Transient structural variations have strong effects on quantitative traits and reproductive isolation in fission yeast

New insights into the cold tolerance of upland switchgrass by integrating a haplotype-resolved genome and multi-omics analysis

BACKGROUND

Switchgrass (Panicum virgatum L.) is a bioenergy and forage crop. Upland switchgrass exhibits superior cold tolerance compared to the lowland ecotype, but the underlying molecular mechanisms remain unclear.

RESULTS

Here, we present a high-quality haplotype-resolved genome of the upland ecotype "Jingji31." We then conduct multi-omics analysis to explore the mechanism underlying its cold tolerance. By comparative transcriptome analysis of the upland and lowland ecotypes, we identify many genes with ecotype-specific differential expression, particularly members of the cold-responsive (COR) gene family, under cold stress. Notably, AFB1, ATL80, HOS10, and STRS2 gene families show opposite expression changes between the two ecotypes. Based on the haplotype-resolved genome of "Jingji31," we detect more cold-induced allele-specific expression genes in the upland ecotype than in the lowland ecotype, and these genes are significantly enriched in the COR gene family. By genome-wide association study, we detect an association signal related to the overwintering rate, which overlaps with a selective sweep region containing a cytochrome P450 gene highly expressed under cold stress. Heterologous overexpression of this gene in rice alleviates leaf chlorosis and wilting under cold stress. We also verify that expression of this gene is suppressed by a structural variation in the promoter region.

CONCLUSIONS

Based on the high-quality haplotype-resolved genome and multi-omics analysis of upland switchgrass, we characterize candidate genes responsible for cold tolerance. This study advances our understanding of plant cold tolerance, which provides crop breeding for improved cold tolerance.

Multi-omics analyses unveil dual genetic loci governing four distinct watermelon flesh color phenotypes

Watermelon fruit flesh displays various colors. Although genetic loci underlying these variations are identified, the molecular mechanism remains elusive. Here, we assembled a chromosome-scale reference genome of an elite watermelon and developed integrated genetic maps using single nucleotide polymorphism (SNP) and structural variation markers. Several key genetic varients for fruit shape and flesh color were identified. Two variants associated with flesh color were further studied, including one copy number variant (CNV, a triplicate of 1.2 kb DNA) in the promoter region of REDUCED CHLOROPLAST COVERAGE 2 (ClREC2) and one SNP in Lycopene β-Cyclase (ClLCYB) coding region. These two variants together explained 99.7% of the flesh color variations in 314 watermelon accessions. The SNP in ClLCYB was the same as previously reported, disrupting ClLCYB function. The CNV could strongly enhance ClREC2 expression, consequently increasing the expression of carotenoid biosynthesis genes, the number of plastoglobules within chromoplasts, and carotenoid level in mature fruit flesh. Finally, we proposed a "two-switch" genetic model by integrating two major causative loci, which can explain the formation of the four main flesh colors in different watermelon accessions. These results provide new insights into the regulation of carotenoid biosynthesis and color formation in plants.

How repeats rearrange chromosomes: The molecular basis of chromosomal inversions in deer mice

Large genomic rearrangements, such as chromosomal inversions, can play a key role in evolution, but the mechanisms by which these rearrangements arise remain poorly understood. To study the origins of inversions, we generated chromosome-level de novo genome assemblies for four subspecies of the deer mouse (Peromyscus maniculatus) with known inversion polymorphisms. We identified ∼8,000 inversions, including 47 megabase-scale inversions, that together affect ∼30% of the genome. Analysis of inversion breakpoints suggests that while most small (<1 Mb) inversions arose via ectopic recombination between retrotransposons, large (>1 Mb) inversions are primarily associated with segmental duplications (SDs). Large inversion breakpoints frequently occur near centromeres, which may be explained by an accumulation of retrotransposons in pericentromeric regions driving SDs. Additionally, multiple large inversions likely arose from ectopic recombination between near-identical centromeric satellite arrays located megabases apart, suggesting that centromeric repeats may also facilitate inversions. Together, our results illuminate how repeats give rise to massive shifts in chromosome architecture.

