The genome of Przewalski's horse (Equus ferus przewalskii).

The Przewalski's horse (Equus ferus przewalskii) is an endangered equid native to the steppes of central Asia. After becoming extinct in the wild, multiple conservation efforts convened to preserve the species including captive breeding programs, reintroduction and monitoring systems, protected lands, and cloning. Availability of a highly contiguous reference genome is essential to support these continued efforts. We used Oxford Nanopore sequencing to produce a scaffold-level 2.5 Gb nuclear assembly and 16,002 bp mitogenome from a captive Przewalski's mare. All assembly drafts were generated from 111 Gb of sequence from a single PromethION R10.4.1 flow cell. The mitogenome contained 37 genes in the standard mammalian configuration and was 99.63% identical to the domestic horse (Equus caballus). The nuclear assembly, EquPr2, contained 2,146 scaffolds with an N50 of 85.1 Mb, 43X mean depth, and BUSCO quality score of 98.92%. EquPr2 successfully improves upon the existing Przewalski's horse reference genome (Burgud), with 25-fold fewer scaffolds, a 166-fold larger N50, and phased pseudohaplotypes. Modified basecalls revealed 79.5% DNA methylation and 2.1% hydroxymethylation globally. Allele-specific methylation analysis between pseudohaplotypes revealed 226 differentially methylated regions (DMRs) in known imprinted genes and loci not previously reported as imprinted. The heterozygosity rate of 0.165% matches previous estimates for the species and compares favorably to other endangered animals. This improved Przewalski's horse assembly will serve as a valuable resource for conservation efforts and comparative genomics investigations.

piOxi database: a web resource of germline and somatic tissue piRNAs identified by chemical oxidation.

PIWI-interacting RNAs (piRNAs) are a class of small non-coding RNAs that are highly expressed and extensively studied from the germline. piRNAs associate with PIWI proteins to maintain DNA methylation for transposon silencing and transcriptional gene regulation for genomic stability. Mature germline piRNAs have distinct characteristics including a 24- to 32-nucleotide length and a 2'-O-methylation signature at the 3' end. Although recent studies have identified piRNAs in somatic tissues, they remain poorly characterized. For example, we recently demonstrated notable expression of piRNA in the murine soma, and while overall expression was lower than that of the germline, unique characteristics suggested tissue-specific functions of this class. While currently available databases commonly use length and association with PIWI proteins to identify piRNA, few have included a chemical oxidation method that detects piRNA based on its 3' modification. This method leads to reproducible and rigorous data processing when coupled with next-generation sequencing and bioinformatics analysis. Here, we introduce piOxi DB, a user-friendly web resource that provides a comprehensive analysis of piRNA, generated exclusively through sodium periodate treatment of small RNA. The current version of piOxi DB includes 435 749 germline and 9828 somatic piRNA sequences robustly identified from M. musculus, M. fascicularis and H. sapiens. The database provides species- and tissue-specific data that are further analyzed according to chromosome location and correspondence to gene and repetitive elements. piOxi DB is an informative tool to assist broad research applications in the fields of RNA biology, cancer biology, environmental toxicology and beyond. Database URL:  https://pioxidb.dcmb.med.umich.edu/.

Genome skimming with nanopore sequencing precisely determines global and transposon DNA methylation in vertebrates.

Genome skimming is defined as low-pass sequencing below 0.05× coverage and is typically used for mitochondrial genome recovery and species identification. Long-read nanopore sequencers enable simultaneous reading of both DNA sequence and methylation and can multiplex samples for low-cost genome skimming. Here I present nanopore sequencing as a highly precise platform for global DNA methylation and transposon assessment. At coverage of just 0.001×, or 30 Mb of reads, accuracy is sub-1%. Biological and technical replicates validate high precision. Skimming 40 vertebrate species reveals conserved patterns of global methylation consistent with whole-genome bisulfite sequencing and an average mapping rate >97%. Genome size directly correlates to global DNA methylation, explaining 39% of its variance. Accurate SINE and LINE transposon methylation in both the mouse and primates can be obtained with just 0.0001× coverage, or 3 Mb of reads. Sample multiplexing, field portability, and the low price of this instrument combine to make genome skimming for DNA methylation an accessible method for epigenetic assessment from ecology to epidemiology and for low-resource groups.

Metagenomic surveillance for bacterial tick-borne pathogens using nanopore adaptive sampling.

