Hepatic lipid-associated macrophages mediate the beneficial effects of bariatric surgery against MASH.

For patients with obesity and metabolic syndrome, bariatric procedures such as vertical sleeve gastrectomy (VSG) have a clear benefit in ameliorating metabolic dysfunction-associated steatohepatitis (MASH). While the effects of bariatric surgeries have been mainly attributed to nutrient restriction and malabsorption, whether immuno-modulatory mechanisms are involved remains unclear. Here we report that VSG ameliorates MASH progression in a weight loss-independent manner. Single-cell RNA sequencing revealed that hepatic lipid-associated macrophages (LAMs) expressing the triggering receptor expressed on myeloid cells 2 (TREM2) increase their lysosomal activity and repress inflammation in response to VSG. Remarkably, TREM2 deficiency in mice ablates the reparative effects of VSG, suggesting that TREM2 is required for MASH resolution. Mechanistically, TREM2 prevents the inflammatory activation of macrophages and is required for their efferocytotic function. Overall, our findings indicate that bariatric surgery improves MASH through a reparative process driven by hepatic LAMs, providing insights into the mechanisms of disease reversal that may result in new therapies and improved surgical interventions.

Dysfunctional T Follicular Helper Cells Cause Intestinal and Hepatic Inflammation in NASH.

Nonalcoholic steatohepatitis (NASH), characterized by hepatic inflammation and cellular damage, is the most severe form of nonalcoholic fatty liver disease and the fastest-growing indication for a liver transplant. The intestinal immune system is a central modulator of local and systemic inflammation. In particular, Peyer's patches (PPs) contain T follicular helper (Tfh) cells that support germinal center (GC) responses required for the generation of high-affinity intestinal IgA and the maintenance of intestinal homeostasis. However, our understanding of the mechanisms regulating mucosal immunity during the pathogenesis of NASH is incomplete. Here, using a preclinical mouse model that resembles the key features of human disease, we discovered an essential role for Tfh cells in the pathogenesis of NASH. We have found that mice fed a high-fat high-carbohydrate (HFHC) diet have an inflamed intestinal microenvironment, characterized by enlarged PPs with an expansion of Tfh cells. Surprisingly, the Tfh cells in the PPs of NASH mice showed evidence of dysfunction, along with defective GC responses and reduced IgA+ B cells. Tfh-deficient mice fed the HFHC diet showed compromised intestinal permeability, increased hepatic inflammation, and aggravated NASH, suggesting a fundamental role for Tfh cells in maintaining gut-liver homeostasis. Mechanistically, HFHC diet feeding leads to an aberrant increase in the expression of the transcription factor KLF2 in Tfh cells which inhibits its function. Thus, transgenic mice with reduced KLF2 expression in CD4 T cells displayed improved Tfh cell function and ameliorated NASH, including hepatic steatosis, inflammation, and fibrosis after HFHC feeding. Overall, these findings highlight Tfh cells as key intestinal immune cells involved in the regulation of inflammation in the gut-liver axis during NASH.

Genetic variations in idiopathic pulmonary fibrosis and patient response to pirfenidone.

Background: Genetic variations in Idiopathic Pulmonary Fibrosis (IPF) affect survival and outcomes. Current antifibrotic agents are managed based on the patient's reported side effects, although certain single nucleotide polymorphisms (SNPs) might alter treatment response and survival depending on the antifibrotic administered. This study investigated variations in response and outcomes to pirfenidone based on patients-specific genetic profiles. Methods: Retrospective clinical data were collected from 56 IPF patients and had blood drawn for DNA extraction between 7/2013 and 3/2016, with the last patient followed until 10/2018. Nine SNPs were selected for pharmacogenetic investigation based on prior associations with IPF treatment outcomes or implications for pirfenidone metabolism. Genetic variants were examined in relation to clinical data and treatment outcomes. Results: Of the 56 patients, 38 were males (67.85%). The average age of IPF at diagnosis was 66.88 years. At the initiation of pirfenidone, the average percent predicted FVC was 70.7%, and the average DLCO percent predicted was 50.02% (IQR 40-61%). Among the genetic variants tested, the TOLLIP rs5743890 risk allele was significantly associated with improved survival, with increasing pirfenidone duration. This finding was observed with CC or CT genotype carriers but not for those with the TT genotype (p = 0.0457). Similarly, the TGF-B1 rs1800470 risk allele was also significantly associated with improved survival with longer pirfenidone therapy (p = 0.0395), even though it was associated with disease progression. Conclusion: This pilot study suggests that in IPF patients, the TOLLIP rs5743890 genotypes CC and CT, as well as TGF-B1 rs 1800470 may be associated with increased survival when treated with pirfenidone.