Pan-genome analysis reveals the evolution and diversity of Malus

Malus Mill., a genus of temperate perennial trees with great agricultural and ecological value, has diversified through hybridization, polyploidy and environmental adaptation. Limited genomic resources for wild Malus species have hindered the understanding of their evolutionary history and genetic diversity. We sequenced and assembled 30 high-quality Malus genomes, representing 20 diploids and 10 polyploids across major evolutionary lineages and geographical regions. Phylogenomic analyses revealed ancient gene duplications and conversions, while six newly defined genome types, including an ancestral type shared by polyploid species, facilitated the detection of strong signals for extensive introgressions. The graph-based pan-genome captured shared and species-specific structural variations, facilitating the development of a molecular marker for apple scab resistance. Our pipeline for analyzing selective sweep identified a mutation in MdMYB5 having reduced cold and disease resistance during domestication. This study advances Malus genomics, uncovering genetic diversity and evolutionary insights while enhancing breeding for desirable traits.

Pangenome analysis reveals structural variation associated with seed size and weight traits in peanut

Peanut (Arachis hypogaea L.) is an important oilseed and food legume crop, with seed size and weight being critical traits for domestication and breeding. However, genomic rearrangements like structural variations (SVs) underlying seed size and weight remain unclear. Here we present a comprehensive pangenome analysis utilizing eight high-quality genomes (two diploid wild, two tetraploid wild and four tetraploid cultivated peanuts) and resequencing data of 269 accessions with diverse seed sizes. We identified 22,222 core or soft-core, 22,232 distributed and 5,643 private gene families. The frequency of SVs in subgenome A is higher than in subgenome B. We identified 1,335 domestication-related SVs and 190 SVs associated with seed size or weight. Notably, a 275-bp deletion in gene AhARF2-2 results in loss of interaction with AhIAA13 and TOPLESS, reducing the inhibitory effect on AhGRF5 and promoting seed expansion. This high-quality pangenome serves as a fundamental resource for the genetic enhancement of peanuts and other legume crops.

SVHunter: long-read-based structural variation detection through the transformer model

Structural variations (SVs) are genomic rearrangements larger than 50 bp, that are widely present in the human genome and are associated with various complex diseases. Existing long-read-based SV detection tools often rely on fixed rules or heuristic algorithms, which can oversimplify the complexity of SV signatures. Therefore, these methods usually lack flexibility and cannot fully capture SV signals, leading to reduced accuracy and robustness. To address these issues, we propose SVHunter, a transformer-based method for long-read SV detection. SVHunter combines convolutional neural networks and transformers to capture both local and global SV signatures, enabling accurate identification of SVs. Additionally, SVHunter employs the mean shift clustering algorithm, which dynamically adjusts bandwidth parameters to accommodate different types of SVs without requiring a preset number of clusters, thus allowing precise breakpoint clustering. Validation across multiple sequencing platforms and datasets demonstrates that SVHunter excels at detecting various types of SVs, with a notable reduction in the false discovery rate. This highlights considerable strong potential for both research and clinical applications.

Pan-genomic analysis highlights genes associated with agronomic traits and enhances genomics-assisted breeding in alfalfa

Alfalfa (Medicago sativa L.), a globally important forage crop, is valued for its high nutritional quality and nitrogen-fixing capacity. Here, we present a high-quality pan-genome constructed from 24 diverse alfalfa accessions, encompassing a wide range of genetic backgrounds. This comprehensive analysis identified 433,765 structural variations and characterized 54,002 pan-gene families, highlighting the pivotal role of genomic diversity in alfalfa domestication and adaptation. Key structural variations associated with salt tolerance and quality traits were discovered, with functional analysis implicating genes such as MsMAP65 and MsGA3ox1. Notably, overexpression of MsGA3ox1 led to a reduced stem-leaf ratio and enhanced forage quality. The integration of genomic selection and marker-assisted breeding strategies improved genomic estimated breeding values across multiple traits, offering valuable genomic resources for advancing alfalfa breeding. These findings provide insights into the genetic basis of important agronomic traits and establish a solid foundation for future crop improvement.

