An integrated morphological and molecular approach to a new species description in the Trypanosomatidae: the case of Leptomonas podlipaevi n. sp., a parasite of Boisea rubrolineata (Hemiptera: Rhopalidae)

Leptomonas podlipaevi n. sp., a new trypanosomatid species, is described herein based on light microscopic, ultrastructural, and molecular phylogenetic data. The organism is pleomorphic both in host and culture, with two predominant forms-a typical promastigote with a long flagellum and a shorter promastigote with a small or barely extending flagellum. Several spliced leader RNA repeat sequences obtained from the original cultures and the clonal lines representing two types of cells were all nearly identical. These sequences formed a tight cluster in the neighbor-joining tree well separated from other trypanosomatid species. Glyceraldehyde phosphate dehydrogenase gene sequences were determined for L. podlipaevi and 10 previously described trypanosomatid species. Molecular phylogenetic analysis has demonstrated that the new species is most closely related to Leptomonas seymouri and Leptomonas pyrrhocoris. The analysis has also highlighted the polyphyly of the genus Leptomonas.     

Triglyceride, nonesterified fatty acids, and prediabetic neuropathy: role for oxidative-nitrosative stress

Peripheral neuropathy develops in human subjects with prediabetes and metabolic syndrome before overt hyperglycemia. The contributions of impaired glucose tolerance and insulin signaling, hypertriglyceridemia and/or increased nonesterified fatty acids (NEFA), and hypercholesterolemia to this condition remain unknown. Niacin and its derivatives alleviate dyslipidemia with a minor effect on glucose homeostasis. This study evaluated the roles of impaired glucose tolerance versus dyslipidemia in prediabetic neuropathy using Zucker fatty (fa/fa) rats and the niacin derivative acipimox, as well as the interplay of hypertriglyceridemia, increased NEFA, and oxidative-nitrosative stress. Sixteen-week-old Zucker fatty rats with impaired glucose tolerance, obesity, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, and increased NEFA displayed sensory nerve conduction velocity deficit, thermal and mechanical hypoalgesia, and tactile allodynia. Acipimox (100 mg kg(-1) day(-1), 4 weeks) reduced serum insulin, NEFA, and triglyceride concentrations without affecting glucose tolerance and hypercholesterolemia. It alleviated sensory nerve conduction velocity deficit and changes in behavioral measures of sensory function and corrected oxidative-nitrosative stress, but not impaired insulin signaling, in peripheral nerve. Elevated NEFA increased total and mitochondrial superoxide production and NAD(P)H oxidase activity in cultured human Schwann cells. In conclusion, hypertriglyceridemia and/or increased NEFA concentrations cause prediabetic neuropathy through oxidative-nitrosative stress. Lipid-lowering agents and antioxidants may find a use in the management of this condition.     

Architecture of the trypanosome RNA editing accessory complex, MRB1

Trypanosoma brucei undergoes an essential process of mitochondrial uridine insertion and deletion RNA editing catalyzed by a 20S editosome. The multiprotein mitochondrial RNA-binding complex 1 (MRB1) is emerging as an equally essential component of the trypanosome RNA editing machinery, with additional functions in gRNA and mRNA stabilization. The distinct and overlapping protein compositions of reported MRB1 complexes and diverse MRB1 functions suggest that the complex is composed of subcomplexes with RNA-dependent and independent interactions. To determine the architecture of the MRB1 complex, we performed a comprehensive yeast two-hybrid analysis of 31 reported MRB1 proteins. We also used in vivo analyses of tagged MRB1 components to confirm direct and RNA-mediated interactions. Here, we show that MRB1 contains a core complex comprised of six proteins and maintained by numerous direct interactions. The MRB1 core associates with multiple subcomplexes and proteins through RNA-enhanced or RNA-dependent interactions. These findings provide a framework for interpretation of previous functional studies and suggest that MRB1 is a dynamic complex that coordinates various aspects of mitochondrial gene regulation.     

Specific binding of a β-cyclodextrin dimer to the amyloid β peptide modulates the peptide aggregation process

