Evaluation of a 3D-Printed Cleft Palate Obturator Using a Low-Dose Cone Beam Computed Tomography Acquisition Protocol: A Proof-of-Concept Study.

Cone beam computed tomography (CBCT) technology is increasingly utilized in the head and neck region and is valuable in treatment planning for cleft palate patients, potentially enabling the creation of 3D-printed obturators to assist with feeding and speech. This technical report investigates the feasibility of using data from a 360-degree CBCT scan to accurately produce a cleft palate obturator and assesses whether a lower-dose 180-degree CBCT scan can achieve a comparable result. A simulated cleft palate was crafted on a dehydrated human skull, which was then scanned using both 360-degree and 180-degree CBCT scanning protocols. Two obturators were digitally designed based on the segmented images from each scan and subsequently 3D printed. Evaluation of the segmented images and 3D-printed obturators from both protocols demonstrated clear visualization of anatomical landmarks and identical scores across all parameters, suggesting that the 180-degree CBCT scan can produce an obturator of comparable quality to that of the 360-degree scan, with the added benefit of reduced radiation exposure.

Erratum: Role of adipocyte Na,K-ATPase oxidant amplification loop in cognitive decline and neurodegeneration.

[This corrects the article DOI: 10.1016/j.isci.2021.103262.].

Investigational treatment strategies in glioblastoma: progress made and barriers to success.

INTRODUCTION: Glioblastoma, isocitrate dehydrogenase wildtype (IDHwt), remains an incurable disease despite considerable research effort. The current standard of care since 2005 comprises maximal safe resection followed by radiation with concurrent and adjuvant temozolomide; more recently, the addition of tumor treating fields was approved in the newly diagnosed and recurrent disease settings. AREAS COVERED: Searches of PubMed, Cochrane Library, and ClinicalTrials.gov provided a foundation for this review. We first describe early research including carmustine wafers, brachytherapy, anti-angiogenesis, and immune checkpoint inhibition for glioblastoma. Next, we discuss challenges precluding the translation of preclinical successes. This is followed by a description of promising treatments such as chimeric antigen receptor T-cell therapy as well as the recent qualified successes of cancer vaccinations. Non-immunotherapy trials are also highlighted, and ongoing or pending phase 2 and 3 clinical trials are codified in study tables. EXPERT OPINION: Unfortunately, hundreds of trials, including of agents effective in systemic malignancy, have not drastically changed management of glioblastoma. This may reflect unique resistance mechanisms and highlights a need for multimodality treatments beyond surgery, radiation, and conventional chemotherapy. Novel techniques, such as those in the emerging field of cancer neuroscience, may help uncover tolerable and effective regimens for this lethal malignancy.

Sting and p53 DNA repair pathways are compromised in Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia. A common finding in AD is DNA damage. Double-strand DNA breaks (DSBs) are particularly hazardous to neurons because their post-mitotic state forces neurons to rely on error-prone and potentially mutagenic mechanisms to repair DNA breaks. However, it remains unclear whether DNA damage results from increased DNA damage or failure of DNA repair. Oligomerization of the tumor suppressor protein p53 is an essential part of DSB repair, and p53 phosphorylated on S15 is an indicator of DNA damage. We report that the monomer:dimer ratio of phosphorylated (S15) p53 is increased by 2.86-fold in temporal lobes of AD patients compared to age-matched controls, indicating that p53 oligomerization is compromised in AD. In vitro oxidation of p53 with 100 nM H2O2 produced a similar shift in the monomer:dimer ratio. A COMET test showed a higher level of DNA degradation in AD consistent with double-strand DNA damage or inhibition of repair. Protein carbonylation was also elevated (190% of control), indicating elevated oxidative stress in AD patients. Levels of the DNA repair support protein 14-3-3σ, γ-H2AX, a phosphorylated histone marking double strand DNA breaks, and phosphorylated ataxia telangiectasia mutated (ATM) protein were all increased. cGAS-STING-interferon signaling was impaired in AD and was accompanied by a depletion of STING protein from Golgi and a failure to elevate interferon despite the presence of DSBs. The results suggest that oxidation of p53 by ROS could inhibit the DDR and decrease its ability to orchestrate DSB repair by altering the oligomerization state of p53. The failure of immune-stimulated DNA repair may contribute to cell loss in AD and suggests new therapeutic targets for AD.

Targeting lung cancer brain metastases: a narrative review of emerging insights for anaplastic lymphoma kinase (ALK)-positive disease.

