Molecular and Clinical Characterization of the Variable Phenotype in Korean Families with Hearing Loss Associated with the Mitochondrial A1555G Mutation

Hearing loss, which is genetically heterogeneous, can be caused by mutations in the mitochondrial DNA (mtDNA). The A1555G mutation of the 12S ribosomal RNA (rRNA) gene in the mtDNA has been associated with both aminoglycoside-induced and non-syndromic hearing loss in many ethnic populations. Here, we report for the first time the clinical and genetic characterization of nine Korean pedigrees with aminoglycoside-induced and non-syndromic hearing loss. These Korean families carry in the A1555G mutation of 12S rRNA gene and exhibit variable penetrance and expressivity of hearing loss. Specifically, the penetrance of hearing loss in these families ranged between 28.6% and 75%, with an average of 60.8%. These results were higher than the 29.8% penetrance that was previously reported in a Chinese population but similar to the 65.4% and 54.1% penetrance observed in a large Arab-Israeli population and nineteen Spanish pedigrees, respectively. The mutational analysis of the complete mtDNA genome in these families showed that the haplogroups of the Korean population, which belongs to the eastern Asian population, were similar to those of the Chinese population but different from the Spanish population, which belongs to the European-Caucasian population. The mtDNA variants that may act as modifier factors were also found to be similar to the Chinese population. Although the mtDNA haplogroups and variants were similar to the eastern Asian population, we did find some differing phenotypes, although some subjects had the same variants. This result suggests that both the ethnic background and environmental factors lead to a variable phenotype of the A1555G mutation.     

A stochastic description of Dictyostelium chemotaxis

Chemotaxis, the directed motion of a cell toward a chemical source, plays a key role in many essential biological processes. Here, we derive a statistical model that quantitatively describes the chemotactic motion of eukaryotic cells in a chemical gradient. Our model is based on observations of the chemotactic motion of the social ameba Dictyostelium discoideum, a model organism for eukaryotic chemotaxis. A large number of cell trajectories in stationary, linear chemoattractant gradients is measured, using microfluidic tools in combination with automated cell tracking. We describe the directional motion as the interplay between deterministic and stochastic contributions based on a Langevin equation. The functional form of this equation is directly extracted from experimental data by angle-resolved conditional averages. It contains quadratic deterministic damping and multiplicative noise. In the presence of an external gradient, the deterministic part shows a clear angular dependence that takes the form of a force pointing in gradient direction. With increasing gradient steepness, this force passes through a maximum that coincides with maxima in both speed and directionality of the cells. The stochastic part, on the other hand, does not depend on the orientation of the directional cue and remains independent of the gradient magnitude. Numerical simulations of our probabilistic model yield quantitative agreement with the experimental distribution functions. Thus our model captures well the dynamics of chemotactic cells and can serve to quantify differences and similarities of different chemotactic eukaryotes. Finally, on the basis of our model, we can characterize the heterogeneity within a population of chemotactic cells.     

Development of multiplexed bead-based immunoassays for the detection of early stage ovarian cancer using a combination of serum biomarkers

CA125 as a biomarker of ovarian cancer is ineffective for the general population. The aim of this study was to evaluate multiplexed bead-based immunoassay of multiple ovarian cancer-associated biomarkers such as transthyretin and apolipoprotein A1, together with CA125, to improve the identification and evaluation of prognosis of ovarian cancer. We measured the serum levels of CA125, transthyretin, and apolipoprotein A1 from the serum of 61 healthy individuals, 84 patients with benign ovarian disease, and 118 patients with ovarian cancer using a multiplex liquid assay system, Luminex 100. The results were then analyzed according to healthy and/or benign versus ovarian cancer subjects. When CA125 was combined with the other biomarkers, the overall sensitivity and specificity were significantly improved in the ROC curve, which showed 95% and 97% sensitivity and specificity, respectively. At 95% specificity for all stages the sensitivity increased to 95.5% compared to 67% for CA125 alone. For stage I+II, the sensitivity increased from 30% for CA125 alone to 93.9%. For stage III+IV, the corresponding values were 96.5% and 91.6%, respectively. Also, the three biomarkers were sufficient for maximum separation between noncancer (healthy plus benign group) and stage I+II or all stages (I-IV) of disease. The new combination of transthyretin, and apolipoprotein A1 with CA125 improved both the sensitivity and the specificity of ovarian cancer diagnosis compared with those of individual biomarkers. These findings suggest the benefit of the combination of these markers for the diagnosis of ovarian cancer.     

