Genome-scale exon perturbation screens uncover exons critical for cell fitness.

CRISPR-Cas technology has transformed functional genomics, yet understanding of how individual exons differentially shape cellular phenotypes remains limited. Here, we optimized and conducted massively parallel exon deletion and splice-site mutation screens in human cell lines to identify exons that regulate cellular fitness. Fitness-promoting exons are prevalent in essential and highly expressed genes and commonly overlap with protein domains and interaction interfaces. Conversely, fitness-suppressing exons are enriched in nonessential genes, exhibiting lower inclusion levels, and overlap with intrinsically disordered regions and disease-associated mutations. In-depth mechanistic investigation of the screen-hit TAF5 alternative exon-8 revealed that its inclusion is required for assembly of the TFIID general transcription initiation complex, thereby regulating global gene expression output. Collectively, our orthogonal exon perturbation screens established a comprehensive repository of phenotypically important exons and uncovered regulatory mechanisms governing cellular fitness and gene expression.

Enhanced Nesquehonite Formation and Stability in the Presence of Dissolved Silica.

One possible carbon dioxide sequestration strategy is via the carbonation of dissolved Mg2+ obtained through olivine ((Mg,Fe)2SiO4) dissolution. However, silica is also produced during the breakdown of olivine. This component may have a detrimental effect on the yield of Mg-carbonate as Mg2+ incorporation into complex Mg silicate phases would limit CO2 uptake by this system. Yet this potential competition is currently not considered. Here, we use crystal growth experiments at temperatures applicable for potential coastal applications to test the effect of silica on the formation of the hydrated Mg-carbonate phase nesquehonite (MgCO3·3H2O). Solution chemistry analysis coupled with phase identification demonstrates that the presence of silica in the solution can actually assist the formation of nesquehonite and increase its yield by as much as 60 times. Our findings suggest that the presence of silica changes interfacial stabilities, lowering the energetic barrier for nesquehonite nucleation. In addition, in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) transformation experiments demonstrated that nesquehonite precipitating in a solution containing a high concentration of dissolved silica exhibits enhanced stability against its transformation into hydromagnesite. These findings will help to better constrain what we expect for applications of olivine during carbon remediation strategies as well as assist yields for industrial applications that use Mg-based cement as building materials to facilitate a CO2-neutral or negative footprint.

Vector-based navigation using grid-like representations in artificial agents.

Deep neural networks have achieved impressive successes in fields ranging from object recognition to complex games such as Go1,2. Navigation, however, remains a substantial challenge for artificial agents, with deep neural networks trained by reinforcement learning3-5 failing to rival the proficiency of mammalian spatial behaviour, which is underpinned by grid cells in the entorhinal cortex 6 . Grid cells are thought to provide a multi-scale periodic representation that functions as a metric for coding space7,8 and is critical for integrating self-motion (path integration)6,7,9 and planning direct trajectories to goals (vector-based navigation)7,10,11. Here we set out to leverage the computational functions of grid cells to develop a deep reinforcement learning agent with mammal-like navigational abilities. We first trained a recurrent network to perform path integration, leading to the emergence of representations resembling grid cells, as well as other entorhinal cell types 12 . We then showed that this representation provided an effective basis for an agent to locate goals in challenging, unfamiliar, and changeable environments-optimizing the primary objective of navigation through deep reinforcement learning. The performance of agents endowed with grid-like representations surpassed that of an expert human and comparison agents, with the metric quantities necessary for vector-based navigation derived from grid-like units within the network. Furthermore, grid-like representations enabled agents to conduct shortcut behaviours reminiscent of those performed by mammals. Our findings show that emergent grid-like representations furnish agents with a Euclidean spatial metric and associated vector operations, providing a foundation for proficient navigation. As such, our results support neuroscientific theories that see grid cells as critical for vector-based navigation7,10,11, demonstrating that the latter can be combined with path-based strategies to support navigation in challenging environments.

Safety and Efficacy of Ceftriaxone in the Treatment of Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections: A Noninferiority Retrospective Cohort Study.

