MLPA diagnostics of complex microbial communities: relative quantification of bacterial species in oral biofilms.

A multitude of molecular methods are currently used for identification and characterization of oral biofilms or for community profiling. However, multiplex PCR techniques that are able to routinely identify several species in a single assay are not available. Multiplex Ligation-dependent Probe Amplification (MLPA) identifies up to 45 unique fragments in a single tube PCR. Here we report a novel use of MLPA in the relative quantification of targeted microorganisms in a community of oral microbiota. We designed 9 species specific probes for: Actinomyces gerencseriae, Actinomyces naeslundii, Actinomyces odontolyticus, Candida albicans, Lactobacillus acidophilus, Rothia dentocariosa, Streptococcus mutans, Streptococcus sanguinis and Veillonella parvula; and genus specific probes for selected oral Streptococci and Lactobacilli based on their 16S rDNA sequences. MLPA analysis of DNA pooled from the strains showed the expected specific MLPA products. Relative quantification of a serial dilution of equimolar DNA showed that as little as 10 pg templates can be detected with clearly discernible signals. Moreover, a 2 to 7% divergence in relative signal ratio of amplified probes observed from normalized peak area values suggests MLPA can be a cheaper alternative to using qPCR for quantification. We observed 2 to 6 fold fluctuations in signal intensities of MLPA products in DNAs isolated from multispecies biofilms grown in various media for various culture times. Furthermore, MLPA analyses of DNA isolated from saliva obtained from different donors gave a varying number and intensity of signals. This clearly shows the usefulness of MLPA in a quantitative description of microbial shifts.

Inflammatory gene haplotype-interaction networks involved in coronary collateral formation.

OBJECTIVES: Formation of collateral circulation is an endogenous response to atherosclerosis, and is a natural escape mechanism by re-routing blood. Inflammatory response- related genes underlie the formation of coronary collaterals. We explored the genetic basis of collateral formation in man postulating interaction networks between functional Single Nucleotide Polymorphisms (SNPs) in these inflammatory gene candidates. METHODS: The contribution of 41 genes as well as the interactions among them was examined in a cohort of 226 coronary artery disease patients, genotyped for 54 candidate SNPs. Patients were classified to the extent of collateral circulation. Stepwise logistic regression analysis and a haplotype entropy procedure were applied to search for haplotype interactions among all 54 polymorphisms. Multiple testing was addressed by using the false discovery rate (FDR) method. RESULTS: The population comprised 84 patients with and 142 without visible collaterals. Among the 41 genes, 16 pairs of SNPs were implicated in the development of collaterals with the FDR of 0.19. Nine SNPs were found to potentially have main effects on collateral formation. Two sets of coupling haplotypes that predispose to collateral formation were suggested. CONCLUSIONS: These findings suggest that collateral formation may arise from the interactions between several SNPs in inflammatory response related genes, which may represent targets in future studies of collateral formation. This may enhance developing strategies for risk stratification and therapeutic stimulation of arteriogenesis.

Mutation screening of EXT1 and EXT2 by denaturing high-performance liquid chromatography, direct sequencing analysis, fluorescence in situ hybridization, and a new multiplex ligation-dependent probe amplification probe set in patients with multiple osteochondromas.

Multiple osteochondromas (MO) is an autosomal-dominant skeletal disorder characterized by the formation of multiple cartilage-capped protuberances. MO is genetically heterogeneous and is associated with mutations in the EXT1 and EXT2 genes. In this study we describe extensive mutation screening in a set of 63 patients with clinical and radiographical diagnosis of MO. Denaturing high-performance liquid chromatography analysis revealed mutations in 43 patients. Additional deletion analysis by fluorescence in situ hybridization and a newly developed multiplex ligation-dependent probe amplification probe set identified one patient with an intragenic EXT1 translocation, three patients with a partial EXT1 deletion, and one patient with a partial EXT2 deletion. Thirty-six patients harbored an EXT1 mutation (57%), and 12 had an EXT2 mutation (19%). We show that our optimized denaturing high-performance liquid chromatography/sequencing/multiplex ligation-dependent probe amplification protocol represents a reliable and highly sensitive diagnostic strategy for mutation screening in MO patients. Clinical analysis showed no clear genotype-phenotype correlation in our cohort of MO patients.

Plakophilin-2 mutations are the major determinant of familial arrhythmogenic right ventricular dysplasia/cardiomyopathy.

BACKGROUND: Mutations in the plakophilin-2 gene (PKP2) have been found in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC). Hence, genetic screening can potentially be a valuable tool in the diagnostic workup of patients with ARVC. METHODS AND RESULTS: To establish the prevalence and character of PKP2 mutations and to study potential differences in the associated phenotype, we evaluated 96 index patients, including 56 who fulfilled the published task force criteria. In addition, 114 family members from 34 of these 56 ARVC index patients were phenotyped. In 24 of these 56 ARVC patients (43%), 14 different (11 novel) PKP2 mutations were identified. Four different mutations were found more than once; haplotype analyses revealed identical haplotypes in the different mutation carriers, suggesting founder mutations. No specific genotype-phenotype correlations could be identified, except that negative T waves in V(2) and V(3) occurred more often in PKP2 mutation carriers (P<0.05). Of the 34 index patients whose family members were phenotyped, 23 familial cases were identified. PKP2 mutations were identified in 16 of these 23 ARVC index patients (70%) with familial ARVC. On the other hand, no PKP2 mutations at all were found in 11 probands without additional affected family members (P<0.001). CONCLUSIONS: PKP2 mutations can be identified in nearly half of the Dutch patients fulfilling the ARVC criteria. In familial ARVC, even the vast majority (70%) is caused by PKP2 mutations. However, nonfamilial ARVC is not related to PKP2. The high yield of mutational analysis in familial ARVC is unique in inherited cardiomyopathies.