Research Article Terminally Differentiated Epithelial Cells of the Thymic Medulla and Skin Express Nicotinic Acetylcholine Receptor Subunit 3 Aichurek Soultanova, Alexandra R. Panneck, Amir Rafiq, and Wolfgang Kummer Institute of Anatomy and Cell Biology, German Center for Lung Research, Justus-Liebig-University Giessen, Aulweg 123, 35385 Giessen, Germany Correspondence should be addressed to Wolfgang Kummer; wolfgang.kummer@anatomie.med.uni-giessen.de Received 22 April 2014; Accepted 13 June 2014; Published 3 July 2014 Academic Editor: Koichiro Kawashima Copyright © 2014 Aichurek Soultanova et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the thymus, T cell maturation is inluenced by cholinergic signaling, and the predominantly expressed receptor is the 3- subunit of nicotinic acetylcholine receptors, encoded by the chrna3 gene. We here determined its cellular distribution utilizing an appropriate eGFP-expressing reporter mouse strain. Neither T cells (CD4, CD8) nor mesenchymal cells (desmin-positive) expressed eGFP. In the thymic medulla, eGFP-positive cells either were scattered or, more frequently, formed small clusters resembling Hassall’s corpuscles. Immunolabeling revealed that these cells were indeed terminally diferentiated epithelial cells expressing keratin 10 (K10) but neither typical cortical (K8, K18) nor medullary keratins (K5, K14). hese labeling patterns relected those in the epidermis of the skin, where overlap of K10 and eGFP expression was seen in the stratum granulosum, whereas underlying basal cells displayed K5-immunoreactivity. A substantial portion of thymic eGFP-positive cells was also immunoreactive to chromogranin A, a peptide previously reported in epidermal keratinocytes in the stratum granulosum. Its fragment catestatin has multiple biological activities, including suppression of proinlammatory cytokine release from macrophages and inhibition of 34 nAChR. he present indings suggest that its thymic production and/or release are under cholinergic control involving nAChR containing the 3-subunit. 1. Introduction he thymus is the site of step-wise maturation of na¨ ıve T cells from immature thymocytes which occurs along with positive and negative selection processes while thymocytes migrate from the cortex to the medulla. hese processes are inluenced by cholinergic signaling [1–4], and acetylcholine (ACh) is endogenously synthesized in the thymus [5–7]. Signaling via nicotinic ACh receptors (nAChR) has received particular attention. hese receptors are pentamers composed of various subunit combinations. he “muscle type” nAChR originally identiied at the motor endplate consists of two 1-, one 1-, one - (or - at fetal stage), and one -subunit, and these are also expressed by myoid [8, 9] and epithelial cells of the thymic medulla [10–13]. hymic expression and presentation of muscle-type nAChR subunits have been associated with a frequent (85%) variant of myasthenia gravis, a disease of the motor endplate, where autoantibodies against such subunits are formed, as the thy- mus frequently shows abnormal structure in this condition and thymectomy is beneicial for the patients [14]. “Neuronal” nAChR are homo- or heteromers of - subunits 2–7 and 9-10 (8 is expressed only in chicken) and -subunits 2–4 [15–17]. Despite their designation as “neu- ronal” they are widely expressed outside the nervous system including the thymus [18, 19]. Amongst them, subunits 3, 5, and 4 exhibit highest expression in early postnatal mouse thymus, reaching 7–15% of mRNA content found in brain as standard [19]. heir genes—chrna3, chrna5, and chrnb4—are clustered on chromosome 9 in mice, and, when coexpressed, the translated proteins assemble to functional 3(5)4 nAChR with either 2 - and 3 -subunit or 3 - and 2 -subunit chains [15, 20]. he 3-subunit is essential for receptor function and may occur with or without an additional 5-subunit in these receptors while the 5-subunit Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 757502, 9 pages http://dx.doi.org/10.1155/2014/757502