Technological and computational advancements in the fields of genomics and bioinformatics are providing exciting new opportunities for pathogen discovery and genomic surveillance. In particular, single-molecule nucleotide sequence data originating from Oxford Nanopore Technologies (ONT) sequencing platforms can be bioinformatically leveraged, in real-time, for enhanced biosurveillance of a vast array of zoonoses. The recently released nanopore adaptive sampling (NAS) strategy facilitates immediate mapping of individual nucleotide molecules to a given reference as each molecule is being sequenced. User-defined thresholds then allow for the retention or rejection of specific molecules, informed by the real-time reference mapping results, as they are physically passing through a given sequencing nanopore. Here, we show how NAS can be used to selectively sequence DNA of multiple bacterial tick-borne pathogens circulating in wild populations of the blacklegged tick vector, Ixodes scapularis.

Chromosome-level, nanopore-only genome and allele-specific DNA methylation of Pallas's cat, Otocolobus manul.

Pallas's cat, or the manul cat (Otocolobus manul), is a small felid native to the grasslands and steppes of central Asia. Population strongholds in Mongolia and China face growing challenges from climate change, habitat fragmentation, poaching, and other sources. These threats, combined with O. manul's zoo collection popularity and value in evolutionary biology, necessitate improvement of species genomic resources. We used standalone nanopore sequencing to assemble a 2.5 Gb, 61-contig nuclear assembly and 17097 bp mitogenome for O. manul. The primary nuclear assembly had 56× sequencing coverage, a contig N50 of 118 Mb, and a 94.7% BUSCO completeness score for Carnivora-specific genes. High genome collinearity within Felidae permitted alignment-based scaffolding onto the fishing cat (Prionailurus viverrinus) reference genome. Manul contigs spanned all 19 felid chromosomes with an inferred total gap length of less than 400 kilobases. Modified basecalling and variant phasing produced an alternate pseudohaplotype assembly and allele-specific DNA methylation calls; 61 differentially methylated regions were identified between haplotypes. Nearest features included classical imprinted genes, non-coding RNAs, and putative novel imprinted loci. The assembled mitogenome successfully resolved existing discordance between Felinae nuclear and mtDNA phylogenies. All assembly drafts were generated from 158 Gb of sequence using seven minION flow cells.

The genome of the soybean gall midge (Resseliella maxima).

The cecidomyiid fly, soybean gall midge, Resseliella maxima Gagné, is a recently discovered insect that feeds on soybean plants in the Midwestern United States. R. maxima larvae feed on soybean stems that may induce plant death and can cause considerable yield losses, making it an important agricultural pest. From three pools of 50 adults each, we used long-read nanopore sequencing to assemble a R. maxima reference genome. The final genome assembly is 206 Mb with 64.88× coverage, consisting of 1,009 contigs with an N50 size of 714 kb. The assembly is high quality with a Benchmarking Universal Single-Copy Ortholog (BUSCO) score of 87.8%. Genome-wide GC level is 31.60%, and DNA methylation was measured at 1.07%. The R. maxima genome is comprised of 21.73% repetitive DNA, which is in line with other cecidomyiids. Protein prediction annotated 14,798 coding genes with 89.9% protein BUSCO score. Mitogenome analysis indicated that R. maxima assembly is a single circular contig of 15,301 bp and shares highest identity to the mitogenome of the Asian rice gall midge, Orseolia oryzae Wood-Mason. The R. maxima genome has one of the highest completeness levels for a cecidomyiid and will provide a resource for research focused on the biology, genetics, and evolution of cecidomyiids, as well as plant-insect interactions in this important agricultural pest.

Nanopore adaptive sampling for targeted mitochondrial genome sequencing and bloodmeal identification in hematophagous insects.