BACKGROUND: Antistaphylococcal penicillins and cefazolin are the treatments of choice for methicillin-susceptible Staphylococcus aureus (MSSA) infections, requiring multiple doses daily. At Parkland, eligible uninsured patients with MSSA bloodstream infections (BSI) receive self-administered outpatient parenteral antimicrobial therapy (S-OPAT). Ceftriaxone was used in a cohort of S-OPAT patients for ease of once-daily dosing. OBJECTIVE: A retrospective study was conducted to evaluate clinical outcomes for patients discharged with ceftriaxone versus cefazolin to treat MSSA BSI. METHODS: A retrospective cohort noninferiority study design was used to assess treatment efficacy of ceftriaxone versus cefazolin among Parkland S-OPAT patients treated from April 2012 to March 2020. Demographic, clinical, and treatment-related adverse events data were collected. Clinical outcomes included treatment failure as defined by repeat positive blood culture or retreatment within 6 months, all-cause 30-day readmission rates, and central line-associated bloodstream infection (CLABSI) rates. RESULTS: Of 368 S-OPAT patients with MSSA BSI, 286 (77.7%) received cefazolin, and 82 (22.3%) received ceftriaxone. Demographics and comorbidities were similar for both groups. There were no treatment failures in the ceftriaxone group compared with 4 (1%) in the cefazolin group (P = 0.58). No difference in 30-day readmission rate between groups was found. The CLABSI rates were lower in ceftriaxone group (2%) compared with cefazolin (11%; P = 0.02). Limitations include retrospective cohort design. CONCLUSIONS: Ceftriaxone was found to be noninferior to cefazolin in this study. Our findings suggest that ceftriaxone is a safe and effective treatment of MSSA BSI secondary to osteoarticular or skin and soft tissue infections when used in the S-OPAT setting. POSTER ABSTRACT: OFID on 2018 Nov; 5(Suppl 1): S316: doi: 10.1093/ofid/ofy210.894.

Addressing inequity in palliative care provision for older people living with multimorbidity. Perspectives of community-dwelling older people on their palliative care needs: A scoping review.

BACKGROUND: Older people living with multimorbidity are projected to become the main recipients of palliative care in the coming decades, yet there is limited evidence regarding their expressed palliative care needs to inform person-centred care. AIM: To understand the palliative care needs of community-dwelling people aged ⩾60 living with multimorbidity in the last 2 years of life. DESIGN: A scoping review following Arksey and O'Malley. DATA SOURCES: Three international electronic databases (CINAHL, Ovid Medline, PsycINFO) were searched from March 2018 to December 2021. Reference lists were hand searched. Eligible papers were those reporting empirical data on older people's needs. RESULTS: From 985 potential papers, 28 studies were included, published between 2002 and 2020; sixteen quantitative, nine qualitative and three mixed methods. Data were extracted and presented under the holistic palliative care domains of need: physical, psychological, social, spiritual, and additionally practical needs. Different measurement tools (n = 29) were used, of which 20 were multidimensional. Primacy in reporting was given to physical needs, most commonly pain and function. Social and practical needs were often prioritised by older people themselves, including maintaining social connections and accessing and receiving individualised care. CONCLUSION: Identifying the palliative care needs that matter most to older people with multimorbidity requires the recognition of their concerns, as well as their symptoms, across a continuum of living and dying. Available evidence is superficial. Supporting end of life provision for this growing and underserved population necessitates a shift to tailored multidimensional tools and community focussed integrated care services.

Implementation of Sexual Health Curriculum Series: Educational Initiative to Increase STI Screening and Treatment in Dallas, Texas.

OBJECTIVE: A new monthly virtual education curriculum on sexual healthcare was launched in 2021. This is an analysis of the pilot education series designed to increase primary care providers' knowledge of sexual health best practices including taking thorough sexual histories, STI screening and treatment, and PrEP prescribing. METHODS: A Sexual Health Curriculum Series was developed as part of a quality improvement initiative at a large urban safety-net hospital in Dallas County, Texas. Didactic sessions were administered to primary care providers and staff via a virtual meeting platform once a month from May 2021 to April 2022. RESULTS: A total of 52 participants completed the pre-series survey, and 21 participants filled out the final post-series survey. 70% of respondents who completed the post-series survey reported that they learned new information that was incorporated into their practice. The average percentage correct on individual pre-session surveys was 60% compared to 63% on individual post-session surveys (p = 0.03). CONCLUSION: Sexual health education is an important tool to help primary care providers adhere to sexual health best practices. There is a need for ongoing implementation of innovative strategies to improve knowledge and adherence to sexual health best practices. A sexual health curriculum may be effective in helping primary providers recognize patients at increased risk and apply evidence-based guidelines to their practices.