Background and Objective: Lung cancer is commonly associated with brain metastasis formation, and certain subtypes, such as anaplastic lymphoma kinase (ALK) rearranged disease, have an especially high propensity for early and frequent central nervous system (CNS) involvement for which treatment can be challenging. Historical management has centered on surgery and radiation therapy (RT), which persist as mainstays of treatment for large, symptomatic lesions and widespread CNS disease. To date, sustained disease control remains elusive, and the role for effective systemic adjunctive therapies is clear. Here we discuss the epidemiology, genomics, pathophysiology, identification, and management of lung cancer brain metastases with a particular emphasis on systemic treatment of ALK-positive disease according to the best available evidence. Methods: Review of PubMed and Google Scholar databases as well as ClinicalTrials.gov provided background and seminal trials for the local and systemic management of ALK rearranged lung cancer brain metastases. Key Content and Findings: The development of effective, CNS-penetrant systemic agents-including alectinib, brigatinib, ceritinib, and lorlatinib-has dramatically changed the management and prevention of ALK rearranged brain metastases. Most notably, there is a burgeoning role for upfront systemic therapy for both symptomatic and incidentally discovered lesions. Conclusions: Novel targeted therapies offer patients a pathway to delay, obviate, or supplement traditional local therapies while minimizing neurologic sequelae of treatment and may reduce the risk of brain metastasis formation. However, the selection of patients to whom local and targeted treatments is offered is not trivial, and the risks and benefits of both must be weighed carefully. More work is needed to establish treatment regimens that yield durable intra- and extracranial disease control.

Early onset adult deafness in the Rhodesian Ridgeback dog is associated with an in-frame deletion in the EPS8L2 gene.

Domestic dogs exhibit diverse types of both congenital and non-congenital hearing losses. Rhodesian Ridgebacks can suffer from a progressive hearing loss in the early stage of their life, a condition known as early onset adult deafness (EOAD), where they lose their hearing ability within 1-2 years after birth. In order to investigate the genetic basis of this hereditary hearing disorder, we performed a genome-wide association study (GWAS) by using a sample of 23 affected and 162 control Rhodesian Ridgebacks. We identified a genomic region on canine chromosome 18 (CFA18) that is strongly associated with EOAD, and our subsequent targeted Sanger sequencing analysis identified a 12-bp inframe deletion in EPS8L2 (CFA18:25,868,739-25,868,751 in the UMICH_Zoey_3.1/canFam5 reference genome build). Additional genotyping confirmed a strong association between the 12-bp deletion and EOAD, where all affected dogs were homozygous for the deletion, while none of the control dogs was a deletion homozygote. A segregation pattern of this deletion in a 2-generation nuclear family indicated an autosomal recessive mode of inheritance. Since EPS8L2 plays a critical role in the maintenance and integrity of the inner ear hair cells in humans and other mammals, the inframe deletion found in this study represents a strong candidate causal mutation for EOAD in Rhodesian Ridgebacks. Genetic and clinical similarities between childhood deafness in humans and EOAD in Rhodesian Ridgebacks emphasizes the potential value of this dog breed in translational research in hereditary hearing disorders.

Population genomic consequences of life-history and mating system adaptation to a geothermal soil mosaic in yellow monkeyflowers.

Local selection can promote phenotypic divergence despite gene flow across habitat mosaics, but adaptation itself may generate substantial barriers to genetic exchange. In plants, life-history, phenology, and mating system divergence have been proposed to promote genetic differentiation in sympatry. In this study, we investigate phenotypic and genetic variation in Mimulus guttatus (yellow monkeyflowers) across a geothermal soil mosaic in Yellowstone National Park (YNP). Plants from thermal annual and nonthermal perennial habitats were heritably differentiated for life-history and mating system traits, consistent with local adaptation to the ephemeral thermal-soil growing season. However, genome-wide genetic variation primarily clustered plants by geographic region, with little variation sorting by habitat. The one exception was an extreme thermal population also isolated by a 200 m geographical gap of no intermediate habitat. Individual inbreeding coefficients (FIS ) were higher (and predicted by trait variation) in annual plants and annual pairs showed greater isolation by distance at local (<1 km) scales. Finally, YNP adaptation does not reuse a widespread inversion that underlies M. guttatus life-history ecotypes range-wide, suggesting a novel genetic mechanism. Overall, this work suggests that life-history and mating system adaptation strong enough to shape individual mating patterns does not necessarily generate incipient speciation without geographical barriers.

Characterization of persistent atrial fibrillation with non-contact charge density mapping and relationship to voltage.