BACKGROUND: Blood-feeding insects are important vectors for an array of zoonotic pathogens. While previous efforts toward generating molecular resources have largely focused on major vectors of global medical and veterinary importance, molecular data across a large number of hematophagous insect taxa remain limited. Advancements in long-read sequencing technologies and associated bioinformatic pipelines provide new opportunities for targeted sequencing of insect mitochondrial (mt) genomes. For engorged hematophagous insects, such technologies can be leveraged for both insect mitogenome genome assembly and identification of vertebrate blood-meal sources. METHODS: We used nanopore adaptive sampling (NAS) to sequence genomic DNA from four species of field-collected, blood-engorged mosquitoes (Aedes and Culex spp.) and one deer fly (Chrysops sp.). NAS was used for bioinformatical enrichment of mtDNA reads of hematophagous insects and potential vertebrate blood-meal hosts using publically available mt genomes as references. We also performed an experimental control to compare results of traditional non-NAS nanopore sequencing to the mt genome enrichment by the NAS method. RESULTS: Complete mitogenomes were assembled and annotated for all five species sequenced with NAS: Aedes trivittatus, Aedes vexans, Culex restuans, Culex territans and the deer fly, Chrysops niger. In comparison to data generated during our non-NAS control experiment, NAS yielded a substantially higher proportion of reference-mapped mtDNA reads, greatly streamlining downstream mitogenome assembly and annotation. The NAS-assembled mitogenomes ranged in length from 15,582 to 16,045 bp, contained between 78.1% and 79.0% A + T content and shared the anticipated arrangement of 13 protein-coding genes, two ribosomal RNAs, and 22 transfer RNAs. Maximum likelihood phylogenies were generated to further characterize each insect species. Additionally, vertebrate blood-meal analysis was successful in three samples sequenced, with mtDNA-based phylogenetic analyses revealing that blood-meal sources for Chrysops niger, Culex restuans and Aedes trivittatus were human, house sparrow (Passer domesticus) and eastern cottontail rabbit (Sylvilagus floridanus), respectively. CONCLUSIONS: Our findings show that NAS has dual utility to simultaneously molecularly identify hematophagous insects and their blood-meal hosts. Moreover, our data indicate NAS can facilitate a wide array of mitogenomic systematic studies through novel 'phylogenetic capture' methods. We conclude that the NAS approach has great potential for broadly improving genomic resources used to identify blood-feeding insects, answer phylogenetic questions and elucidate complex pathways for the transmission of vector-borne pathogens.

The Genome of the Soybean Gall Midge ( Resseliella maxima ).

The cecidomyiid fly, soybean gall midge, Resseliella maxima Gagné, is a recently discovered insect that feeds on soybean plants in the Midwest US. Resseliella maxima larvae feed on soybean stems which may induce plant death and can cause considerable yield losses, making it an important agricultural pest. From three pools of 50 adults each, we used long-read nanopore sequencing to assemble a R. maxima reference genome. The final genome assembly is 206 Mb with 64.88X coverage, consisting of 1009 contigs with an N50 size of 714 kb. The assembly is high quality with a BUSCO score of 87.8%. Genome-wide GC level is 31.60% and DNA methylation was measured at 1.07%. The R. maxima genome is comprised of 21.73% repetitive DNA, which is in line with other cecidomyiids. Protein prediction annotated 14,798 coding genes with 89.9% protein BUSCO score. Mitogenome analysis indicated that R. maxima assembly is a single circular contig of 15,301 bp and shares highest identity to the mitogenome of the Asian rice gall midge, Orseolia oryzae (Wood-Mason). The R. maxima genome has one of the highest completeness levels for a cecidomyiid and will provide a resource for research focused on the biology, genetics, and evolution of cecidomyiids, as well as plant-insect interactions in this important agricultural pest.

Genome Skimming with Nanopore Sequencing Precisely Determines Global and Transposon DNA Methylation in Vertebrates.

Genome skimming is defined as low-pass sequencing below 0.05X coverage and is typically used for mitochondrial genome recovery and species identification. Long read nanopore sequencers enable simultaneous reading of both DNA sequence and methylation and can multiplex samples for low-cost genome skimming. Here I present nanopore sequencing as a highly precise platform for global DNA methylation and transposon assessment. At coverage of just 0.001X, or 30 Mb of reads, accuracy is sub-1%. Biological and technical replicates validate high precision. Skimming 40 vertebrate species reveals conserved patterns of global methylation consistent with whole genome bisulfite sequencing and an average mapping rate above 97%. Genome size directly correlates to global DNA methylation, explaining 44% of its variance. Accurate SINE and LINE transposon methylation in both mouse and primates can be obtained with just 0.0001X coverage, or 3 Mb of reads. Sample multiplexing, field portability, and the low price of this instrument combine to make genome skimming for DNA methylation an accessible method for epigenetic assessment from ecology to epidemiology, and by low resource groups.