Impact of a clinical pharmacist within an HIV PrEP program for patients experiencing homelessness.

BACKGROUND: Human immunodeficiency virus (HIV) continues to be a concern in the United States despite pre-exposure prophylaxis (PrEP) being a highly recommended preventative option. Homeless populations have a significantly increased risk of HIV acquisition, and recent literature found attrition to PrEP care being concentrated in demographics common to these populations. Pharmacist-led PrEP programs may be a feasible option to combat this attrition, as they have shown high rates of patient satisfaction and pharmacist comfortability in other populations. OBJECTIVES: To evaluate PrEP uptake and the continuum of care before and after a Clinical Pharmacy Specialist (CPS) expanded HIV prevention services within a primary care setting for persons experiencing homelessness. METHODS: We compared a retrospective cohort of patients experiencing homelessness who received an initial PrEP prescription during a pre-CPS period and those with an initial PrEP prescription after CPS. Charts were reviewed through the surrounding time period of a 3-month and a 6-month PrEP follow-up appointment. Outcomes evaluated included number of initial PrEP prescriptions, dispensations of PrEP, PrEP discontinuations, patient retention in PrEP care, and new HIV diagnoses. RESULTS: A total of 40 patients were included, with 10 initial PrEP prescriptions in the pre-CPS population and 30 in the post-CPS one. Both groups largely represented those disproportionately impacted by HIV. After CPS, more patients were enrolled in patient assistance programs (100% vs. 44%; P < 0.01), and more patients picked up the first PrEP dispensation (80% vs. 40%; P = 0.04). The overall population had low dispensation rates and retention to care. Having no CPS management and a lack of medical appointment attendance trended toward attrition of care, and having no patient assistance program enrollment significantly led to attrition of care. CONCLUSION: These findings may prompt further studies and adaptations to PrEP care among persons experiencing homelessness, including the utilization of pharmacists to improve patient outcomes.

Hybrid computing using a neural network with dynamic external memory.

Artificial neural networks are remarkably adept at sensory processing, sequence learning and reinforcement learning, but are limited in their ability to represent variables and data structures and to store data over long timescales, owing to the lack of an external memory. Here we introduce a machine learning model called a differentiable neural computer (DNC), which consists of a neural network that can read from and write to an external memory matrix, analogous to the random-access memory in a conventional computer. Like a conventional computer, it can use its memory to represent and manipulate complex data structures, but, like a neural network, it can learn to do so from data. When trained with supervised learning, we demonstrate that a DNC can successfully answer synthetic questions designed to emulate reasoning and inference problems in natural language. We show that it can learn tasks such as finding the shortest path between specified points and inferring the missing links in randomly generated graphs, and then generalize these tasks to specific graphs such as transport networks and family trees. When trained with reinforcement learning, a DNC can complete a moving blocks puzzle in which changing goals are specified by sequences of symbols. Taken together, our results demonstrate that DNCs have the capacity to solve complex, structured tasks that are inaccessible to neural networks without external read-write memory.

Decreasing Chlamydial Reinfections in a Female Urban Population.

BACKGROUND: Chlamydia is the most reported bacterial sexually transmitted infection (STI). The rates of chlamydia rose by 19% between 2011 and 2018. The STI National Strategic Plan (2021-2025), encourages coordinated solutions to address STIs and reduce disparities in disadvantaged populations. METHODS: We implemented institutional policy changes, clinical decision support, including a Best Practice Advisory, and defaulted SmartSet with provider and patient education for women's health clinics at a large county health system. The advisory prompted providers to follow best practices when treating Chlamydia trachomatis infections. New C. trachomatis diagnosis cohorts were compared preintervention and postintervention for 6-month reinfection rates and patient and expedited partner treatment (EPT) practices. RESULTS: Five hundred and nineteen women were included in the final analysis. Six-month chlamydia reinfection was lower in the postintervention cohort after adjusting for age (12.3% [26/211] vs 6.5% [20/308], P = 0.02). There was an increase in directly observed therapy of primary patients (17.5% [37/211] vs 77.3% [238/308], P < 0.001), an increase in EPT prescriptions written (4.3% [9/211] vs 79.5% [245/308], P < 0.0001), and a decrease of partners referred out for treatment (61.6% [130/211] vs 5.2% [16/308], P < 0.001) when compared with the control group. The majority of EPT was patient-delivered partner therapy postintervention (3.3% [7/211] vs 69.2% [213/308], P < 0.001). CONCLUSIONS: A multifaceted, streamlined approach was effective in changing provider practices in the treatment of C. trachomatis. Increased rates of directly observed therapy for primary patient treatment and increased rates of patient-delivered partner therapy were observed postimplementation in addition to lower 6-month reinfection rates in a public women's health clinic setting.

