Genetic Variation in Reproductive Investment Across an Ephemerality Gradient in Daphnia pulex.

Species across the tree of life can switch between asexual and sexual reproduction. In facultatively sexual species, the ability to switch between reproductive modes is often environmentally dependent and subject to local adaptation. However, the ecological and evolutionary factors that influence the maintenance and turnover of polymorphism associated with facultative sex remain unclear. We studied the ecological and evolutionary dynamics of reproductive investment in the facultatively sexual model species, Daphnia pulex. We found that patterns of clonal diversity, but not genetic diversity varied among ponds consistent with the predicted relationship between ephemerality and clonal structure. Reconstruction of a multi-year pedigree demonstrated the coexistence of clones that differ in their investment into male production. Mapping of quantitative variation in male production using lab-generated and field-collected individuals identified multiple putative quantitative trait loci (QTL) underlying this trait, and we identified a plausible candidate gene. The evolutionary history of these QTL suggests that they are relatively young, and male limitation in this system is a rapidly evolving trait. Our work highlights the dynamic nature of the genetic structure and composition of facultative sex across space and time and suggests that quantitative genetic variation in reproductive strategy can undergo rapid evolutionary turnover.

Dendrimer-N-acetyl-L-cysteine modulates monophagocytic response in adrenoleukodystrophy.

OBJECTIVE: X-linked adrenoleukodystrophy (ALD) is a neurodegenerative disorder due to mutations in the peroxisomal very long-chain fatty acyl-CoA transporter, ABCD1, with limited therapeutic options. ALD may manifest in a slowly progressive adrenomyeloneuropathy (AMN) phenotype, or switch to rapid inflammatory demyelinating cerebral disease (cALD), in which microglia have been shown to play a pathophysiological role. The aim of this study was to determine the role of patient phenotype in the immune response of ex vivo monophagocytic cells to stimulation, and to evaluate the efficacy of polyamidoamine dendrimer conjugated to the antioxidant precursor N-acetyl-cysteine (NAC) in modulating this immune response. METHODS: Human monophagocytic cells were derived from fresh whole blood, from healthy (n = 4), heterozygote carrier (n = 4), AMN (n = 7), and cALD (n = 4) patients. Cells were exposed to very long-chain fatty acids (VLCFAs; C24:0 and C26:0) and treated with dendrimer-NAC (D-NAC). RESULTS: Ex vivo exposure to VLCFAs significantly increased tumor necrosis factor α (TNFα) and glutamate secretion from cALD patient macrophages. Additionally, a significant reduction in total intracellular glutathione was observed in cALD patient cells. D-NAC treatment dose-dependently reduced TNFα and glutamate secretion and replenished total intracellular glutathione levels in cALD patient macrophages, more efficiently than NAC. Similarly, D-NAC treatment decreased glutamate secretion in AMN patient cells. INTERPRETATION: ALD phenotypes display unique inflammatory profiles in response to VLCFA stimulation, and therefore ex vivo monophagocytic cells may provide a novel test bed for therapeutic agents. Based on our findings, D-NAC may be a viable therapeutic strategy for the treatment of cALD. Ann Neurol 2018;84:452-462.

Balancing selection and the functional effects of shared polymorphism in cryptic Daphnia species.

The patterns of genetic variation within and between related taxa represent the genetic history of a species. Shared polymorphisms, loci with identical alleles across species, are of unique interest as they may represent cases of ancient selection maintaining functional variation post-speciation. In this study, we investigate the abundance of shared polymorphism in the Daphnia pulex species complex. We test whether shared mutations are consistent with the action of balancing selection or alternative hypotheses such as hybridization, incomplete lineage sorting, or convergent evolution. We analyzed over 2,000 genomes from North American and European D. pulex and several outgroup species to examine the prevalence and distribution of shared alleles between the focal species pair, North American and European D. pulex. We show that while North American and European D. pulex diverged over ten million years ago, they retained tens of thousands of shared alleles. We found that the number of shared polymorphisms between North American and European D. pulex cannot be explained by hybridization or incomplete lineage sorting alone. Instead, we show that most shared polymorphisms could be the product of convergent evolution, that a limited number appear to be old trans-specific polymorphisms, and that balancing selection is affecting young and ancient mutations alike. Finally, we provide evidence that a blue wavelength opsin gene with trans-specific polymorphisms has functional effects on behavior and fitness in the wild. Ultimately, our findings provide insights into the genetic basis of adaptation and the maintenance of genetic diversity between species.

A cosmopolitan inversion facilitates seasonal adaptation in overwintering Drosophila.

Fluctuations in the strength and direction of natural selection through time are a ubiquitous feature of life on Earth. One evolutionary outcome of such fluctuations is adaptive tracking, wherein populations rapidly adapt from standing genetic variation. In certain circumstances, adaptive tracking can lead to the long-term maintenance of functional polymorphism despite allele frequency change due to selection. Although adaptive tracking is likely a common process, we still have a limited understanding of aspects of its genetic architecture and its strength relative to other evolutionary forces such as drift. Drosophila melanogaster living in temperate regions evolve to track seasonal fluctuations and are an excellent system to tackle these gaps in knowledge. By sequencing orchard populations collected across multiple years, we characterized the genomic signal of seasonal demography and identified that the cosmopolitan inversion In(2L)t facilitates seasonal adaptive tracking and shows molecular footprints of selection. A meta-analysis of phenotypic studies shows that seasonal loci within In(2L)t are associated with behavior, life history, physiology, and morphological traits. We identify candidate loci and experimentally link them to phenotype. Our work contributes to our general understanding of fluctuating selection and highlights the evolutionary outcome and dynamics of contemporary selection on inversions.

