title: Molecular cloning, genomic structure, and expression analysis of MUC20, a novel mucin protein, up-regulated in injured kidney.
abstract: Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis in the world. Here, we identify a cDNA encoding a novel mucin protein, shown previously to be up-regulated in IgAN patients, from a human kidney cDNA library. This protein contains a mucin tandem repeat of 19 amino acids consisting of many threonine, serine, and proline residues and likely to be extensively O-glycosylated; thus, this gene was classified in the mucin family and named MUC20. The human MUC20 gene contains at least four exons and is localized close to MUC4 on chromosome 3q29. We found variations in repeat numbers in the mucin tandem domain, suggesting polymorphism of this region. Northern blot and reverse transcription-PCR analyses revealed that human MUC20 mRNA was expressed most highly in kidney and moderately in placenta, colon, lung, prostate, and liver. Immunohistochemical analysis of human kidney revealed that MUC20 protein was localized in the proximal tubules. Immunoblotting analysis of MUC20 proteins produced in Madin-Darby canine kidney and HEK293 cells indicated the localization of MUC20 protein in a membrane fraction and extensive posttranslational modification. Immunoelectron microscopy of MUC20-producing Madin-Darby canine kidney cells demonstrated that MUC20 protein was localized on the plasma membrane. Expression of MUC20 mRNA in a human kidney cell line was up-regulated by tumor necrosis factor-alpha, phorbol 12-myristate 13-acetate, or lipopolysaccharide. Two species of MUC20 mRNA (hMUC20-L and hMUC20-S), resulting from alternative transcription, were identified in human tissue, whereas only one variant was observed in mouse tissues. Mouse MUC20 mRNA was expressed in the epithelial cells of proximal tubules, and the expression increased dramatically with the progression of lupus nephritis in the kidney of MRL/MpJ-lpr/lpr mice. Moreover, the expression of mouse MUC20 was augmented in renal tissues acutely injured by cisplatin or unilateral ureteral obstruction. These characteristics suggest that the production of MUC20 is correlated with development and progression of IgAN and other renal injuries.
authors.affiliation: Central Pharmaceutical Research Institute, Pharmaceutical Frontier Research Laboratories, Japan Tobacco Inc., Yokohama, Kanagawa 236-0004, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Higuchi
authors.forename: Takuya
authors.initials: T
authors.lastname: Orita
authors.forename: Setsuko
authors.initials: S
authors.lastname: Nakanishi
authors.forename: Ken
authors.initials: K
authors.lastname: Katsuya
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Watanabe
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamasaki
authors.forename: Iwao
authors.initials: I
authors.lastname: Waga
authors.forename: Toyomichi
authors.initials: T
authors.lastname: Nanayama
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: William
authors.initials: W
authors.lastname: Munger
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Sun
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Falk
authors.forename: J Charles
authors.initials: JC
authors.lastname: Jennette
authors.forename: David A
authors.initials: DA
authors.lastname: Alcorta
authors.forename: Huiping
authors.initials: H
authors.lastname: Li
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Saito
authors.forename: Motonao
authors.initials: M
authors.lastname: Nakamura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005260:Female; D040342:Genetic Structures; D005922:Glomerulonephritis, IGA / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007674:Kidney Diseases / Q000378:metabolism*; D008181:Lupus Nephritis / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D008969:Molecular Sequence Data; D009077:Mucins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D011110:Polymorphism, Genetic; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D009077:Mucins