Organelle segregation into Plasmodium liver stage merozoites

The liver stage of the Plasmodium parasite remains one of the most promising targets for intervention against malaria as it is clinically silent, precedes the symptomatic blood stage and represents a bottleneck in the parasite life cycle. However, many aspects of the development of the parasite during this stage are far from understood. During the liver stage, the parasite undergoes extensive replication, forming tens of thousands of infectious merozoites from each invading sporozoite. This implies a very efficient and accurate process of cytokinesis and thus also of organelle development and segregation. We have generated for the first time Plasmodium berghei double-fluorescent parasite lines, allowing visualization of the apicoplast, mitochondria and nuclei in live liver stage parasites. Using these we have seen that in parallel with nuclear division, the apicoplast and mitochondrion become two extensively branched and intertwining structures. The organelles then undergo impressive morphological and positional changes prior to cell division. To form merozoites, the parasite undergoes cytokinesis and the complex process of organelle development and segregation into the forming daughter merozoites could be analysed in detail using the newly generated transgenic parasites.     

ATAQS: A computational software tool for high throughput transition optimization and validation for selected reaction monitoring mass spectrometry

Background

Copy number variants (CNVs), including deletions, amplifications, and other rearrangements, are common in human and cancer genomes. Copy number data from array comparative genome hybridization (aCGH) and next-generation DNA sequencing is widely used to measure copy number variants. Comparison of copy number data from multiple individuals reveals recurrent variants. Typically, the interior of a recurrent CNV is examined for genes or other loci associated with a phenotype. However, in some cases, such as gene truncations and fusion genes, the target of variant lies at the boundary of the variant.

Results

We introduce Neighborhood Breakpoint Conservation (NBC), an algorithm for identifying rearrangement breakpoints that are highly conserved at the same locus in multiple individuals. NBC detects recurrent breakpoints at varying levels of resolution, including breakpoints whose location is exactly conserved and breakpoints whose location varies within a gene. NBC also identifies pairs of recurrent breakpoints such as those that result from fusion genes. We apply NBC to aCGH data from 36 primary prostate tumors and identify 12 novel rearrangements, one of which is the well-known TMPRSS2-ERG fusion gene. We also apply NBC to 227 glioblastoma tumors and predict 93 novel rearrangements which we further classify as gene truncations, germline structural variants, and fusion genes. A number of these variants involve the protein phosphatase PTPN12 suggesting that deregulation of PTPN12, via a variety of rearrangements, is common in glioblastoma.

Conclusions

We demonstrate that NBC is useful for detection of recurrent breakpoints resulting from copy number variants or other structural variants, and in particular identifies recurrent breakpoints that result in gene truncations or fusion genes. Software is available at http://http.//cs.brown.edu/people/braphael/software.html.     

Hostile takeover by Plasmodium: reorganization of parasite and host cell membranes during liver stage egress

The protozoan parasite Plasmodium is transmitted by female Anopheles mosquitoes and undergoes obligatory development within a parasitophorous vacuole in hepatocytes before it is released into the bloodstream. The transition to the blood stage was previously shown to involve the packaging of exoerythrocytic merozoites into membrane-surrounded vesicles, called merosomes, which are delivered directly into liver sinusoids. However, it was unclear whether the membrane of these merosomes was derived from the parasite membrane, the parasitophorous vacuole membrane or the host cell membrane. This knowledge is required to determine how phagocytes will be directed against merosomes. Here, we fluorescently label the candidate membranes and use live cell imaging to show that the merosome membrane derives from the host cell membrane. We also demonstrate that proteins in the host cell membrane are lost during merozoite liberation from the parasitophorous vacuole. Immediately after the breakdown of the parasitophorous vacuole membrane, the host cell mitochondria begin to degenerate and protein biosynthesis arrests. The intact host cell plasma membrane surrounding merosomes allows Plasmodium to mask itself from the host immune system and bypass the numerous Kupffer cells on its way into the bloodstream. This represents an effective strategy for evading host defenses before establishing a blood stage infection.     

Indicators for sustainable land use management in Santiago de Chile

Indicators are helpful tools for land use management; especially in the context of sustainable urban development, they are indispensable information bases for decision making, communication, and awareness rising. For Santiago de Chile, like many other large and dynamic cities, a high complexity of geographical conditions, social and land use pattern, diverging interests, and a high velocity of development are characteristic. In this situation, the Risk Habitat Megacity (RHM) initiative seeks to support local and regional authorities in elaborating indicators applicable in land use and flood risk management.In this article, the indicator approach of the Land Use Management group within the RHM initiative is presented. Based on the analysis of characteristics of and demands on sustainability indicators, existing indicator sets for Santiago de Chile are analysed. Thereafter, the indicator set for sustainable land use management in Santiago de Chile is presented. It was elaborated in a combined bottom–up and top–down approach in discussion with Chilean scientists and stakeholders in order to guarantee its relevancy to practice. The analysis of the already existing indicators in Santiago de Chile shows that the newly developed toolset forms a valuable and complementary addition, mainly for two reasons: the interdisciplinary nature of the set and its reproducibility.     

The function and phylogenetic implications of the tentorium in adult Neuroptera (Insecta)

Despite several recent analyses on the phylogeny of Neuroptera some questions still remain to be answered. In the present analysis we address these questions by exploring a hitherto unexplored character complex: the tentorium, the internal cuticular support structure of the insect head. We described in detail the tentoria of representatives of all extant neuropteran families and the muscles originating on the tentorium using 3D microCT images and analyzed differences in combination with a large published matrix based on larval characters. We find that the tentorium and associated musculature are a source of phylogenetically informative characters. The addition of the tentorial characters to the larval matrix causes a basad shift of the Sisyridae and clearly supports a clade of all Neuroptera except Sisyridae and Nevrorthidae. A sister group relationship of Coniopterygidae and the dilarid clade is further corroborated. A general trend toward a reduction of the dorsal tentorial arms and the development of laminatentoria is observed. In addition to the phylogenetic analysis, a correlation among the feeding habits, the development of the maxillary muscles, and the laminatentoria is demonstrated.