Epithelia Use Butyrophilin-like Molecules to Shape Organ-Specific γδ T Cell Compartments.

Many body surfaces harbor organ-specific γδ T cell compartments that contribute to tissue integrity. Thus, murine dendritic epidermal T cells (DETCs) uniquely expressing T cell receptor (TCR)-Vγ5 chains protect from cutaneous carcinogens. The DETC repertoire is shaped by Skint1, a butyrophilin-like (Btnl) gene expressed specifically by thymic epithelial cells and suprabasal keratinocytes. However, the generality of this mechanism has remained opaque, since neither Skint1 nor DETCs are evolutionarily conserved. Here, Btnl1 expressed by murine enterocytes is shown to shape the local TCR-Vγ7(+) γδ compartment. Uninfluenced by microbial or food antigens, this activity evokes the developmental selection of TCRαß(+) repertoires. Indeed, Btnl1 and Btnl6 jointly induce TCR-dependent responses specifically in intestinal Vγ7(+) cells. Likewise, human gut epithelial cells express BTNL3 and BTNL8 that jointly induce selective TCR-dependent responses of human colonic Vγ4(+) cells. Hence, a conserved mechanism emerges whereby epithelia use organ-specific BTNL/Btnl genes to shape local T cell compartments.

The γδTCR combines innate immunity with adaptive immunity by utilizing spatially distinct regions for agonist selection and antigen responsiveness.

T lymphocytes expressing γδ T cell antigen receptors (TCRs) comprise evolutionarily conserved cells with paradoxical features. On the one hand, clonally expanded γδ T cells with unique specificities typify adaptive immunity. Conversely, large compartments of γδTCR+ intraepithelial lymphocytes (γδ IELs) exhibit limited TCR diversity and effect rapid, innate-like tissue surveillance. The development of several γδ IEL compartments depends on epithelial expression of genes encoding butyrophilin-like (Btnl (mouse) or BTNL (human)) members of the B7 superfamily of T cell co-stimulators. Here we found that responsiveness to Btnl or BTNL proteins was mediated by germline-encoded motifs within the cognate TCR variable γ-chains (Vγ chains) of mouse and human γδ IELs. This was in contrast to diverse antigen recognition by clonally restricted complementarity-determining regions CDR1-CDR3 of the same γδTCRs. Hence, the γδTCR intrinsically combines innate immunity and adaptive immunity by using spatially distinct regions to discriminate non-clonal agonist-selecting elements from clone-specific ligands. The broader implications for antigen-receptor biology are considered.

Parallel vector memories in the brain of a bee as foundation for flexible navigation.

Insects rely on path integration (vector-based navigation) and landmark guidance to perform sophisticated navigational feats, rivaling those seen in mammals. Bees in particular exhibit complex navigation behaviors including creating optimal routes and novel shortcuts between locations, an ability historically indicative of the presence of a cognitive map. A mammalian cognitive map has been widely accepted. However, in insects, the existence of a centralized cognitive map is highly contentious. Using a controlled laboratory assay that condenses foraging behaviors to short distances in walking bumblebees, we reveal that vectors learned during path integration can be transferred to long-term memory, that multiple such vectors can be stored in parallel, and that these vectors can be recalled at a familiar location and used for homeward navigation. These findings demonstrate that bees meet the two fundamental requirements of a vector-based analog of a decentralized cognitive map: Home vectors need to be stored in long-term memory and need to be recalled from remembered locations. Thus, our data demonstrate that bees possess the foundational elements for a vector-based map. By utilizing this relatively simple strategy for spatial organization, insects may achieve high-level navigation behaviors seen in vertebrates with the limited number of neurons in their brains, circumventing the computational requirements associated with the cognitive maps of mammals.

Exogenous stimuli maintain intraepithelial lymphocytes via aryl hydrocarbon receptor activation.

The body's surfaces form the interface with the external environment, protecting the host. These epithelial barriers are also colonized by a controlled diversity of microorganisms, disturbances of which can give rise to disease. Specialized intraepithelial lymphocytes (IELs), which reside at these sites, are important as a first line of defense as well as in epithelial barrier organization and wound repair. We show here that the aryl hydrocarbon receptor (AhR) is a crucial regulator in maintaining IEL numbers in both the skin and the intestine. In the intestine, AhR deficiency or the lack of AhR ligands compromises the maintenance of IELs and the control of the microbial load and composition, resulting in heightened immune activation and increased vulnerability to epithelial damage. AhR activity can be regulated by dietary components, such as those present in cruciferous vegetables, providing a mechanistic link between dietary compounds, the intestinal immune system, and the microbiota.

