Association analysis of Notch pathway signalling genes in diabetic nephropathy

Several studies have provided compelling evidence implicating the Notch signalling pathway in diabetic nephropathy. Co-regulation of Notch signalling pathway genes with GREM1 has recently been demonstrated and several genes involved in the Notch pathway are differentially expressed in kidney biopsies from individuals with diabetic nephropathy. We assessed single-nucleotide polymorphisms (SNPs; n = 42) in four of these key genes (JAG1, HES1, NOTCH3 and ADAM10) for association with diabetic nephropathy using a case-control design.
Tag SNPs and potentially functional SNPs were genotyped using Sequenom or Taqman technologies in a total of 1371 individuals with type 1 diabetes (668 patients with nephropathy and 703 controls without nephropathy). Patients and controls were white and recruited from the UK and Ireland. Association analyses were performed using PLINK (http://pngu.mgh.harvard.edu/similar to purcell/plink/) and haplotype frequencies in patients and controls were compared. Adjustment for multiple testing was performed by permutation testing.
In analyses stratified by centre, we identified six SNPs, rs8708 and rs11699674 (JAG1), rs10423702 and rs1548555 (NOTCH3), rs2054096 and rs8027998 (ADAM10) as being associated with diabetic nephropathy before, but not after, adjustment for multiple testing. Haplotype and subgroup analysis according to duration of diabetes also failed to find an association with diabetic nephropathy.
Our results suggest that common variants in JAG1, HES1, NOTCH3 and ADAM10 are not strongly associated with diabetic nephropathy in type 1 diabetes among white individuals. Our findings, however, cannot entirely exclude these genes from involvement in the pathogenesis of diabetic nephropathy.

Investigation of ACE, ACE2 and AGTR1 genes for association with nephropathy in Type 1 diabetes mellitus

Background Polymorphisms in ACE and AGTR1 genes have been assessed in multiple studies for association with diabetic nephropathy; however, results are conflicting. The ACE2 gene has not been studied extensively for association with diabetic nephropathy.

Resequencing of the CCL5 and CCR5 genes and investigation of variants for association with diabetic nephropathy

Chemokine (C-C motif) ligand 5 (CCL5) and chemokine (C-C motif) receptor 5 are implicated in the pathogenesis of diabetic nephropathy (DN). We hypothesize that variants in these genes may be associated with DN. The CCL5 and chemokine receptor type 5 (CCR5) genes were resequenced, variants identified (n=58), allele frequencies determined in 46 individuals (92 chromosomes) and efficient haplotype tag single-nucleotide polymorphisms (htSNPs) selected to effectively evaluate the common variation in these genes. One reportedly functional gene variant and eight htSNPs were genotyped in a case-control association study involving Caucasian individuals with type 1 diabetes (267 cases with DN and 442 non-nephropathic diabetic controls). Genotyping was performed using MassARRAY iPLEX, TaqMan, gel electrophoresis and direct capillary sequencing. After correction for multiple testing, there were no statistically significant associations between variants in the CCL5 and CCR5 genes and DN. Journal of Human Genetics (2010) 55, 248-251; doi:10.1038/jhg.2010.15; published online 5 March 2010

Association of Caveolin-1 gene polymorphism with kidney transplant fibrosis and allograft failure

