title: Expression of Nephrin Homologue in the Freshwater Planarian, Dugesia japonica.
abstract: Excretory organs contain epithelial cells that form a filtration membrane specialized for ultrafiltration to produce primary urine. In vertebrates, the filtration membrane is made up of slit diaphragm (SD) formed by glomerular podocytes. Basal metazoans such as flatworms are also known have filtration epithelial cells, called flame cells, which exhibit SD-like structures. The molecular components of podocyte SD have been studied in detail, while those of the SD-like structures in basal metazoans including flatworms remain to be clarified. To determine whether the SD-like structures in flatworms have molecular components common to the SD in vertebrate podocytes, we examined the expression of gene homologue for mammalian nephrin, which encodes an essential transmembrane protein that participates in the formation of the SD, in a species of flatworms, planarian (Dugesia japonica). Flame cells were distributed throughout the entire body of the planarian, but the nephrin-expressing cells identified by in situ hybridization were mainly detected at body periphery excluding head region. The distribution pattern of nephrin-expressing cells was similar to that of proliferating cell nuclear antigen-expressing neoblasts, which are pluripotent stem cells characteristic to planarians. These findings indicated that the SD-like structures can be formed without the Nephrin protein in planarian flame cells.
authors: Department of Anatomy and Life Structure, Juntendo University School of Medicine , 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan ; Department of Biological Science and Technology, Graduate School of Industrial Science and Technology, Tokyo University of Science , 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan.
authors: Tomomi
authors: T
authors: Nakamura
authors: Department of Biological Sciences and Informatics, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
authors: Sota
authors: S
authors: Takagi
authors: Department of Biological Sciences and Informatics, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
authors: Midori
authors: M
authors: Matsumoto
authors: Department of Biological Science and Technology, Graduate School of Industrial Science and Technology, Tokyo University of Science , 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan.
authors: Fumio
authors: F
authors: Tashiro
authors: Department of Anatomy and Life Structure, Juntendo University School of Medicine , 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors: Tatsuo
authors: T
authors: Sakai
authors: Department of Anatomy and Life Structure, Juntendo University School of Medicine , 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors: Koichiro
authors: K
authors: Ichimura
keywords: flame cell; nephrin; planarian; protonephridium; slit diaphragm