The evolutionary history and spectral tuning of vertebrate visual opsins.

Many animals depend on the sense of vision for survival. In eumetazoans, vision requires specialized, light-sensitive cells called photoreceptors. Light reaches the photoreceptors and triggers the excitation of light-detecting proteins called opsins. Here, we describe the story of visual opsin evolution from the ancestral bilaterian to the extant vertebrate lineages. We explain the mechanisms determining color vision of extant vertebrates, focusing on opsin gene losses, duplications, and the expression regulation of vertebrate opsins. We describe the sequence variation both within and between species that has tweaked the sensitivities of opsin proteins towards different wavelengths of light. We provide an extensive resource of wavelength sensitivities and mutations that have diverged light sensitivity in many vertebrate species and predict how these mutations were accumulated in each lineage based on parsimony. We suggest possible natural and sexual selection mechanisms underlying these spectral differences. Understanding how molecular changes allow for functional adaptation of animals to different environments is a major goal in the field, and therefore identifying mutations affecting vision and their relationship to photic selection pressures is imperative. The goal of this review is to provide a comprehensive overview of our current understanding of opsin evolution in vertebrates.

Four System Enablers of Large-System Transformation in Health Care: A Mixed Methods Realist Evaluation.

Policy Points The implementation of large-scale health care interventions relies on a shared vision, commitment to change, coordination across sites, and a spanning of siloed knowledge. Enablers of the system should include building an authorizing environment; providing relevant, meaningful, transparent, and timely data; designating and distributing leadership and decision making; and fostering the emergence of a learning culture. Attention to these four enablers can set up a positive feedback loop to foster positive change that can protect against the loss of key staff, the presence of lone disruptors, and the enervating effects of uncertainty. CONTEXT: Large-scale transformative initiatives have the potential to improve the quality, efficiency, and safety of health care. However, change is expensive, complex, and difficult to implement and sustain. This paper advances system enablers, which will help to guide large-scale transformation in health care systems. METHODS: A realist study of the implementation of a value-based health care program between 2017 and 2021 was undertaken in every public hospital (n = 221) in New South Wales (NSW), Australia. Four data sources were used to elucidate initial program theories beginning with a set of literature reviews, a program document review, and informal discussions with key stakeholders. Semistructured interviews were then conducted with 56 stakeholders to confirm, refute, or refine the theories. A retroductive analysis produced a series of context-mechanism-outcome (CMO) statements. Next, the CMOs were validated with three health care quality expert panels (n = 51). Synthesized data were interrogated to distill the overarching system enablers. FINDINGS: Forty-two CMO statements from the eight initial program theory areas were developed, refined, and validated. Four system enablers were identified: (1) build an authorizing environment; (2) provide relevant, authentic, timely, and meaningful data; (3) designate and distribute leadership and decision making; and (4) support the emergence of a learning culture. The system enablers provide a nuanced understanding of large-system transformation that illustrates when, for whom, and in what circumstances large-system transformation worked well or worked poorly. CONCLUSIONS: System enablers offer nuanced guidance for the implementation of large-scale health care interventions. The four enablers may be portable to similar contexts and provide the empirical basis for an implementation model of large-system value-based health care initiatives. With concerted application, these findings can pave the way not just for a better understanding of greater or lesser success in intervening in health care settings but ultimately to contribute higher quality, higher value, and safer care.

Implementation of large, multi-site hospital interventions: a realist evaluation of strategies for developing capability.