Role of the endocannabinoid system in fragile X syndrome: potential mechanisms for benefit from cannabidiol treatment.

Multiple lines of evidence suggest a central role for the endocannabinoid system (ECS) in the neuronal development and cognitive function and in the pathogenesis of fragile X syndrome (FXS). This review describes the ECS, its role in the central nervous system, how it is dysregulated in FXS, and the potential role of cannabidiol as a treatment for FXS. FXS is caused by deficiency or absence of the fragile X messenger ribonucleoprotein 1 (FMR1) protein, FMRP, typically due to the presence of >200 cytosine, guanine, guanine sequence repeats leading to methylation of the FMR1 gene promoter. The absence of FMRP, following FMR1 gene-silencing, disrupts ECS signaling, which has been implicated in FXS pathogenesis. The ECS facilitates synaptic homeostasis and plasticity through the cannabinoid receptor 1, CB1, on presynaptic terminals, resulting in feedback inhibition of neuronal signaling. ECS-mediated feedback inhibition and synaptic plasticity are thought to be disrupted in FXS, leading to overstimulation, desensitization, and internalization of presynaptic CB1 receptors. Cannabidiol may help restore synaptic homeostasis by acting as a negative allosteric modulator of CB1, thereby attenuating the receptor overstimulation, desensitization, and internalization. Moreover, cannabidiol affects DNA methylation, serotonin 5HT1A signal transduction, gamma-aminobutyric acid receptor signaling, and dopamine D2 and D3 receptor signaling, which may contribute to beneficial effects in patients with FXS. Consistent with these proposed mechanisms of action of cannabidiol in FXS, in the CONNECT-FX trial the transdermal cannabidiol gel, ZYN002, was associated with improvements in measures of social avoidance, irritability, and social interaction, particularly in patients who are most affected, showing ≥90% methylation of the FMR1 gene.

Intergenerational arsenic exposure on the mouse epigenome and metabolic physiology.

Inorganic arsenic (iAs) is one of the largest toxic exposures to impact humanity worldwide. Exposure to iAs during pregnancy may disrupt the proper remodeling of the epigenome of F1 developing offspring and potentially their F2 grand-offspring via disruption of fetal primordial germ cells (PGCs). There is a limited understanding between the correlation of disease phenotype and methylation profile within offspring of both generations and whether it persists to adulthood. Our study aims to understand the intergenerational effects of in utero iAs exposure on the epigenetic profile and onset of disease phenotypes within F1 and F2 adult offspring, despite the lifelong absence of direct arsenic exposure within these generations. We exposed F0 female mice (C57BL6/J) to the following doses of iAs in drinking water 2 weeks before pregnancy until the birth of the F1 offspring: 1, 10, 245, and 2300 ppb. We found sex- and dose-specific changes in weight and body composition that persist from early time to adulthood within both generations. Fasting blood glucose challenge suggests iAs exposure causes dysregulation of glucose metabolism, revealing generational, exposure, and sex-specific differences. Toward understanding the mechanism, genome-wide DNA methylation data highlights exposure-specific patterns in liver, finding dysregulation within genes associated with cancer, T2D, and obesity. We also identified regions containing persistently differentially methylated CpG sites between F1 and F2 generations. Our results indicate the F1 developing embryos and their PGCs, which will result in F2 progeny, retain epigenetic damage established during the prenatal period and are associated with adult metabolic dysfunction.

Allergen-induced DNA release by the airway epithelium amplifies type 2 immunity.

