Lack of major involvement of human uroplakin genes in vesicoureteral reflux: implications for disease heterogeneity.
BACKGROUND
Primary vesicoureteral reflux (VUR) is a hereditary disorder characterized by the retrograde flow of urine into the ureters and kidneys. It affects about 1% of the young children and is thus one of the most common hereditary diseases. Its associated nephropathy is an important cause of end-stage renal failure in children and adults. Recent studies indicate that genetic ablation of mouse uroplakin (UP) III gene, which encodes a 47 kD urothelial-specific integral membrane protein forming urothelial plaques, causes VUR and hydronephrosis.


METHODS
To begin to determine whether mutations in UP genes might play a role in human VUR, we genotyped all four UP genes in 76 patients with radiologically proven primary VUR by polymerase chain reaction (PCR) amplification and sequencing of all their exons plus 50 to 150 bp of flanking intronic sequences.


RESULTS
Eighteen single nucleotide polymorphisms (SNPs) were identified, seven of which were missense, with no truncation or frame shift mutations. Since healthy relatives of the VUR probands are not reliable negative controls for VUR, we used a population of 90 race-matched, healthy individuals, unrelated to the VUR patients, as controls to perform an association study. Most of the SNPs were not found to be significantly associated with VUR. However, SNP1 of UP Ia gene affecting a C to T conversion and an Ala7Val change, and SNP7 of UP III affecting a C to G conversion and a Pro154Ala change, were marginally associated with VUR (both P= 0.08). Studies of additional cases yielded a second set of data that, in combination with the first set, confirmed a weak association of UP III SNP7 in VUR (P= 0.036 adjusted for both subsets of cases vs. controls).


CONCLUSIONS
Such a weak association and the lack of families with simple dominant Mendelian inheritance suggest that missense changes of uroplakin genes cannot play a dominant role in causing VUR in humans, although they may be weak risk factors contributing to a complex polygenic disease. The fact that no truncation or frame shift mutations have been found in any of the VUR patients, coupled with our recent finding that some breeding pairs of UP III knockout mice yield litters that show not only VUR, but also severe hydronephrosis and neonatal death, raises the possibility that major uroplakin mutations could be embryonically or postnatally lethal in humans.
Jiang
Songshan
S
Epithelial Biology Unit, Ronald O. Perelman Department of Dermatology, Kaplan Comprehensive Cancer Center, New York University Medical School, New York, New York, USA.
Gitlin
Jordan
J
Deng
Fang-Ming
FM
Liang
Feng-Xia
FX
Lee
Andy
A
Atala
Anthony
A
Bauer
Stuart B
SB
Ehrlich
Garth D
GD
Feather
Sally A
SA
Goldberg
Judith D
JD
Goodship
Judith A
JA
Goodship
Timothy H J
TH
Hermanns
Monika
M
Hu
Fen Ze
FZ
Jones
Katrin E
KE
Malcolm
Sue
S
Mendelsohn
Cathy
C
Preston
Robert A
RA
Retik
Alan B
AB
Schneck
Francis X
FX
Wright
Victoria
V
Ye
Xiang Y
XY
Woolf
Adrian S
AS
Wu
Xue-Ru
XR
Ostrer
Harry
H
Shapiro
Ellen
E
Yu
Jun
J
Sun
Tung-Tien
TT
D000409:Alanine; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D016022:Case-Control Studies; D002874:Chromosome Mapping; D003596:Cytosine; D004622:Embryo, Mammalian / Q000378:metabolism; D005091:Exons; D015870:Gene Expression; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006147:Guanine; D006801:Humans; D007438:Introns; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D011392:Proline; D013941:Thymine; D060170:Uroplakin II; D060171:Uroplakin III; D060167:Uroplakin Ia; D060169:Uroplakin Ib; D019459:Urothelium / Q000196:embryology; D014718:Vesico-Ureteral Reflux / Q000235:genetics*
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C086451:UPK1A protein, human; C086452:UPK1B protein, human; C554658:UPK2 protein, human; C554659:Upk2 protein, mouse; D060170:Uroplakin II; D060171:Uroplakin III; D060167:Uroplakin Ia; D060169:Uroplakin Ib; D006147:Guanine; D003596:Cytosine; D011392:Proline; D000409:Alanine; D013941:Thymine