Immune tolerance of food is mediated by layers of CD4+ T cell dysfunction.

Gastrointestinal health depends on the adaptive immune system tolerating the foreign proteins in food1,2. This tolerance is paradoxical because the immune system normally attacks foreign substances by generating inflammation. Here we addressed this conundrum by using a sensitive cell enrichment method to show that polyclonal CD4+ T cells responded to food peptides, including a natural one from gliadin, by proliferating weakly in secondary lymphoid organs of the gut-liver axis owing to the action of regulatory T cells. A few food-specific T cells then differentiated into T follicular helper cells that promoted a weak antibody response. Most cells in the expanded population, however, lacked canonical T helper lineage markers and fell into five subsets dominated by naive-like or T follicular helper-like anergic cells with limited capacity to form inflammatory T helper 1 cells. Eventually, many of the T helper lineage-negative cells became regulatory T cells themselves through an interleukin-2-dependent mechanism. Our results indicate that exposure to food antigens causes cognate CD4+ naive T cells to form a complex set of noncanonical hyporesponsive T helper cell subsets that lack the inflammatory functions needed to cause gut pathology and yet have the potential to produce regulatory T cells that may suppress it.

The genome of the zebra mussel, Dreissena polymorpha: a resource for comparative genomics, invasion genetics, and biocontrol.

The zebra mussel, Dreissena polymorpha, continues to spread from its native range in Eurasia to Europe and North America, causing billions of dollars in damage and dramatically altering invaded aquatic ecosystems. Despite these impacts, there are few genomic resources for Dreissena or related bivalves. Although the D. polymorpha genome is highly repetitive, we have used a combination of long-read sequencing and Hi-C-based scaffolding to generate a high-quality chromosome-scale genome assembly. Through comparative analysis and transcriptomics experiments, we have gained insights into processes that likely control the invasive success of zebra mussels, including shell formation, synthesis of byssal threads, and thermal tolerance. We identified multiple intact steamer-like elements, a retrotransposon that has been linked to transmissible cancer in marine clams. We also found that D. polymorpha have an unusual 67 kb mitochondrial genome containing numerous tandem repeats, making it the largest observed in Eumetazoa. Together these findings create a rich resource for invasive species research and control efforts.

Discovery of clinically relevant fusions in pediatric cancer.

