Search

Abstract While the field of precision oncology is rapidly expanding and more targeted options are revolutionizing cancer treatment paradigms, therapeutic resistance particularly to immunotherapy remains a pressing challenge. This can be largely attributed to the dynamic tumor-stroma interactions that continuously alter the microenvironment. While to date most advancements have been made through examining the clinical utility of tissue-based biomarkers, their invasive nature and lack of a holistic representation of the evolving disease in a real-time manner could result in suboptimal treatment decisions. Thus, using minimally-invasive approaches to identify biomarkers that predict and monitor treatment response as well as alert to the emergence of recurrences is of a critical need. Currently, research efforts are shifting towards developing liquid biopsy-based biomarkers obtained from patients over the course of disease. Liquid biopsy represents a unique opportunity to monitor intercellular communication within the tumor microenvironment which could occur through the exchange of extracellular vesicles (EVs). EVs are lipid bilayer membrane nanoscale vesicles which transfer a plethora of biomolecules that mediate intercellular crosstalk, shape the tumor microenvironment, and modify drug response. The capture of EVs using innovative approaches, such as microfluidics, magnetic beads, and aptamers, allow their analysis via high throughput multi-omics techniques and facilitate their use for biomarker discovery. Artificial intelligence, using machine and deep learning algorithms, is advancing multi-omics analyses to uncover candidate biomarkers and predictive signatures that are key for translation into clinical trials. With the increasing recognition of the role of EVs in mediating immune evasion and as a valuable biomarker source, these real-time snapshots of cellular communication are promising to become an important tool in the field of precision oncology and spur the recognition of strategies to block resistance to immunotherapy. In this review, we discuss the emerging role of EVs in biomarker research describing current advances in their isolation and analysis techniques as well as their function as mediators in the tumor microenvironment. We also highlight recent lung cancer and melanoma studies that point towards their application as predictive biomarkers for immunotherapy and their potential clinical use in precision immuno-oncology.

Background: In 2017, inflammatory bowel disease, including Crohn's disease (CD) and ulcerative colitis (UC) affected more than 6.8 million people worldwide, with increased incidence in newly industrialized countries. Although treatment options were previously limited to symptom reduction, current approaches benefit from disease-modifying biologics. In this study, we aimed to explore disease characteristics, treatment, and outcomes of patients with CD or UC treated with infliximab or golimumab in routine clinical practice in the Middle East and Northern Africa. Methods: HARIR was a prospective, observational, multicenter study (NCT03006198), in patients who were treatment naïve or who received two or fewer biologic agents. Observed data from routine clinical practice were presented descriptively. Results: Data from 86 patients enrolled from five countries (Algeria, Egypt, Kuwait, Qatar, and Saudi Arabia) were analyzed, 62 with CD and 24 with UC. All patients received infliximab. Clinically meaningful efficacy data were observed only for the CD group (up to Month 3) due to limited patient numbers. Crohn's Disease Activity Index (CDAI) scores at Month 3 indicated a positive response to treatment (reduced score of ≥70 and ≥25% compared with baseline) for 14/48 (29.2%) patients; notably, 28/52 (53.8%) patients had CDAI score

Summary: The emergence of castration-resistant prostate cancer remains an area of unmet clinical need. We recently identified a subpopulation of normal prostate progenitor cells, characterized by an intrinsic resistance to androgen deprivation and expression of LY6D. We here demonstrate that conditional deletion of PTEN in the murine prostate epithelium causes an expansion of transformed LY6D+ progenitor cells without impairing stem cell properties. Transcriptomic analyses of LY6D+ luminal cells identified an autocrine positive feedback loop, based on the secretion of amphiregulin (AREG)-mediated activation of mitogen-activated protein kinase (MAPK) signaling, increasing cellular fitness and organoid formation. Pharmacological interference with this pathway overcomes the castration-resistant properties of LY6D+ cells with a suppression of organoid formation and loss of LY6D+ cells in vivo. Notably, LY6D+ tumor cells are enriched in high-grade and androgen-resistant prostate cancer, providing clinical evidence for their contribution to advanced disease. Our data indicate that early interference with MAPK inhibitors can prevent progression of castration-resistant prostate cancer.

