@article {1327, title = {Genetic association for renal traits among participants of African ancestry reveals new loci for renal function.}, journal = {PLoS Genet}, volume = {7}, year = {2011}, month = {2011 Sep}, pages = {e1002264}, abstract = {

Chronic kidney disease (CKD) is an increasing global public health concern, particularly among populations of African ancestry. We performed an interrogation of known renal loci, genome-wide association (GWA), and IBC candidate-gene SNP association analyses in African Americans from the CARe Renal Consortium. In up to 8,110 participants, we performed meta-analyses of GWA and IBC array data for estimated glomerular filtration rate (eGFR), CKD (eGFR <60 mL/min/1.73 m(2)), urinary albumin-to-creatinine ratio (UACR), and microalbuminuria (UACR >30 mg/g) and interrogated the 250 kb flanking region around 24 SNPs previously identified in European Ancestry renal GWAS analyses. Findings were replicated in up to 4,358 African Americans. To assess function, individually identified genes were knocked down in zebrafish embryos by morpholino antisense oligonucleotides. Expression of kidney-specific genes was assessed by in situ hybridization, and glomerular filtration was evaluated by dextran clearance. Overall, 23 of 24 previously identified SNPs had direction-consistent associations with eGFR in African Americans, 2 of which achieved nominal significance (UMOD, PIP5K1B). Interrogation of the flanking regions uncovered 24 new index SNPs in African Americans, 12 of which were replicated (UMOD, ANXA9, GCKR, TFDP2, DAB2, VEGFA, ATXN2, GATM, SLC22A2, TMEM60, SLC6A13, and BCAS3). In addition, we identified 3 suggestive loci at DOK6 (p-value = 5.3{\texttimes}10(-7)) and FNDC1 (p-value = 3.0{\texttimes}10(-7)) for UACR, and KCNQ1 with eGFR (p = 3.6{\texttimes}10(-6)). Morpholino knockdown of kcnq1 in the zebrafish resulted in abnormal kidney development and filtration capacity. We identified several SNPs in association with eGFR in African Ancestry individuals, as well as 3 suggestive loci for UACR and eGFR. Functional genetic studies support a role for kcnq1 in glomerular development in zebrafish.

}, keywords = {Adaptor Proteins, Vesicular Transport, Adult, African Continental Ancestry Group, Aged, Animals, Female, Gene Knockdown Techniques, Genetic Association Studies, Genetic Loci, Genome-Wide Association Study, Glomerular Filtration Rate, Humans, KCNQ1 Potassium Channel, Kidney, Kidney Failure, Chronic, Male, Middle Aged, Neoplasm Proteins, Phenotype, Polymorphism, Single Nucleotide, Zebrafish}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1002264}, author = {Liu, Ching-Ti and Garnaas, Maija K and Tin, Adrienne and K{\"o}ttgen, Anna and Franceschini, Nora and Peralta, Carmen A and de Boer, Ian H and Lu, Xiaoning and Atkinson, Elizabeth and Ding, Jingzhong and Nalls, Michael and Shriner, Daniel and Coresh, Josef and Kutlar, Abdullah and Bibbins-Domingo, Kirsten and Siscovick, David and Akylbekova, Ermeg and Wyatt, Sharon and Astor, Brad and Mychaleckjy, Josef and Li, Man and Reilly, Muredach P and Townsend, Raymond R and Adeyemo, Adebowale and Zonderman, Alan B and de Andrade, Mariza and Turner, Stephen T and Mosley, Thomas H and Harris, Tamara B and Rotimi, Charles N and Liu, Yongmei and Kardia, Sharon L R and Evans, Michele K and Shlipak, Michael G and Kramer, Holly and Flessner, Michael F and Dreisbach, Albert W and Goessling, Wolfram and Cupples, L Adrienne and Kao, W Linda and Fox, Caroline S} } @article {6587, title = {Association of a cystatin C gene variant with cystatin C levels, CKD, and risk of incident cardiovascular disease and mortality.}, journal = {Am J Kidney Dis}, volume = {63}, year = {2014}, month = {2014 Jan}, pages = {16-22}, abstract = {

BACKGROUND: Carriers of the T allele of the single-nucleotide polymorphism rs13038305 tend to have lower cystatin C levels and higher cystatin C-based estimated glomerular filtration rate (eGFRcys). Adjusting for this genetic effect on cystatin C concentrations may improve GFR estimation, reclassify cases of chronic kidney disease (CKD), and strengthen risk estimates for cardiovascular disease (CVD) and mortality.

STUDY DESIGN: Observational.

SETTING \& POPULATION: 4 population-based cohorts: Atherosclerosis Risk in Communities (ARIC), Cardiovascular Health (CHS), Framingham Heart (FHS), and Health, Aging, and Body Composition (Health ABC) studies.

PREDICTORS: We estimated the association of rs13038305 with eGFRcys and serum creatinine-based eGFR (eGFRcr) and performed longitudinal analyses of the associations of eGFRcys with mortality and cardiovascular events following adjustment for rs13038305.

OUTCOMES: We assessed reclassification by genotype-adjusted eGFRcys across CKD categories: <45, 45-59, 60-89, and >= 90 mL/min/1.73 m(2). We compared mortality and CVD outcomes in those reclassified to a worse eGFRcys category with those unaffected. Results were combined using fixed-effect inverse-variance meta-analysis.

RESULTS: In 14,645 participants, each copy of the T allele of rs13038305 (frequency, 21\%) was associated with a 6.4\% lower cystatin C concentration, 5.5-mL/min/1.73 m(2) higher eGFRcys, and 36\% [95\% CI, 29\%-41\%] lower odds of CKD. Associations with CVD (HR, 1.17; 95\% CI, 1.14-1.20) and mortality (HR, 1.22; 95\% CI, 1.19-1.24) per 10-mL/min/1.73 m(2) lower eGFRcys were similar with or without rs13038305 adjustment. 1,134 (7.7\%) participants were reclassified to a worse CKD category following rs13038305 adjustment, and rates of CVD and mortality were higher in individuals who were reclassified. However, the overall net reclassification index was not significant for either outcome, at 0.009 (95\% CI, -0.003 to 0.022) for mortality and 0.014 (95\% CI, 0.0 to 0.028) for CVD.

LIMITATIONS: rs13038305 explains only a small proportion of cystatin C variation.

CONCLUSIONS: Statistical adjustment can correct a genetic bias in GFR estimates based on cystatin C in carriers of the T allele of rs13038305 and result in changes in disease classification. However, on a population level, the effects on overall reclassification of CKD status are modest.

}, keywords = {Aged, Bias, Biomarkers, Cardiovascular Diseases, Creatinine, Cystatin C, Female, Genetic Variation, Glomerular Filtration Rate, Humans, Male, Middle Aged, Polymorphism, Single Nucleotide, Renal Insufficiency, Chronic, Risk Assessment, Risk Factors, Severity of Illness Index, Statistics as Topic, Survival Rate}, issn = {1523-6838}, doi = {10.1053/j.ajkd.2013.06.015}, author = {O{\textquoteright}Seaghdha, Conall M and Tin, Adrienne and Yang, Qiong and Katz, Ronit and Liu, Yongmei and Harris, Tamara and Astor, Brad and Coresh, Josef and Fox, Caroline S and Kao, W H Linda and Shlipak, Michael G} }