No evidence for an intragenomic arms race under paternal genome elimination in Planococcus mealybugs

Genomic conflicts arising during reproduction might play an important role in shaping the striking diversity of reproductive strategies across life. Among these is paternal genome elimination (PGE), a form of haplodiploidy which has independently evolved several times in arthropods. PGE males are diploid but transmit maternally inherited chromosomes only, whereas paternal homologues are excluded from sperm. Mothers thereby effectively monopolize the parentage of sons, at the cost of the father's reproductive success. This creates striking conflict between the sexes that could result in a co-evolutionary arms race between paternal and maternal genomes over gene transmission, yet empirical evidence that such an arms race indeed takes place under PGE is scarce. This study addresses this by testing whether PGE is complete when paternal genotypes are exposed to divergent maternal backgrounds in intraspecific and hybrid crosses of the citrus mealybug, Planococcus citri, and the closely related Planococcus ficus. We determined whether males can transmit genetic information through their sons by tracking inheritance of two traits in a three-generation pedigree: microsatellite markers and sex-specific pheromone preferences. Our results suggest leakages of single paternal chromosomes through males occurring at a low frequency, but we find no evidence for transmission of paternal pheromone preferences from fathers to sons. The absence of differences between hybrid and intraspecific crosses in leakage rate of paternal alleles suggests that a co-evolutionary arms race cannot be demonstrated on this evolutionary timescale, but we conclude that there is scope for intragenomic conflict between parental genomes in mealybugs. Finally, we discuss how these paternal escapes can occur and what these findings may reveal about the evolutionary dynamics of this bizarre genetic system.

Significance of anti-neutrophil cytoplasmic antibodies in systemic sclerosis

Background

Up to 12% of patients with systemic sclerosis (SSc) have anti-neutrophil cytoplasmic antibodies (ANCA). However, the majority of these patients do not manifest ANCA-associated vasculitis (AAV) and the significance of ANCA in these patients is unclear. The aim of this study is to determine the prevalence of ANCA in a well-characterised SSc cohort and to examine the association between ANCA and SSc clinical characteristics, other autoantibodies, treatments and mortality.

Methods

Clinical data were obtained from 5 centres in the Australian Scleroderma Cohort Study (ASCS). ANCA positive was defined as the presence of any one or combination of cytoplasmic ANCA (c-ANCA), perinuclear ANCA (p-ANCA), atypical ANCA, anti-myeloperoxidase (anti-MPO) or anti-proteinase-3 (anti-PR3). Associations of demographic and clinical features with ANCA were investigated by logistic or linear regression. Survival analysis was performed using Kaplan-Meyer curves and Cox regression models.

Results

Of 1303 patients, 116 (8.9%) were ANCA positive. Anti-PR3 was more common than anti-MPO (13.8% and 11.2% of ANCA-positive patients, respectively). Only 3 ANCA-positive patients had AAV. Anti-Scl-70 was more common in ANCA positive vs ANCA negative (25% vs 12.8%, p < 0.001), anti-MPO positive vs anti-MPO negative (38.5% vs 13.6%, p = 0.006) and anti-PR3 positive vs anti-PR3 negative patients (44.4% vs 13.4%, p < 0.001). A higher prevalence of interstitial lung disease (ILD) was found in the ANCA positive (44.8% vs 21.8%, p < 0.001) and the anti-PR3 positive groups (50.0% vs 23.4%, p = 0.009). In multivariable analysis, ANCA-positive status remained associated with ILD after adjusting for anti-Scl-70 antibodies. Pulmonary embolism (PE) was more common in ANCA-positive patients (8.6% vs 3.0%, p = 0.002) and anti-PR3-positive patients (16.7% vs 3.3%, p = 0.022). ANCA-positive status remained associated with PE in a multivariable analysis adjusting for anti-phospholipid antibodies. Kaplan-Meier analysis revealed increased mortality in ANCA-positive patients (p = 0.006). In Cox regression analysis, ANCA was associated with increased mortality, after adjusting for age and sex.

Conclusions

ANCA is associated with increased prevalence of ILD and PE in SSc. ANCA should be tested in SSc, as it identifies individuals with worse prognosis who require close monitoring for adverse outcomes.

Do stroke patients screened as lower-nutritional-risk still receive dietitian assessment if indicated? A retrospective evaluation of two dietetic models of care for adult stroke patients

BACKGROUND

Dietetic models of care at Logan Hospital changed from all patients with a confirmed stroke receiving dietitian assessment (Old pathway) to only those patients screened as high-nutritional-risk (Modified pathway). However, it was unknown whether all low-nutritional-risk patients who were indicated for dietitian assessment for nutrition support actually received assessment. This pre-post retrospective study evaluated whether the Old pathway and the Modified pathway were equally effective in identifying low-nutritional-risk stroke patients who were indicated for dietitian assessment and compared the time spent providing Dietetic care.