Gnotobiotic models have had a crucial role in studying the effect that commensal microbiota has on the health of their animal hosts. Despite their physiological and ecological diversity, teleost fishes are still underrepresented in gnotobiotic research. Moreover, a better understanding of host-microbe interactions in farmed fish has the potential to contribute to sustainable global food supply. We have developed a novel gnotobiotic experimental system that includes the derivation of fertilized eggs of farmed and wild Atlantic salmon, and gnotobiotic husbandry of fry during the yolk sac stage. We used a microscopy-based approach to estimate the barrier function of the skin mucus layer and used this measurement to select the derivation procedure that minimized adverse effects on the skin mucosa. We also used this method to demonstrate that the mucus barrier was reduced in germ-free fry when compared to fry colonized with two different bacterial communities. This alteration in the mucus barrier was preceded by an increase in the number of cells containing neutral mucosubstances in the anterior segment of the body, but without changes in the number of cells containing acidic substances in any of the other segments studied along the body axis. In addition, we showed how the microbial status of the fry temporarily affected body size and the utilization of internal yolk stores during the yolk sac stage. Finally, we showed that the presence of bacterial communities associated with the fry, as well as their composition, affected the size of adipose tissue. Fry colonized with water from a lake had a larger visceral adipose tissue depot than both conventionally raised and germ-free fry. Together, our results show that this novel gnotobiotic experimental system is a useful tool for the study of host-microbe interactions in this species of aquacultural importance.

Abstract Background Fish skin represents an ancient vertebrate mucosal surface, sharing characteristics with other mucosal surfaces including those of the intestine. The skin mucosa is continuously exposed to microbes in the surrounding water and is therefore important in the first line defense against environmental pathogens by preventing bacteria from accessing the underlying surfaces. Understanding the microbe-host interactions at the fish skin mucosa is highly relevant in order to understand and control infection, commensalism, colonization, persistence, infection, and disease. Here we investigate the interactions between the pathogenic bacteria Aeromonas salmonicida (A. salmonicida) and Yersinia ruckeri (Y. ruckeri), respectively, and the skin mucosal surface of Atlantic salmon fry using AFM force spectroscopy. Results The results obtained revealed that when retracting probes functionalized with bacteria from surfaces coated with immobilized mucins, isolated from salmon mucosal surfaces, rupture events reflecting the disruption of adhesive interactions were observed, with rupture strengths centered around 200 pN. However, when retracting probes functionalized with bacteria from the intact mucosal surface of salmon fish fry no adhesive interactions could be detected. Furthermore, rheological measurements revealed a near fluid-like behavior for the fish fry skin mucus. Taken together, the experimental data indicate that the adhesion between the mucin molecules within the mucous layer may be significantly weaker than the interaction between the bacteria and the mucin molecules. The bacteria, immobilized on the AFM probe, do bind to individual mucins in the mucosal layer, but are released from the near fluid mucus with little resistance upon retraction of the AFM probe, to which they are immobilized. Conclusion The data provided in the current paper reveal that A. salmonicida and Y. ruckeri do bind to the immobilized mucins. However, when retracting the bacteria from intact mucosal surfaces, no adhesive interactions are detected. These observations suggest a mechanism underlying the protective function of the mucosal surface based on the clearing of potential threats by adhering them to loosely attached mucus that is subsequently released from the fish skin.

The Population Health Research Network (PHRN) is an Australian national data linkage infrastructure that links a wide range of health and human services data in privacy-preserving ways. The data linkage infrastructure enables researchers to apply for access to routinely collected, linked, administrative data from the six states and two territories which make up the Commonwealth of Australia, as well as data collected by the Australian Government. The PHRN is a distributed network where data is collected and managed at the respective jurisdictional and/or cross-jurisdictional levels. As a result, access to linked data from multiple jurisdictions requires complex approval processes. This paper describes Australia's approach to enabling access to linked data from multiple jurisdictions. It covers the identification of, and agreement to, a minimum set of data items to be included in a unified national application form, the development and implementation of a national online application system and the harmonisation of business processes for cross-jurisdictional research projects. Utilisation of the online application system and the ongoing challenges of data linkage across jurisdictions are discussed. Changes to the data custodian and ethics committee approval criteria were out of scope for this project.

