A mild mutator phenotype arises in a mouse model for malignancies associated with neurofibromatosis type 1

Defects in genes that control DNA repair, proliferation, and apoptosis can increase genomic instability, and thus promote malignant progression. Although most tumors that arise in humans with neurofibromatosis type 1 (NF1) are benign, these individuals are at increased risk for malignant peripheral nerve sheath tumors (MPNST). To characterize additional mutations required for the development of MPNST from benign plexiform neurofibromas, we generated a mouse model for these tumors by combining targeted null mutations in Nf1 and p53, in cis. CisNf1+/-; p53+/- mice spontaneously develop PNST, and these tumors exhibit loss-of-heterozygosity at both the Nf1 and p53 loci. Because p53 has well-characterized roles in the DNA damage response, DNA repair, and apoptosis, and because DNA repair genes have been proposed to act as modifiers in NF1, we used the cisNf1+/-; p53+/- mice to determine whether a mutator phenotype arises in NF1-associated malignancies. To quantitate spontaneous mutant frequencies (MF), we crossed the Big Blue mouse, which harbors a lacI transgene, to the cisNf1+/-; p53+/- mice, and isolated genomic DNA from both tumor and normal tissues in compound heterozygotes and wild-type siblings. Many of the PNST exhibited increased mutant frequencies (MF=4.70) when compared to normal peripheral nerve and brain (MF=2.09); mutations occurred throughout the entire lacI gene, and included base substitutions, insertions, and deletions. Moreover, the brains, spleens, and livers of these cisNf1+/-; p53+/- animals exhibited increased mutant frequencies when compared to tissues from wild-type littermates. We conclude that a mild mutator phenotype arises in the tumors and tissues of cisNf1+/-; p53+/- mice, and propose that genomic instability influences NF1 tumor progression and disease severity.     

Neuroendocrine immunity in patients with Alzheimer's disease: toward translational epigenetics

The emerging domain of epigenetics in molecular medicine finds application for a variety of patient populations. Here, we present fundamental neuroendocrine immune evidence obtained in patients with senile dementia of the Alzheimer's type (sDAT), and discuss the implications of these data from the viewpoint of translational epigenetics of Alzheimer's disease. We followed 18 subjects with mild sDAT treated with acetylcholinesterase inhibitors, and 10 control subjects matched for age in a repeated measure design every six months for 18 months. We monitored psychosocial profile (Mini-Mental State Examination, Functional Assessment Staging, Independence in Activities of Daily Living, Depression, Profile of Moods States) in parallel to immunophenotypic parameters of T cell subpopulations by flow cytometry. Based on change in the mini-mental state score at entry and at 18 months, patients with sDAT were assigned to a "fast progression" (delta greater than 2 points) or to a "slow progression" group (delta less than or equal to 2 points). The change in circulating activated T cells (CD3+Dr+) with time in patients with sDAT was significantly inversely correlated with the change in time in natural killer (NK) cytotoxic activity to cortisol modulation in these patients, which was greater in patients with fast progression, compared to slow progression sDAT. These data indicate underlying neuroendocrine immune processes during progression of sDAT. Our observations suggest that psychoimmune measures such as those we have monitored in this study provide relevant information about the evolving physiological modulation in patients with sDAT during progression of Alzheimer's disease, and point to new or improved translational epigenetic treatment interventions.     

Novel nickel transport mechanism across the bacterial outer membrane energized by the TonB/ExbB/ExbD machinery

Nickel is a cofactor for various microbial enzymes, yet as a trace element, its scavenging is challenging. In the case of the pathogen Helicobacter pylori, nickel is essential for the survival in the human stomach, because it is the cofactor of the important virulence factor urease. While nickel transport across the cytoplasmic membrane is accomplished by the nickel permease NixA, the mechanism by which nickel traverses the outer membrane (OM) of this Gram-negative bacterium is unknown. Import of iron-siderophores and cobalamin through the bacterial OM is carried out by specific receptors energized by the TonB/ExbB/ExbD machinery. In this study, we show for the first time that H. pylori utilizes TonB/ExbB/ExbD for nickel uptake in addition to iron acquisition. We have identified the nickel-regulated protein FrpB4, homologous to TonB-dependent proteins, as an OM receptor involved in nickel uptake. We demonstrate that ExbB/ExbD/TonB and FrpB4 deficient bacteria are unable to efficiently scavenge nickel at low pH. This condition mimics those encountered by H. pylori during stomach colonization, under which nickel supply and full urease activity are essential to combat acidity. We anticipate that this nickel scavenging system is not restricted to H. pylori, but will be represented more largely among Gram-negative bacteria.     

Trans-Atlantic genetic uniformity in the rare snowbed sedge <Emphasis Type="Italic">Carex rufina</Emphasis>

The red-listed, amphi-Atlantic sedge Carex rufina is highly specialized to certain alpine snowbeds, and threatened by current changes in snow cover duration and moisture conditions. Here we address its range-wide genetic diversity, history, and conservation using amplified fragment length polymorphisms (AFLPs). Despite extensive primer testing, we detected very low overall diversity (4.1% polymorphic markers). Only a single AFLP phenotype was found throughout Norway and across the Atlantic to Iceland and Greenland, while another was found in Canada, suggesting glacial survival in one East and one West Atlantic refugium. East Atlantic C. rufina has probably been heavily bottlenecked in a small refugium, possibly situated within the maximum limits of the ice sheets. Its lack of diversity is likely maintained through local clonal growth causing longevity of genotypes. Habitat availability appears as the main limiting factor for C. rufina, and its currently occupied habitats need to be preserved to ensure its long-time survival.     

Molecular diet analysis of two african free-tailed bats (molossidae) using high throughput sequencing

Given the diversity of prey consumed by insectivorous bats, it is difficult to discern the composition of their diet using morphological or conventional PCR-based analyses of their faeces. We demonstrate the use of a powerful alternate tool, the use of the Roche FLX sequencing platform to deep-sequence uniquely 5' tagged insect-generic barcode cytochrome c oxidase I (COI) fragments, that were PCR amplified from faecal pellets of two free-tailed bat species Chaerephon pumilus and Mops condylurus (family: Molossidae). Although the analyses were challenged by the paucity of southern African insect COI sequences in the GenBank and BOLD databases, similarity to existing collections allowed the preliminary identification of 25 prey families from six orders of insects within the diet of C. pumilus, and 24 families from seven orders within the diet of M. condylurus. Insects identified to families within the orders Lepidoptera and Diptera were widely present among the faecal samples analysed. The two families that were observed most frequently were Noctuidae and Nymphalidae (Lepidoptera). Species-level analysis of the data was accomplished using novel bioinformatics techniques for the identification of molecular operational taxonomic units (MOTU). Based on these analyses, our data provide little evidence of resource partitioning between sympatric M. condylurus and C. pumilus in the Simunye region of Swaziland at the time of year when the samples were collected, although as more complete databases against which to compare the sequences are generated this may have to be re-evaluated.