Nephronophthisis 13: implications of its association with Caroli disease and altered intracellular localization of WDR19 in the kidney.
BACKGROUND
Nephronophthisis 13 (NPHP 13) is associated with mutations in the WDR19 gene, which encodes for a protein in the intraflagellar transport complex. Herein, we describe six additional cases accompanied by Caroli syndrome or disease.


METHODS
Targeted exome sequencing covering 96 ciliopathy-related genes was performed for 48 unrelated Korean patients with a clinical suspicion of NPHP. Mutations were confirmed by Sanger sequencing. We evaluated the expression of WDR19 in the biopsied kidney by immunohistochemistry in patients and controls.


RESULTS
We detected three (3/48, 6.3 %) unrelated index cases with WDR19 mutations. One of the cases involved two siblings with the same mutation. Later, we detected an additional index case with a similar phenotype of kidney and liver involvement by Sanger sequencing of WDR19. The p.R1178Q mutation was common in all patients. All of the six affected patients from four families progressed to chronic kidney disease. Of note, all six patients had Caroli syndrome or disease. Immunohistochemistry for WDR19 showed localized expression along the luminal borders of the renal tubular epithelium in controls, whereas it showed diffuse cytoplasmic staining in the affected patients.


CONCLUSIONS
Caroli disease is a major extra-renal phenotype associated with mutations in WDR19 in the Korean population. In this study, we visually validated the expression pattern of mutant WDR19 protein in the kidneys of NPHP 13 patients. More data are needed to identify the true frequency of p.R1178Q. Functional studies including transfection assay will provide solid grounds for the pathogenicity of each mutation.
Department of Pediatrics, Seoul National University Children's Hospital, 101 Daehak-Ro, Jongno-Gu, Seoul, 110-744, Korea.
Jiwon M
JM
Lee
Yo Han
YH
Ahn
Hee Gyung
HG
Kang
I I Soo
II
Ha
Kyoungbun
K
Lee
Kyung Chul
KC
Moon
Joo Hoon
JH
Lee
Young Seo
YS
Park
Yong Mee
YM
Cho
Jun-Seok
JS
Bae
Nayoung K D
NK
Kim
Woong-Yang
WY
Park
Hae I I
HI
Cheong
D000293:Adolescent; D016767:Caroli Disease / Q000175:diagnosis / Q000235:genetics; D002648:Child; D003598:Cytoskeletal Proteins; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000473:pathology*; D008297:Male; D009154:Mutation; D017044:Polycystic Kidney, Autosomal Recessive / Q000175:diagnosis / Q000235:genetics; D011506:Proteins / Q000235:genetics*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D056910:Republic of Korea; D055815:Young Adult
D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; C486869:WDR19 protein, human