This study explored the secondary school transition experiences of children with cleft lip and/or palate (CL/P). Data were collected via semi-structured interviews and analysed using interpretative phenomenological analysis (IPA). Participants were recruited from a National Health Service (NHS) specialist cleft service covering a large geographical area in the United Kingdom. Six participants with CL/P (aged 11–12 years old) in their first 12 months following transition to secondary school were interviewed. Four themes describe participants’ transition experiences: (a) managing and valuing difference: the impact on self-worth and identity; (b) managing and valuing difference within the social context; (c) disclosure and the process of informing others about CL/P; and (d) developing positive peer relationships. Children with CL/P experience several psychosocial challenges during the transition to secondary school. Professionals involved with working with and supporting these children (and their families), such as psychologists, school nurses or wellbeing staff, child psychiatrists, social workers, mental health nurses and paediatricians, should attend to these issues when preparing for this transition in order to foster resilience and adjustment.

Abstract Several studies have demonstrated the potential uses of extracellular vesicles (EVs) for liquid biopsy‐based diagnostic tests and therapeutic applications; however, clinical use of EVs presents a challenge as many currently‐available EV isolation methods have limitations related to efficiency, purity, and complexity of the methods. Moreover, many EV isolation methods do not perform efficiently in all biofluids due to their differential physicochemical properties. Thus, there continues to be a need for novel EV isolation methods that are simple, robust, non‐toxic, and/or clinically‐amenable. Here we demonstrate a rapid and efficient method for small extracellular vesicle (sEV) isolation that uses chitosan, a linear cationic polyelectrolyte polysaccharide that exhibits biocompatibility, non‐immunogenicity, biodegradability, and low toxicity. Chitosan‐precipitated material was characterized using Western blotting, nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and relevant proteomic‐based gene ontology analyses. We find that chitosan facilitates the isolation of sEVs from multiple biofluids, including cell culture‐conditioned media, human urine, plasma and saliva. Overall, our data support the potential for chitosan to isolate a population of sEVs from a variety of biofluids and may have the potential to be a clinically amenable sEV isolation method.

Despite the addition of several new agents to the armamentarium for the treatment of multiple myeloma (MM) in the last decade and improvements in outcomes, the refractory and relapsing disease continues to take a great toll, limiting overall survival. Therefore, additional novel approaches are needed to improve outcomes for MM patients. The oncogenic transcription factor MYC drives cell growth, differentiation and tumor development in many cancers. MYC protein levels are tightly regulated by the proteasome and an increase in MYC protein expression is found in more than 70% of all human cancers, including MM. In addition to the ubiquitin-dependent degradation of MYC by the 26S proteasome, MYC levels are also regulated in a ubiquitin-independent manner through the REGγ activation of the 20S proteasome. Here, we demonstrate that a small molecule activator of the 20S proteasome, TCH-165, decreases MYC protein levels, in a manner that parallels REGγ protein-mediated MYC degradation. TCH-165 enhances MYC degradation and reduces cancer cell growth in vitro and in vivo models of multiple myeloma by enhancing apoptotic signaling, as assessed by targeted gene expression analysis of cancer pathways. Furthermore, 20S proteasome enhancement is well tolerated in mice and dogs. These data support the therapeutic potential of small molecule-driven 20S proteasome activation for the treatments of MYC-driven cancers, especially MM.