Pan-Genome Analysis Reveals Local Adaptation to Climate Driven by Introgression in Oak Species

The genetic base of local adaptation has been extensively studied in natural populations. However, a comprehensive genome-wide perspective on the contribution of structural variants (SVs) and adaptive introgression to local adaptation remains limited. In this study, we performed de novo assembly and annotation of 22 representative accessions of Quercus variabilis, identifying a total of 543,372 SVs. These SVs play crucial roles in shaping genomic structure and influencing gene expression. By analyzing range-wide genomic data, we identified both SNPs and SVs associated with local adaptation in Q. variabilis and Quercus acutissima. Notably, SV-outliers exhibit selection signals that did not overlap with SNP-outliers, indicating that SNP-based analyses may not detect the same candidate genes associated with SV-outliers. Remarkably, 29%-37% of candidate SNPs were located in a 250 kb region on chromosome 9, referred to as Chr9-ERF. This region contains 8 duplicated ethylene-responsive factor (ERF) genes, which may have contributed to local adaptation of Q. variabilis and Q. acutissima. We also found that a considerable number of candidate SNPs were shared between Q. variabilis and Q. acutissima in the Chr9-ERF region, suggesting a pattern of repeated selection. We further demonstrated that advantageous variants in this region were introgressed from western populations of Q. acutissima into Q. variabilis, providing compelling evidence that introgression facilitates local adaptation. This study offers a valuable genomic resource for future studies on oak species and highlights the importance of pan-genome analysis in understating mechanism driving adaptation and evolution.

Advanced analysis of retrotransposon variation in the human genome with nanopore sequencing using RetroInspector

Transposable elements (TEs) make up 45% of the human genome, are a source of genetic variability difficult to detect, and involved in processes related to gene regulation and disease. Nanopore sequencing is recognized as one of the best technologies for detecting TEs; however, tools for analyzing of human TE insertions and deletions with nanopore-based data can be improved. RetroInspector is an easy to use, configurable Snakemake pipeline that performs detection, annotation, enrichment, and genotyping of TEs. RetroInspector requires the FASTQ files of the samples and the reference genome to start the identification and analysis of TEs. The user can also set the threshold for the number of supporting reads for the variant filtering. RetroInspector also allows users to compare the results of two samples. Different versions of the reference genome can be used and the presence of retrotransposition features can be annotated. RetroInspector has been run on three nanopore sequencing datasets and validated experimentally using proprietary and public data with over 80% precision.

Structural features of somatic and germline retrotransposition events in humans

BACKGROUND

Transposons are DNA sequences able to move or copy themselves to other genomic locations leading to insertional mutagenesis. Although transposon-derived sequences account for half of the human genome, most elements are no longer transposition competent. Moreover, transposons are normally repressed through epigenetic silencing in healthy adult tissues but become derepressed in several human cancers, with high activity detected in colorectal cancer. Their impact on non-malignant and malignant tissue as well as the differences between somatic and germline retrotransposition remain poorly understood. With new sequencing technologies, including long read sequencing, we can access intricacies of retrotransposition, such as insertion sequence details and nested repeats, that have been previously challenging to characterize.

RESULTS

In this study, we investigate somatic and germline retrotransposition by analyzing long read sequencing from 56 colorectal cancers and 112 uterine leiomyomas. We identified 1495 somatic insertions in colorectal samples, while striking lack of insertions was detected in uterine leiomyomas. Our findings highlight differences between somatic and germline events, such as transposon type distribution, insertion length, and target site preference. Leveraging long-read sequencing, we provide an in-depth analysis of the twin-priming phenomenon, detecting it across transposable element types that remain active in humans, including Alus. Additionally, we detect an abundance of germline transposons in repetitive DNA, along with a relationship between replication timing and insertion target site.

