tanycyte

Tanycytes are highly specialized ependymal cells (also called ependymoglial cells) with long basal processes.{{cite journal |vauthors=Imbernon M, Saponaro C, Helms HC, Duquenne M, Fernandois D, Deligia E, Denis RG, Chao DH, Rasika S, Staels B, Pattou F, Pfrieger FW, Brodin B, Luquet S, Bonner C, Prevot V |title=Tanycytes control hypothalamic liraglutide uptake and its anti-obesity actions |journal=Cell Metab |volume=34 |issue=7 |pages=1054–1063.e7 |date=July 2022 |pmid=35716660 |pmc=7613793 |doi=10.1016/j.cmet.2022.06.002 |url=}} Tanycytes in adult mammals are found in the ventricular system, and the median eminence, a circumventricular organ. They are most numerous in the third ventricle of the brain, are also found in the fourth ventricle, and can also be seen in the spinal cord radiating from the central canal (also known as the ependymal canal), to the spinal cord surface. The long processes extend through the layer of astrocytes to cross the median eminence and form end-feet on neuropil, and blood vessels near the portal perivascular space.

Along the process from each tanycyte are some unusual protrusions as spikes, and swellings, and at their end feet are boutons or claws. The different protrusions contain blood vessels, and contact different neurons, and cells.{{cite journal |vauthors=Pasquettaz R, Kolotuev I, Rohrbach A, Gouelle C, Pellerin L, Langlet F |title=Peculiar protrusions along tanycyte processes face diverse neural and nonneural cell types in the hypothalamic parenchyma |journal=J Comp Neurol |volume=529 |issue=3 |pages=553–575 |date=February 2021 |pmid=32515035 |pmc=7818493 |doi=10.1002/cne.24965 |url=}} The protrusions contain ribosomes, mitochondria, varied vesicles, and transporters.

In the third ventricle four different subtypes of tanycte populations with differing structure, morphology, genetics, and function have been defined. These are named beta 2 (β2) and beta 1 (β1), and alpha 2 (α2) and alpha 1 (α1).

β2 tanycytes line the median eminence; β1 tanycytes line part of the infundibular recess.

α2 tanycytes line the dorsomedial arcuate nucleus; α1 tanycytes line the ventromedial nucleus and the dorsomedial nucleus.

A tanycyte has a single long basal process that crosses into the hypothalamic parenchyma to make contact with blood vessels and an array of neurons.{{cite journal |last1=Dali |first1=Rafik |last2=Estrada-Meza |first2=Judith |last3=Langlet |first3=Fanny |title=Tanycyte, the neuron whisperer |journal=Physiology & Behavior |date=May 2023 |volume=263 |pages=114108 |doi=10.1016/j.physbeh.2023.114108|pmid=36740135 }} The different components of the tanycyte process protrusions that include ribosomes, mitochondria, and transporters, indicate communication between the tanycytes and blood vessels, and between the tanycytes and neurons. These interactions are associated with the regulation of different neuroendocrine functions.

Tanycytes have been shown in vivo to serve as a diet-responsive neurogenic niche.{{cite journal|last=Lee|first=DA |author2=Bedont, JL |author3=Pak, T |author4=Wang, H |author5=Song, J |author6=Miranda-Angulo, A |author7=Takiar, V |author8=Charubhumi, V |author9=Balordi, F |author10=Takebayashi, H |author11=Aja, S |author12=Ford, E |author13=Fishell, G |author14=Blackshaw, S|title=Tanycytes of the hypothalamic median eminence form a diet-responsive neurogenic niche.|journal=Nature Neuroscience|date=Mar 25, 2012|volume=15|issue=5|pages=700–2|doi=10.1038/nn.3079|pmid=22446882|pmc=3380241}}{{cite journal |last1=Bolborea |first1=M |last2=Dale |first2=N |title=Hypothalamic tanycytes: potential roles in the control of feeding and energy balance. |journal=Trends in Neurosciences |date=February 2013 |volume=36 |issue=2 |pages=91–100 |doi=10.1016/j.tins.2012.12.008 |pmid=23332797|pmc=3605593 |doi-access=free }} The targeted neurons in the hypothalamus are in the arcuate nucleus, the ventromedial nucleus, and the dorsomedial nucleus.The neurons contacted by the tanycyte processes include orexigenic, and anorexigenic neurons that control energy balance.