METHODS

For both pathways, medical charts were reviewed for low-nutritional-risk patients admitted between December 2012 and November 2017 with a confirmed stroke, who were given a standard food and fluid diet code and scored MST < 2 (Malnutrition Screening Tool) on admission. Data collected included demographics, anthropometrics, malnutrition assessment, dietetic intervention and time spent caring for patients. Malnutrition-related clinical indicators were used to classify patients as either Dietitian Assessment for Nutrition Support Indicated or Not Indicated.

RESULTS

Low-nutritional-risk patients were similar on the Old (n = 180) and Modified (n = 206) pathways [mean (SD) 66 (13) years, 63% male, 4% malnutrition]. Those classified as Dietitian Assessment for Nutrition Support Indicated (n = 61 of 180) were older, had a longer length of stay (P < 0.05), and were all identified by the Dietitian on both pathways. Ten minutes less dietetic time per patient was required on the Modified pathway (P < 0.001).

CONCLUSIONS

The Modified Nutrition Stroke pathway performed more efficiently than the Old pathway and was equally effective at ensuring that stroke patients who were determined as being low-nutritional-risk received dietitian assessment during admission if indicated.

Fish consumption is associated with a decreased risk of death among adults with diabetes: 18-year follow-up of a national cohort

BACKGROUND

There is a paucity of studies examining the beneficial effects of fish consumption on cardiovascular diseases (CVDs) among adults with diabetes, who experience a substantially high risk of CVDs.

METHODS AND RESULTS

We analyzed the data of 1136 adults with diabetes mellitus aged 18 years and older who participated in the National Health and Nutrition Examination Survey, 1988-1994, and were followed up through December 31, 2010. We used Cox regression to estimate the adjusted hazard ratios (HRs) for the relative risk across the levels of fish consumption. A total of 698 deaths were recorded at the end of 11,465 person-years follow-up with a mortality rate of 60.88 per 1000 person-years. CVDs were listed as a contributing cause for 326 deaths, thus accounting for 46.4% of total deaths. Stroke-specific mortality rate among patients who ate fish less than once a week was more than twice as high as that among patients who ate fish more than twice a week, 6.23 vs. 2.36 per 1000 person-years, respectively. The corresponding CVD-specific rate was 34.38 vs. 22.99 per 1000 person-years, respectively. The adjusted HRs of death due to stroke were 1.00 (reference), 0.55 (95% confidence interval = 0.28-1.07), and 0.30 (0.11-0.80) among patients who ate fish <1, 1-2, and 2 + times a week, and the corresponding HRs of death due to CVDs were 1.00 (reference), 0.78 (0.60-1.02), and 0.69 (0.50-0.96), respectively.

CONCLUSIONS

A high consumption of fish was associated with a low risk of death due to CVDs, especially stroke, among adults with diabetes.

An Interim Report of the Scleroderma Clinical Trials Consortium Working Groups

The Scleroderma Clinical Trials Consortium (SCTC) represents many of the clinical researchers in the world who are interested in improving the efficiency of clinical trials in Systemic Sclerosis (SSc). The SCTC has established 11 working groups (WGs) to develop and validate better ways of measuring and recording multiple aspects of this heterogeneous disease. These include groups working on arthritis, disease damage, disease activity, cardiac disease, juvenile SSc, the gastrointestinal tract, vascular component, calcinosis, scleroderma renal crisis, interstitial lung disease, and skin measurement. Members of the SCTC may join any one or more of these groups. Some of the WGs have only recently started their work, some are nearing completion of their mandated tasks and others are in the midst of their projects. All these projects, which are described in this paper, will help to improve clinical trials and observational studies by improving or developing better, more sensitive ways of measuring various aspects of the disease. As Lord Kelvin stated, "To measure is to know. If you cannot measure it you cannot improve it." The SCTC is dedicated to improving the lives of patients with SSc and it is our hope that the contributions of the WGs will be one important step in this process.

The role of inflammatory markers in assessment of disease activity in systemic sclerosis

OBJECTIVES

The role of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in the assessment of disease activity in systemic sclerosis (SSc) remains controversial. We sought to evaluate the relationship between clinical features of SSc and raised inflammatory markers and to determine if changes in ESR and CRP reflect changes in other disease features over time.

METHODS

One thousand, five hundred and forty-five patients enrolled in the Australian Scleroderma Cohort Study were observed over a mean 3.52±2.91 years and assessed at 6,119 study visits. Generalised estimating equations were used to determine the relationship between ESR≥20mm/hr and CRP≥5mg/L and features of disease. The associations between change in inflammatory markers and change in skin scores and respiratory function tests were analysed.