CONCLUSIONS

Our study reveals a stark contrast in somatic transposon activity between colorectal cancers and uterine leiomyomas, and highlights differences between somatic and germline transposition. This suggests potentially different conditions in malignant and non-malignant tissues, as well as in germline and somatic tissues, which could be involved in the transposition process. Long-read sequencing provided important insights into transposon behavior, allowing detailed examination of structural features such as twin priming and nested elements.

A pangenome reference of wild and cultivated rice

Oryza rufipogon, the wild progenitor of Asian cultivated rice Oryza sativa, is an important resource for rice breeding1. Here we present a wild-cultivated rice pangenome based on 145 chromosome-level assemblies, comprising 129 genetically diverse O. rufipogon accessions and 16 diverse varieties of O. sativa. This pangenome contains 3.87 Gb of sequences that are absent from the O. sativa ssp. japonica cv. Nipponbare reference genome. We captured alternate assemblies that include heterozygous information missing in the primary assemblies, and identified a total of 69,531 pan-genes, with 28,907 core genes and 13,728 wild-rice-specific genes. We observed a higher abundance and a significantly greater diversity of resistance-gene analogues in wild rice than in cultivars. Our analysis indicates that two cultivated subpopulations, intro-indica and basmati, were generated through gene flows among cultivars in South Asia. We also provide strong evidence to support the theory that the initial domestication of all Asian cultivated rice occurred only once. Furthermore, we captured 855,122 differentiated single-nucleotide polymorphisms and 13,853 differentiated presence-absence variations between indica and japonica, which could be traced to the divergence of their respective ancestors and the existence of a larger genetic bottleneck in japonica. This study provides reference resources for enhancing rice breeding, and enriches our understanding of the origins and domestication process of rice.

Unraveling the hidden complexity of cancer through long-read sequencing

Cancer is fundamentally a disease of the genome, characterized by extensive genomic, transcriptomic, and epigenomic alterations. Most current studies predominantly use short-read sequencing, gene panels, or microarrays to explore these alterations; however, these technologies can systematically miss or misrepresent certain types of alterations, especially structural variants, complex rearrangements, and alterations within repetitive regions. Long-read sequencing is rapidly emerging as a transformative technology for cancer research by providing a comprehensive view across the genome, transcriptome, and epigenome, including the ability to detect alterations that previous technologies have overlooked. In this Perspective, we explore the current applications of long-read sequencing for both germline and somatic cancer analysis. We provide an overview of the computational methodologies tailored to long-read data and highlight key discoveries and resources within cancer genomics that were previously inaccessible with prior technologies. We also address future opportunities and persistent challenges, including the experimental and computational requirements needed to scale to larger sample sizes, the hurdles in sequencing and analyzing complex cancer genomes, and opportunities for leveraging machine learning and artificial intelligence technologies for cancer informatics. We further discuss how the telomere-to-telomere genome and the emerging human pangenome could enhance the resolution of cancer genome analysis, potentially revolutionizing early detection and disease monitoring in patients. Finally, we outline strategies for transitioning long-read sequencing from research applications to routine clinical practice.

Graph-based pangenome provides insights into structural variations and genetic basis of metabolic traits in potato

Potato is the world's most important nongrain crop. In this study, to assess genetic diversity within the Petota section, 29 genomes from Petota and Etuberosum sections were newly de novo assembled and 248 accessions of wild potatoes, landraces, and modern cultivars were re-sequenced at >25× depth. Subsequently, a graph-based pangenome was constructed using DM8.1 as the backbone, integrating194,330 nonredundant structural variants. To characterize the metabolome of tubers and illuminate the genomic basis of metabolic traits, LC-MS/MS was employed to obtain the metabolome of 157 accessions, and 9,321 structural variants (SVs) were detected to be significantly associated with 1,258 distinct metabolites via PAV (presence and absence variations)-based metabolomics-GWAS analysis, including metabolites of flavonoids, phenolic acids, and phospholipids. To facilitate the utilization of pangenome resources, a comprehensive platform, the Potato Pangenome Database (PPDB), was developed. Our study provides a comprehensive genomic resource for dissecting the genomic basis of agronomic and metabolic traits in potato, which will accelerate functional genomics studies and genetic improvements in potato.