Studies suggests that tanycyte cells bridge the gap between the central nervous system (CNS) via cerebrospinal fluid (CSF) to the hypophyseal portal blood.{{cite journal|last=Mullier|first=A|author2=Bouret, SG |author3=Prevot, V |author4= Dehouck, B |title=Differential distribution of tight junction proteins suggests a role for tanycytes in blood-hypothalamus barrier regulation in the adult mouse brain.|journal=The Journal of Comparative Neurology|date=Apr 1, 2010|volume=518|issue=7|pages=943–62|doi=10.1002/cne.22273|pmid=20127760 |pmc=2892518}}{{cite journal|last=Langlet|first=F|author2=Mullier, A |author3=Bouret, SG |author4=Prevot, V |author5= Dehouck, B |title=Tanycyte-like cells form a blood-cerebrospinal fluid barrier in the circumventricular organs of the mouse brain.|date=Oct 15, 2013|volume=521|issue=15|pages=3389–405|doi=10.1002/cne.23355|pmid=23649873 |journal=J. Comp. Neurol.|pmc=3973970}} Tanycytes provide a link that is both structural and functional between the CSF and the perivascular space of the hypophyseal portal vessels.{{cite book |last1=Carpenter |first1=Malcolm Breckenridge |title=Core text of neuroanatomy |date=1985 |publisher=Williams & Wilkins |location=Baltimore |isbn=0683014552 |page=265 |edition=3.}} Unlike regular ependymal cells there are tight junctions between them, and between their adjacent ependymal cells. There are also desmosomes present which together with the tight junctions provide structural support.{{cite book |last1=Haines |first1=Duane |last2=Mihailoff |first2=Gregory |title=Fundamental neuroscience for basic and clinical applications |date=2018 |publisher=Elsevier |location=Philadelphia, PA |isbn=9780323396325 |pages=98–99 |edition=Fifth}}

Researches in 2005 and 2010{{cite journal|last=Prevot|first=V|author2=Bellefontaine, N |author3=Baroncini, M |author4=Sharif, A |author5=Hanchate, NK |author6=Parkash, J |author7=Campagne, C |author8= de Seranno, S |title=Gonadotrophin-releasing hormone nerve terminals, tanycytes and neurohaemal junction remodelling in the adult median eminence: functional consequences for reproduction and dynamic role of vascular endothelial cells.|journal=Journal of Neuroendocrinology|date=Jul 2010|volume=22|issue=7|pages=639–49|pmid=20492366|pmc=3168864 |doi=10.1111/j.1365-2826.2010.02033.x}}{{cite journal|last=Rodríguez|first=EM|author2=Blázquez, JL |author3=Pastor, FE |author4=Peláez, B |author5=Peña, P |author6=Peruzzo, B |author7= Amat, P |title=Hypothalamic tanycytes: a key component of brain-endocrine interaction.|journal=International Review of Cytology|year=2005|volume=247|pages=89–164|doi=10.1016/S0074-7696(05)47003-5|pmid=16344112|hdl=10366/17544|url=https://gredos.usal.es/jspui/bitstream/10366/17544/1/DAHH_Hypothalamic%20tanycytes.pdf|hdl-access=free}} found that tanycytes participate in the release of gonadotropin-releasing hormone (GnRH). GnRH is released by GnRH neurons located in the arcuate nucleus in the hypothalamus.{{cite journal |last1=Marques |first1=Pedro |last2=Skorupskaite |first2=Karolina |last3=Rozario |first3=Kavitha S. |last4=Anderson |first4=Richard A. |last5=George |first5=Jyothis T. |title=Physiology of GnRH and Gonadotropin Secretion |url=https://www.ncbi.nlm.nih.gov/books/NBK279070/# |website=Endotext |publisher=MDText.com, Inc. |access-date=2 July 2024 |date=2000|pmid=25905297 }} These nerve fibers are concentrated in the region that exactly matches the distribution of β1 tanycytes. β1 and β2 tanycytes are found nearer the arcuate nucleus and the median eminence.

List of distinct cell types in the adult human body

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• {{cite journal|last=Prieto|first=M|author2=Chauvet, N |author3=Alonso, G |title=Tanycytes transplanted into the adult rat spinal cord support the regeneration of lesioned axons.|journal=Experimental Neurology|date=Jan 2000|volume=161|issue=1|pages=27–37|doi=10.1006/exnr.1999.7223|pmid=10683271|s2cid=42078438}}

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• http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Nervous/Nervous.htm
• [https://www.neuinfo.org/mynif/search.php?q=%22Tanycyte%22&t=data&s=cover&b=0&r=20 NIF Search - Tanycyte] via the Neuroscience Information Framework

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