RESULTS

Overall, there was a significant association between raised ESR and forced vital capacity (FVC)<80% predicted, diffusing capacity of the lung (DLCO)<80% predicted, pulmonary arterial hypertension (PAH), body mass index (BMI), proximal muscle strength, anaemia, and hypocomplementaemia (p<0.05). Raised CRP was significantly associated with modified Rodnan Skin Score>20, FVC<80%, DLCO<80%, PAH, digital ulcers, BMI, synovitis, tendon friction rub, anaemia, and hypocomplementaemia (p<0.05). A significant deterioration in respiratory function tests (RFTs) was associated with a 2-fold increase in both ESR and CRP (p<0.05).

CONCLUSIONS

Raised inflammatory markers are associated with pulmonary, cutaneous and musculoskeletal manifestations of SSc. Rising inflammatory markers are correlated with declining respiratory function tests. This suggests inflammatory markers have a role in the assessment of SSc disease activity.

The challenges and controversies of measuring disease activity in systemic sclerosis

Major alteration of the natural history of systemic sclerosis is limited with current treatments, and the development of novel therapies has been hampered, in part, by the lack of fully validated multi-system outcome measures. There remains a lack of consensus as to the very definition of systemic sclerosis disease activity, complicating efforts to measure activity in clinical trials. Previously published multi-system measures of disease status are yet to be fully validated according to the Outcome Measures in Rheumatology (OMERACT) filter. There is currently significant research interest in developing new systemic sclerosis-specific measures to better describe and compare patient cohorts and measure therapeutic responses in clinical trials. An accurate measure of disease activity in systemic sclerosis will facilitate the enrichment of clinical trials with patients who have active disease, targeting a group of patients most likely to benefit from therapeutic intervention. In addition, following on from successes in other rheumatic conditions, a state of low disease activity, measured by an activity index, may become a clinical trial end point and therapeutic target. The Scleroderma Clinical Trials Consortium has undertaken to develop a definition of disease activity and fully validate a new systemic sclerosis activity index. The Scleroderma Clinical Trials Consortium Activity Index will be developed using consensus and data-driven methods and is envisaged to be widely used in research and clinical settings.

Does a plant-eating insect's diet govern the evolution of insecticide resistance? Comparative tests of the pre-adaptation hypothesis

According to the pre‐adaptation hypothesis, the evolution of insecticide resistance in plant‐eating insects co‐opts adaptations that initially evolved during chemical warfare with their host plants. Here, we used comparative statistics to test two predictions of this hypothesis: (i) Insects with more diverse diets should evolve resistance to more diverse insecticides. (ii) Feeding on host plants with strong or diverse qualitative chemical defenses should prime an insect lineage to evolve insecticide resistance. Both predictions are supported by our tests. What makes this especially noteworthy is that differences in the diets of plant‐eating insect species are typically ignored by the population genetic models we use to make predictions about insecticide resistance evolution. Those models surely capture some of the differences between host‐use generalists and specialists, for example, differences in population size and migration rates into treated fields, but they miss other potentially important differences, for example, differences in metabolic diversity and gene expression plasticity. Ignoring these differences could be costly.

Sex Determination, Sex Chromosomes, and Karyotype Evolution in Insects

Insects harbor a tremendous diversity of sex determining mechanisms both within and between groups. For example, in some orders such as Hymenoptera, all members are haplodiploid, whereas Diptera contain species with homomorphic as well as male and female heterogametic sex chromosome systems or paternal genome elimination. We have established a large database on karyotypes and sex chromosomes in insects, containing information on over 13000 species covering 29 orders of insects. This database constitutes a unique starting point to report phylogenetic patterns on the distribution of sex determination mechanisms, sex chromosomes, and karyotypes among insects and allows us to test general theories on the evolutionary dynamics of karyotypes, sex chromosomes, and sex determination systems in a comparative framework. Phylogenetic analysis reveals that male heterogamety is the ancestral mode of sex determination in insects, and transitions to female heterogamety are extremely rare. Many insect orders harbor species with complex sex chromosomes, and gains and losses of the sex-limited chromosome are frequent in some groups. Haplodiploidy originated several times within insects, and parthenogenesis is rare but evolves frequently. Providing a single source to electronically access data previously distributed among more than 500 articles and books will not only accelerate analyses of the assembled data, but also provide a unique resource to guide research on which taxa are likely to be informative to address specific questions, for example, for genome sequencing projects or large-scale comparative studies.

