High-density single nucleotide polymorphism genome-wide linkage scan for susceptibility genes for diabetic nephropathy in type 1 diabetes: discordant sibpair approach.
OBJECTIVE
Epidemiological and family studies have demonstrated that susceptibility genes play an important role in the etiology of diabetic nephropathy, defined as persistent proteinuria or end-stage renal disease (ESRD) in type 1 diabetes.


METHODS
To efficiently search for genomic regions harboring diabetic nephropathy genes, we conducted a scan using 5,382 informative single nucleotide polymorphisms on 100 sibpairs concordant for type 1 diabetes but discordant for diabetic nephropathy. In addition to being powerful for detecting linkage to diabetic nephropathy, this design allows linkage analysis on type 1 diabetes via traditional affected sibpair (ASP) analysis. In weighing the evidence for linkage, we considered maximum logarithm of odds score (maximum likelihood score [MLS]) values and corresponding allelic sharing patterns, calculated and viewed graphically using the software package SPLAT.


RESULTS
Our primary finding for diabetic nephropathy, broadly defined, is on chromosome 19q (MLS = 3.1), and a secondary peak exists on chromosome 2q (MLS = 2.1). Stratification of discordant sibpairs based on whether disease had progressed to ESRD suggested four tertiary peaks on chromosome 1q (ESRD only), chromosome 20p (proteinuria only), and chromosome 3q (two loci 58 cm apart, one for ESRD only and another for proteinuria only). Additionally, analysis of 130 ASPs for type 1 diabetes confirmed the linkage to the HLA region on chromosome 6p (MLS = 9.2) and IDDM15 on chromosome 6q (MLS = 3.1).


CONCLUSIONS
This study identified several novel loci as candidates for diabetic nephropathy, none of which appear to be the sole genetic determinant of diabetic nephropathy in type 1 diabetes. In addition, this study confirms two previously reported type 1 diabetes loci.
Research Division, Joslin Diabetes Center, Boston, Massachusetts, USA.
John J
JJ
Rogus
G David
GD
Poznik
Marcus G
MG
Pezzolesi
Adam M
AM
Smiles
Jonathon
J
Dunn
William
W
Walker
Krzysztof
K
Wanic
Dariusz
D
Moczulski
Luis
L
Canani
Shinichi
S
Araki
Yuichiro
Y
Makita
James H
JH
Warram
Andrzej S
AS
Krolewski
D000328:Adult; D002890:Chromosomes, Human, Pair 20; D002893:Chromosomes, Human, Pair 3; D002896:Chromosomes, Human, Pair 6; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics*; D003928:Diabetic Nephropathies / Q000453:epidemiology / Q000235:genetics*; D005192:Family Health; D005260:Female; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D023281:Genomics; D006801:Humans; D007676:Kidney Failure, Chronic / Q000453:epidemiology / Q000235:genetics; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D035781:Siblings