Human-level control through deep reinforcement learning.

The theory of reinforcement learning provides a normative account, deeply rooted in psychological and neuroscientific perspectives on animal behaviour, of how agents may optimize their control of an environment. To use reinforcement learning successfully in situations approaching real-world complexity, however, agents are confronted with a difficult task: they must derive efficient representations of the environment from high-dimensional sensory inputs, and use these to generalize past experience to new situations. Remarkably, humans and other animals seem to solve this problem through a harmonious combination of reinforcement learning and hierarchical sensory processing systems, the former evidenced by a wealth of neural data revealing notable parallels between the phasic signals emitted by dopaminergic neurons and temporal difference reinforcement learning algorithms. While reinforcement learning agents have achieved some successes in a variety of domains, their applicability has previously been limited to domains in which useful features can be handcrafted, or to domains with fully observed, low-dimensional state spaces. Here we use recent advances in training deep neural networks to develop a novel artificial agent, termed a deep Q-network, that can learn successful policies directly from high-dimensional sensory inputs using end-to-end reinforcement learning. We tested this agent on the challenging domain of classic Atari 2600 games. We demonstrate that the deep Q-network agent, receiving only the pixels and the game score as inputs, was able to surpass the performance of all previous algorithms and achieve a level comparable to that of a professional human games tester across a set of 49 games, using the same algorithm, network architecture and hyperparameters. This work bridges the divide between high-dimensional sensory inputs and actions, resulting in the first artificial agent that is capable of learning to excel at a diverse array of challenging tasks.

PrEP University: A Multi-Disciplinary University-Based HIV Prevention Education Program.

The introduction of emtricitabine/tenofovir diphosphate (FTC/TDF) as pre-exposure prophylaxis (PrEP) for HIV prevention has raised questions regarding which clinicians will serve as prescribers and how providers will be educated about this HIV prevention strategy. We piloted an HIV Prevention Education Program called PrEP University (PrEP U) to address knowledge gaps in HIV prevention among medical trainees. We examined PrEP awareness and assessed learning as a result of the program, measuring knowledge before and after the lectures with an anonymous 5-question multiple choice test. A total of 198 learners participated in PrEP University, which included 127 first year medical students, and post-graduate trainees in internal medicine (n = 23), family medicine (n = 16), OBGYN (n = 13) and pharmacy (n = 19). Prior to PrEP U, 27% of all participants were not aware of PrEP and an additional 8% were unsure if they had heard of it. Knowledge increased significantly after the education program among trainees in OBGYN (2.3 vs 3.8, p < 0.001), pharmacy (1.4 vs 2.5, p = 0.012) and school of medicine (3.3 vs 4.4, p < 0.001), with a trend seen in family medicine (2.7 vs. 3.7, p = 0.067) and internal medicine (2.7 vs 3.4, p = 0.068). Overall, an HIV Prevention Education Program was successfully administered to nearly 200 participants and resulted in improved knowledge of HIV prevention and PrEP across. Pharmacists and OBGYN physicians are two groups with an expanding role in the use of PrEP. Similar programs at other medical schools should be implemented to ensure that future physicians and pharmacists are comfortable with PrEP prescription.

Subduction zone forearc serpentinites as incubators for deep microbial life.

Serpentinization-fueled systems in the cool, hydrated forearc mantle of subduction zones may provide an environment that supports deep chemolithoautotrophic life. Here, we examine serpentinite clasts expelled from mud volcanoes above the Izu-Bonin-Mariana subduction zone forearc (Pacific Ocean) that contain complex organic matter and nanosized Ni-Fe alloys. Using time-of-flight secondary ion mass spectrometry and Raman spectroscopy, we determined that the organic matter consists of a mixture of aliphatic and aromatic compounds and functional groups such as amides. Although an abiotic or subduction slab-derived fluid origin cannot be excluded, the similarities between the molecular signatures identified in the clasts and those of bacteria-derived biopolymers from other serpentinizing systems hint at the possibility of deep microbial life within the forearc. To test this hypothesis, we coupled the currently known temperature limit for life, 122 °C, with a heat conduction model that predicts a potential depth limit for life within the forearc at ∼10,000 m below the seafloor. This is deeper than the 122 °C isotherm in known oceanic serpentinizing regions and an order of magnitude deeper than the downhole temperature at the serpentinized Atlantis Massif oceanic core complex, Mid-Atlantic Ridge. We suggest that the organic-rich serpentinites may be indicators for microbial life deep within or below the mud volcano. Thus, the hydrated forearc mantle may represent one of Earth's largest hidden microbial ecosystems. These types of protected ecosystems may have allowed the deep biosphere to thrive, despite violent phases during Earth's history such as the late heavy bombardment and global mass extinctions.