BACKGROUND: Despite studies using localized high density contact mapping and lower resolution panoramic approaches, the mechanisms that sustain human persistent atrial fibrillation (AF) remain unresolved. Voltage mapping is commonly employed as a surrogate of atrial substrate to guide ablation procedures. OBJECTIVE: To study the distribution and temporal stability of activation during persistent AF using a global non-contact charge density approach and compare the findings with bipolar contact mapping. METHODS: Patients undergoing either redo or de novo ablation for persistent AF underwent charge density and voltage mapping to guide the ablation procedure. Offline analysis was performed to measure the temporal stability of three specific charge density activation (CDA) patterns, and the degree of spatial overlap between CDA patterns and low voltage regions. RESULTS: CDA was observed in patient-specific locations that partially overlapped, comprising local rotational activity (18% of LA), local irregular activity (41% of LA), and focal activity (39% of LA). Local irregular activity had the highest temporal stability. LA voltage was similar in regions with and without CDA. CONCLUSION: In persistent AF, CDA patterns appear unrelated to low voltage areas but occur in varying locations with high temporal stability.

Modulation of proteasome activity by curcumin and didemethylcurcumin.

Modulation of proteasome function by pharmacological interventions and molecular biology tools is an active area of research in cancer biology and neurodegenerative diseases. Curcumin (diferuloylmethane) is a naturally occurring polyphenol that affects multiple signaling pathways. Curcumin shows anti-inflammatory, antioxidant, anti-angiogenic, or anti-apoptotic properties. Recent research suggests that the therapeutic efficacy of curcumin may be due to its activity as a potent inhibitor of the proteasome. Using in vitro cell culture and molecular docking methods, here we show that both curcumin and its synthetic polyphenolic derivative (didemethylcurcumin, CUIII) modulated proteasome activity in a biphasic manner. Curcumin and CUIII increased proteasome activity at nanomolar concentrations, but inhibited proteasome activity at micromolar concentrations. Curcumin was more effective than CUIII in increasing relative proteasome activity at nanomolar concentrations. Also, curcumin was more effective than CUIII in inhibiting relative proteasome activity at micromolar concentrations. Docking simulations of curcumin and didemethylcurcumin binding to the 20S proteasome catalytic subunit estimated Kd values of 0.0054 µM and 1.3167 µM, respectively. These values correlate well with the results of the effectiveness of modulation by curcumin compared to CUIII. The small size of CUIII allows it to dock to the narrow cavity of the active site, but the binding interaction is not strong compared to curcumin. These results indicate that curcumin and its didemethyl derivative can be used to modulate proteasome activity and suggest that curcumin and its didemethyl derivative may be useful in treating two different disease classes: neurodegeneration and cancer.Communicated by Ramaswamy H. Sarma.

Morphology of the nutrient artery and its foramen in relation to femoral bone perfusion rates of laying and non-laying hens.

If arteries penetrate bones through foramina, regional artery blood flow rates can be estimated from the foramen sizes. Femoral bone blood flow rates estimated from nutrient foramen sizes were previously not absolute, but only a relative blood flow index (Qi ), because the size relationship between the foramen and the occupying artery was unknown. The current study used vascular contrast and micro-computerized tomographic scanning to investigate femoral nutrient foramen and nutrient artery sizes in three groups of sub-adult chickens (non-laying hens, laying hens, and roosters) of similar ages. The results indicate that the cross-sectional area of the nutrient artery lumen occupies approximately 20.2 ± 4.1% of the foramen for femora with only one foramen. Artery lumen size is significantly correlated with foramen size. Vascular contrast imaging is capable of estimating blood flow rates through nutrient arteries, as blood flow rates estimated from artery lumen casts are similar to blood flow rates measured by infusion of fluorescent-labeled microspheres. Laying hens tend to have higher nutrient artery perfusion rates than non-laying hens, probably due to extra oxygen and calcium requirements for eggshell production, although the calculated blood flow difference was not statistically significant. Histological embedding and sectioning along with vascular contrast imaging reveal variable nutrient foramen morphology and nutrient artery location among femora with more than one nutrient foramen.

Differential effect of clopidogrel and ticagrelor on leukocyte count in relation to patient characteristics, biomarkers and genotype: a PLATO substudy.

