title: Transforming growth factor-alpha is expressed in astrocytes of the suprachiasmatic nucleus in hamster: role of glial cells in circadian clocks.
abstract: Transforming growth factor-alpha (TGF-alpha) is abundantly expressed in the suprachiasmatic nucleus of several rodent species. It was recently suggested to be a clock output signal regulating the activity/rest rhythm. In this study we further characterized the cellular identity of TGF-alpha-expressing cells in the suprachiasmatic nucleus of the Syrian hamster (Mesocricetus auratus). Using confocal laser scanning fluorescence imaging on brain sections immuno-histologically processed for TGF-alpha and GFAP double staining, we observed that in the suprachiasmatic nucleus, TGF-alpha staining is located mainly in GFAP-positive cells, indicating suprachiasmatic nucleus astrocytes produce TGF-alpha. Glial expression of TGF-alpha was also observed in the 3rd ventricle tanycytes of the retrochiasmatic area. In other brain regions where the TGF-alpha message is abundant, such as in the piriform cortex, we observed that TGF-alpha staining is mainly located in neurons. Our results provide the first evidence that glial cells are involved in the regulation of output from the suprachiasmatic nucleus circadian clock through a diffusible mechanism.
authors.affiliation: Department of Biology, 414 Mugar, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.forename: Nagarajan
authors.initials: N
authors.lastname: Sankrithi
authors.forename: Fred C
authors.initials: FC
authors.lastname: Davis
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000737:chemistry*; D002540:Cerebral Cortex / Q000737:chemistry; D002940:Circadian Rhythm; D006224:Cricetinae; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008647:Mesocricetus; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D013493:Suprachiasmatic Nucleus / Q000737:chemistry*; D020542:Third Ventricle / Q000737:chemistry; D016211:Transforming Growth Factor alpha / Q000032:analysis*
chemical_list: D005904:Glial Fibrillary Acidic Protein; D016211:Transforming Growth Factor alpha