Prion infection promotes extensive accumulation of α-synuclein in aged human α-synuclein transgenic mice

In neurodegenerative disorders of the aging population, misfolded proteins, such as PrP^Sc, α-synuclein, amyloid β protein and tau, can interact resulting in enhanced aggregation, cross seeding and accelerated disease progression. Previous reports have shown that in Creutzfeldt-Jakob disease and scrapie, α-synuclein accumulates near PrP^Sc deposits. However, it is unclear if pre-existing human α-synuclein aggregates modified prion disease pathogenesis, or if PrP^Sc exacerbates the α-synuclein pathology. Here, we inoculated infectious prions into aged α-synuclein transgenic (tg) and non-transgenic littermate control mice by the intracerebral route. Remarkably, inoculation of RML and mNS prions into α-synuclein tg mice resulted in more extensive and abundant intraneuronal and synaptic α-synuclein accumulation. In addition, infectious prions led to the formation of perineuronal α-synuclein deposits with a neuritic plaque-like appearance. Prion pathology was unmodified by the presence of α-synuclein. However, with the mNS prion strain there was a modest but significant acceleration in the time to terminal prion disease in mice having α-synuclein aggregates as compared with non-tg mice. Taken together, these studies support the notion that PrP^Sc directly or indirectly promotes α-synuclein pathology.     

Fish pheromones and related cues (Eds. Sorensen and Wisenden)

Environmental Biology of Fishes -     

Interaction of quantitative trait loci for resistance to common bacterial blight and pathogen isolates in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.

Common bacterial blight (CBB) is a major disease of common bean (Phaseolus vulgaris L.) worldwide. Genetic resistance is the most effective and environmentally safe approach for controlling CBB, and identification of resistance quantitative trait loci (QTL) can improve response to selection when breeding for CBB resistance. Interactions of CBB resistance QTL and pathogen isolates with different levels of aggressiveness were studied using an F _4:5 recombinant inbreed line (RIL) population, derived from a cross between the susceptible cultivar “Sanilac” and the resistant breeding line “OAC 09-3.” Disease phenotyping was performed under field and growth room conditions using multiple bacterial isolates with differential levels of aggressiveness. QTL analysis was performed with 237 molecular markers. The effect of pathogen isolate on the average phenotypic value in the RIL population and the interaction of RILs and the pathogen isolates were highly significant. Two QTL underlying CBB resistance were detected on Pv08 and Pv03. A major QTL (R ² _p between 15 and 56%) was identified in a 5-cM (380 kbp) interval in the distal end of the long arm of Pv08. This genomic region was significantly associated with multiple disease evaluation traits in field and growth room assays and against different isolates of the pathogen, which included the previously known CBB marker SU91. A new QTL on Pv03 (Xa3.3^SO), associated with the PvSNP85p745405 allele from the susceptible parent, Sanilac, appeared to be an isolate-specific QTL against the aggressive fuscans isolate ISO118. Interaction between the SU91 and Xa3.3^SO QTL resulted in a significant reduction in mean disease severity for almost all disease evaluation traits after plants were challenged with the isolate ISO118. The 7.92 and 7.79% diseased areas in RILs with both QTL, compared with 14.92 and 13.81% in RILs without either in test1 and in test2 quantified by image analysis, showed a 44 and 47% reduction of percent diseased areas, indicating that the two QTL interact to limit the expansion of CBB symptoms after infection by ISO118. The information obtained in this study indicates that while the broad-spectrum SU91 QTL is useful in breeding programs, isolate-specific QTL, such as Xa3.3^SO, will aid in breeding bean varieties with enhanced resistance against aggressive regional isolates.     