Severus detects somatic structural variation and complex rearrangements in cancer genomes using long-read sequencing

For the detection of somatic structural variation (SV) in cancer genomes, long-read sequencing is advantageous over short-read sequencing with respect to mappability and variant phasing. However, most current long-read SV detection methods are not developed for the analysis of tumor genomes characterized by complex rearrangements and heterogeneity. Here, we present Severus, a breakpoint graph-based algorithm for somatic SV calling from long-read cancer sequencing. Severus works with matching normal samples, supports unbalanced cancer karyotypes, can characterize complex multibreak SV patterns and produces haplotype-specific calls. On a comprehensive multitechnology cell line panel, Severus consistently outperforms other long-read and short-read methods in terms of SV detection F1 score (harmonic mean of the precision and recall). We also illustrate that compared to long-read methods, short-read sequencing systematically misses certain classes of somatic SVs, such as insertions or clustered rearrangements. We apply Severus to several clinical cases of pediatric leukemia/lymphoma, revealing clinically relevant cryptic rearrangements missed by standard genomic panels.

Structural variation-based and gene-based pangenome construction reveals untapped diversity of hexaploid wheat

Increasing number of structural variations (SVs) have been identified as causative mutations for diverse agronomic traits. However, the systematic exploration of SVs quantity, distribution, and contribution in wheat was lacking. Here, we report high-quality gene-based and SV-based pangenomes comprising 22 hexaploid wheat assemblies showing a wide range of chromosome size, gene number, and TE component, which indicates their representativeness of wheat genetic diversity. Pan-gene analyses uncover 140,261 distinct gene families, of which only 23.2 % are shared in all accessions. Moreover, we build a ∼16.15 Gb graph pangenome containing 695,897 bubbles, intersecting 5132 genes and 230,307 cis-regulatory regions. Pairwise genome comparisons identify ∼1,978,221 non-redundant SVs and 497 SV hotspots. Notably, the density of bubbles as well as SVs show remarkable aggregation in centromeres, which probably play an important role in chromosome plasticity and stability. As for functional SVs exploration, we identify 2769 SVs with absolute relative frequency differences exceeding 0.7 between spring and winter growth habit groups. Additionally, several reported functional genes in wheat display complex structural graphs, for example, PPD-A1, VRT-A2, and TaNAAT2-A. These findings deepen our understanding of wheat genetic diversity, providing valuable graphical pangenome and variation resources to improve the efficiency of genome-wide association mapping in wheat.

Long-read genome and RNA sequencing resolve a pathogenic intronic germline LINE-1 insertion in APC

Familial adenomatous polyposis (FAP) is caused by pathogenic germline variants in the tumor suppressor gene APC. Confirmation of diagnosis was not achieved by cancer gene panel and exome sequencing or custom array-CGH in a family with suspected FAP across five generations. Long-read genome sequencing (PacBio), short-read genome sequencing (Illumina), short-read RNA sequencing, and further validations were performed in different tissues of multiple family members. Long-read genome sequencing resolved a 6 kb full-length intronic insertion of a heterozygous LINE-1 element between exons 7 and 8 of APC that could be detected but not fully resolved by short-read genome sequencing. Targeted RNA analysis revealed aberrant splicing resulting in the formation of a pseudo-exon with a premature stop codon. The variant segregated with the phenotype in several family members allowing its evaluation as likely pathogenic. This study supports the utility of long-read DNA sequencing and complementary RNA approaches to tackle unsolved cases of hereditary disease.