BACKGROUND: Alternaria alternata and house dust mite exposure evokes IL-33 secretion from the airway epithelium, which functions as an alarmin to stimulate type 2 immunity. Extracellular DNA (eDNA) is also an alarmin that intensifies inflammation in cystic fibrosis, chronic obstructive pulmonary disease, and asthma. OBJECTIVE: We investigated the mechanisms underlying allergen-evoked DNA mobilization and release from the airway epithelium and determined the role of eDNA in type 2 immunity. METHODS: Human bronchial epithelial (hBE) cells were used to characterize allergen-induced DNA mobilization and extracellular release using comet assays to measure DNA fragmentation, Qubit double-stranded DNA assays to measure DNA release, and DNA sequencing to determine eDNA composition. Mice were used to investigate the role of eDNA in type 2 immunity. RESULTS: Alternaria extract rapidly induces mitochondrial and nuclear DNA release from human bronchial epithelial cells, whereas house dust mite extract induces mitochondrial DNA release. Caspase-3 is responsible for nuclear DNA fragmentation and becomes activated after cleavage by furin. Analysis of secreted nuclear DNA showed disproportionally higher amounts of promotor and exon sequences and lower intron and intergenic regions compared to predictions of random DNA fragmentation. In mice, Alternaria-induced type 2 immune responses were blocked by pretreatment with a DNA scavenger. In caspase-3-deficient mice, Alternaria-induced DNA release was suppressed. Furthermore, intranasal administration of mouse genomic DNA with Alternaria amplified secretion of IL-5 and IL-13 into bronchoalveolar lavage fluid while DNA alone had no effect. CONCLUSION: These findings highlight a novel, allergen-induced mechanism of rapid DNA release that amplifies type 2 immunity in airways.

De novo sequencing, diploid assembly, and annotation of the black carpenter ant, Camponotus pennsylvanicus, and its symbionts by one person for $1000, using nanopore sequencing.

The black carpenter ant (Camponotus pennsylvanicus) is a pest species found widely throughout North America. From a single individual I used long-read nanopore sequencing to assemble a phased diploid genome of 306 Mb and 60X coverage, with quality assessed by a 97.0% BUSCO score, improving upon other ant assemblies. The mitochondrial genome reveals minor rearrangements from other ants. The reads also allowed assembly of parasitic and symbiont genomes. I include a complete Wolbachia bacterial assembly with a size of 1.2 Mb, as well as a commensal symbiont Blochmannia pennsylvanicus, at 791 kb. DNA methylation and hydroxymethylation were measured at base-pair resolution level from the same reads and confirmed extremely low levels seen in the Formicidae family. There was moderate heterozygosity, with 0.16% of bases being biallelic from the parental haplotypes. Protein prediction yielded 14 415 amino acid sequences with 95.8% BUSCO score and 86% matching to previously known proteins. All assemblies were derived from a single MinION flow cell generating 20 Gb of sequence for a cost of $1047 including consumable reagents. Adding fixed costs for equipment brings the total for an ant-sized genome to less than $5000. All analyses were performed in 1 week on a single desktop computer.

Creating reference animal genomes is typically a large, expensive process. Here I sequenced the genome of the black carpenter ant for only $1000 as a sole researcher in just one week. Along with the nuclear genome, I assembled the mitochondrial genome and two commensal bacteria species living within the ant. Nanopore technology also enabled epigenetic measurements from the same ant and replicated other studies showing very low DNA methylation. The reference genome compared favorably to other ant species in continuity and protein prediction accuracy. This method will allow other low-resource labs to create high quality genome assemblies with a low cost.

Epigenetics, DNA damage, and aging.

Over the course of a human lifespan, genome integrity erodes, leading to an increased abundance of several types of chromatin changes. The abundance of DNA lesions (chemical perturbations to nucleotides) increases with age, as does the number of genomic mutations and transcriptional disruptions caused by replication or transcription of those lesions, respectively. At the epigenetic level, precise DNA methylation patterns degrade, likely causing increasingly stochastic variations in gene expression. Similarly, the tight regulation of histone modifications begins to unravel. The genomic instability caused by these mechanisms allows transposon element reactivation and remobilization, further mutations, gene dysregulation, and cytoplasmic chromatin fragments. This cumulative genomic instability promotes cell signaling events that drive cell fate decisions and extracellular communications known to disrupt tissue homeostasis and regeneration. In this Review, we focus on age-related epigenetic changes and their interactions with age-related genomic changes that instigate these events.

Sequencing Bait: Nuclear and Mitogenome Assembly of an Abundant Coastal Tropical and Subtropical Fish, Atherinomorus stipes.

Genetic data from nonmodel species can inform ecology and physiology, giving insight into a species' distribution and abundance as well as their responses to changing environments, all of which are important for species conservation and management. Moreover, reduced sequencing costs and improved long-read sequencing technology allows researchers to readily generate genomic resources for nonmodel species. Here, we apply Oxford Nanopore long-read sequencing and low-coverage (∼1x) whole genome short-read sequencing technology (Illumina) to assemble a genome and examine population genetics of an abundant tropical and subtropical fish, the hardhead silverside (Atherinomorus stipes). These fish are found in shallow coastal waters and are frequently included in ecological models because they serve as abundant prey for commercially and ecologically important species. Despite their importance in sub-tropical and tropical ecosystems, little is known about their population connectivity and genetic diversity. Our A. stipes genome assembly is about 1.2 Gb with comparable repetitive element content (∼47%), number of protein duplication events, and DNA methylation patterns to other teleost fish species. Among five sampled populations spanning 43 km of South Florida and the Florida Keys, we find little population structure suggesting high population connectivity.