Inhibition of osteoclast function by adenovirus expressing antisense protein-tyrosine kinase 2

Osteoclast activation is initiated by adhesion to bone, cytoskeletal rearrangement, formation of the sealing zone, and formation of the polarized ruffled membrane. Previous findings suggest that protein-tyrosine kinase 2 (PYK2), a cytoplasmic kinase related to focal adhesion kinase, participates in these events. This study examines the role of PYK2 in adhesion-mediated signaling and osteoclast function, using PYK2 antisense. We produced a recombinant adenovirus containing a 300-base pair reversed 5'-coding region of PYK2 and used full-length PYK2 as a control. Murine osteoclast-like cells or their mononuclear precursors were generated in a co-culture of bone marrow and osteoblasts. Infection with antisense adenovirus significantly reduced the expression of endogenous PYK2 protein relative to uninfected cells or to cells infected with sense PYK2 and caused: 1) a reduction in osteoclast formation in vitro; 2) inhibition of cell spreading and of actin ring formation in osteoclasts plated on glass or bone and of attachment and spreading of osteoclast precursors plated on vitronectin; 3) inhibition of bone resorption in vitro; 4) marked reduction in p130(Cas) tyrosine phosphorylation; and 5) no change in alpha(v)beta(3) integrin expression or c-Src tyrosine phosphorylation. Taken together, these findings support the hypothesis that PYK2 plays a central role in the adhesion-dependent cytoskeletal organization and sealing zone formation required for osteoclastic bone resorption.     

PYK2 autophosphorylation,but not kinase activity,is necessary for adhesion-induced association with c-Src,osteoclast spreading,and bone resorption

Proline-rich tyrosine kinase 2 (PYK2) is the main adhesion-induced kinase in bone-resorbing osteoclasts. Previous studies have shown that ligation of alpha(v)beta(3) integrin in osteoclasts induces c-Src-dependent tyrosine phosphorylation and PYK2 activation, leading to cytoskeletal rearrangement, migration, and polarization of these cells. In this study, we examined the role of PYK2 kinase activity and its major autophosphorylation site in adhesion-dependent signaling and cytoskeletal organization during osteoclast spreading and migration. By infecting pre-fusion osteoclasts using recombinant adenovirus expressing PYK2 and its mutants, we demonstrated that mutation at the autophosphorylation site (Y402F) abolishes PYK2 association with c-Src and reduces significantly phosphorylation at tyrosines 579/580 and 881 resulting in inhibition of osteoclast spreading and bone resorption. Overexpression of the kinase-dead PYK2(K475A) mutant had no effect on cell spreading, interaction with c-Src, or the phosphorylation level of Tyr-402, Tyr-579/580, and Tyr-881 relative to PYK2(wt)-expressing cells. Taken together these findings suggest that Tyr-402 is the major docking site for c-Src and can be phosphorylated by another tyrosine kinase in osteoclasts but not in HEK293 cells. Interestingly, both PYK2(Y402F) and PYK2(K457A) translocate normally to podosomes and have no effect on macrophage colony-stimulating factor-induced osteoclast migration. Whereas PYK2(Y402F) dominant negatively blocks osteoclast spreading and bone resorption, PYK2(K457A) may function in part as an adaptor by initially recruiting c-Src to the adhesion complex, which appears to activate PYK2 by phosphorylating additional tyrosines in its regulatory and C-terminal domains. We thus concluded that phosphorylation at Tyr-402 in PYK2 is essential in the regulation of adhesion-dependent cytoskeletal organization in osteoclasts.     

A mechanism for modulation of cellular responses to VEGF: activation of the integrins

Many similarities exist in the cellular responses elicited by VEGF and governed by integrins. Here, we identify a basis for these interrelationships: VEGF activates integrins. VEGF enhanced cell adhesion, migration, soluble ligand binding, and adenovirus gene transfer mediated by alphavbeta3 and also activated other integrins, alphavbeta5, alpha5beta1, and alpha2beta1, involved in angiogenesis. Certain tumor cells exhibited high spontaneous adhesion and migration, which were attributable to a VEGF-dependent autocrine/paracrine activation of integrins. This activation was mediated by the VEGFR2 receptor and regulated via phosphatidylinositol-3-kinase, Akt, and the PTEN signaling axis. Thus, integrin activation provides a mechanism for VEGF to induce a broad spectrum of cellular responses.     