A telomere-to-telomere genome assembly of cotton provides insights into centromere evolution and short-season adaptation

Cotton (Gossypium hirsutum L.) is a key allopolyploid crop with global economic importance. Here we present a telomere-to-telomere assembly of the elite variety Zhongmian 113. Leveraging technologies including PacBio HiFi, Oxford Nanopore Technology (ONT) ultralong-read sequencing and Hi-C, our assembly surpasses previous genomes in contiguity and completeness, resolving 26 centromeric and 52 telomeric regions, 5S rDNA clusters and nucleolar organizer regions. A phylogenetically recent centromere repositioning on chromosome D08 was discovered specific to G. hirsutum, involving deactivation of an ancestral centromere and the formation of a unique, satellite repeat-based centromere. Genomic analyses evaluated favorable allele aggregation for key agronomic traits and uncovered an early-maturing haplotype derived from an 11 Mb pericentric inversion that evolved early during G. hirsutum domestication. Our study sheds light on the genomic origins of short-season adaptation, potentially involving introgression of an inversion from primitively domesticated forms, followed by subsequent haplotype differentiation in modern breeding programs.

Whole-genome sequencing reveals genetic architecture and selection signatures of Kazakh cattle

Local cattle breeds play a critical role in breeding programs due to their genetic adaptations to diverse environmental conditions. However, the genomic architecture of local cattle breeds in Kazakhstan remains largely unexplored. This study utilized whole-genome sequencing data from Kazakh cattle to elucidate their genetic composition, uncovering three primary ancestral components: European, Eurasian, and East Asian taurine. The East Asian taurine lineage likely represents the earliest genetic contribution to Kazakh cattle but was largely replaced by subsequent waves of cattle migrations across Eurasia, leaving only a minor genetic signature in the current cattle population. In contrast, Eurasian taurine ancestry predominated in the Alatau and Kazakh local breeds, while the European taurine component was most prevalent in Kazakh white-headed cattle, consistent with their documented breeding history. Kazakh cattle exhibited higher genetic diversity and lower inbreeding coefficients compared to European commercial breeds, reflecting reduced exposure to intense artificial selection. A strong selection signal was identified on chromosome 6 at a locus encompassing PDGFRA, KIT, and KDR, which may be associated with the white-headed pigmentation characteristic of Kazakh white-headed cattle. Additional genes under selection were linked to lipid metabolism ( IRS1, PRKG1, and ADCY8), meat production traits ( KCNMA1, PDGFRA, HIF1A, and ANTXR1), and dairy production ( ATP2B1, DHX15, FUK, NEGR1, CCDC91, COG4, and PTK2B). This study represents the first comprehensive analysis of nuclear genome data from local Kazakh cattle. It highlights the impact of historical cattle migrations across Eurasia on their genetic landscape and identifies key genomic regions under selection. These findings advance our understanding of the evolutionary history of cattle and offer valuable genetic resources for future breeding strategies.

Benchmarking long-read structural variant calling tools and combinations for detecting somatic variants in cancer genomes

Cancer genomes have a complicated landscape of mutations, including large-scale rearrangements known as structural variants (SVs). These SVs can disrupt genes or regulatory elements, playing a critical role in cancer development and progression. Despite their importance, accurate identification of somatic structural variants (SVs) remains a significant bottleneck in cancer genomics. Long-read sequencing technologies hold great promise in SV discovery, and there is an increasing number of efforts to develop new tools to detect them. In this study, we employ eight widely used SV callers on paired tumor and matched normal samples from both the NCI-H2009 lung cancer cell line and the COLO829 melanoma cell line, the latter of which has a well-established somatic SV truth set. Following separate variation detection in both tumor and normal DNA, the VCF merging procedure and a subtraction method were used to identify candidate somatic SVs. Additionally, we explored different combinations of the tools to enhance the accuracy of true somatic SV detection. Our analysis adopts a comprehensive approach, evaluating the performance of each SV caller across a spectrum of variant types and numbers in finding cancer-related somatic SVs. This study, by comparing eight different tools and their combinations, not only reveals the benefits and limitations of various techniques but also establishes a framework for developing more robust SV calling pipelines. Our findings highlight the strengths and weaknesses of current SV calling tools and suggest that combining multiple tools and testing different combinations can significantly enhance the validation of somatic alterations.