BACKGROUND: Pediatric cancers typically have a distinct genomic landscape when compared to adult cancers and frequently carry somatic gene fusion events that alter gene expression and drive tumorigenesis. Sensitive and specific detection of gene fusions through the analysis of next-generation-based RNA sequencing (RNA-Seq) data is computationally challenging and may be confounded by low tumor cellularity or underlying genomic complexity. Furthermore, numerous computational tools are available to identify fusions from supporting RNA-Seq reads, yet each algorithm demonstrates unique variability in sensitivity and precision, and no clearly superior approach currently exists. To overcome these challenges, we have developed an ensemble fusion calling approach to increase the accuracy of identifying fusions. RESULTS: Our Ensemble Fusion (EnFusion) approach utilizes seven fusion calling algorithms: Arriba, CICERO, FusionMap, FusionCatcher, JAFFA, MapSplice, and STAR-Fusion, which are packaged as a fully automated pipeline using Docker and Amazon Web Services (AWS) serverless technology. This method uses paired end RNA-Seq sequence reads as input, and the output from each algorithm is examined to identify fusions detected by a consensus of at least three algorithms. These consensus fusion results are filtered by comparison to an internal database to remove likely artifactual fusions occurring at high frequencies in our internal cohort, while a "known fusion list" prevents failure to report known pathogenic events. We have employed the EnFusion pipeline on RNA-Seq data from 229 patients with pediatric cancer or blood disorders studied under an IRB-approved protocol. The samples consist of 138 central nervous system tumors, 73 solid tumors, and 18 hematologic malignancies or disorders. The combination of an ensemble fusion-calling pipeline and a knowledge-based filtering strategy identified 67 clinically relevant fusions among our cohort (diagnostic yield of 29.3%), including RBPMS-MET, BCAN-NTRK1, and TRIM22-BRAF fusions. Following clinical confirmation and reporting in the patient's medical record, both known and novel fusions provided medically meaningful information. CONCLUSIONS: The EnFusion pipeline offers a streamlined approach to discover fusions in cancer, at higher levels of sensitivity and accuracy than single algorithm methods. Furthermore, this method accurately identifies driver fusions in pediatric cancer, providing clinical impact by contributing evidence to diagnosis and, when appropriate, indicating targeted therapies.

Cardiac Resident Macrophages Prevent Fibrosis and Stimulate Angiogenesis.

RATIONALE: The initial hypertrophy response to cardiac pressure overload is considered compensatory, but with sustained stress, it eventually leads to heart failure. Recently, a role for recruited macrophages in determining the transition from compensated to decompensated hypertrophy has been established. However, whether cardiac resident immune cells influence the early phase of hypertrophy development has not been established. OBJECTIVE: To assess the role of cardiac immune cells in the early hypertrophy response to cardiac pressure overload induced by transverse aortic constriction (TAC). METHODS AND RESULTS: We performed cytometry by time-of-flight to determine the identity and abundance of immune cells in the heart at 1 and 4 weeks after TAC. We observed a substantial increase in cardiac macrophages 1 week after TAC. We then conducted Cite-Seq single-cell RNA sequencing of cardiac immune cells isolated from 4 sham and 6 TAC hearts. We identified 12 clusters of monocytes and macrophages, categorized as either resident or recruited macrophages, that showed remarkable changes in their abundance between sham and TAC conditions. To determine the role of cardiac resident macrophages early in the response to a hypertrophic stimulus, we used a blocking antibody against macrophage colony-stimulating factor 1 receptor (CD115). As blocking CD115 initially depletes all macrophages, we allowed the replenishment of recruited macrophages by monocytes before performing TAC. This preferential depletion of resident macrophages resulted in enhanced fibrosis and a blunted angiogenesis response to TAC. Macrophage depletion in CCR2 (C-C chemokine receptor type 2) knockout mice showed that aggravated fibrosis was primarily caused by the recruitment of monocyte-derived macrophages. Finally, 6 weeks after TAC these early events lead to depressed cardiac function and enhanced fibrosis, despite complete restoration of cardiac immune cells. CONCLUSIONS: Cardiac resident macrophages are a heterogeneous population of immune cells with key roles in stimulating angiogenesis and inhibiting fibrosis in response to cardiac pressure overload.

Microbiota-Driven Activation of Intrahepatic B Cells Aggravates NASH Through Innate and Adaptive Signaling.

