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Expression of Nephrin Homologue in the Freshwater Planarian, Dugesia japonica.

Nakamura T, Takagi S, Matsumoto M, Tashiro F, Sakai T, Ichimura K - Acta Histochem Cytochem (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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.

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.

No MeSH data available.


Related in: MedlinePlus

Ultrastructure of flame cells in the planarian D. japonica. Transmission electron micrographs of rat podocytes (A, C) and planarian flame cells (B, D, E), both of which form a primary-urine producing apparatus. The cell bodies of podocyte (A) and flame cell (B) are shown in low magnification view. Flame cell forms a flame bulb at the most proximal blunt end of protonephridial tubule, and possesses a bundle of motile cilia in the lumen (arrows in B, E). The slit diaphragm and slit diaphragm-like structure are recognized in podocytes and flame cells, respectively (arrowheads in C, D). Magnification of an inset in E is shown as D. CL, capillary lumen; GBM, glomerular basement membrane; IS, interstitial space; US, urinary space. Bars=1 μm (A, B, E); 200 nm (C, D).
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Figure 1: Ultrastructure of flame cells in the planarian D. japonica. Transmission electron micrographs of rat podocytes (A, C) and planarian flame cells (B, D, E), both of which form a primary-urine producing apparatus. The cell bodies of podocyte (A) and flame cell (B) are shown in low magnification view. Flame cell forms a flame bulb at the most proximal blunt end of protonephridial tubule, and possesses a bundle of motile cilia in the lumen (arrows in B, E). The slit diaphragm and slit diaphragm-like structure are recognized in podocytes and flame cells, respectively (arrowheads in C, D). Magnification of an inset in E is shown as D. CL, capillary lumen; GBM, glomerular basement membrane; IS, interstitial space; US, urinary space. Bars=1 μm (A, B, E); 200 nm (C, D).

Mentions: The main portion of the primary-urine producing apparatus is made up of an epithelium layer specialized for ultrafiltration. In eucoelomates including vertebrates, which possess a coelom lined with mesothelium, the filtration epithelium consists of podocytes and their basement membrane [20, 21]. These podocytes, together with several capillary loops, form a number of glomeruli within the mesonephric and metanephric kidneys in vertebrates. This basic cytoarchitecture of the podocyte is highly conserved among the taxonomic groups of eucoelomates. Neighboring podocytes, which are interdigitated with each other by their numerous foot processes and separated by filtration slits, are bridged by specialized intercellular junctions called slit diaphragms (SD) (Fig. 1A, C). The SD in the vertebrate podocytes serve as a highly selective filtration barrier in the glomerulus. Three kinds of SD-specific membrane proteins are essential to form and maintain the SD in vertebrate podocytes: Nephrin, Podocin, and Neph1 [3, 6, 12, 16]. Mutations in nephrin and podocin genes cause congenital nephrotic syndrome of the Finnish type and autosomal recessive steroid-resistant nephrotic syndrome, respectively [1, 10].


Expression of Nephrin Homologue in the Freshwater Planarian, Dugesia japonica.

Nakamura T, Takagi S, Matsumoto M, Tashiro F, Sakai T, Ichimura K - Acta Histochem Cytochem (2014)

Ultrastructure of flame cells in the planarian D. japonica. Transmission electron micrographs of rat podocytes (A, C) and planarian flame cells (B, D, E), both of which form a primary-urine producing apparatus. The cell bodies of podocyte (A) and flame cell (B) are shown in low magnification view. Flame cell forms a flame bulb at the most proximal blunt end of protonephridial tubule, and possesses a bundle of motile cilia in the lumen (arrows in B, E). The slit diaphragm and slit diaphragm-like structure are recognized in podocytes and flame cells, respectively (arrowheads in C, D). Magnification of an inset in E is shown as D. CL, capillary lumen; GBM, glomerular basement membrane; IS, interstitial space; US, urinary space. Bars=1 μm (A, B, E); 200 nm (C, D).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4387267&req=5

Figure 1: Ultrastructure of flame cells in the planarian D. japonica. Transmission electron micrographs of rat podocytes (A, C) and planarian flame cells (B, D, E), both of which form a primary-urine producing apparatus. The cell bodies of podocyte (A) and flame cell (B) are shown in low magnification view. Flame cell forms a flame bulb at the most proximal blunt end of protonephridial tubule, and possesses a bundle of motile cilia in the lumen (arrows in B, E). The slit diaphragm and slit diaphragm-like structure are recognized in podocytes and flame cells, respectively (arrowheads in C, D). Magnification of an inset in E is shown as D. CL, capillary lumen; GBM, glomerular basement membrane; IS, interstitial space; US, urinary space. Bars=1 μm (A, B, E); 200 nm (C, D).
Mentions: The main portion of the primary-urine producing apparatus is made up of an epithelium layer specialized for ultrafiltration. In eucoelomates including vertebrates, which possess a coelom lined with mesothelium, the filtration epithelium consists of podocytes and their basement membrane [20, 21]. These podocytes, together with several capillary loops, form a number of glomeruli within the mesonephric and metanephric kidneys in vertebrates. This basic cytoarchitecture of the podocyte is highly conserved among the taxonomic groups of eucoelomates. Neighboring podocytes, which are interdigitated with each other by their numerous foot processes and separated by filtration slits, are bridged by specialized intercellular junctions called slit diaphragms (SD) (Fig. 1A, C). The SD in the vertebrate podocytes serve as a highly selective filtration barrier in the glomerulus. Three kinds of SD-specific membrane proteins are essential to form and maintain the SD in vertebrate podocytes: Nephrin, Podocin, and Neph1 [3, 6, 12, 16]. Mutations in nephrin and podocin genes cause congenital nephrotic syndrome of the Finnish type and autosomal recessive steroid-resistant nephrotic syndrome, respectively [1, 10].

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: 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.

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.

No MeSH data available.


Related in: MedlinePlus