Introduction Cardiovascular disease (CVD) represents a significant burden of disease for Aboriginal and Torres Strait Islander people, a population that continues to experience a lower life expectancy than other Australians. The aim of the Better Cardiac Care Data Linkage project is to describe patient care pathways and to identify disparities in care and health outcomes between Aboriginal and Torres Strait Islander people and other Queensland residents diagnosed with CVD in the state of Queensland.Methods This is a population-based retrospective cohort study using linked regional, state and national health and administrative data collections to describe disparities in CVD healthcare in primary and secondary prevention settings and during hospitalisation. The CVD cohort will be identified from the Queensland Hospital Admitted Patient Data Collection for admissions that occurred between 1 July 2010 and 31 June 2016 and will include relevant International Classification of Disease codes for ischaemic heart disease, congestive heart failure, stroke, acute rheumatic fever and rheumatic heart disease. Person-level data will be linked by Data Linkage Queensland and the Australian Institute of Health and Welfare (AIHW) in accordance with ethical and public health approvals to describe the patient journey prior to, during and post the hospital admission.Analysis This project will focus largely on descriptive epidemiological measures and multivariate analysis of clinical care standards and outcomes for Aboriginal and Torres Strait Islander people compared with other Queenslanders, including identification of risk factors for suboptimal care and change over time. Variation in care pathways and patient outcomes will be compared by Indigenous status, sex, age group, remoteness of residence, year of index hospitalisation and socioeconomic status. Cox models for time-to-event data and mixed models or generalised estimating equations for longitudinal data will be used to measure change over time where temporal effects exist.Ethics and dissemination Ethical approval has been granted by Human Research Ethics Committees of the Prince Charles Hospital (HREC/15/QPCH/289) and the AIHW (EO2016-1-233). The Northern Territory Department of Health and Menzies School of Health Research have also provided reciprocal ethical approval of the project (HREC 2019–3490). The deidentified results will be summarised in a report and shared with investigators, advisory groups, Queensland Health and key stakeholders. Findings will be disseminated through workshops, conferences and will be published in peer-reviewed journals.

We evaluated the effects of a discrimination training procedure for establishing praise as a reinforcer for three children with autism spectrum disorder. After establishing two praise words as discriminative stimuli and two nonsense words as S-deltas, we evaluated whether the stimuli then functioned as reinforcers by presenting each stimulus as a consequence for a new response. The results demonstrated that previously neutral praise words functioned as reinforcers and nonsense words did not. As in previous studies on establishing reinforcers, the effects were transitory, and praise words did not continue to function as reinforcers after repeated exposure without discrimination training. Recommendations are provided for future research and maintaining reinforcement effects.

Liquid biopsy is a minimally-invasive diagnostic method that may improve access to molecular profiling for non-small cell lung cancer (NSCLC) patients. Although cell-free DNA (cf-DNA) isolation from plasma is the standard liquid biopsy method for detecting DNA mutations in cancer patients, the sensitivity can be highly variable. Vn96 is a peptide with an affinity for both extracellular vesicles (EVs) and circulating cf-DNA. In this study, we evaluated whether peptide-affinity (PA) precipitation of EVs and cf-DNA from NSCLC patient plasma improves the sensitivity of single nucleotide variants (SNVs) detection and compared observed SNVs with those reported in the matched tissue biopsy. NSCLC patient plasma was subjected to either PA precipitation or cell-free methods and total nucleic acid (TNA) was extracted; SNVs were then detected by next-generation sequencing (NGS). PA led to increased recovery of DNA as well as an improvement in NGS sequencing parameters when compared to cf-TNA. Reduced concordance with tissue was observed in PA-TNA (62%) compared to cf-TNA (81%), mainly due to identification of SNVs in PA-TNA that were not observed in tissue. EGFR mutations were detected in PA-TNA with 83% sensitivity and 100% specificity. In conclusion, PA-TNA may improve the detection limits of low-abundance alleles using NGS.