BACKGROUND AND AIMS: Nonalcoholic steatohepatitis is rapidly becoming the leading cause of liver failure and indication for liver transplantation. Hepatic inflammation is a key feature of NASH but the immune pathways involved in this process are poorly understood. B lymphocytes are cells of the adaptive immune system that are critical regulators of immune responses. However, the role of B cells in the pathogenesis of NASH and the potential mechanisms leading to their activation in the liver are unclear. APPROACH AND RESULTS: In this study, we report that NASH livers accumulate B cells with elevated pro-inflammatory cytokine secretion and antigen-presentation ability. Single-cell and bulk RNA sequencing of intrahepatic B cells from mice with NASH unveiled a transcriptional landscape that reflects their pro-inflammatory function. Accordingly, B-cell deficiency ameliorated NASH progression, and adoptively transferring B cells from NASH livers recapitulates the disease. Mechanistically, B-cell activation during NASH involves signaling through the innate adaptor myeloid differentiation primary response protein 88 (MyD88) as B cell-specific deletion of MyD88 reduced hepatic T cell-mediated inflammation and fibrosis, but not steatosis. In addition, activation of intrahepatic B cells implicates B cell-receptor signaling, delineating a synergy between innate and adaptive mechanisms of antigen recognition. Furthermore, fecal microbiota transplantation of human NAFLD gut microbiotas into recipient mice promoted the progression of NASH by increasing the accumulation and activation of intrahepatic B cells, suggesting that gut microbial factors drive the pathogenic function of B cells during NASH. CONCLUSION: Our findings reveal that a gut microbiota-driven activation of intrahepatic B cells leads to hepatic inflammation and fibrosis during the progression of NASH through innate and adaptive immune mechanisms.

Patterns of genetic variation in a prairie wildflower, Silphium integrifolium, suggest a non-prairie origin and locally adaptive variation.

PREMISE: Understanding the relationship between genetic structure and geography provides information about a species' history and can be used for breeding and conservation goals. The North American prairie is interesting because of its recent origin and subsequent fragmentation. Silphium integrifolium, an iconic perennial American prairie wildflower, is targeted for domestication, having undergone a few generations of improvement. We present the first application of population genetic data in this species to address the following goals: (1) improve breeding by characterizing genetic structure and (2) identify the species geographic origin and potential targets and drivers of selection during range expansion. METHODS: We developed a reference transcriptome as a genotyping reference for samples from throughout the species range. Population genetic analyses were used to describe patterns of genetic variation, and demographic modeling was used to characterize potential processes that shaped variation. Outlier scans for selection and associations with environmental variables were used to identify loci linked to putative targets and drivers of selection. RESULTS: Genetic variation partitioned samples into three geographic clusters. Patterns of variation and demographic modeling suggest that the species origin is in the American Southeast. Breeding program accessions are from the region with lowest observed genetic variation. CONCLUSIONS: This prairie species did not originate within the prairie. Breeding may be improved by including accessions from outside of the germplasm founding region. The geographic structuring and the identified targets and drivers of adaptation can guide collecting efforts toward populations with beneficial agronomic traits.

RNA sequencing of whole blood in dogs with primary immune-mediated hemolytic anemia (IMHA) reveals novel insights into disease pathogenesis.

Immune-mediated hemolytic anemia (IMHA) is a life-threatening autoimmune disorder characterized by a self-mediated attack on circulating red blood cells. The disease occurs naturally in both dogs and humans, but is significantly more prevalent in dogs. Because of its shared features across species, dogs offer a naturally occurring model for studying IMHA in people. In this study, we used RNA sequencing of whole blood from treatment-naïve dogs to study transcriptome-wide changes in gene expression in newly diagnosed animals compared to healthy controls. We found many overexpressed genes in pathways related to neutrophil function, coagulation, and hematopoiesis. In particular, the most highly overexpressed gene in cases was a phospholipase scramblase, which mediates the externalization of phosphatidylserine from the inner to the outer leaflet of cell membranes. This family of genes has been shown to be critically important for programmed cell death of erythrocytes as well as the initiation of the clotting cascade. Unexpectedly, we found marked underexpression of many genes related to lymphocyte function. We also identified groups of genes that are highly associated with the inflammatory response and red blood cell regeneration in affected dogs. We did not find any genes that distinguished dogs that lived vs. those that died at 30 days following diagnosis, nor did we find any relevant genomic signatures of microbial organisms in the blood of affected animals. Future studies are warranted to validate these findings and assess their implication in developing novel therapeutic approaches for dogs and humans with IMHA.

A negative reciprocal regulatory axis between cyclin D1 and HNF4α modulates cell cycle progression and metabolism in the liver.