BACKGROUND: This study presents guidelines for implementation distilled from the findings of a realist evaluation. The setting was local health districts in New South Wales, Australia that implemented three clinical improvement initiatives as part of a state-wide program. We focussed on implementation strategies designed to develop health professionals' capability to deliver value-based care initiatives for multisite programs. Capability, which increases implementers' ability to cope with unexpected scenarios is key to managing change. METHODS: We used a mixed methods realist evaluation which tested and refined program theories elucidating the complex dynamic between context (C), mechanism (M) and outcome (O) to determine what works, for whom, under what circumstances. Data was drawn from program documents, a realist synthesis, informal discussions with implementation designers, and interviews with 10 key informants (out of 37 identified) from seven sites. Data analysis employed a retroductive approach to interrogate the causal factors identified as contributors to outcomes. RESULTS: CMO statements were refined for four initial program theories: Making it Relevant- where participation in activities was increased when targeted to the needs of the staff; Investment in Quality Improvement- where engagement in capability development was enhanced when it was valued by all levels of the organisation; Turnover and Capability Loss- where the effects of staff turnover were mitigated; and Community-Wide Priority- where there was a strategy of spanning sites. From these data five guiding principles for implementers were distilled: (1) Involve all levels of the health system to effectively implement large-scale capability development, (2) Design capability development activities in a way that supports a learning culture, (3) Plan capability development activities with staff turnover in mind, (4) Increased capability should be distributed across teams to avoid bottlenecks in workflows and the risk of losing key staff, (5) Foster cross-site collaboration to focus effort, reduce variation in practice and promote greater cohesion in patient care. CONCLUSIONS: A key implementation strategy for interventions to standardise high quality practice is development of clinical capability. We illustrate how leadership support, attention to staff turnover patterns, and making activities relevant to current issues, can lead to an emergent learning culture.

The diversity of invertebrate visual opsins spanning Protostomia, Deuterostomia, and Cnidaria.

Across eumetazoans, the ability to perceive and respond to visual stimuli is largely mediated by opsins, a family of proteins belonging to the G protein-coupled receptor (GPCR) superclass. Lineage-specific gains and losses led to a striking diversity in the numbers, types, and spectral sensitivities conferred by visual opsin gene expression. Here, we review the diversity of visual opsins and differences in opsin gene expression from well-studied protostome, invertebrate deuterostome, and cnidarian groups. We discuss the functional significance of opsin expression differences and spectral tuning among lineages. In some cases, opsin evolution has been linked to the detection of relevant visual signals, including sexually selected color traits and host plant features. In other instances, variation in opsins has not been directly linked to functional or ecological differences. Overall, the array of opsin expression patterns and sensitivities across invertebrate lineages highlight the diversity of opsins in the eumetazoan ancestor and the labile nature of opsins over evolutionary time.

Genetic basis of ecologically relevant body shape variation among four genera of cichlid fishes.

Divergence in body shape is one of the most widespread and repeated patterns of morphological variation in fishes and is associated with habitat specification and swimming mechanics. Such ecological diversification is the first stage of the explosive adaptive radiation of cichlid fishes in the East African Rift Lakes. We use two hybrid crosses of cichlids (Metriaclima sp. × Aulonocara sp. and Labidochromis sp. × Labeotropheus sp., >975 animals total) to determine the genetic basis of body shape diversification that is similar to benthic-pelagic divergence across fishes. Using a series of both linear and geometric shape measurements, we identified 34 quantitative trait loci (QTL) that underlie various aspects of body shape variation. These QTL are spread throughout the genome, each explaining 3.2-8.6% of phenotypic variation, and are largely modular. Further, QTL are distinct both between these two crosses of Lake Malawi cichlids and compared to previously identified QTL for body shape in fishes such as sticklebacks. We find that body shape is controlled by many genes of small effect. In all, we find that convergent body shape phenotypes commonly observed across fish clades are most likely due to distinct genetic and molecular mechanisms.

Does ASMR propensity reflect a mentally flexible mindset? Exploring the relationship between ASMR propensity, transliminality, emotional contagion, schizotypal traits, roleplaying ability, and creativity.

Autonomous Sensory Meridian Response (ASMR) is an alternative state of consciousness characterised by changes in affect, feelings of relaxation, and tingling sensations on the body. Online videos designed to stimulate ASMR in viewers have become increasingly popular. Although there is evidence that ASMR may improve sleep, emotion regulation, and relaxation, the current understanding of ASMR propensity remains limited. This study examined whether a mentally flexible cognitive style may underlie the ability to experience ASMR. Undergraduate students (N = 376) completed an online survey involving a series of self-report questionnaires and two performance-based creative ability tasks. Findings did not provide support for an overall mentally flexible mindset, however, transliminality, emotional contagion susceptibility, positive schizotypal traits, and roleplaying ability all significantly positively predicted ASMR propensity. These findings suggest that ASMR propensity represents several possible underlying cognitive styles relating to enhanced imagination and perceptual ability, and cannot be simply characterised by mental flexibility.

Perioperative interventions to improve early mobilisation and physical function after hip fracture: a systematic review and meta-analysis.

