Biology subjects

Jones, K.

Publications and source records attributed to Jones, K..

6 recordsLinked to original sources

bioRxiv2018

Giardia’s ventral disc is hyperstable and composed of over 80 disc-associated proteins

Giardia is a common protistan parasite that causes diarrheal disease worldwide. Motile trophozoites colonize the small intestine, attaching to the villi with the ventral disc, a unique and complex microtubule (MT) organelle. Attachment to the host epithelium allows Giardia to resist peristalsis during infection of the host gastrointestinal tract. Despite our emerging view of the complexity of ventral disc architecture, we are still in the very preliminary stages of understanding how specific structural elements contribute to disc stability or generate forces for attachment. The ventral disc is a large, dome-shaped, spiral MT array decorated with microribbon-crossbridge protein complexes (MR-CB) that extend upward into the cytoplasm. To find additional disc-associated proteins (DAPs), we used a modified method for disc biochemical fractionation in high salt followed by shotgun proteomic analyses and validation by GFP-tagging. Using this method in conjunction with an ongoing subcellular localization screen, we identified 54 new DAPs. Of the 87 DAPs confirmed to date, 54 localize only to the disc, and the remainder localize to additional structures including the flagella, basal bodies, or median body. Almost one third of the known DAPs lack any homology to proteins in other eukaryotes and another one third simply contain ankyrin repeat domains. Many DAPs localize to specific structural regions of the disc, including the ventral groove region and disc margin. Lastly, we show that spiral singlet MT array comprising the disc is hyperstable and lacks dynamic instability, and we attribute these unique properties to the presence of both novel DAPs as well conserved MAPs and MIPs that are known to stabilize ciliary doublet and triplet MTs.

microbiology↗

bioRxiv2018

Robust and stable transcriptional repression in Giardia using CRISPRi

Giardia lamblia is a binucleate protistan parasite causing significant diarrheal disease worldwide. An inability to target Cas9 to both nuclei, combined with the lack of non-homologous end joining and markers for positive selection, has stalled the adaptation of CRISPR/Cas9-mediated genetic tools for this widespread parasite. CRISPR interference (CRISPRi) is a modification of the CRISPR/Cas9 system that directs catalytically inactive Cas9 (dCas9) to target loci for stable transcriptional repression. Using a Giardia nuclear localization signal to target dCas9 to both nuclei, we developed efficient and stable CRISPRi-mediated transcriptional repression of exogenous and endogenous genes in Giardia. Specifically, CRISPRi knockdown of kinesin-2a and kinesin-13 causes severe flagellar length defects that mirror defects with morpholino knockdown. Knockdown of the ventral disc MBP protein also causes severe structural defects that are highly prevalent and persist in the population more than five days longer than transient morpholino-based knockdown. By expressing two gRNAs in tandem to simultaneously knock down kinesin-13 and MBP, we created a stable dual knockdown strain with both flagellar length and disc defects. The efficiency and simplicity of CRISPRi in polyploid Giardia allows for rapid evaluation of knockdown phenotypes and highlights the utility of CRISPRi for emerging model systems.

microbiology↗

bioRxiv2018

Repeat-driven generation of antigenic diversity in a major human pathogen, Trypanosoma cruzi

Trypanosoma cruzi, a zoonotic kinetoplastid protozoan with a complex genome, is the causative agent of American trypanosomiasis (Chagas disease). The parasite uses a highly diverse repertoire of surface molecules, with roles in cell invasion, immune evasion and pathogenesis. Thus far, the genomic regions containing these genes have been impossible to resolve and it has been impossible to study the structure and function of the several thousand repetitive genes encoding the surface molecules of the parasite. We here present an improved genome assembly of a T. cruzi clade I (TcI) strain using high coverage PacBio single molecule sequencing, together with Illumina sequencing of 34 T. cruzi TcI isolates and clones from different geographic locations, sample sources and clinical outcomes. Resolution of the surface molecule gene structure reveals an unusual duality in the organisation of the parasite genome, a core genomic region syntenous with related protozoa flanked by unique and highly plastic subtelomeric regions encoding surface antigens. The presence of abundant interspersed retrotransposons in the subtelomeres suggests that these elements are involved in a recombination mechanism for the generation of antigenic variation and evasion of the host immune response. The comparative genomic analysis of the cohort of TcI strains revealed multiple cases of such recombination events involving surface molecule genes and has provided new insights into T. cruzi population structure.

genomics↗

bioRxiv2017

Impact of global change on future Ebola emergence and epidemic potential in Africa