Hepatocyte nuclear factor 4α (HNF4α) is a master regulator of liver function and a tumor suppressor in hepatocellular carcinoma (HCC). In this study, we explore the reciprocal negative regulation of HNF4α and cyclin D1, a key cell cycle protein in the liver. Transcriptomic analysis of cultured hepatocyte and HCC cells found that cyclin D1 knockdown induced the expression of a large network of HNF4α-regulated genes. Chromatin immunoprecipitation-sequencing (ChIP-seq) demonstrated that cyclin D1 inhibits the binding of HNF4α to thousands of targets in the liver, thereby diminishing the expression of associated genes that regulate diverse metabolic activities. Conversely, acute HNF4α deletion in the liver induces cyclin D1 and hepatocyte cell cycle progression; concurrent cyclin D1 ablation blocked this proliferation, suggesting that HNF4α maintains proliferative quiescence in the liver, at least, in part, via repression of cyclin D1. Acute cyclin D1 deletion in the regenerating liver markedly inhibited hepatocyte proliferation after partial hepatectomy, confirming its pivotal role in cell cycle progression in this in vivo model, and enhanced the expression of HNF4α target proteins. Hepatocyte cyclin D1 gene ablation caused markedly increased postprandial liver glycogen levels (in a HNF4α-dependent fashion), indicating that the cyclin D1-HNF4α axis regulates glucose metabolism in response to feeding. In AML12 hepatocytes, cyclin D1 depletion led to increased glucose uptake, which was negated if HNF4α was depleted simultaneously, and markedly elevated glycogen synthesis. To summarize, mutual repression by cyclin D1 and HNF4α coordinately controls the cell cycle machinery and metabolism in the liver.

An alpha-defensin gene single nucleotide polymorphism modulates the gut microbiota and may alter the risk of acute graft-versus-host disease.

We previously reported a protective association between single nucleotide polymorphisms (SNPs; rs4415345G and rs4610776A alleles) of Paneth cell α-defensin-5 against acute graft-versus-host disease (aGVHD). Because dysbiosis has been associated with aGVHD, we hypothesized that these SNPs may have a gut microbiota signature. In Lasso regression analysis of 248 healthy individuals, rs4415345G was associated with a higher abundance of Odoribacter splanchnicus, an anaerobic butyrogenic commensal. In multivariable analysis of data from 613 allogeneic haematopoietic cell transplant recipients, peri-engraftment presence of O. splanchnicus was associated with ~50% lower risk for grade II-IV aGVHD (hazard ratio 0·53, 95% confidence interval 0·28-1·00, P = 0·05). O. splanchnicus may protect rs4415345G individuals against aGVHD.

The role of gene flow in rapid and repeated evolution of cave-related traits in Mexican tetra, Astyanax mexicanus.

Understanding the molecular basis of repeatedly evolved phenotypes can yield key insights into the evolutionary process. Quantifying gene flow between populations is especially important in interpreting mechanisms of repeated phenotypic evolution, and genomic analyses have revealed that admixture occurs more frequently between diverging lineages than previously thought. In this study, we resequenced 47 whole genomes of the Mexican tetra from three cave populations, two surface populations and outgroup samples. We confirmed that cave populations are polyphyletic and two Astyanax mexicanus lineages are present in our data set. The two lineages likely diverged much more recently than previous mitochondrial estimates of 5-7 mya. Divergence of cave populations from their phylogenetically closest surface population likely occurred between ~161 and 191 k generations ago. The favoured demographic model for most population pairs accounts for divergence with secondary contact and heterogeneous gene flow across the genome, and we rigorously identified gene flow among all lineages sampled. Therefore, the evolution of cave-related traits occurred more rapidly than previously thought, and trogolomorphic traits are maintained despite gene flow with surface populations. The recency of these estimated divergence events suggests that selection may drive the evolution of cave-derived traits, as opposed to disuse and drift. Finally, we show that a key trogolomorphic phenotype QTL is enriched for genomic regions with low divergence between caves, suggesting that regions important for cave phenotypes may be transferred between caves via gene flow. Our study shows that gene flow must be considered in studies of independent, repeated trait evolution.