Background and challenges to implementation The North East of England (pop 2.6m) has significant health challenges, largely resulting from an historic industrial past, and subsequent high rates of tobacco use. The region united in pooling public health budgets in order to deliver key interventions at scale. Eight key strands of tobacco control have been delivered synergistically over the last decade including smoking cessation, advocacy and media, regulation, research, secondhand smoke protection. Intervention or response The overall annual budget of USD 915k is used cost-effectively and funds a small regional multidisciplinary team supporting the work of the localities providing expertise, strategic support, advocacy, mass media campaigns, coordinating practice sharing and industrializing system wide reform, and delivering work at scale on complex issues. The work is guided by international best practise and informed by national tobacco strategies including those from ASH UK, Department of Health and Public Health England. Results and lessons learnt There has been a 41% reduction in the smoker population - the biggest regional decline in the last decade. A social movement has grown with high levels of public support for future regulation. Making tobacco control 'everyone's business' has been important and having a clear vision for the future vital to maintain funding commitment and focus. It is important to constantly reinforce the rationale for this investment from a health inequalities perspective and the strong return on investment tobacco control gives. Conclusions and key recommendations Significant economies of scale have been achieved with high value for money. In the UK there is a need for effective tobacco action from the community grass roots level right up to the national and international stage. A similar approach is in place around alcohol denormalisation now through the regional programme "Balance" and the two programmes are working together with notable success.The North East England provides a useful model for others.

Background and challenges to implementation With tobacco advertising, sponsorship and promotion (2003) and point of sale displays (2015) prohibited, tobacco packaging had become the main source of promotion in the UK. Evidence shows that branding helps to recruit young people to a lifetime of addiction. A concerted national advocacy campaign on standardised packaging was undertaken from 2011 through the Smokefree Action Coalition (SFAC) with strong support by Fresh (North East England) and local authorities in the region. Intervention or response Fresh, along with colleagues in the NE, supported the campaign from its inception and responded in force to two governmental consultations with submissions from local authorities and in particular regulatory teams, the health service, the police and the voluntary sector. All NE authorities had robust policies in place to counter the efforts by the tobacco industry to derail progress towards implementation of the measure. Results and lessons learnt In 2015, the UK became the second country in the world to pass legislation on standardised packs with full compliance achieved by May 2017. The tobacco industry issued legal challenges and appeals to both the UK and the European Union, but they lost. Public support for the measure was 60% by February 2017. Early results from NE research shows that the measure is having an impact on smokers who had seen the packs, with 60% thinking they looked less attractive and 51% noticing the health warnings more. There is also no evidence to suggest that standard packs will lead to an increase in the illicit tobacco market. Conclusions and key recommendations Working through the SFAC ensured that there was a huge ground swell of support in the NE and scores of organisations were able to unite around an effective campaign. Collaboration internationally was also pivotal including the leadership from Australia. The introduction of standardised packaging is another key milestone in the NE ambition to Make Smoking History.

Background and challenges to implementation North East (NE) England has had the fastest drops in smoking prevalence in the country. The UK's illicit tobacco market has almost halved following successful national strategies but still remains a problem in some communities because price and availability increases accessibility for children and reduces smokers' motivation to quit. In 2009, 16% of the NE tobacco market was illicit. Fresh, the NE's comprehensive tobacco control programme, has implemented an innovative and successful strategic framework to reduce the supply and demand. Intervention or response Since 2007, Fresh has worked with health and regulatory partners to reduce the illicit tobacco market. Several waves of quantitative and qualitative research with the public and stakeholders have informed the development of a multi-component strategic framework based on international principles which enhances national strategies and can be implemented locally or sub-nationally. Its eight objectives are to develop partnerships, engage frontline workers, generate intelligence, deliver enforcement, deliver marketing and communications, work with businesses, protect policies from the tobacco industry and assess progress. [Illicit Tobacco Programme Strategic Framework] Results and lessons learnt The illicit tobacco market in the NE has declined from 16% in 2009 to 12% in 2017. The proportion of smokers who buy illicit tobacco has reduced from 24% to 18% over the same timeframe. In-depth qualitative research has supported the development of effective, evidence-based demand reduction campaigns which have led to increases in intelligence and reductions in comfort levels with the illicit tobacco trade. Regulatory partners are prioritising illicit tobacco as part of their broader enforcement policies. Conclusions and key recommendations The success of this strategic framework demonstrates that activity can be co-ordinated locally or sub-nationally to support national strategies to reduce the illicit tobacco market. Activity should always be placed within the broader context of 'all tobacco kills' and should contain measures to reduce both supply and demand. Useful resources for other programmes and settings can be found at www.illicit-tobacco.co.uk.