Inflammation plays a key role in cardiovascular disease by contributing to atherothrombosis. The PLATelet inhibition and patient Outcomes (PLATO) study (NCT00391872) compared ticagrelor to clopidogrel in patients with acute coronary syndromes and demonstrated fewer cardiovascular events with ticagrelor but lower white blood cell counts (WBC) with clopidogrel. In this further analysis of the PLATO biomarker substudy, we assessed associations between WBC and clinical characteristics, biomarker levels, and CYP2C19 polymorphisms.On-treatment mean (SD) WBC in the clopidogrel group was mildly reduced at each stage of follow-up compared with either the ticagrelor group (1 month: 7.27 (2.1) and 7.67 (2.23) x109/L for clopidogrel and ticagrelor, respectively; p < .001) or following cessation of clopidogrel (7.23 (1.97) x109/L, at 6 months vs 7.56 (2.28) x109/L after treatment cessation; P < .001). This occurred independently of baseline biomarkers and CYP2C19 genotype (where known). Adjusting for clinical characteristics and other biomarkers, no significant interaction was detected between clinical risk factors and the observed effect of clopidogrel on WBC.Clopidogrel weakly suppresses WBC, independent of clinical characteristics, baseline inflammatory biomarker levels, and CYP2C19 genotype. Further work is required to determine the mechanism for this effect and whether it contributes to clopidogrel's efficacy as well as therapeutic interaction with anti-inflammatory drugs.

Role of adipocyte Na,K-ATPase oxidant amplification loop in cognitive decline and neurodegeneration.

Recent studies suggest that a western diet may contribute to clinical neurodegeneration and dementia. Adipocyte-specific expression of the Na,K-ATPase signaling antagonist, NaKtide, ameliorates the pathophysiological consequences of murine experimental obesity and renal failure. In this study, we found that a western diet produced systemic oxidant stress along with evidence of activation of Na,K-ATPase signaling within both murine brain and peripheral tissues. We also noted this diet caused increases in circulating inflammatory cytokines as well as behavioral, and brain biochemical changes consistent with neurodegeneration. Adipocyte specific NaKtide affected by a doxycycline on/off expression system ameliorated all of these diet effects. These data suggest that a western diet produces cognitive decline and neurodegeneration through augmented Na,K-ATPase signaling and that antagonism of this pathway in adipocytes ameliorates the pathophysiology. If this observation is confirmed in humans, the adipocyte Na,K-ATPase may serve as a clinical target in the therapy of neurodegenerative disorders.

Regional femoral bone blood flow rates in laying and non-laying chickens estimated with fluorescent microspheres.

The metabolic rate of vertebrate bone tissue is related to bone growth, repair and homeostasis, which are all dependent on life stage. Bone metabolic rate is difficult to measure directly, but absolute blood flow rate () should reflect local tissue oxygen requirements. A recent 'foramen technique' has derived an index of blood flow rate () by measuring nutrient foramen sizes of long bones. is assumed to be proportional to ; however, the assumption has never been tested. This study used fluorescent microsphere infusion to measure femoral bone in anaesthetized non-laying hens, laying hens and roosters. Mean mass-specific cardiac output was 338±38 ml min-1 kg-1, and the two femora received 0.63±0.10% of this. Laying hens had higher wet bone mass-specific to femora (0.23±0.09 ml min-1 g-1) than the non-laying hens (0.12±0.06 ml min-1 g-1) and roosters (0.14±0.04 ml min-1 g-1), presumably associated with higher bone calcium mobilization during eggshell production. Estimated metabolic rate of femoral bone was 0.019 ml O2 min-1 g-1. Femoral increased significantly with body mass, but was not correlated with nutrient foramen radius (r), probably because of a narrow range in foramen radius. Over all 18 chickens, femoral shaft was 1.07±0.30 ml min-1 mm-1. Mean in chickens was significantly higher than predicted by an allometric relationship for adult cursorial bird species, possibly because the birds were still growing.

Quantitative trait locus mapping reveals an independent genetic basis for joint divergence in leaf function, life-history, and floral traits between scarlet monkeyflower (Mimulus cardinalis) populations.