Neo-Domestication of an Interspecific Tetraploid Helianthus annuus × Helianthus tuberous Population That Segregates for Perennial Habit.

Perennial agriculture has been proposed as an option to improve the sustainability of cropping systems, by increasing the efficiency of resource use, while also providing ecosystem services. Neo-domestication, the contemporary domestication of plants that have not previously been used in agriculture, can be used to generate new crops for these systems. Here we explore the potential of a tetraploid (2n = 4x = 68) interspecific hybrid sunflower as a perennial oilseed for use in multifunctional agricultural systems. A population of this novel tetraploid was obtained from crosses between the annual diploid oilseed crop Helianthus annuus (2n = 2x = 34) and the perennial hexaploid tuber crop Helianthus tuberosus (2n = 6x = 102). We selected for classic domestication syndrome traits for three generations. Substantial phenotypic gains were made, in some cases approaching 320%. We also analyzed the genetic basis of tuber production (i.e., perenniality), with the goal of obtaining molecular markers that could be used to facilitate future breeding in this system. Results from quantitative trait locus (QTL) mapping suggest that tuber production has an oligogenic genetic basis. Overall, this study indicates that substantial gains towards domestication goals can be achieved over contemporary time scales.

Pre-clinical Safety and Off-Target Studies to Support Translation of AAV-Mediated RNAi Therapy for FSHD.

RNAi emerged as a prospective molecular therapy nearly 15 years ago. Since then, two major RNAi platforms have been under development: oligonucleotides and gene therapy. Oligonucleotide-based approaches have seen more advancement, with some promising therapies that may soon reach market. In contrast, vector-based approaches for RNAi therapy have remained largely in the pre-clinical realm, with limited clinical safety and efficacy data to date. We are developing a gene therapy approach to treat the autosomal-dominant disorder facioscapulohumeral muscular dystrophy. Our strategy involves silencing the myotoxic gene DUX4 using adeno-associated viral vectors to deliver targeted microRNA expression cassettes (miDUX4s). We previously demonstrated proof of concept for this approach in mice, and we are now taking additional steps here to assess safety issues related to miDUX4 overexpression and sequence-specific off-target silencing. In this study, we describe improvements in vector design and expansion of our miDUX4 sequence repertoire and report differential toxicity elicited by two miDUX4 sequences, of which one was toxic and the other was not. This study provides important data to help advance our goal of translating RNAi gene therapy for facioscapulohumeral muscular dystrophy.

The unusual S locus of Leavenworthia is composed of two sets of paralogous loci.

The Leavenworthia self-incompatibility locus (S locus) consists of paralogs (Lal2, SCRL) of the canonical Brassicaceae S locus genes (SRK, SCR), and is situated in a genomic position that differs from the ancestral one in the Brassicaceae. Unexpectedly, in a small number of Leavenworthia alabamica plants examined, sequences closely resembling exon 1 of SRK have been found, but the function of these has remained unclear. BAC cloning and expression analyses were employed to characterize these SRK-like sequences. An SRK-positive Bacterial Artificial Chromosome clone was found to contain complete SRK and SCR sequences located close by one another in the derived genomic position of the Leavenworthia S locus, and in place of the more typical Lal2 and SCRL sequences. These sequences are expressed in stigmas and anthers, respectively, and crossing data show that the SRK/SCR haplotype is functional in self-incompatibility. Population surveys indicate that < 5% of Leavenworthia S loci possess such alleles. An ancestral translocation or recombination event involving SRK/SCR and Lal2/SCRL likely occurred, together with neofunctionalization of Lal2/SCRL, and both haplotype groups now function as Leavenworthia S locus alleles. These findings suggest that S locus alleles can have distinctly different evolutionary origins.