Pandemic intake questionnaire to improve quality, effectiveness, and efficiency of outpatient neurologic and developmental care at the Kennedy Krieger institute during the COVID-19 pandemic.

Background: The COVID-19 pandemic uniquely affects patients with neurologic and developmental disabilities at the Kennedy Krieger Institute. These patients are at increased risk of co-morbidities, increasing their risk of contracting COVID-19. Disruptions in their home and school routines, and restrictions accessing crucial healthcare services has had a significant impact. Methods: A Pandemic Intake questionnaire regarding COVID-19 related medical concerns of guardians of patients was distributed using Qualtrics. Data from May-December 2020 were merged with demographic information of patients from 10 clinics (Center for Autism and Related Disorders (CARD), Neurology, Epigenetics, Neurogenetics, Center for Development and Learning (CDL) Sickle Cell, Spinal Cord, Sturge-Weber syndrome (SWS), Tourette's, and Metabolism). A provider feedback survey was distributed to program directors to assess the effectiveness of this intervention. Results: Analysis included responses from 1643 guardians of pediatric patients (mean age 9.5 years, range 0-21.6 years). Guardians of patients in more medically complicated clinics reported perceived increased risk of COVID-19 (p < 0.001) and inability to obtain therapies (p < 0.001) and surgeries (p < 0.001). Guardian responses from CARD had increased reports of worsening behavior (p = 0.01). Providers increased availability of in-person and virtual therapies and visits and made referrals for additional care to address this. In a survey of medical providers, five out of six program directors who received the responses to this survey found this questionnaire helpful in caring for their patients. Conclusion: This quality improvement project successfully implemented a pre-visit questionnaire to quickly assess areas of impact of COVID-19 on patients with neurodevelopmental disorders. During the pandemic, results identified several major areas of impact, including patient populations at increased risk for behavioral changes, sleep and/or disruptions of medical care. Most program directors reported improved patient care as a result.

Neuronal ablation of mt-AspRS in mice induces immune pathway activation prior to severe and progressive cortical and behavioral disruption.

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare, slowly progressive white matter disease caused by mutations in the mitochondrial aspartyl-tRNA synthetase (mt-AspRS, or DARS2). While patients show characteristic MRI T2 signal abnormalities throughout the cerebral white matter, brainstem, and spinal cord, the phenotypic spectrum is broad and a multitude of gene variants have been associated with the disease. Here, Dars2 disruption in CamKIIα-expressing cortical and hippocampal neurons results in slowly progressive increases in behavioral activity at five months, and culminating by nine months as severe brain atrophy, behavioral dysfunction, reduced corpus callosum thickness, and microglial morphology indicative of neuroinflammation. Interestingly, RNAseq based gene expression studies performed prior to the presentation of this severe phenotype reveal the upregulation of several pathways involved in immune activation, cytokine production and signaling, and defense response regulation. RNA transcript analysis demonstrates that activation of immune and cell stress pathways are initiated in advance of a behavioral phenotype and cerebral deficits. An understanding of these pathways and their contribution to significant neuronal loss in CamKII-Dars2 deficient mice may aid in deciphering mechanisms of LBSL pathology.

Does echocardiography accurately reflect CMR-determined changes in left ventricular parameters following exercise training? A prospective longitudinal study.

Cardiac adaptation in response to exercise has historically been described using echocardiography. Cardiac magnetic resonance (CMR), however, has evolved as a preferred imaging methodology for cardiac morphological assessment. While direct imaging modality comparisons in athletes suggest that large absolute differences in cardiac dimensions exist, it is currently unknown whether changes in cardiac morphology in response to exercise training are comparable when using echocardiography and CMR. Twenty-two young men were randomly assigned to undertake a supervised and intensive endurance or resistance exercise-training program for 24 wk. Echocardiography and CMR assessment of left ventricular (LV) mass, LV end-diastolic volume, internal cavity dimensions, and wall thicknesses were completed before and after training. At baseline, pooled data for all cardiac parameters were significantly different between imaging methods, while LV mass (r = 0.756, P < 0.001) and volumes (LV end-diastolic volume, r = 0.792, P < 0.001) were highly correlated across modalities. Changes in cardiac morphology data with exercise training were not significantly related when echocardiographic and CMR measures were compared. For example, posterior wall thickness increased by 8.3% (P < 0.05) when assessed using echocardiography, but decreased by 2% when using CMR. In summary, echocardiography and CMR imaging modalities produce findings that differ with respect to changes in cardiac size and volume following exercise training.

Pre-ablation magnetic resonance imaging of the cavotricuspid isthmus.

AIMS: In this prospective pilot study, pre-procedural MRI was performed on patients undergoing radiofrequency ablation of the cavotricuspid isthmus (CTI) to assess variation in isthmus anatomy and its impact on catheter ablation. METHODS: In 41 patients, 34 males, mean age 56 +/- 11.5 years, pre-procedural MRI was performed prior to ablation. On the basis of the magnetic resonance imaging (MRI), isthmus length and description of isthmus morphology was determined. Catheter ablation of the CTI was then performed using a standard technique by an experienced operator without prior knowledge of the MRI findings. RESULTS: The following morphological variants of isthmus morphology were demonstrated: long isthmus, concave isthmus shape, simple pouches, and eccentric septally directed pouches distinct from the coronary sinus. There was a trend towards longer RF times for long and concave shaped CTI. Eccentric septally directed pouches were associated with significantly longer radiofrequency energy delivery times (29.5 +/- 24.5 min RF versus 14.5 +/- 12.9 min RF; P = 0.037). CONCLUSION: The anatomy of the CTI is highly variable. Ablation difficulty can be predicted by the presence or absence of morphological variants and the length of CTI demonstrated by cardiac MRI.