricle of the brain, and on the floor of the fourth ventricle and have processes extending deep into the hypothalamus. It is possible that their function is to transfer chemical signals from the cerebrospinal fluid to the central nervous system. The term tanycyte comes from the Greek word tanus which means elongated. Tanycytes share some features with radial glia cells and astrocytes. Their form and location have led some authors to regard them as radial glia cells that remain in the hypothalamus throughout life. This has led some to believe that these cells share the same lineage. Even so, tanycytes also display certain characteristics that distinguish them from radial glia cells. Tanycytes in rats begin to develop in the last two days of gestation and continue on until they reach their full differentiation in the first month of life. Radial glia cells on the other hand, are a key component of the embryonic brain. Tanycytes also contain many proteins not found in radial glia cells. Thus, evidence now suggests that tanycytes are genealogical descendants of radial glia cells that do not develop into astrocytes, but rather into their own subpopulation. Tanycytes in adult mammals are found in the ventricular system and the circumventricular organs. They are most numerous in the third ventricle of the brain, but can also be seen in the spinal cord radiating from the ependyma of the central canal to the spinal cord surface. Tanycytes represent approximately 0.6% of the population of the lateral ventricular wall, as described by Doetsch et al. Tanycytes have also been shown in vivo to serve as a diet-responsive neurogenic niche. Recent work suggests that tanycyte cells bridge the gap between the central nervous system (CNS) via cerebrospinal fluid (CSF) to the hypophyseal portal blood. This may also link the CSF to neuroendocrine events. Researches in 2005 and 2010 found that tanycytes participate in the release of gonadotropin-releasing hormone (GnRH). GnRH is released by neurons located in the rostral hypothalamus. These nerve fibers are concentrated in the region that exactly matches the distribution of β1 tanycytes.