BACKGROUND: Perioperative interventions could enhance early mobilisation and physical function after hip fracture surgery. OBJECTIVE: Determine the effectiveness of perioperative interventions on early mobilisation and physical function after hip fracture. METHODS: Ovid MEDLINE, CINAHL, Embase, Scopus and Web of Science were searched from January 2000 to March 2022. English language experimental and quasi-experimental studies were included if patients were hospitalised for a fractured proximal femur with a mean age 65 years or older and reported measures of early mobilisation and physical function during the acute hospital admission. Data were pooled using a random effect meta-analysis. RESULTS: Twenty-eight studies were included from 1,327 citations. Studies were conducted in 26 countries on 8,192 participants with a mean age of 80 years. Pathways and models of care may provide a small increase in early mobilisation (standardised mean difference [SMD]: 0.20, 95% confidence interval [CI]: 0.01-0.39, I2 = 73%) and physical function (SMD: 0.07, 95% CI 0.00 to 0.15, I2 = 0%) and transcutaneous electrical nerve stimulation analgesia may provide a moderate improvement in function (SMD: 0.65, 95% CI: 0.24-1.05, I2 = 96%). The benefit of pre-operative mobilisation, multidisciplinary rehabilitation, recumbent cycling and clinical supervision on mobilisation and function remains uncertain. Evidence of no effect on mobilisation or function was identified for pre-emptive analgesia, intraoperative periarticular injections, continuous postoperative epidural infusion analgesia, occupational therapy training or nutritional supplements. CONCLUSIONS: Perioperative interventions may improve early mobilisation and physical function after hip fracture surgery. Future studies are needed to model the causal mechanisms of perioperative interventions on mobilisation and function after hip fracture.

The diversity of providers' and consumers' views of virtual versus inpatient care provision: a qualitative study.

BACKGROUND: A broad-based international shift to virtual care models over recent years has accelerated following COVID-19. Although there are increasing numbers of studies and reviews, less is known about clinicians' and consumers' perspectives concerning virtual modes in contrast to inpatient modes of delivery. METHODS: We conducted a mixed-methods study in late 2021 examining consumers' and providers' expectations of and perspectives on virtual care in the context of a new facility planned for the north-western suburbs of Sydney, Australia. Data were collected via a series of workshops, and a demographic survey. Recorded qualitative text data were analysed thematically, and surveys were analysed using SPSS v22. RESULTS: Across 12 workshops, 33 consumers and 49 providers from varied backgrounds, ethnicities, language groups, age ranges and professions participated. Four advantages, strengths or benefits of virtual care reported were: patient factors and wellbeing, accessibility, better care and health outcomes, and additional health system benefits, while four disadvantages, weaknesses or risks of virtual care were: patient factors and wellbeing, accessibility, resources and infrastructure, and quality and safety of care. CONCLUSIONS: Virtual care was widely supported but the model is not suitable for all patients. Health and digital literacy and appropriate patient selection were key success criteria, as was patient choice. Key concerns included technology failures or limitations and that virtual models may be no more efficient than inpatient care models. Considering consumer and provider views and expectations prior to introducing virtual models of care may facilitate greater acceptance and uptake.

What do consumer and providers view as important for integrated care? A qualitative study.

BACKGROUND: Integrated care is a model recognised internationally, however, there is limited evidence about its usability in the community. This study aimed to elicit community and provider views about integrated care and how implementation could meet their healthcare needs in a new hospital. METHODS: Using a qualitative approach, consumer and provider views on the strengths, barriers and enablers for integrated care were collected via a series of online workshops and supplementary interviews. RESULTS: A total of 22 consumers and 49 providers participated in 11 focus groups; all perceived integrated care to be an accessible and efficient model that offers a high level of care which enhanced staff and patient well-being. Providers expressed concerns about longer waiting times and safety risks associated with communication gaps and insufficient staff. Enablers include supporting consumers in navigating the integrated care process, co-ordinating and integrating primary care into the model as well as centralising patient electronic medical records. DISCUSSION: Primary, tertiary and community linkages are key for integrated care. Successful interoperability of services and networks requires an investment in resources and infrastructure to build the capability for providers to seamlessly access information at all points along the patient pathway. CONCLUSION: Integrated care is perceived by consumers and providers to be a flexible and patient-focused model of healthcare that offers benefits for a hospital of the future.

The Digital Hospital: A Scoping Review of How Technology Is Transforming Cardiopulmonary Care.

