title: Variable proopiomelanocortin expression in tanycytes of the adult rat hypothalamus and pituitary stalk.
abstract: It is generally believed that proopiomelanocortin (POMC) is expressed exclusively by neurons in the adult rodent brain. Unbeknownst to most researchers, however, Pomc in situ hybridization studies in the rat show specific labeling in the ventral wall of the hypothalamic third ventricle, which is formed by specialized ependymal cells, called tanycytes. Here we characterized this non-neuronal POMC expression in detail using in situ hybridization and immunohistochemical techniques, and report two unique characteristics. First, POMC mRNA and precursor protein expression in non-neuronal cells varies to a great degree as to the extent and abundance of expression. In brains with low-level expression, POMC mRNA and protein was largely confined to a population of tanycytes within the infundibular stalk/caudal median eminence, termed here γ tanycytes, and a subset of closely located β and α2 tanycytes. In brains with high-level expression, POMC mRNA and protein was observed in the vast majority of α2, β, and γ tanycytes. This variability was observed in both adult males and females; of 41 rats between 8 and 15 weeks of age, 17 had low-, 9 intermediate-, and 15 high-level POMC expression in tanycytes. Second, unlike other known POMC-expressing cells, tanycytes rarely contained detectable levels of adrenocorticotropin or α-melanocyte-stimulating hormone. The results indicate either a dynamic spatiotemporal pattern whereby low and high POMC syntheses in tanycytes occur periodically in each brain, or marked interindividual differences that may persist throughout adulthood. Future studies are required to examine these possibilities and elucidate the physiologic importance of POMC in tanycytes. J. Comp. Neurol. 525:411-441, 2017. © 2016 Wiley Periodicals, Inc.
authors: Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts, 02111.
authors: Gábor
authors: G
authors: Wittmann
authors: Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary.|Pázmány Péter Catholic University, Multidisciplinary Doctoral School of Sciences and Technology, Budapest, 1083, Hungary.
authors: Erzsébet
authors: E
authors: Farkas
authors: Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary.|Semmelweis University, János Szentágothai PhD School of Neurosciences, Budapest, 1085, Hungary.
authors: Anett
authors: A
authors: Szilvásy-Szabó
authors: Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary.
authors: Balázs
authors: B
authors: Gereben
authors: Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts, 02111.|Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary.
authors: Csaba
authors: C
authors: Fekete
authors: Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts, 02111.|Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, 02111.
authors: Ronald M
authors: RM
authors: Lechan
mesh_terms: D000818:Animals; D063928:Ependymoglial Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism*; D017403:In Situ Hybridization; D008297:Male; D016253:Microscopy, Immunoelectron; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar
chemical_list: D012333:RNA, Messenger; D011333:Pro-Opiomelanocortin
keywords: POMC; RRID: AB_2216104; RRID: AB_2307442; RRID: AB_2314007; RRID: AB_2572293; RRID: AB_91683; RRID:AB_221448; beta-endorphin; infundibulum; median eminence