PREMISE: Across taxa, vegetative and floral traits that vary along a fast-slow life-history axis are often correlated with leaf functional traits arrayed along the leaf economics spectrum, suggesting a constrained set of adaptive trait combinations. Such broad-scale convergence may arise from genetic constraints imposed by pleiotropy (or tight linkage) within species, or from natural selection alone. Understanding the genetic basis of trait syndromes and their components is key to distinguishing these alternatives and predicting evolution in novel environments. METHODS: We used a line-cross approach and quantitative trait locus (QTL) mapping to characterize the genetic basis of twenty leaf functional/physiological, life history, and floral traits in hybrids between annualized and perennial populations of scarlet monkeyflower (Mimulus cardinalis). RESULTS: We mapped both single and multi-trait QTLs for life history, leaf function and reproductive traits, but found no evidence of genetic co-ordination across categories. A major QTL for three leaf functional traits (thickness, photosynthetic rate, and stomatal resistance) suggests that a simple shift in leaf anatomy may be key to adaptation to seasonally dry habitats. CONCLUSIONS: Our results suggest that the co-ordination of resource-acquisitive leaf physiological traits with a fast life-history and more selfing mating system results from environmental selection rather than functional or genetic constraint. Independent assortment of distinct trait modules, as well as a simple genetic basis to leaf physiological traits associated with drought escape, may facilitate adaptation to changing climates.

Five genetic variants explain over 70% of hair coat pheomelanin intensity variation in purebred and mixed breed domestic dogs.

In mammals, the pigment molecule pheomelanin confers red and yellow color to hair, and the intensity of this coloration is caused by variation in the amount of pheomelanin. Domestic dogs exhibit a wide range of pheomelanin intensity, ranging from the white coat of the Samoyed to the deep red coat of the Irish Setter. While several genetic variants have been associated with specific coat intensity phenotypes in certain dog breeds, they do not explain the majority of phenotypic variation across breeds. In order to gain further insight into the extent of multigenicity and epistatic interactions underlying coat pheomelanin intensity in dogs, we leveraged a large dataset obtained via a direct-to-consumer canine genetic testing service. This consisted of genome-wide single nucleotide polymorphism (SNP) genotype data and owner-provided photos for 3,057 pheomelanic mixed breed and purebred dogs from 63 breeds and varieties spanning the full range of canine coat pheomelanin intensity. We first performed a genome-wide association study (GWAS) on 2,149 of these dogs to search for additional genetic variants that underlie intensity variation. GWAS identified five loci significantly associated with intensity, of which two (CFA15 29.8 Mb and CFA20 55.8 Mb) replicate previous findings and three (CFA2 74.7 Mb, CFA18 12.9 Mb, CFA21 10.9 Mb) have not previously been reported. In order to assess the combined predictive power of these loci across dog breeds, we used our GWAS data set to fit a linear model, which explained over 70% of variation in coat pheomelanin intensity in an independent validation dataset of 908 dogs. These results introduce three novel pheomelanin intensity loci, and further demonstrate the multigenic nature of coat pheomelanin intensity determination in domestic dogs.

Big Data in Conservation Genomics: Boosting Skills, Hedging Bets, and Staying Current in the Field.

A current challenge in the fields of evolutionary, ecological, and conservation genomics is balancing production of large-scale datasets with additional training often required to handle such datasets. Thus, there is an increasing need for conservation geneticists to continually learn and train to stay up-to-date through avenues such as symposia, meetings, and workshops. The ConGen meeting is a near-annual workshop that strives to guide participants in understanding population genetics principles, study design, data processing, analysis, interpretation, and applications to real-world conservation issues. Each year of ConGen gathers a diverse set of instructors, students, and resulting lectures, hands-on sessions, and discussions. Here, we summarize key lessons learned from the 2019 meeting and more recent updates to the field with a focus on big data in conservation genomics. First, we highlight classical and contemporary issues in study design that are especially relevant to working with big datasets, including the intricacies of data filtering. We next emphasize the importance of building analytical skills and simulating data, and how these skills have applications within and outside of conservation genetics careers. We also highlight recent technological advances and novel applications to conservation of wild populations. Finally, we provide data and recommendations to support ongoing efforts by ConGen organizers and instructors-and beyond-to increase participation of underrepresented minorities in conservation and eco-evolutionary sciences. The future success of conservation genetics requires both continual training in handling big data and a diverse group of people and approaches to tackle key issues, including the global biodiversity-loss crisis.

Selfish chromosomal drive shapes recent centromeric histone evolution in monkeyflowers.