Alzheimer's disease involves progressive neuronal loss. Linked to the disease is the amyloid β (Aβ) peptide, a 38-43-amino acid peptide found in extracellular amyloid plaques in the brain. Cyclodextrins are nontoxic, cone-shaped oligosaccharides with a hydrophilic exterior and a hydrophobic cavity making them suitable hosts for aromatic guest molecules in water. β-Cyclodextrin consists of seven α-d-glucopyranoside units and has been shown to reduce the level of fibrillation and neurotoxicity of Aβ. We have studied the interaction between Aβ and a β-cyclodextrin dimer, consisting of two β-cyclodextrin monomers connected by a flexible linker. The β-cyclodextrin monomer has been found to interact with Aβ(1-40) at sites Y10, F19, and/or F20 with a dissociation constant (K(D)) of 3.9 ± 2.0 mM. Here (1)H-(15)N and (1)H-(13)C heteronuclear single-quantum correlation nuclear magnetic resonance (NMR) spectra show that in addition, the β-cyclodextrin monomer and dimer bind to the histidines. NMR translational diffusion experiments reveal the increased affinity of the β-cyclodextrin dimer (apparent K(D) of 1.1 ± 0.5 mM) for Aβ(1-40) compared to that of the β-cyclodextrin monomer. Kinetic aggregation experiments based on thioflavin T fluorescence indicate that the dimer at 0.05-5 mM decreases the lag time of Aβ aggregation, while a concentration of 10 mM increases the lag time. The β-cyclodextrin monomer at a high concentration decreases the lag time of the aggregation. We conclude that cyclodextrin monomers and dimers have specific, modulating effects on the Aβ(1-40) aggregation process. Transmission electron microscopy shows that the regular fibrillar aggregates formed by Aβ(1-40) alone are replaced by a major fraction of amorphous aggregates in the presence of the β-cyclodextrin dimer.     

Impact of subunit and oligomeric structure on the thermal and conformational stability of chlorite dismutases

Chlorite dismutases (Cld) are unique heme b containing oxidoreductases that convert chlorite to chloride and dioxygen. Recent phylogenetic and structural analyses demonstrated that these metalloproteins significantly differ in oligomeric and subunit structure. Here we have analyzed two representatives of two phylogenetically separated lineages, namely pentameric Cld from Candidatus "Nitrospira defluvii" and dimeric Cld from Nitrobacter winogradskyi having a similar enzymatic activity at room temperature. By application of a broad set of techniques including differential scanning calorimetry, electronic circular dichroism, UV-vis and fluorescence spectroscopy the temperature-mediated and chemical unfolding of both recombinant proteins were analyzed. Significant differences in thermal and conformational stability are reported. The pentameric enzyme is very stable between pH 3 and 10 (T(m)=92°C at pH 7.0) and active at high temperatures thus being an interesting candidate for bioremediation of chlorite. By contrast the dimeric protein starts to unfold already at 53°C. The observed unfolding pathways are discussed with respect to the known subunit structure and subunit interaction.     

Lack of evidence for integration of Trypanosoma cruzi minicircle DNA in South American human genomes

Horizontal gene transfer involving kinetoplast DNA minicircles between Trypanosoma cruzi and its mammalian hosts has recently been proposed as a usual consequence of infection (Hecht et al., 2010). However, we have found no sequences longer than 29 bp perfectly matching minicircles of T. cruzi in the unassembled reads from Colombian and Peruvian human populations provided by the 1,000 Genome project (129 individuals in total, coverage from 1.4× to 36.3×, read length from 42 to 101 bp). The weak sequence matches that were identified are shared with a Finnish population used as a control from a non-endemic area.     

Genome wide QTL mapping to identify candidate genes for carcass traits in Hanwoo (Korean Cattle)

Meat quality traits are the most economically important traits affecting the beef industry in Korea. We performed a whole genome quantitative trait locus (QTL) mapping study of carcass data in Hanwoo Korean cattle. Two hundred sixty-six Hanwoo steers from 65 sires were genotyped using a 10K Affymetrix SNP chip. The average SNP interval across the bovine genome was 1.5Mb. Associations between each individual SNP and four carcass traits [carcass weight (CWT), eye muscle area (EMA), back fat thickness (BFT), and marbling (MAR)] were assessed using a linear mixed model of each trait. Combined linkage and linkage disequilibrium analysis (LDLA) detected six potential QTL on BTA04, 06, 13, 16, 17, and 23 at the chromosome-wise level (P<0.05). Two MAR QTL were detected at 52.2 cM of BTA06 and 46.04 cM of BTA17. We identified three genes (ARAP2, LOC539460, and LOC511424) in the QTL region of BTA06 and seven genes (RPS14, SCARB1, LOC782103, BRI3BP, AACS, DHX37, and UBC) in the QTL region of BTA17. One significant QTL for CWT was detected at 100 cM on BTA04 and the corresponding QTL region spanned 1.7 cM from 99.7 to 101.4 cM. For EMA QTL, one significant QTL was detected at 3.9 cM of BTA23 and the most likely QTL interval was 1.4 cM, placing 15 candidate genes in the marker bracket. Finally, two QTL for BFT were identified at 68 cM on BTA13 and 24 cM on BTA16. The LPIN3 gene, which is functionally associated with lipodystrophy in humans, is located in the BFT QTL on BTA13. Thus, two potential candidate genes, acetoacetyl-CoA synthetase (AACS) and lipin (LPIN), were detected in QTL regions on BTA17 for MAR and BTA13 for BFT, respectively. In conclusion, LDLA analysis can be used to detect chromosome regions harboring QTL and candidate genes with a low density SNP panel, yielding relatively narrow confidence intervals regarding location.