Animal-borne or zoonotic human diseases (e.g., SARS, Rabies) represent major health and economic burdens throughout the world, disproportionately impacting poor communities. In 2013-2016, an outbreak of the Ebola virus disease (EVD), a zoonotic disease spread from animal reservoirs caused by the Zaire Ebola virus (EBOV), infected approximately 30,000 people, causing considerable negative social and economic impacts in an unexpected geographical location(Sierra Leone, Guinea, and Liberia). It is not known whether the spatial distribution of this outbreak and unprecedented severity was precipitated by environmental changes and, if so, which areas might be at risk in the future. To better address the major health and economic impacts of zoonotic diseases we develop a system-dynamics approach to capture the impact of future climate, land use and human population change on Ebola (EVD). We create future risk maps for affected areas and predict between a 1.75-3.2 fold increase in EVD outbreaks per year by 2070. While the best case future scenarios we test saw a reduction in the likelihood of epidemics, other future scenarios with high human population growth and low rates of socioeconomic development saw a fourfold increase in the risk of epidemics occurring and almost 50% increase in the risk of catastrophic epidemics. As well as helping to target where health infrastructure might be further developed or vaccines best deployed, our modelling framework can be used to target global interventions and forecast risk for many other zoonotic diseases.\n\nSignificance StatementDespite the severe health and economic impacts of outbreaks of diseases like SARS or Zika, there has been surprisingly little progress in predicting where and when human infectious disease outbreaks will occur next. By modelling the impacts of future climate, land use and human population change on one particular disease Ebola, we develop future risk maps for the affected areas and predict 1.7-3.2 times as many human Ebola outbreaks per year by 2070, and a 50% increase in the chance that these outbreaks will become epidemics. As well as helping to target where health infrastructure might be further developed or vaccines deployed, our approach can also be used to target actions and predict risk hotspots for many other infectious diseases.

epidemiology↗

bioRxiv2017

Disruption of the interfacial membrane leads to Magnaporthe oryzae effector re-location and lifestyle switch during rice blast disease

The hemibiotrophic fungus Magnaporthe oryzae produces invasive hyphae enclosed in a plant-derived interfacial membrane, known as the extra-invasive hyphal membrane (EIHM), in living rice cells. Little is known about when the EIHM is disrupted and how the disruption contributes to blast disease. Here we show that EIHM disruption correlates with the hyphal growth stage in first-invaded susceptible rice cells. Our approach utilized GFP secreted from invasive hyphae as an EIHM integrity reporter. Secreted-GFP accumulated in the EIHM compartment but appeared in the rice cytoplasm when the EIHM integrity was compromised. Live-cell imaging of secreted-GFP and various fluorescent reporters revealed that EIHM disruption led to rice vacuole rupture and cell death limited to the invaded cell with closed plasmodesmata. We report that EIHM disruption and host cell death are landmarks delineating three distinct infection phases (early biotrophic, late biotrophic, and transient necrotrophic phases) within the first-invaded cell before reestablishment of biotrophy in second-invaded cells. M. oryzae effectors exhibited phase-specific localizations, including entry of the apoplastic effector Bas4 into the rice cytoplasm during the late biotrophic phase. Understanding how the phase-specific dynamics are regulated and linked to host susceptibility will offer potential targets that can be exploited to control blast disease.

cell biology↗

bioRxiv2017

Temporal Niche Expansion In Mammals From A Nocturnal Ancestor After Dinosaur Extinction

Most modern mammals, including strictly diurnal species, exhibit sensory adaptations to nocturnal activity, thought to be the result of a prolonged nocturnal phase or bottleneck during early mammalian evolution. Nocturnality may have allowed mammals to avoid antagonistic interactions with diurnal dinosaurs during the Mesozoic. However, understanding the evolution of mammalian activity patterns is hindered by scant and ambiguous fossil evidence. While ancestral reconstructions of behavioural traits from extant species have the potential to elucidate these patterns, existing studies have been limited in taxonomic scope. Here, we use an extensive behavioural dataset for 2415 species from all extant orders to reconstruct ancestral activity patterns across Mammalia. We find strong support for the nocturnal origin of mammals and the Cenozoic appearance of diurnality, although cathemerality (mixed diel periodicity) may have appeared in the late Cretaceous. Simian primates are among the earliest mammals to exhibit strict diurnal activity, some 52-33Mya. Our study is consistent with the hypothesis that temporal partitioning between early mammals and dinosaurs during the Mesozoic led to a mammalian nocturnal bottleneck, but also demonstrates the need for improved phylogenetic estimates for Mammalia.

evolutionary biology↗