Dominant, Heritable Resistance to Stewart's Wilt in Maize Is Associated with an Enhanced Vascular Defense Response to Infection with Pantoea stewartii.

Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart's bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.

3D Raman Spectroscopy of Large Zeolite ZSM-5 Crystals.

Hydrothermal treatment is a common method used to modify the physicochemical properties of zeolite-based catalyst materials. It alters the number and type of acid sites through dealumination and increases molecular diffusion by mesopore formation. Steaming also reduces the structural integrity of zeolite frameworks. In this study, Raman microscopy has been used to map large zeolite ZSM-5 crystals before and after steaming. 3D elemental maps of T-O (T: Al or Si) sites of the zeolite were obtained. The Raman active vibrational bands were determined, which are indicative of (non-) framework Al, as well as of structural integrity. Zeolite steaming caused the introduction of additional heterogeneities within the zeolite framework. Al migration and the formation of extra-framework Al species were observed. The described experiments demonstrate the capability of 3D Raman spectroscopy as a valuable tool to obtain information on the spatial distributions of framework elements as well as defects within a zeolite-based material.

Sequestration of Antimony on Calcite Observed by Time-Resolved Nanoscale Imaging.

Antimony, which has damaging effects on the human body and the ecosystem, can be released into soils, ground-, and surface waters either from ore minerals that weather in near surface environments, or due to anthropogenic releases from waste rich in antimony, a component used in batteries, electronics, ammunitions, plastics, and many other industrial applications. Here, we show that dissolved Sb can interact with calcite, a widespread carbonate mineral, through a coupled dissolution-precipitation mechanism. The process is imaged in situ, at room temperature, at the nanometer scale by using an atomic force microscope equipped with a flow-through cell. Time-resolved imaging allowed following the coupled process of calcite dissolution, nucleation of precipitates at the calcite surface and growth of these precipitates. Sb(V) forms a precipitate, whereas Sb(III) needs to be oxidized to Sb(V) before being incorporated in the new phase. Scanning-electron microscopy and Raman spectroscopy allowed identification of the precipitates as two different calcium-antimony phases (Ca2Sb2O7). This coupled dissolution-precipitation process that occurs in a boundary layer at the calcite surface can sequester Sb as a solid phase on calcite, which has environmental implications as it may reduce the mobility of this hazardous compound in soils and groundwaters.

The importance of landscape characteristics for the delivery of cultural ecosystem services.

The importance of Cultural Ecosystem Services (CES) to human wellbeing is widely recognised. However, quantifying these non-material benefits is challenging and consequently they are often not assessed. Mapping approaches are increasingly being used to understand the spatial distribution of different CES and how this relates to landscape characteristics. This study uses an online Public Participation Geographic Information System (PPGIS) to elicit information on outdoor locations important to respondents in Wiltshire, a dynamic lowland landscape in southern England. We analysed these locations in a GIS with spatial datasets representing potential influential factors, including protected areas, land use, landform, and accessibility. We assess these characteristics at different spatial and visual scales for different types of cultural engagement. We find that areas that are accessible, near to urban centres, with larger views, and a high diversity of protected habitats, are important for the delivery of CES. Other characteristics including a larger area of woodland and the presence of sites of historic interest in the surrounding landscape were also influential. These findings have implications for land-use planning and the management of ecosystems, by demonstrating the benefits of high quality ecological sites near to towns. The importance of maintaining and restoring landscape features, such as woodlands, to enhance the delivery of CES were also highlighted.

Imaging Organophosphate and Pyrophosphate Sequestration on Brucite by in Situ Atomic Force Microscopy.