Estimating the Basic Reproductive Number (R0) for African Swine Fever Virus (ASFV) Transmission between Pig Herds in Uganda

African swine fever (ASF) is a highly contagious, lethal and economically devastating haemorrhagic disease of domestic pigs. Insights into the dynamics and scale of virus transmission can be obtained from estimates of the basic reproduction number (R₀). We estimate R₀ for ASF virus in small holder, free-range pig production system in Gulu, Uganda. The estimation was based on data collected from outbreaks that affected 43 villages (out of the 289 villages with an overall pig population of 26,570) between April 2010 and November 2011. A total of 211 outbreaks met the criteria for inclusion in the study. Three methods were used, specifically; (i) GIS- based identification of the nearest infectious neighbour based on the Euclidean distance between outbreaks, (ii) epidemic doubling time, and (iii) a compartmental susceptible-infectious (SI) model. For implementation of the SI model, three approaches were used namely; curve fitting (CF), a linear regression model (LRM) and the SI/N proportion. The R₀ estimates from the nearest infectious neighbour and epidemic doubling time methods were 3.24 and 1.63 respectively. Estimates from the SI-based method were 1.58 for the CF approach, 1.90 for the LRM, and 1.77 for the SI/N proportion. Since all these values were above one, they predict the observed persistence of the virus in the population. We hypothesize that the observed variation in the estimates is a consequence of the data used. Higher resolution and temporally better defined data would likely reduce this variation. This is the first estimate of R₀ for ASFV in a free range smallholder pig keeping system in sub-Saharan Africa and highlights the requirement for more efficient application of available disease control measures.     

A Quantitative Photographic Survey of ‘Spoke-Burrow’ Type Lebensspuren on the Cape Verde Abyssal Plain

A photographic survey of the seafloor was conducted during RRS Discovery cruise 204 in September/October 1993 at the oligotrophic site of the French EUMELI programme at c. 21° N: 31° W (4650 m) on the Cape Verde Abyssal Plain. Two systems were used, a wide angle system (WASP) obtaining usable photographs covering 10 to 30m², and an epibenthic sledge mounted system obtaining photographs of about 2 m². A total of more than 3000 usable frames were obtained, covering about 64000 m² of seafloor. The photographs indicated an epibenthic invertebrate megafaunal density of 5.2 hectare⁻¹ and a demersal fish density of 1.8 hectare ^−1. In contrast, the photographs were dominated by lebensspuren, particularly of the ‘spoke-burrow’ type usually attributed to echiurans. Spoke-burrow density, where related burrows and other features such as sediment mounds are considered unitary, is estimated at 871 hectare ^−1. We describe and quantify the five principal types of spoke burrow encountered in this study and, on the basis of these observations and some morphometric studies of the lebensspuren, discuss the possible behaviour of their producers. We have no direct knowledge of the production rate of, or longevity of, lebensspuren in the study area. However, based on a number of assumptions and limited data from other areas we suggest that trace producer (mainly echiurans) density is on the order of tens of individuals per hectare. These trace producers probably greatly outnumber the rest of the invertebrate megabenthos, and we can only guess at the role this potential large population of hidden benthos might have in the overall structure and function of the deep-sea floor ecosystem.     

ZW sex-chromosome evolution and contagious parthenogenesis in Artemia brine shrimp

Eurasian brine shrimp (genus Artemia) have closely related sexual and asexual lineages of parthenogenetic females, which produce rare males at low frequencies. Although they are known to have ZW chromosomes, these are not well characterized, and it is unclear whether they are shared across the clade. Furthermore, the underlying genetic architecture of the transmission of asexuality, which can occur when rare males mate with closely related sexual females, is not well understood. We produced a chromosome-level assembly for the sexual Eurasian species Artemia sinica and characterized in detail the pair of sex chromosomes of this species. We combined this new assembly with short-read genomic data for the sexual species Artemia sp. Kazakhstan and several asexual lineages of Artemia parthenogenetica, allowing us to perform an in-depth characterization of sex-chromosome evolution across the genus. We identified a small differentiated region of the ZW pair that is shared by all sexual and asexual lineages, supporting the shared ancestry of the sex chromosomes. We also inferred that recombination suppression has spread to larger sections of the chromosome independently in the American and Eurasian lineages. Finally, we took advantage of a rare male, which we backcrossed to sexual females, to explore the genetic basis of asexuality. Our results suggest that parthenogenesis is likely partly controlled by a locus on the Z chromosome, highlighting the interplay between sex determination and asexuality.