Background and challenges to implementation England's comprehensive smokefree law (workplaces and enclosed public places), introduced in 2007, has been effective in protecting public health and has enjoyed increasing public support (86% in the NE in 2017) and consistent high compliance. The decade since has seen continued focus in the North East of England around protection from secondhand smoke, normalising smokefree spaces and building public support through a social movement around 'Making Smoking History'. Intervention or response Working with partners in local government and the health service, Fresh - the NE's regional comprehensive tobacco control programme - has delivered sustained activity to reinforce the importance of protection from secondhand smoke including training of front line staff and also voluntary policies around smokefree outdoor areas frequented by children, lobbied for further evidence based legislation whilst highlighting the ultimate aim of encouraging smokers to quit. Results and lessons learnt New regulations were introduced in 2015 to extend the smokefree law to cover private vehicles carrying children under 18 (91% NE public support). With 40% of NE smokers reporting they still smoke in the home, the need for ongoing education is clear and in 2017 Fresh ran a “secondhand smoke is poison” campaign with a hard hitting message around taking smoking right outside the home and the importance of protecting children from exposure. Conclusions and key recommendations The success of the smokefree law has led the way in increasing public support for existing and potential tobacco control measures. It has provided the opportunity to go beyond the scope of the law by introducing new smokefree areas. Further legislation to make all private vehicles smokefree would be welcome. It has been important to place this work within an overall programme where quitting tobacco remains the goal. Overall smoking in the NE has declined by 41% in this decade.

ABSTRACT Objectives 1) To examine the reading trajectories of children with different levels of child protection involvement from Year 3-9 of school 2) To estimate the ‘effects’ of entering care on Year 9 reading achievement, attendance and suspensions among children with substantiated maltreatment Approach Record-linkage of population data was used to investigate educational outcomes for children born in Western Australia from 1990-2010. Data from the Departments of Health, Child Protection and Family Support, Education, and Disability Services were used. Multi-level modelling was used to assess children’s reading trajectories from Year 3-9, and identify child, family, neighbourhood and child protection factors associated with reading achievement over time. Educational outcomes for maltreated children placed in out-of-home care were compared to a propensity-matched comparison group of children that remained at home using regression analyses. Results Child protection involved children most often showed a stable pattern of low achievement from Year 3-9. Of those with mid-level Year 3 scores, 45%-50% showed declining achievement with scores in the lowest third of their Year 9 cohort. Particularly low achievement in Year 3 and 9 was found among children with early unsubstantiated maltreatment followed by older-aged entry to care. Propensity matched analysis showed that after controlling for maltreatment, child, family, and neighbourhood characteristics, maltreated children did not significantly differ by placement status on reading or suspensions. Absences were significantly lower among children that entered care versus those remaining at home (OR=0.36,95%CI[0.15, 0.91). Conclusion Findings suggest that poor educational outcomes for children that have entered care are not primarily caused by out-of-home care, but reflect prior disadvantage and maltreatment. Child protection involved children are more likely to show stable low and declining patterns of achievement than other children, highlighting a need not only for early intervention, but also for interventions to address academic problems that arise later in childhood.

ABSTRACT Introduction It is well established that parental mental health disorders increase children’s risk of deliberate self-harm (DSH). However, little is known about how early life exposure to social disadvantage influences DSH among children whose parents have a mental health disorder. Aims To examine how early life exposure to high neighbourhood socioeconomic disadvantage and having a teen mother influence the DSH risk among children whose parents have a mental health disorder. Methods This study was based on the linkage of population-level records routinely collected by government agencies in Western Australia. A birth cohort including 474,860 non-Aboriginal individuals born between 1981 and 2001 was followed up until 2011. A nested case-control sample was compiled from the birth cohort for data analysis. A total of 7,151 people with DSH-related contacts (cases) and 143,020 matched controls were analysed. Conditional logistic regression models were utilised in this study. Results Exposure to high neighbourhood socioeconomic disadvantage was associated with additionally increased odds of DSH among children exposed to maternal mental health disorders during early childhood (1-4 years) (OR=1.75, 95%CI:1.30-2.36, p

