RESUMEN
BACKGROUND: There is substantial evidence for a genetic contribution to diabetic nephropathy susceptibility in the African American population, but little is known about location or identity of susceptibility genes. METHODS: DNA samples were collected from 206 type 2 diabetes (T2DM) and end-stage renal disease (ESRD)/nephropathy-affected sib pairs from 166 African American families (355 affected individuals). A genome scan was performed and data analyzed using nonparametric linkage regression (NPLR) analysis and ordered subsets analysis (OSA) methods. RESULTS: In initial NPLR analyses no logarithm of odds (LOD) scores >2.0 were observed. Four loci had LOD scores > or =1.0, with LOD = 1.43 at 29 cM on chromosome 7p the highest. NPLR analyses of multilocus interactions detected 6 loci (7p, 12p, 14q, 16p, 18q, and 21q) with LOD scores 1.15 to 1.63. NPLR analyses evaluating phenotypic interactions revealed multiple locations with evidence (P < 0.05) for interactions with age-at-onset of ESRD (9 loci), duration of diabetes before onset of ESRD (19 loci), and age-at-onset of diabetes (14 loci). Several loci identified by NPLR analyses were also identified using OSA. OSA revealed evidence for a nephropathy locus at 135 cM on chromosome 3 in an estimated 29% of the families (LOD = 4.55 in the optimal subset). Additional linkage evidence, LOD = 3.59, was observed on chromosome 7p (37% of the families, longer duration of diabetes prior to diagnosis of ESRD), and 18q (max. LOD = 3.72; 64% of the families, early diabetes diagnosis). The 7p linkage has been observed in a recent genome scan of African American type 2 diabetes. CONCLUSION: This first genome scan of diabetic nephropathy in African Americans reveals evidence for susceptibility loci on chromosomes 3q, 7p, and 18q. The 7p locus may represent a type 2 diabetes susceptibility locus.
Asunto(s)
Negro o Afroamericano/genética , Nefropatías Diabéticas/etnología , Nefropatías Diabéticas/genética , Genoma Humano , Adulto , Edad de Inicio , Femenino , Predisposición Genética a la Enfermedad , Humanos , Fallo Renal Crónico/etnología , Fallo Renal Crónico/genética , Escala de Lod , Masculino , Persona de Mediana Edad , FenotipoRESUMEN
African Americans are at increased risk of type 2 diabetes and many diabetes complications. We have carried out a genome-wide scan for African American type 2 diabetes using 638 affected sibling pairs (ASPs) from 247 families ascertained through impaired renal function to identify type 2 diabetes loci in this high-risk population. Of the 638 ASPs, 210 were concordant for diabetes with impaired renal function. A total of 390 markers, at an average spacing of 9 cM, were genotyped by the Center for Inherited Disease Research (CIDR) as part of the International Type 2 Diabetes Linkage Analysis Consortium. Nonparametric linkage (NPL) analyses conducted using the exponential model implemented in Genehunter Plus provided suggestive evidence for linkage at 6q24-q27 (163.5 cM, logarithm of odds [LOD] 2.26). Multilocus NPL regression analysis identified the 6q locus (D6S1035, LOD 2.67) and two additional regions: 7p (LOD 1.06) and 18q (LOD 0.87) as important in this model. NPL regression-based interaction analyses and ordered subset analyses (OSAs) supported the presence of a locus at chromosome 7p (29-34 cM) in the pedigrees with the earliest mean age of diagnosis of type 2 diabetes (P = 0.009 for interaction, DeltaP = 0.0034 for OSA) and lower mean BMI (P = 0.009 for interaction, DeltaP = 0.070 for OSA). These results provide evidence that genes predisposing African-American individuals to type 2 diabetes are located in the 6q and 7p regions of the genome.
Asunto(s)
Negro o Afroamericano/genética , Cromosomas Humanos Par 6 , Diabetes Mellitus Tipo 2/genética , Genoma Humano , Adulto , Edad de Inicio , Albuminuria , Índice de Masa Corporal , Mapeo Cromosómico , Marcadores Genéticos , Hemoglobina Glucada/análisis , Humanos , Escala de Lod , Fenotipo , Estadísticas no Paramétricas , Estados UnidosRESUMEN
A dense gene-based SNP map was constructed across a 360-kb region containing the interleukin-1 gene cluster (IL1A, IL1B, and IL1RN), focusing on IL1RN. In total, 95 polymorphisms were confirmed or identified primarily by direct sequencing. Polymorphisms were precisely mapped to completed BAC and genomic sequences spanning this region. The polymorphisms were typed in 443 case-control subjects from Caucasian and African American groups. Consecutive pair-wise marker linkage disequilibrium was not strictly correlated with distance and ranged from D'=0.0079 to 1.000 and D'=0.0521 to 1.0000 in Caucasians and African Americans, respectively. Single markers and haplotypes in IL1 cluster genes were evaluated for association with end-stage renal disease (ESRD). Eleven SNPs show some evidence of association with ESRD, with the strongest associations in two IL1A variants, one SNP, rs1516792-3, in intron 5 (p=0.0015) and a 4-bp insertion/deletion within the 3'UTR, rs16347-2 (p=0.0024), among African Americans with non-T2DM-associated ESRD.
Asunto(s)
Variación Genética , Haplotipos/genética , Interleucina-1/genética , Fallo Renal Crónico/genética , Negro o Afroamericano , Cartilla de ADN , Electroforesis , Frecuencia de los Genes , Humanos , Desequilibrio de Ligamiento , Polimorfismo de Nucleótido Simple , Análisis de Secuencia de ADN , Población BlancaRESUMEN
BACKGROUND: Matrix metalloproteinases are Zn2+- and Ca2+-dependent endopeptidases secreted by many cells. Expression of the matrix metalloproteinase 9 (MMP9) gene is increased in a variety of renal diseases. Several genetic studies have associated MMP9 with end-stage renal disease (ESRD). METHODS: In this study, 2.2 kb of the promoter region and all 13 exons (3.3 kb) of MMP9 genomic DNA were scanned for polymorphisms. Genetic associations between MMP9 polymorphisms and renal disease were evaluated. RESULTS: Eleven single-nucleotide polymorphisms (SNPs; 4 promoter, 6 coding region, and 1 3' untranslated region [UTR]) were identified in Caucasians and 19 SNPs (11 promoter, 8 coding region, 1 3' UTR) were identified in African Americans. A previously identified highly polymorphic (CA)n repeat in the promoter region of MMP9 also was evaluated. We found 15 alleles in Caucasians and 14 alleles in African Americans. Allele frequencies, genotypes, and 3-marker haplotypes were compared between patient and control populations. Differences were not observed using single-locus analyses. Two haplotypes that included the (CA)n repeat allele in African-American patients with type 2 diabetic nephropathy (T2DM/ESRD) showed borderline significant differences. Dichotomizing the (CA)n repeat distribution showed that shorter alleles in Caucasian cases were associated with ESRD using an additive disease-predisposing model (P = 0.05). Analysis of the (CA)n repeat in expanded sets of subjects showed strong evidence for an association of shorter alleles with ESRD in Caucasians (P = 0.00012) and suggested a similar trend in African Americans with T2DM/ESRD (P = 0.086) and subjects without T2DM/ESRD (P = 0.047). CONCLUSION: This comprehensive analysis of MMP9 and renal disease suggests a possible role for the (CA)n repeat in renal disease, consistent with previous reports.