Effect of supplementing lactation and nursery pig diets with capsaicin on growth performance and gene expression of nursery pigs.

The objective of this study was to determine the effects of supplementing capsaicin in diets for lactating sows and their offspring on the growth performance and gene expression of pigs postweaning. Twenty-eight multiparous sows were fed corn-soybean meal-based diets without (n = 14) and with (n = 14) capsaicin (2.5 mg/kg) during a 19-d lactation period. Litters from these sows (n = 288 pigs) were weaned and assigned to 36 blocks (pens) based on maternal dietary treatment and initial body weight (BW) to provide 8 pigs/pen. Blocks were assigned randomly to one of two nursery dietary treatments (control or capsaicin supplemented diets) in a 2 × 2 factorial arrangement of treatments to provide nine replications per treatment combination. A three-phase nursery feeding program was used and consisted of feeding phase 1 (weaning to d 7), phase 2 (d 8-21), and phase 3 (d 22-38) diets postweaning, without and with 1.0, 1.3, and 1.6 mg capsaicin/kg of diet, respectively. Data were analyzed using a mixed model with the effect of nursery dietary treatment nested within sow lactation treatment, the effect of time with repeated measures, and interactions between treatments and wk postweaning. On d 38 postweaning, blood samples were collected from one pig in each pen (n = 36) with BW closest to the pen average for RNA sequencing and gene expression analysis. There were no effects of feeding capsaicin diets to lactating sows and/or their weaned offspring on BW, average daily gain, or average daily feed intake of pigs during the 35-d nursery period. However, pigs weaned from sows fed capsaicin during lactation and continuing to be fed capsaicin diets during the nursery period tended (P = 0.09) to have greater gain:feed (G:F) than pigs fed the other dietary treatments. Furthermore, there was an interaction (P < 0.01) for G:F for dietary treatment and week postweaning, where the magnitude of improvement was greater during the first week postweaning than subsequent wks. There were a limited number of differentially expressed genes among dietary treatment combinations but the greatest number occurred in offspring from sows that were fed capsaicin during lactation. In conclusion, the combination of feeding capsaicin to sows during lactation and to their offspring after weaning appears to improve gain efficiency for the first wk postweaning and may alter gene expression to a greater extent than when capsaicin is supplemented only in the nursery diets.

The mitochondrial genome and Epigenome of the Golden lion Tamarin from fecal DNA using Nanopore adaptive sequencing.

BACKGROUND: The golden lion tamarin (Leontopithecus rosalia) is an endangered Platyrrhine primate endemic to the Atlantic coastal forests of Brazil. Despite ongoing conservation efforts, genetic data on this species remains scarce. Complicating factors include limitations on sample collection and a lack of high-quality reference sequences. Here, we used nanopore adaptive sampling to resequence the L. rosalia mitogenome from feces, a sample which can be collected non-invasively. RESULTS: Adaptive sampling doubled the fraction of both host-derived and mitochondrial sequences compared to sequencing without enrichment. 258x coverage of the L. rosalia mitogenome was achieved in a single flow cell by targeting the unfinished genome of the distantly related emperor tamarin (Saguinus imperator) and the mitogenome of the closely related black lion tamarin (Leontopithecus chrysopygus). The L. rosalia mitogenome has a length of 16,597 bp, sharing 99.68% sequence identity with the L. chrysopygus mitogenome. A total of 38 SNPs between them were identified, with the majority being found in the non-coding D-loop region. DNA methylation and hydroxymethylation were directly detected using a neural network model applied to the raw signal from the MinION sequencer. In contrast to prior reports, DNA methylation was negligible in mitochondria in both CpG and non-CpG contexts. Surprisingly, a quarter of the 642 CpG sites exhibited DNA hydroxymethylation greater than 1% and 44 sites were above 5%, with concentration in the 3' side of several coding regions. CONCLUSIONS: Overall, we report a robust new mitogenome assembly for L. rosalia and direct detection of cytosine base modifications in all contexts.