Characteristics of bifunctional acidic endoglucanase (Cel5B) from Gloeophyllum trabeum

The endoglucanase (Cel5B) from the filamentous fungus Gloeophyllum trabeum was cloned and expressed without a signal peptide, and alanine residue 22 converted to glutamine in Pichia pastoris GS115. The DNA sequence of Cel5B had an open reading frame of 1,077 bp, encoding a protein of 359 amino acid residues with a molecular weight of 47 kDa. On the basis of sequence similarity, Cel5B displayed active site residues at Glu-175 and Glu-287. Both residues lost full hydrolytic activity when replaced with alanine through point mutation. The purified recombinant Cel5B showed very high specific activity, about 80- to 1,000-fold and 13- to 70-fold in comparison with other endoglucanases and cellobiohydrolase, on carboxymethylcellulose and filter paper, respectively, at pH 3.5 and 55°C. Cel5B displayed bifunctional characteristics under acidic conditions. The kinetic properties of the enzyme determined using a Lineweaver-Burk plot indicated that Cel5B is a catalytically efficient cellulolytic enzyme. These results suggest that Cel5B has high bifunctional endo- and exoglucanase activity under acidic conditions and is a good candidate for bioconversion of lignocellulose.     

Coproantigen capture ELISA for detection of Clonorchis sinensis infection in experimentally infected rats

The present study investigated the diagnostic value of an ELISA for the detection of Clonorchis sinensis antigen in the feces of experimentally infected rats. A mouse polyclonal IgG antibody against adult C. sinensis crude antigen (CsAg) was used to capture the C. sinensis coproantigen. The detection limit for pure CsAg was 20 ng/ml in sample buffer and 40 ng/ml in uninfected fecal extract. The test was evaluated using a follow-up of five groups of rats experimentally infected with 100, 50, 10, 5 and 1 metacercariae of C. sinensis and an uninfected control group. Coproantigen was detected in all infected groups of rats from 2 weeks of infection, whereas fecal eggs were not observed until 3 weeks of infection. As the infection period progressed, the fecal CsAg concentration increased in all groups of infected rats, even those infected with a single metacercaria. The fecal CsAg concentration was correlated positively with fecal egg counts and worm burden. This coproantigen capture ELISA is highly sensitive for the detection of CsAg in rat feces, and with further development, should be useful for mass screening of human subjects in clonorchiasis-endemic areas.     

<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> Cmr1 protein preferentially binds to UV-damaged DNA <Emphasis Type="Italic">in vitro</Emphasis>

DNA metabolic processes such as DNA replication, recombination, and repair are fundamentally important for the maintenance of genome integrity and cell viability. Although a large number of proteins involved in these pathways have been extensively studied, many proteins still remain to be identified. In this study, we isolated DNA-binding proteins from Saccharomyces cerevisiae using DNA-cellulose columns. By analyzing the proteins using mass spectrometry, an uncharacterized protein, Cmr1/YDL156W, was identified. Cmr1 showed sequence homology to human Damaged-DNA binding protein 2 in its C-terminal WD40 repeats. Consistent with this finding, the purified recombinant Cmr1 protein was found to be intrinsically associated with DNA-binding activity and exhibited higher affinity to UV-damaged DNA substrates. Chromatin isolation experiments revealed that Cmr1 localized in both the chromatin and supernatant fractions, and the level of Cmr1 in the chromatin fraction increased when yeast cells were irradiated with UV. These results suggest that Cmr1 may be involved in DNA-damage responses in yeast.     

Association between the CTLA-4 +49 A/G polymorphism and susceptibility to rheumatoid arthritis: a meta-analysis

The aim of this study was to explore whether the cytotoxic T lymphocyte antigen-4 (CTLA-4) +49 A/G polymorphism confers susceptibility to rheumatoid arthritis (RA). A meta-analysis was conducted on the associations between CTLA-4 +49 A/G polymorphism and RA using; 1) allele contrast, 2) the recessive model, 3) the dominant model, and 4) an additive model. A total of 19 studies, 5,752 RA patients and 5,508 controls, encompassing 9 Caucasian, 8 Asian, 1 Mexican, and 1 Tunisian population were included in this meta-analysis. Ethnicity-specific meta-analysis was performed on Caucasian and Asian populations. Meta-analysis of the CTLA-4 +49 A/G polymorphism revealed an association between RA and the CTLA-4 +49 G allele in all 11,260 study subjects (odds ratio (OR) 1.118, 95% confidence interval (CI) 1.033–1.210, P = 0.005). Stratification by ethnicity showed an association between the CTLA-4 +49 G allele and RA in Asians (OR 1.164, 95% CI 1.056–1.283, P = 0.002), but no evidence of an association in Caucasians (OR 1.085, 95% CI 0.973–1.209, P = 0.431). Furthermore, associations were found between RA and the CTLA-4 +49 A/G polymorphism in Asians using the dominant and additive models, but not using the recessive model. On the other hand, no association was found between RA and the CTLA-4 +49 A/G polymorphism using the recessive, dominant, or additive models in Caucasians. This meta-analysis demonstrates that the CTLA-4 +49 A/G polymorphism confers susceptibility to RA in Asians, but not in Caucasians.