Context: Caveolin-1 (CAV1) is an inhibitor of tissue fibrosis.
Objective: To study the association of CAV1 gene variation with kidney transplant outcome, using kidney transplantation as a model of accelerated fibrosis.
Design, Setting, and Patients: Candidate gene association and validation study. Genomic DNA from 785 white kidney transplant donors and their respective recipients (transplantations in Birmingham, England, between 1996 and 2006; median followup, 81 months) were analyzed for common variation in CAV1 using a singlenucleotide polymorphism (SNP) tagging approach. Validation of positive findings was sought in an independent kidney transplant donor-recipient cohort (transplantations in Belfast, Northern Ireland, between 1986 and 2005; n=697; median follow-up, 69 months). Association between genotype and allograft failure was initially assessed by Kaplan-Meier analysis, then in an adjusted Cox model.
Main Outcome Measure: Death-censored allograft failure, defined as a return to dialysis or retransplantation.
Results: The presence of donor AA genotype for the CAV1 rs4730751 SNP was associated with increased risk of allograft failure in the Birmingham group (donor AA vs non-AA genotype in adjusted Cox model, hazard ratio [HR], 1.97; 95% confidence interval [CI], 1.29-3.16; P=.002). No other tag SNPs showed a significant association. This finding was validated in the Belfast cohort (in adjusted Cox model, HR, 1.56; 95% CI, 1.07-2.27; P=.02). Overall graft failure rates were as follows: for the Birmingham cohort, donor genotype AA, 22 of 57 (38.6%); genotype CC, 96 of 431 (22.3%); and genotype AC, 66 of 297 (22.2%); and for the Belfast cohort, donor genotype AA, 32 of 48 (67%); genotype CC, 150 of 358 (42%); and genotype AC, 119 of 273 (44%).
Conclusion: Among kidney transplant donors, the CAV1 rs4730751 SNP was significantly associated with allograft failure in 2 independent cohorts.

Association of VEGF-1499C -> T polymorphism with diabetic nephropathy in type 1 diabetes mellitus

Vascular endothelial growth factor (VEGF) is reported to be implicated in the development of diabetic nephropathy. We performed a case-control study to determine if VEGF-2578C -> A, VEGF-1499C -> T, and VEGF-635G -> C single-nucleotide polymorphisms (SNPs) in the VEGF gene are associated with predisposition to diabetic nephropathy in type I diabetes. Genomic DNA was obtained from Irish type I diabetic individuals with nephropathy (cases, n=242) and those without nephropathy (controls, n=301), in addition to 400 healthy control samples. These samples were genotyped for the three SNPs using TaqMan or Pyrosequencing technology. Chi-squared analyses revealed no significant differences in genotype or allele frequencies in cases versus controls for VEGF-2578C -> A (genotype, P=.58; allele, P=.52) and VEGF-635G -> C (genotype, P=.58; allele, P=.33). However, a positive association with diabetic nephropathy was observed for the VEGF-1499T allele in the Northern Ireland population (P

Association of Genetic Variants at 3q22 with Nephropathy in Patients with Type 1 Diabetes Mellitus

Diabetic nephropathy (DN) is the primary cause of morbidity and mortality in patients with type 1 diabetes mellitus (T1DM) and affects about 30% of these patients. We have previously localized a DN locus on chromosome 3q with suggestive linkage in Finnish individuals. Linkage to this region has also been reported earlier by several other groups. To fine map this locus, we conducted a multistage case-control association study in T1DM patients, comprising 1822 cases with nephropathy and 1874 T1DM patients free of nephropathy, from Finland, Iceland, and the British Isles. At the screening stage, we genotyped 3072 tag SNPs, spanning a 28 Mb region, in 234 patients and 215 controls from Finland. SNPs that met the significance threshold of p

Association of LETM1 and MRPL36 Contributes to the Regulation of Mitochondrial ATP Production and Necrotic Cell Death

Leucine zipper/EF hand-containing transmembrane-1 (LETM1) is a mitochondrial inner membrane protein that was first identified in Wolf-Hirschhorn syndrome, and was deleted in nearly all patients with the syndrome. LETM1 encodes for the human homologue of yeast Mdm38p, which is a mitochondria-shaping protein of unclear function. Here, we describe LETM1-mediated regulation of mitochondrial ATP production and biogenesis. We show that LETM1 overexpression can induce necrotic cell death in HeLa cells, in which LETM1 reduces mitochondria) biogenesis and ATP production. LETM1 acts as an anchor protein and associates with mitochondrial ribosome protein L36. Adenovirus-mediated overexpression of LETM1 reduced mitochondrial mass and expression of many mitochondrial proteins. LETM1-mediated inhibition of mitochondrial biogenesis enhanced glycolytic ATP supply and activated protein kinase B activity and cell survival signaling. The expression levels of LETM1 were significantly increased in multiple human cancer tissues compared with normals. These data suggest that LETM1 serves as an anchor protein for complex formation with the mitochondrial ribosome and regulates mitochondrial biogenesis. The increased expression of LETM1 in human cancer suggests that deregulation of LETM1 is a key feature of tumorigenesis. [Cancer Res 2009;69(8):3397-404]