Suggested Absence of Horizontal Transfer of Retrotransposons between Humans and Domestic Mammal Species.

Transposable element sequences are usually vertically inherited but have also spread across taxa via horizontal transfer. Previous investigations of ancient horizontal transfer of transposons have compared consensus sequences, but this method resists detection of recent single or low copy number transfer events. The relationship between humans and domesticated animals represents an opportunity for potential horizontal transfer due to the consistent shared proximity and exposure to parasitic insects, which have been identified as plausible transfer vectors. The relatively short period of extended human-animal contact (tens of thousands of years or less) makes horizontal transfer of transposons between them unlikely. However, the availability of high-quality reference genomes allows individual element comparisons to detect low copy number events. Using pairwise all-versus-all megablast searches of the complete suite of retrotransposons of thirteen domestic animals against human, we searched a total of 27,949,823 individual TEs. Based on manual comparisons of stringently filtered BLAST search results for evidence of vertical inheritance, no plausible instances of HTT were identified. These results indicate that significant recent HTT between humans and domesticated animals has not occurred despite the close proximity, either due to the short timescale, inhospitable recipient genomes, a failure of vector activity, or other factors.

Early-life social experience affects offspring DNA methylation and later life stress phenotype.

Studies in rodents and captive primates suggest that the early-life social environment affects future phenotype, potentially through alterations to DNA methylation. Little is known of these associations in wild animals. In a wild population of spotted hyenas, we test the hypothesis that maternal care during the first year of life and social connectedness during two periods of early development leads to differences in DNA methylation and fecal glucocorticoid metabolites (fGCMs) later in life. Here we report that although maternal care and social connectedness during the den-dependent life stage are not associated with fGCMs, greater social connectedness during the subadult den-independent life stage is associated with lower adult fGCMs. Additionally, more maternal care and social connectedness after den independence correspond with higher global (%CCGG) DNA methylation. We also note differential DNA methylation near 5 genes involved in inflammation, immune response, and aging that may link maternal care with stress phenotype.

Developmental cannabidiol exposure increases anxiety and modifies genome-wide brain DNA methylation in adult female mice.

BACKGROUND: Use of cannabidiol (CBD), the primary non-psychoactive compound found in cannabis, has recently risen dramatically, while relatively little is known about the underlying molecular mechanisms of its effects. Previous work indicates that direct CBD exposure strongly impacts the brain, with anxiolytic, antidepressant, antipsychotic, and other effects being observed in animal and human studies. The epigenome, particularly DNA methylation, is responsive to environmental input and can direct persistent patterns of gene regulation impacting phenotype. Epigenetic perturbation is particularly impactful during embryogenesis, when exogenous exposures can disrupt critical resetting of epigenetic marks and impart phenotypic effects lasting into adulthood. The impact of prenatal CBD exposure has not been evaluated; however, studies using the psychomimetic cannabinoid Δ9-tetrahydrocannabinol (THC) have identified detrimental effects on psychological outcomes in developmentally exposed adult offspring. We hypothesized that developmental CBD exposure would have similar negative effects on behavior mediated in part by the epigenome. Nulliparous female wild-type Agouti viable yellow (Avy) mice were exposed to 20 mg/kg CBD or vehicle daily from two weeks prior to mating through gestation and lactation. Coat color shifts, a readout of DNA methylation at the Agouti locus in this strain, were measured in F1 Avy/a offspring. Young adult F1 a/a offspring were then subjected to tests of working spatial memory and anxiety/compulsive behavior. Reduced-representation bisulfite sequencing was performed on both F0 and F1 cerebral cortex and F1 hippocampus to identify genome-wide changes in DNA methylation for direct and developmental exposure, respectively. RESULTS: F1 offspring exposed to CBD during development exhibited increased anxiety and improved memory behavior in a sex-specific manner. Further, while no significant coat color shift was observed in Avy/a offspring, thousands of differentially methylated loci (DMLs) were identified in both brain regions with functional enrichment for neurogenesis, substance use phenotypes, and other psychologically relevant terms. CONCLUSIONS: These findings demonstrate for the first time that despite positive effects of direct exposure, developmental CBD is associated with mixed behavioral outcomes and perturbation of the brain epigenome.