Structural variants linked to Alzheimer's disease and other common age-related clinical and neuropathologic traits

BACKGROUND

Alzheimer's disease (AD) is a complex neurodegenerative disorder with substantial genetic influence. While genome-wide association studies (GWAS) have identified numerous risk loci for late-onset AD (LOAD), the functional mechanisms underlying most of these associations remain unresolved. Large genomic rearrangements, known as structural variants (SVs), represent a promising avenue for elucidating such mechanisms within some of these loci.

METHODS

By leveraging data from two ongoing cohort studies of aging and dementia, the Religious Orders Study and Rush Memory and Aging Project (ROS/MAP), we performed genome-wide association analysis testing 20,205 common SVs from 1088 participants with whole genome sequencing (WGS) data. A range of Alzheimer's disease and other common age-related clinical and neuropathologic traits were examined.

RESULTS

First, we mapped SVs across 81 AD risk loci and discovered 22 SVs in linkage disequilibrium (LD) with GWAS lead variants and directly associated with the phenotypes tested. The strongest association was a deletion of an Alu element in the 3'UTR of the TMEM106B gene, in high LD with the respective AD GWAS locus and associated with multiple AD and AD-related disorders (ADRD) phenotypes, including tangles density, TDP-43, and cognitive resilience. The deletion of this element was also linked to lower TMEM106B protein abundance. We also found a 22-kb deletion associated with depression in ROS/MAP and bearing similar association patterns as GWAS SNPs at the IQCK locus. In addition, we leveraged our catalog of SV-GWAS to replicate and characterize independent findings in SV-based GWAS for AD and five other neurodegenerative diseases. Among these findings, we highlight the replication of genome-wide significant SVs for progressive supranuclear palsy (PSP), including markers for the 17q21.31 MAPT locus inversion and a 1483-bp deletion at the CYP2A13 locus, along with other suggestive associations, such as a 994-bp duplication in the LMNTD1 locus, suggestively linked to AD and a 3958-bp deletion at the DOCK5 locus linked to Lewy body disease (LBD) (P = 3.36 × 10-4).

CONCLUSIONS

While still limited in sample size, this study highlights the utility of including analysis of SVs for elucidating mechanisms underlying GWAS loci and provides a valuable resource for the characterization of the effects of SVs in neurodegenerative disease pathogenesis.

The Genome of the Lima Bean Variety Baiyu Bean Highlights Its Evolutionary Characteristics

The baiyu bean (Phaseolus lunatus), also known as the lima bean, is a plant belonging to the Fabaceae family, has a long and distinguished history of cultivation in China and is a highly regarded local variety of lima bean. In the current study, we present the reference genome of the baiyu bean variety, which has a scaffold N50 length of 47.545 Mb. A comparative genomic analysis was conducted using genomes of seven legume species, and the results demonstrated that 1564 and 1275 genes of baiyu bean exhibited expansion and contraction, respectively. Moreover, 543 genes were identified as exclusive to the baiyu bean. The analysis of adaptive evolution genes revealed the presence of 61 genes under adaptive evolution between P. lunatus and the common bean P. vulgaris. An examination of the branch model revealed the presence of five genes undergoing adaptive evolution in the P. lunatus branch. Additionally, the evolutionary selective pressure acting on other branches of legume plants was analyzed. A comprehensive analysis of structural variations (SVs) between the baiyu bean and G27455 genome was conducted, resulting in the identification of 5549 SVs. Among these, 333 genes were identified as high-impact SV genes. The acquisition of the genome sequence of this excellent variety will facilitate the exploration and utilization of its characteristics, providing a foundation for the genetic improvement of the lima bean.

