title: Novel UMOD mutations in familial juvenile hyperuricemic nephropathy lead to abnormal uromodulin intracellular trafficking.
abstract: BACKGROUND
  Familial juvenile hyperuricemic nephropathy (FJHN) is an autosomal dominant disorder characterized by hyperuricemia and progressive chronic kidney disease. Uromodulin gene (UMOD) mutations, leading to abnormalities of uromodulin intracellular trafficking contribute to the progress of the disease.
  
  
  METHODS
  We did UMOD screening in three Chinese FJHN families. We thus constructed mutant uromodulin express plasmids by site-mutagenesis from wild type uromodulin vector and transfected them into HEK293 (human embryonic kidney) cells. And then we detected uromodulin expression by western blot and observed intracellular distribution by immunofluorescence.
  
  
  RESULTS
  We found three heterozygous mutations. Mutation Val109Glu (c.326T/A; p.Val109Glu) and mutation Pro236Gln (c.707C/A; p.Pro236Gln) were newly indentified mutations in two distinct families (family F1 and family F3). Another previously reported UMOD mutation Cys248Trp (c.744C/G; p.Cys248Trp) was detected in family F2. Phenotypes varied both within the same family and between different families. Uromodulin expression is abnormal in the patient biopsy. Functional analysis of mutation showed that mutant types of uromodulin were secreted into the supernatant medium much less when compared with wild type. In mutant type uromodulin transfected cells, intracellular uromodulin localized less in the Golgi apparatus and more in endoplasmic reticulum(ER).
  
  
  CONCLUSIONS
  Our results suggested that the novel uromodulin mutations found in the Chinese families lead to misfolded protein, which was retained in the endoplasmic reticulum, finally contributed to the phenotype of FJHN.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing 100034, China.
authors.forename: Maojing
authors.initials: M
authors.lastname: Liu
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Chen
authors.forename: Yu
authors.initials: Y
authors.lastname: Liang
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Suxia
authors.initials: S
authors.lastname: Wang
authors.forename: Ping
authors.initials: P
authors.lastname: Hou
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Minghui
authors.initials: M
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People / Q000235:genetics; D004252:DNA Mutational Analysis; D005190:Family; D005260:Female; D006073:Gout / Q000235:genetics* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D033461:Hyperuricemia / Q000235:genetics* / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism; D007674:Kidney Diseases / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000502:physiology; D010375:Pedigree; D017510:Protein Folding; D021381:Protein Transport / Q000235:genetics; D058949:Uromodulin / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D055815:Young Adult
chemical_list: C548612:UMOD protein, human; D058949:Uromodulin
keywords: CRF; D8C; DCT; EGF-like; ER; ESRD; FEUA; FJHN; Familial juvenile hyperuricemic nephropathy; Fraction of excretion of uric acid; GFR; GPI; HEK293; JNK; MCKD2; NF-κB; SDS-PAGE; Sodium dodecylsulfate-polyacrylamide gel electrophoresis; TAL; Tamm–Horsfall protein; UAKD; UMOD; Uromodulin; ZP; c-Jun N-terminal kinase; chronic renal failure; distal convoluted tubule; eight cysteine domain; end stage renal disease; endoplasmic reticulum; epidermal growth factor like; glomerular filtration rate; glycosylphosphatidylinositol; human embryonic kidney 293; medullary cystic kidney disease type 2; nuclear factor-κB; thick ascending limb; uromodulin gene; uromodulin-associated kidney disease; zona pellucid