The ecology of sex explains patterns of helping in arthropod societies

Across arthropod societies, sib-rearing (e.g. nursing or nest defence) may be provided by females, by males or by both sexes. According to Hamilton's 'haplodiploidy hypothesis', this diversity reflects the relatedness consequences of diploid vs. haplodiploid inheritance. However, an alternative 'preadaptation hypothesis' instead emphasises an interplay of ecology and the co-option of ancestral, sexually dimorphic traits for sib-rearing. The preadaptation hypothesis has recently received empirical support, but remains to be formalised. Here, we mathematically model the coevolution of sex-specific helping and sex allocation, contrasting these hypotheses. We find that ploidy per se has little effect. Rather, the ecology of sex shapes patterns of helping: sex-specific preadaptation strongly influences who helps; a freely adjustable sex ratio magnifies sex biases and promotes helping; and sib-mating, promiscuity, and reproductive autonomy also modulate the sex and abundance of helpers. An empirical survey reveals that patterns of sex-specific helping in arthropod taxa are consistent with the preadaptation hypothesis.

A simple prognostic model for overall survival in metastatic renal cell carcinoma

INTRODUCTION

The primary purpose of this study was to develop a simpler prognostic model to predict overall survival for patients treated for metastatic renal cell carcinoma (mRCC) by examining variables shown in the literature to be associated with survival.

METHODS

We conducted a retrospective analysis of patients treated for mRCC at two Canadian centres. All patients who started first-line treatment were included in the analysis. A multivariate Cox proportional hazards regression model was constructed using a stepwise procedure. Patients were assigned to risk groups depending on how many of the three risk factors from the final multivariate model they had.

RESULTS

There were three risk factors in the final multivariate model: hemoglobin, prior nephrectomy, and time from diagnosis to treatment. Patients in the high-risk group (two or three risk factors) had a median survival of 5.9 months, while those in the intermediate-risk group (one risk factor) had a median survival of 16.2 months, and those in the low-risk group (no risk factors) had a median survival of 50.6 months.

CONCLUSIONS

In multivariate analysis, shorter survival times were associated with hemoglobin below the lower limit of normal, absence of prior nephrectomy, and initiation of treatment within one year of diagnosis.

The evolutionary dynamics of haplodiploidy: Genome architecture and haploid viability

Haplodiploid reproduction, in which males are haploid and females are diploid, is widespread among animals, yet we understand little about the forces responsible for its evolution. The current theory is that haplodiploidy has evolved through genetic conflicts, as it provides a transmission advantage to mothers. Male viability is thought to be a major limiting factor; diploid individuals tend to harbor many recessive lethal mutations. This theory predicts that the evolution of haplodiploidy is more likely in male heterogametic lineages with few chromosomes, as genes on the X chromosome are often expressed in a haploid environment, and the fewer the chromosome number, the greater the proportion of the total genome that is X-linked. We test this prediction with comparative phylogenetic analyses of mites, among which haplodiploidy has evolved repeatedly. We recover a negative correlation between chromosome number and haplodiploidy, find evidence that low chromosome number evolved prior to haplodiploidy, and that it is unlikely that diplodiploidy has reevolved from haplodiploid lineages of mites. These results are consistent with the predicted importance of haploid male viability.

What haplodiploids can teach us about hybridization and speciation

Most evolutionary theory focuses on species that reproduce through sexual reproduction where both sexes have a diploid chromosome count. Yet a substantial proportion of multicellular species display complex life cycles, with both haploid and diploid life stages. A classic example is haplodiploidy, where females develop from fertilized eggs and are diploid, while males develop from unfertilized eggs and are haploid. Although haplodiploids make up about 15% of all animals (de la Filia et al. ), this type of reproduction is rarely considered in evolutionary theory. In this issue of Molecular Ecology, Patten et al. () develop a theoretical model to compare the rate of nuclear and mitochondrial introgression in haplodiploid and diploid species. They show that when two haplodiploid species hybridize, nuclear genes are much less likely to cross the species barrier than if both species were to be diploids. The reason for this is that only half of the offspring resulting from matings between haplodiploid species are true hybrids: sons from such mating only inherit their mother genes and therefore only contain genes of the maternal species. Truly, hybrid males can only occur through backcrossing of a hybrid female to a male of one of the parental species. While this twist of haplodiploid transmission genetics limits nuclear introgression, mitochondrial genes, which are maternally inherited, are unaffected by the scarcity of hybrid males. In other words, the rate of mitochondrial introgression is the same for haplodiploid and diploid species. As a result, haplodiploid species on average show a bias of mitochondrial compared to nuclear introgression.

Haplodiploidy and the reproductive ecology of Arthropods

Approximately 15% of all arthropods reproduce through haplodiploidy. Yet it is unclear how this mode of reproduction affects other aspects of reproductive ecology. In this review we outline predictions on how haplodiploidy might affect mating system evolution, the evolution of traits under sexual or sexual antagonistic selection, sex allocation decisions and the evolution of parental care. We also give an overview of the phylogenetic distribution of haplodiploidy. Finally, we discuss how comparisons between different types of haplodiploidy (arrhenotoky, PGE with haploid vs somatically diploid males) might help to discriminate between the effects of virgin birth, haploid gene expression and those of haploid gene transmission.