End stage renal disease (ESRD) has a four times higher incidence in African Americans compared to European Americans. This led to the hypothesis that susceptibility alleles for ESRD have a higher frequency in West African than European gene pool. We performed a genome-wide admixture scan in 1,372 ESRD cases and 806 controls and demonstrated a highly significant association between excess African ancestry and non-diabetic ESRD (LOD 5.70) but not diabetic ESRD (LOD 0.47) on chromosome 22q12. Each copy of the European ancestral allele conferred a relative risk of 0.50 (95% credible interval 0.39 -0.63) compared to African ancestry. Multiple common SNPs (allele frequency ranging from 0.2 to 0.6) in the gene that encodes non-muscle myosin heavy chain type II isoform A (MYH9) were associated with 2-4 times greater risk of non-diabetic ESRD and accounted for a large proportion of the excess risk of ESRD observed in African compared to European Americans.End stage renal disease (ESRD) is the near-total loss of kidney function requiring treatment of 472,000 patients with dialysis or transplantation in the US 1 . Diabetes and hypertension are the two leading reported causes of treated ESRD in the U.S. accounting for 44% and 27% of incident cases respectively 1 . African Americans have consistently had a much higher rate of ESRD than European Americans in the US. In 2005, African-Americans had a 3.7 times higher age adjusted risk of ESRD. The risk ratio by assigned primary cause of ESRD was 3.8 for hypertension, 2.6 for diabetes, 2.3 for glomerulonephritis, 2.1 for the other causes of kidney disease 1 . While lower socioeconomic status and poorer access to health care explains some of this excess risk 2-4 , African Americans appear to have greater risk than European Americans after these factors are taken into account. Family studies show clustering of ESRD independent of hypertension and diabetes 5, 6 with one large study shows stronger aggregation in African Americans 6 . Studies attempting to detect susceptibility genes for ESRD and other complex diseases are challenging due to the late age of onset, causing difficulty in collecting multiply-affected families, and because linkage analysis has suggested that there are no genes of high penetrance (>4-fold increased risk) in populations of European descent, the focus of most published studies 7, 8 . For these reasons, ESRD is an excellent phenotype for whole genome association analysis, an approach with enhanced power to detect common variants of modest penetrance, and with the further advantage that unrelated individuals can be studied.We performed a scan for ESRD genes using a particular type of whole genome association analysis, termed admixture mapping or mapping by admixture linkage disequilibrium (MALD) Linda NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript 9-11 . Admixture mapping is particularly suitable for finding genetic risk alleles that differ in frequency between populations which we hypothesized might be the case for ESRD.The...

Ring rot of potato, caused by Clavibacter michiganensis subsp. sepedonicus, is one of the most regulated diseases of potatoes world wide. The organism is often difficult to detect in symptomless tubers because of low populations and slow competitive growth on available media. Polymerase chain reaction (PCR) primers and a fluorescent probe for use in the Perkin Elmer 7700 automated real time PCR detection system (TaqMan) were designed from a C. michiganensis subsp. sepedonicus-specific genomic DNA fragment for development of a BIO-PCR assay for C. michiganensis subsp. sepedonicus in potato tubers. Results of screening the primers with strains of C. michiganensis subsp. sepedonicus and other bacteria showed the primers to be specific. A total of 30 naturally infected ring rot suspect tubers were sampled by the core extract, shaker incubation procedure and assayed by (i) plating aliquots onto agar media, (ii) classical PCR, and (iii) BIO-PCR. In all, 4 tubers were positive by agar plating and pathogenicity tests, 8 by classical TaqMan PCR, and 26 by TaqMan BIO-PCR. We conclude that BIO-PCR combined with the TaqMan automated closed detection system is a rapid, reliable method of assaying large numbers of potato tuber extracts for C. michiganensis subsp. sepedonicus. Furthermore, for a large central laboratory running large numbers of PCR assays, the high-throughput TaqMan system can reduce costs per sample over the more labor-intensive classical PCR.