Lee Daniels’ award-winning film, Precious: Based on the Novel “Push” by Sapphire is a powerful and controversial cinematic narrative of resilience. After its release at the 2009 Sundance Film Festival, Daniels recruited Oprah Winfrey and Tyler Perry as executive producers to help promote this independent, African-American art film (Mask, 2012). Precious was released nationwide on November 6 of that year, and won Academy Awards for Best Supporting Actress (Mo-Nique) and Best Screenplay. The film is based on Sapphire’s 1996 novel Push, which tells the story of Claireece “Precious” Jones, an overweight, illiterate, African-American 16 year old growing up in Harlem in the 1980s. According to Sapphire, in telling this story Push does not beat people over the head with a heavy-handed political commentary, but instead opens people’s hearts (Push Pictures, 2009). As a faithful adaptation of Push, the film portrays the world from Precious’ perspective and, although understated, Sapphire’s critical social commentary comes alive through Precious’ story (Push Pictures, 2009).

Plants continuously extend their root and shoot systems through the action of meristems at their growing tips. By regulating which meristems are active, plants adjust their body plans to suit local environmental conditions. The transport network of the phytohormone auxin has been proposed to mediate this systemic growth coordination, due to its self-organising, environmentally sensitive properties. In particular, a positive feedback mechanism termed auxin transport canalization, which establishes auxin flow from active shoot meristems (auxin sources) to the roots (auxin sinks), has been proposed to mediate competition between shoot meristems and to balance shoot and root growth. Here we provide strong support for this hypothesis by demonstrating that a second hormone, strigolactone, regulates growth redistribution in the shoot by rapidly modulating auxin transport. A computational model in which strigolactone action is represented as an increase in the rate of removal of the auxin export protein, PIN1, from the plasma membrane can reproduce both the auxin transport and shoot branching phenotypes observed in various mutant combinations and strigolactone treatments, including the counterintuitive ability of strigolactones either to promote or inhibit shoot branching, depending on the auxin transport status of the plant. Consistent with this predicted mode of action, strigolactone signalling was found to trigger PIN1 depletion from the plasma membrane of xylem parenchyma cells in the stem. This effect could be detected within 10 minutes of strigolactone treatment and was independent of protein synthesis but dependent on clathrin-mediated membrane trafficking. Together these results support the hypothesis that growth across the plant shoot system is balanced by competition between shoot apices for a common auxin transport path to the root and that strigolactones regulate shoot branching by modulating this competition.

Gnotobiotic models have had a crucial role in studying the effect that commensal microbiota has on the health of their animal hosts. Despite their physiological and ecological diversity, teleost fishes are still underrepresented in gnotobiotic research. Moreover, a better understanding of host-microbe interactions in farmed fish has the potential to contribute to sustainable global food supply. We have developed a novel gnotobiotic experimental system that includes the derivation of fertilized eggs of farmed and wild Atlantic salmon, and gnotobiotic husbandry of fry during the yolk sac stage. We used a microscopy-based approach to estimate the barrier function of the skin mucus layer and used this measurement to select the derivation procedure that minimized adverse effects on the skin mucosa. We also used this method to demonstrate that the mucus barrier was reduced in germ-free fry when compared to fry colonized with two different bacterial communities. This alteration in the mucus barrier was preceded by an increase in the number of cells containing neutral mucosubstances in the anterior segment of the body, but without changes in the number of cells containing acidic substances in any of the other segments studied along the body axis. In addition, we showed how the microbial status of the fry temporarily affected body size and the utilization of internal yolk stores during the yolk sac stage. Finally, we showed that the presence of bacterial communities associated with the fry, as well as their composition, affected the size of adipose tissue. Fry colonized with water from a lake had a larger visceral adipose tissue depot than both conventionally raised and germ-free fry. Together, our results show that this novel gnotobiotic experimental system is a useful tool for the study of hostmicrobe interactions in this species of aquacultural importance. [ABSTRACT FROM AUTHOR]