Long-term right ventricular implantable cardioverter-defibrillator lead performance in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive disease characterized by replacement of normal myocardium by fibrofatty tissue. The right ventricular (RV) apex is the typical target for implantable cardioverter-defibrillator (ICD) lead placement, raising concerns for suboptimal lead performance in medium- to long-term follow-up. OBJECTIVE: The purpose of this study was to determine whether placement of ICD leads at the RV apex was associated with performance deterioration of medium-term leads in ARVC patients compared to non-ARVC patients. METHODS: In this multicenter, retrospective, case-control study, ICD lead performance measures of R-wave, impedance, and pacing thresholds were compared at baseline and between 1-year and 5-year postimplantation follow-up using mixed-effect models adjusted for age and sex. RESULTS: One hundred one ARVC patients (49 women, age 50.6 ± 14.5 years) were compared to 56 control patients (37 women, age 48.2 ± 14.2 years). The mean difference in R wave between years 1 and 2 was -0.85 mV (P = .16) compared to a mean difference at years 5 and 6 of -1.85 mV (P = .02). There was no difference in impedance or pacing threshold or in lead lifetime between the 2 groups over 6-year follow-up (5.91 ± 3.89 years vs 5.48 ± 3.70 years, P = .239). CONCLUSION: In ARVC patients with ICD leads implanted in the RV apex, ventricular sensing deteriorates significantly during medium-term follow-up. Septal RV lead placement should be explored as the first choice at implantation.

Recent selection for self-compatibility in a population of Leavenworthia alabamica.

The evolution of self-compatibility (SC) is the first step in the evolutionary transition in plants from outcrossing enforced by self-incompatibility (SI) to self-fertilization. In the Brassicaceae, SI is controlled by alleles of two tightly linked genes at the S-locus. Despite permitting inbreeding, mutations at the S-locus leading to SC may be selected if they provide reproductive assurance and/or gain a transmission advantage in a population when SC plants self- and outcross. Positive selection can leave a genomic signature in the regions physically linked to the focus of selection when selection has occurred recently. From an SC population of Leavenworthia alabamica with a known nonfunctional mutation at the S-locus, we collected sequence data from a ∼690 Kb region surrounding the S-locus, as well as from regions not linked to the S-locus. To test for recent positive selection acting at the S-locus, we examined polymorphism and the site-frequency spectra. Using forward simulations, we demonstrate that recent selection of the strength expected for SC at a locus formerly under balancing selection can generate patterns similar to those seen in our empirical data.

Outcome of Apparently Unexplained Cardiac Arrest: Results From Investigation and Follow-Up of the Prospective Cardiac Arrest Survivors With Preserved Ejection Fraction Registry.

BACKGROUND: The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) enrolls patients with apparently unexplained cardiac arrest and no evident cardiac disease to identify the pathogenesis of cardiac arrest through systematic clinical testing. Exercise testing, drug provocation, advanced cardiac imaging, and genetic testing may be useful when a cause is not apparent. METHODS AND RESULTS: The first 200 survivors of unexplained cardiac arrest from 14 centers across Canada were evaluated to determine the results of investigation and follow-up (age, 48.6±14.7 years, 41% female). Patients were free of evidence of coronary artery disease, left ventricular dysfunction, or evident repolarization syndromes. Advanced testing determined a diagnosis in 34% of patients at baseline, with a diagnosis emerging during follow-up in 7% of patients. Of those who were diagnosed, 28 (35%) had an underlying structural condition and 53 (65%) had a primary electric disease. During a mean follow-up of 3.15±2.34 years, 23% of patients had either a shock or an appropriate antitachycardia pacing from their implantable cardioverter defibrillator, or both. The implantable cardioverter defibrillator appropriate intervention rate was 8.4% at 1 year and 18.1% at 3 years, with no clear difference between diagnosed and undiagnosed subjects, or between those diagnosed with a primary electric versus structural pathogenesis. CONCLUSIONS: Obtaining a diagnosis in previously unexplained cardiac arrest patients requires systematic clinical testing and regular follow-up to unmask the cause. Nearly half of apparently unexplained cardiac arrest patients ultimately received a diagnosis, allowing for improved treatment and family screening. A substantial proportion of patients received appropriate implantable cardioverter defibrillator therapy during medium-term follow-up. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00292032.