BACKGROUND: Innovative models of health care that involve advanced technology in the form of a digital hospital are emerging globally. Models include technology such as machine learning and smart wearables, that can be used to integrate patient data and improve continuity of care. This model may have benefits in situations where patient deterioration must be detected quickly so that a rapid response can occur such as cardiopulmonary settings. AIM: The purpose of this scoping review was to examine the evidence for a digital hospital model of care, in the context of cardiac and pulmonary settings. DESIGN: Scoping review. DATA SOURCES: Databases searched were using PsycInfo, Ovid MEDLINE, and CINAHL. Studies written in English and containing key terms related to digital hospital and cardiopulmonary care were included. The Joanna Briggs Institute methodology for systematic reviews was used to assess the risk of bias. RESULTS: Thirteen (13) studies fulfilled the inclusion criteria. For cardiac conditions, a deep-learning-based rapid response system warning system for predicting patient deterioration leading to cardiac arrest had up to 257% higher sensitivity than conventional methods. There was also a reduction in the number of patients who needed to be examined by a physician. Using continuous telemonitoring with a wireless real-time electrocardiogram compared with non-monitoring, there was improved initial resuscitation and 24-hour post-event survival for high-risk patients. However, there were no benefits for survival to discharge. For pulmonary conditions, a natural language processing algorithm reduced the time to asthma diagnosis, demonstrating high predictive values. Virtual inhaler education was found to be as effective as in-person education, and prescription error was reduced following the implementation of computer-based physician order entry electronic medical records and a clinical decision support tool. CONCLUSIONS: While we currently have only a brief glimpse at the impact of technology care delivery for cardiac and respiratory conditions, technology presents an opportunity to improve quality and safety in care, but only with the support of adequate infrastructure and processes. PROTOCOL REGISTRATION: Open Science Framework (OSF: DOI 10.17605/OSF.IO/PS6ZU).

Rank signaling links the development of invariant γδ T cell progenitors and Aire(+) medullary epithelium.

The thymic medulla provides a specialized microenvironment for the negative selection of T cells, with the presence of autoimmune regulator (Aire)-expressing medullary thymic epithelial cells (mTECs) during the embryonic-neonatal period being both necessary and sufficient to establish long-lasting tolerance. Here we showed that emergence of the first cohorts of Aire(+) mTECs at this key developmental stage, prior to αß T cell repertoire selection, was jointly directed by Rankl(+) lymphoid tissue inducer cells and invariant Vγ5(+) dendritic epidermal T cell (DETC) progenitors that are the first thymocytes to express the products of gene rearrangement. In turn, generation of Aire(+) mTECs then fostered Skint-1-dependent, but Aire-independent, DETC progenitor maturation and the emergence of an invariant DETC repertoire. Hence, our data attributed a functional importance to the temporal development of Vγ5(+) γδ T cells during thymus medulla formation for αß T cell tolerance induction and demonstrated a Rank-mediated reciprocal link between DETC and Aire(+) mTEC maturation.

A mixed-methods examination of autonomous sensory meridian response: Comparison to frisson.

Autonomous Sensory Meridian Response (ASMR) is a pleasurable, head-oriented tingling sensation, typically induced by exposure to audiovisual triggers, producing feelings of relaxation and euphoria. This article explores the induction of ASMR experiences in a laboratory setting amongst non-specialised participants, as well as the relationship between ASMR and frisson, or 'musical chills'. In previous work, the ASMR-15 was found to be a reliable measure of ASMR propensity, however, the predictive validity of the measure has yet to be determined. The aim of this study was to assess whether ASMR-15 scores predict greater ASMR induction in an experimental setting. To address this, N = 100 undergraduate psychology students completed the ASMR-15 and a measure of frisson, before viewing ASMR stimuli under controlled conditions. Mixed-methods analyses indicated the successful induction of ASMR amongst some participants, convergence between ASMR-15 scores and video ratings, as well as divergence between ASMR and frisson scores.

Prdm1 Regulates Thymic Epithelial Function To Prevent Autoimmunity.

Autoimmunity is largely prevented by medullary thymic epithelial cells (TECs) through their expression and presentation of tissue-specific Ags to developing thymocytes, resulting in deletion of self-reactive T cells and supporting regulatory T cell development. The transcription factor Prdm1 has been implicated in autoimmune diseases in humans through genome-wide association studies and in mice using cell type-specific deletion of Prdm1 in T and dendritic cells. In this article, we demonstrate that Prdm1 functions in TECs to prevent autoimmunity in mice. Prdm1 is expressed by a subset of mouse TECs, and conditional deletion of Prdm1 in either Keratin 14- or Foxn1-expressing cells in mice resulted in multisymptom autoimmune pathology. Notably, the development of Foxp3+ regulatory T cells occurs normally in the absence of Blimp1. Importantly, nude mice developed anti-nuclear Abs when transplanted with Prdm1 null TECs, but not wild-type TECs, indicating that Prdm1 functions in TECs to regulate autoantibody production. We show that Prdm1 acts independently of Aire, a crucial transcription factor implicated in medullary TEC function. Collectively, our data highlight a previously unrecognized role for Prdm1 in regulating thymic epithelial function.