Centromeres are essential mediators of chromosomal segregation, but both centromeric DNA sequences and associated kinetochore proteins are paradoxically diverse across species. The selfish centromere model explains rapid evolution by both components via an arms-race scenario: centromeric DNA variants drive by distorting chromosomal transmission in female meiosis and attendant fitness costs select on interacting proteins to restore Mendelian inheritance. Although it is clear than centromeres can drive and that drive often carries costs, female meiotic drive has not been directly linked to selection on kinetochore proteins in any natural system. Here, we test the selfish model of centromere evolution in a yellow monkeyflower (Mimulus guttatus) population polymorphic for a costly driving centromere (D). We show that the D haplotype is structurally and genetically distinct and swept to a high stable frequency within the past 1500 years. We use quantitative genetic mapping to demonstrate that context-dependence in the strength of drive (from near-100% D transmission in interspecific hybrids to near-Mendelian in within-population crosses) primarily reflects variable vulnerability of the non-driving competitor chromosomes, but also map an unlinked modifier of drive coincident with kinetochore protein Centromere-specific Histone 3 A (CenH3A). Finally, CenH3A exhibits a recent (<1000 years) selective sweep in our focal population, implicating local interactions with D in ongoing adaptive evolution of this kinetochore protein. Together, our results demonstrate an active co-evolutionary arms race between DNA and protein components of the meiotic machinery in Mimulus, with important consequences for individual fitness and molecular divergence.

Ancient and recent introgression shape the evolutionary history of pollinator adaptation and speciation in a model monkeyflower radiation (Mimulus section Erythranthe).

Inferences about past processes of adaptation and speciation require a gene-scale and genome-wide understanding of the evolutionary history of diverging taxa. In this study, we use genome-wide capture of nuclear gene sequences, plus skimming of organellar sequences, to investigate the phylogenomics of monkeyflowers in Mimulus section Erythranthe (27 accessions from seven species). Taxa within Erythranthe, particularly the parapatric and putatively sister species M. lewisii (bee-pollinated) and M. cardinalis (hummingbird-pollinated), have been a model system for investigating the ecological genetics of speciation and adaptation for over five decades. Across >8000 nuclear loci, multiple methods resolve a predominant species tree in which M. cardinalis groups with other hummingbird-pollinated taxa (37% of gene trees), rather than being sister to M. lewisii (32% of gene trees). We independently corroborate a single evolution of hummingbird pollination syndrome in Erythranthe by demonstrating functional redundancy in genetic complementation tests of floral traits in hybrids; together, these analyses overturn a textbook case of pollination-syndrome convergence. Strong asymmetries in allele sharing (Patterson's D-statistic and related tests) indicate that gene tree discordance reflects ancient and recent introgression rather than incomplete lineage sorting. Consistent with abundant introgression blurring the history of divergence, low-recombination and adaptation-associated regions support the new species tree, while high-recombination regions generate phylogenetic evidence for sister status for M. lewisii and M. cardinalis. Population-level sampling of core taxa also revealed two instances of chloroplast capture, with Sierran M. lewisii and Southern Californian M. parishii each carrying organelle genomes nested within respective sympatric M. cardinalis clades. A recent organellar transfer from M. cardinalis, an outcrosser where selfish cytonuclear dynamics are more likely, may account for the unexpected cytoplasmic male sterility effects of selfer M. parishii organelles in hybrids with M. lewisii. Overall, our phylogenomic results reveal extensive reticulation throughout the evolutionary history of a classic monkeyflower radiation, suggesting that natural selection (re-)assembles and maintains species-diagnostic traits and barriers in the face of gene flow. Our findings further underline the challenges, even in reproductively isolated species, in distinguishing re-use of adaptive alleles from true convergence and emphasize the value of a phylogenomic framework for reconstructing the evolutionary genetics of adaptation and speciation.

Complex pleiotropic genetic architecture of evolved heat stress and oxidative stress resistance in the nematode Caenorhabditis remanei.

The adaptation of complex organisms to changing environments has been a central question in evolutionary quantitative genetics since its inception. The structure of the genotype-phenotype maps is critical because pleiotropic effects can generate widespread correlated responses to selection and potentially restrict the extent of evolutionary change. In this study, we use experimental evolution to dissect the genetic architecture of natural variation for acute heat stress and oxidative stress response in the nematode Caenorhabiditis remanei. Previous work in the classic model nematode Caenorhabiditis elegans has found that abiotic stress response is controlled by a handful of genes of major effect and that mutations in any one of these genes can have widespread pleiotropic effects on multiple stress response traits. Here, we find that acute heat stress response and acute oxidative response in C. remanei are polygenic, complex traits, with hundreds of genomic regions responding to selection. In contrast to expectation from mutation studies, we find that evolved acute heat stress and acute oxidative stress response for the most part display independent genetic bases. This lack of correlation is reflected at the levels of phenotype, gene expression, and in the genomic response to selection. Thus, while these findings support the general view that rapid adaptation can be generated by changes at hundreds to thousands of sites in the genome, the architecture of segregating variation is likely to be determined by the pleiotropic structure of the underlying genetic networks.