It is unknown whether IL-6, a central regulator of inflammation, is a cause of or just a marker of atherosclerosis. Studies of genetic susceptibility to inflammation, however, avoid the potential for reverse causality. Variation in IL6 gene was studied as a predictor of cardiovascular disease (CVD) risk in a cohort of 775 incident dialysis patients, in whom IL-6 levels are elevated. On the basis of published resequencing data on the IL6 gene, a phylogenetic tree with three main branches (clades 1 to 3) was constructed. Two "clade tag" polymorphisms, ؊174G/C and 1888G/T, and two missense variants, Pro32Ser and Asp162Val, were genotyped. Circulating IL-6 and albumin were measured a median of 5 mo after the start of dialysis. CVD events were ascertained from medical records. During a median follow-up of 2.5 yr, 294 CVD events occurred. The two coding variants, Pro32Ser (present only in black patients, 10% Ser allele) and Asp162Val (present only in white patients, 1% Val), were associated with lower levels of IL-6 and higher levels of albumin. The common variant in the promoter region, ؊174G/C, was strongly associated with higher CVD risk and weakly with IL-6 levels. Clade 3 (؊174C carriers in the absence of 162 Val allele) was associated with higher IL-6 levels (P ‫؍‬ 0.03) and higher CVD risk (hazard ratio 1.44, P ‫؍‬ 0.006) after adjustment for covariates. The IL6 gene has functional variants that affect inflammation and risk for CVD among dialysis patients, supporting a causal role for IL6 in CVD.

Background: The extent which universally common or population-specific alleles can explain betweenpopulation variations in phenotypes is unknown. The heritable coronary heart disease risk factor lipoprotein(a) (Lp(a)) level provides a useful case study of between-population variation, as the aetiology of twofold higher Lp(a) levels in African populations compared with non-African populations is unknown. Objective: To evaluate the association between LPA sequence variations and Lp(a) in European Americans and African Americans and to determine the extent to which LPA sequence variations can account for between-population variations in Lp(a). Methods: Serum Lp(a) and isoform measurements were examined in 534 European Americans and 249 African Americans from the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease Study. In addition, 12 LPA variants were genotyped, including 8 previously reported LPA variants with a frequency of .2% in European Americans or African Americans, and four new variants. Results: Isoform-adjusted Lp(a) level was 2.23-fold higher among African Americans. Three singlenucleotide polymorphisms (SNPs) were independently associated with Lp(a) level (p,0.02 in both populations). The Lp(a)-increasing SNP (G-21A, which increases promoter activity) was more common in African Americans, whereas the Lp(a)-lowering SNPs (T3888P and G+1/inKIV-8A, which inhibit Lp(a) assembly) were more common in European Americans, but all had a frequency of ,20% in one or both populations. Together, they reduced the isoform-adjusted African American Lp(a) increase from 2.23 to 1.37-fold(a 60% reduction) and the between-population Lp(a) variance from 5.5% to 0.5%. Conclusions: Multiple low-prevalence alleles in LPA can account for the large between-population difference in serum Lp(a) levels between European Americans and African Americans.

Karnal bunt of wheat, caused by Tilletia indica, was found in regions of the southwestern United States in 1996. Yield losses due to Karnal bunt are slight, and the greatest threat of Karnal bunt to the U.S. wheat industry is the loss of its export market. Many countries either prohibit or restrict wheat imports from countries with Karnal bunt. In 1997, teliospores morphologically resembling T. indica were isolated from bunted ryegrass seeds and wheat seed washes. Previously developed PCR assays failed to differentiate T. indica from the recently discovered ryegrass pathogen, T. walkeri. The nucleotide sequence of a 2.3 kb region of mitochondrial DNA, previously amplified by PCR only from T. indica, was determined for three isolates of T. indica and three isolates of T. walkeri. There was greater than 99% identity within either the T. indica group or the T. walkeri group of isolates, whereas there was =3% divergence between isolates of these two Tilletia species. Five sets of PCR primers were made specific to T. indica, and three sets were designed specifically for T. walkeri based upon nucleotide differences within the mitochondrial DNA region. In addition, a 212 bp amplicon was developed as a target sequence in a fluorogenic 5' nuclease PCR assay using the TaqMan system for the detection and discrimination of T. indica and T. walkeri.