Synthesis and profiling of benzylmorpholine 1,2,4,5-tetraoxane analogue N205: Towards tetraoxane scaffolds with potential for single dose cure of malaria.

A series of aryl carboxamide and benzylamino dispiro 1,2,4,5-tetraoxane analogues have been designed and synthesized in a short synthetic sequence from readily available starting materials. From this series of endoperoxides, molecules with in vitro IC50s versus Plasmodium falciparum (3D7) as low as 0.84 nM were identified. Based on an assessment of blood stability and in vitro microsomal stability, N205 (10a) was selected for rodent pharmacokinetic and in vivo antimalarial efficacy studies in the mouse Plasmodium berghei and Plasmodium falciparum Pf3D70087/N9 severe combined immunodeficiency (SCID) mouse models. The results indicate that the 4-benzylamino derivatives have excellent profiles with a representative of this series, N205, an excellent starting point for further lead optimization studies.

Genetic sex determination in Astatotilapia calliptera, a prototype species for the Lake Malawi cichlid radiation.

East African cichlids display extensive variation in sex determination systems. The species Astatotilapia calliptera is one of the few cichlids that reside both in Lake Malawi and in surrounding waterways. A. calliptera is of interest in evolutionary studies as a putative immediate outgroup species for the Lake Malawi species flock and possibly as a prototype ancestor-like species for the radiation. Here, we use linkage mapping to test association of sex in A. calliptera with loci that have been previously associated with genetic sex determination in East African cichlid species. We identify a male heterogametic XY system segregating at linkage group (LG) 7 in an A. calliptera line that originated from Lake Malawi, at a locus previously shown to act as an XY sex determination system in multiple species of Lake Malawi cichlids. Significant association of genetic markers and sex produce a broad genetic interval of approximately 26 megabases (Mb) using the Nile tilapia genome to orient markers; however, we note that the marker with the strongest association with sex is near a gene that acts as a master sex determiner in other fish species. We demonstrate that alleles of the marker are perfectly associated with sex in Metriaclima mbenjii, a species from the rock-dwelling clade of Lake Malawi. While we do not rule out the possibility of other sex determination loci in A. calliptera, this study provides a foundation for fine mapping of the cichlid sex determination gene on LG7 and evolutionary context regarding the origin and persistence of the LG7 XY across diverse, rapidly evolving lineages.

Polygenic sex determination in the cichlid fish Astatotilapia burtoni.

BACKGROUND: The East African riverine cichlid species Astatotilapia burtoni serves as an important laboratory model for sexually dimorphic physiology and behavior, and also serves as an outgroup species for the explosive adaptive radiations of cichlid species in Lake Malawi and Lake Victoria. An astounding diversity of genetic sex determination systems have been revealed within the adaptive radiation of East African cichlids thus far, including polygenic sex determination systems involving the epistatic interaction of multiple, independently segregating sex determination alleles. However, sex determination has remained unmapped in A. burtoni. Here we present mapping results supporting the presence of multiple, novel sex determination alleles, and thus the presence of polygenic sex determination in A. burtoni. RESULTS: Using mapping in small families in conjunction with restriction-site associated DNA sequencing strategies, we identify associations with sex at loci on linkage group 13 and linkage group 5-14. Inheritance patterns support an XY sex determination system on linkage group 5-14 (a chromosome fusion relative to other cichlids studied), and an XYW system on linkage group 13, and these associations are replicated in multiple families. Additionally, combining our genetic data with comparative genomic analysis identifies another fusion that is unassociated with sex, with linkage group 8-24 and linkage group 16-21 fused in A. burtoni relative to other East African cichlid species. CONCLUSIONS: We identify genetic signals supporting the presence of three previously unidentified sex determination alleles at two loci in the species A. burtoni, strongly supporting the presence of polygenic sex determination system in the species. These results provide a foundation for future mapping of multiple sex determination genes and their interactions. A better understanding of sex determination in A. burtoni provides important context for their use in behavioral studies, as well as studies of the evolution of genetic sex determination and sexual conflicts in East African cichlids.