In order to evaluate the organic phosphorus (OP) and pyrophosphate (PyroP) cycle and their fate in the environment, it is critical to understand the effects of mineral interfaces on the reactivity of adsorption and precipitation of OP and PyroP. Here, in situ atomic force microscopy (AFM) is used to directly observe the kinetics of coupled dissolution-precipitation on cleaved (001) surfaces of brucite [Mg(OH)2] in the presence of phytate, glucose-6-phosphate (G6P) and pyrophosphate, respectively. AFM results show that the relative order of contribution to mineral surface adsorption and precipitation is phytate > pyrophosphate > G6P under the same solution conditions and can be quantified by the induction time of OP/PyroP-Mg nucleation in a boundary layer at the brucite-water interface. Calculations of solution speciation during brucite dissolution in the presence of phytate or pyrophosphate at acidic pH conditions show that the solutions may reach supersaturation with respect to Mg5H2Phytate.6H2O as a Mg-phytate phase or Mg2P2O7 as a Mg-pyrophosphate phase that becomes thermodynamically stable before equilibrium with brucite is reached. This is consistent with AFM dynamic observations for the new phase formations on brucite. Direct nanoscale observations of the transformation of adsorption/complexation-surface precipitation, combined with spectroscopic characterizations and species simulations may improve the mechanistic understanding of organophosphate and pyrophosphate sequestration by mineral replacement reactions through a mechanism of coupled dissolution-precipitation occurring at mineral-solution interfaces in the environment.

Visualizing Organophosphate Precipitation at the Calcite-Water Interface by in Situ Atomic-Force Microscopy.

Esters of phosphoric acid constitute a large fraction of the total organic phosphorus (OP) in the soil environment and, thus, play an important role in the global phosphorus cycle. These esters, such as glucose-6-phosphate (G6P), exhibit unusual reactivity toward various mineral particles in soils, especially those containing calcite. Many important processes of OP transformation, including adsorption, hydrolysis, and precipitation, occur primarily at mineral-fluid interfaces, which ultimately governs the fate of organophosphates in the environment. However, little is known about the kinetics of specific mineral-surface-induced adsorption and precipitation of organophosphates. Here, by using in situ atomic-force microscopy (AFM) to visualize the dissolution of calcite (1014) faces, we show that the presence of G6P results in morphology changes of etch pits from the typical rhombohedral to a fan-shaped form. This can be explained by a site-selective mechanism of G6P-calcite surface interactions that stabilize the energetically unfavorable (0001) or (0112) faces through step-specific adsorption of G6P. Continuous dissolution at calcite (1014)-water interfaces caused a boundary layer at the calcite-water interface to become supersaturated with respect to a G6P-Ca phase that then drives the nucleation and growth of a G6P-Ca precipitate. Furthermore, after the introduction of the enzyme alkaline phosphatase (AP), the precipitates were observed to contain a mixture of components associated with G6P-Ca, amorphous calcium phosphate (ACP)-hydroxyapatite (HAP) and dicalcium phosphate dihydrate (DCPD). These direct dynamic observations of the transformation of adsorption- and complexation-surface precipitation and enzyme-mediated pathways may improve the mechanistic understanding of the mineral-interface-induced organophosphate sequestration in the soil environment.

A PAK6-IQGAP1 complex promotes disassembly of cell-cell adhesions.

p-21 activated 6 (PAK6), first identified as interacting with the androgen receptor (AR), is over-expressed in multiple cancer tissues and has been linked to the progression of prostate cancer, however little is known about PAK6 function in the absence of AR signaling. We report here that PAK6 is specifically required for carcinoma cell-cell dissociation downstream of hepatocyte growth factor (HGF) for both DU145 prostate cancer and HT29 colon cancer cells. Moreover, PAK6 overexpression can drive cells to escape from adhesive colonies in the absence of stimulation. We have localized PAK6 to cell-cell junctions and have detected a direct interaction between the kinase domain of PAK6 and the junctional protein IQGAP1. Co-expression of IQGAP1 and PAK6 increases cell colony escape and leads to elevated PAK6 activation. Further studies have identified a PAK6/E-cadherin/IQGAP1 complex downstream of HGF. Moreover, we find that ß-catenin is also localized with PAK6 in cell-cell junctions and is a novel PAK6 substrate. We propose a unique role for PAK6, independent of AR signaling, where PAK6 drives junction disassembly during HGF-driven cell-cell dissociation via an IQGAP1/E-cadherin complex that leads to the phosphorylation of ß-catenin and the disruption of cell-cell adhesions.