Association Study of SNAP25 and Schizophrenia in Irish Family and Case-Control Samples

SNAP25 occurs on chromosome 20p12.2, which has been linked to schizophrenia in some samples, and recently linked to latent classes of psychotic illness in our sample. SNAP25 is crucial to synaptic functioning, may be involved in axonal growth and dendritic sprouting, and its expression may be decreased in schizophrenia. We genotyped 18 haplotype-tagging SNPs in SNAP25 in a sample of 270 Irish high-density families. Single marker and haplotype analyses were performed in FBAT and PDT. We adjusted for multiple testing by computing q values. Association was followed up in an independent sample of 657 cases and 411 controls. We tested for allelic effects on the clinical phenotype by using the method of sequential addition and 5 factor-derived scores of the OPCRIT. Nine of 18 SNPs had Pvalues

No Association of Dysbindin With Symptom Factors of Schizophrenia in an Irish Case-Control Sample

Robust associations between the dysbindin gene (DTNBP1) and schizophrenia have been demonstrated in many but not all samples, and evidence that this gene particularly predisposes to negative symptoms in this illness has been presented. The current study sought to replicate the previously reported negative symptom associations in an Irish case-control sample. Association between dysbindin and schizophrenia has been established in this cohort, and a factor analysis of the assessed symptoms yielded three factors, Positive, Negative, and Schneiderian. The sequential addition method was applied using UNPHASED to assess the relationship between these symptom factors and the high-risk haplotype. No associations were detected for any of the symptom factors indicating that the dysbindin risk haplotype does not predispose to a particular group of symptoms in this sample. Several possibilities, such as differing risk haplotypes, may explain this finding. (C) 2009 Wiley-Liss, Inc.

Association Analysis of the PIP4K2A Gene on Chromosome 10p12 and Schizophrenia in the Irish Study of High Density Schizophrenia Families (ISHDSF) and the Irish Case-Control Study of Schizophrenia (ICCSS)

Molecular studies support pharmacological evidence that phosphoinositide signaling is perturbed in schizophrenia and bipolar disorder. The phosphatidylinositol-4-phosphate-5-kinase type-II alpha (PIP4K2A) gene is located on chromosome 10p12. This region has been implicated in both diseases by linkage, and PIP4K2A directly by association. Given linkage evidence in the Irish Study of High Density Schizophrenia Families (ISHDSF) to a region including 10p12, we performed an association study between genetic variants at PIP4K2A and disease. No association was detected through single-marker or haplotype analysis of the whole sample. However, stratification into families positive and negative for the ISHDSF schizophrenia high-risk haplotype (HRH) in the DTNBP1 gene and re-analysis for linkage showed reduced amplitude of the 10p12 linkage peak in the DTNBP1 HRH positive families. Association analysis of the stratified sample showed a trend toward association of PIP4K2A SNPs rs1417374 and rs1409395 with schizophrenia in the DTNBP1 HRH positive families. Despite this apparent paradox, our data may therefore suggest involvement of PIP4K2A in schizophrenia in those families for whom genetic variation in DTNBP1 appears also to be a risk factor. This trend appears to arise from under-transmission of common alleles to female cases. Follow-up association analysis in a large Irish schizophrenia case-control control sample (ICCSS) showed significant association with disease of a haplotype comprising these same SNPs rs1417374-rs1409395, again more so in affected females, and in cases with negative family history of the disease. This study supports a minor role for PIP4K2A in schizophrenia etiology in the Irish population. (C) 2009 Wiley-Liss, Inc.