Three single-nucleotide polymorphisms in LPA account for most of the increase in lipoprotein(a) level elevation in African Americans compared with European Americans.

BACKGROUND: The extent which universally common or population-specific alleles can explain between-population 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 single-nucleotide 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.

Identification and Differentiation of Tilletia indica and T. walkeri Using the Polymerase Chain Reaction.

ABSTRACT 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.

Detection of Clavibacter michiganensis subsp. sepedonicus in Potato Tubers by BIO-PCR and an Automated Real-Time Fluorescence Detection System.

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.