Recurrent Increased Nuchal Translucency Led to the Identification of Novel NUP107 Variants

Five percent of fetuses presents increased fetal nuchal translucency. It is a well-known marker for aneuploidy (T21, Turner syndrome) and a variety of monogenic syndromes such as Noonan syndrome and certain skeletal dysplasias, as well as associated with structural malformations such as congenital heart disease. Current diagnostic algorithms for increased nuchal translucency include a rapid test for aneuploidy (fluorescence in situ hybridization, FISH, or quantitative PCR), a cytogenetic analysis (karyotype or chromosomal microarray, CMA) followed by or concurrent with targeted gene panel analysis for RASopathies/Noonan syndrome. Some centers now propose whole exome sequencing as an adjunct, but its usefulness in isolated increased nuchal translucency remains debated. We describe the recurrence of apparently isolated increased nuchal translucency in 2 euploid fetuses. Whole genome sequencing identified two compound heterozygous variants in the NUP107 gene in both fetuses. Biallelic variants in NUP107 are responsible for severe steroid-resistant nephrotic syndrome, either isolated or syndromic (Galloway-Mowat syndrome); in addition to the renal phenotype, the latter also includes intellectual deficiency and dysmorphic features. Pregnancy termination made it impossible to assess whether the NUP107 variants found would have resulted in isolated or syndromic steroid-resistant nephrotic syndrome. However, identifying the responsible gene improved the accuracy of the genetic counseling. This family is an example of the added benefit of introducing WES/WGS in standardized protocols for prenatal diagnosis of euploid fetuses in "isolated" increased nuchal translucency.

Super pangenome of Vitis empowers identification of downy mildew resistance genes for grapevine improvement

Grapevine (Vitis) is one of the oldest domesticated fruit crops with great cultural and economic importance. Here we assembled and annotated haplotype-resolved genomes of 72 global Vitis accessions including 25 wild and 47 cultivated grapevines, among which genomes for 60 grapevines are newly released. Haplotype-aware phylogenomics disentangled the mysterious hybridization history of grapevines, revealing the enormous genetic diversity of the Vitis genus. Pangenomic analysis reveals that European cultivars, more susceptible to the destructive disease downy mildew (DM), have a smaller repertoire of resistance genes in the NLR family encoding the TIR-NBARC-LRR domain. Through extensive structural variation (SV) characterization, phenotyping, DM-infection transcriptome profiling of 113 Vitis accessions, and SV-expression quantitative trait loci analysis, we have identified over 63 SVs and their relevant genes significantly associated with DM resistance, exemplified by a lysine histidine transporter, VvLHT8. This haplotype-resolved super pangenome of the Vitis genus will accelerate breeding and enrich our understanding of the evolution and biology of grapevines.

Whole-genome sequencing analysis identifies rare, large-effect noncoding variants and regulatory regions associated with circulating protein levels

The contribution of rare noncoding genetic variation to common phenotypes is largely unknown, as a result of a historical lack of population-scale whole-genome sequencing data and the difficulty of categorizing noncoding variants into functionally similar groups. To begin addressing these challenges, we performed a cis association analysis using whole-genome sequencing data, consisting of 1.1 billion variants, 123 million noncoding aggregate-based tests and 2,907 circulating protein levels in ~50,000 UK Biobank participants. We identified 604 independent rare noncoding single-variant associations with circulating protein levels. Unlike protein-coding variation, rare noncoding genetic variation was almost as likely to increase or decrease protein levels. Rare noncoding aggregate testing identified 357 conditionally independent associated regions. Of these, 74 (21%) were not detectable by single-variant testing alone. Our findings have important implications for the identification, and role, of rare noncoding genetic variation associated with common human phenotypes, including the importance of testing aggregates of noncoding variants.

iPSCs and iPSC-derived cells as a model of human genetic and epigenetic variation

Understanding the interaction between genetic and epigenetic variation remains a challenge due to confounding environmental factors. We propose that human induced Pluripotent Stem Cells (iPSCs) are an excellent model to study the relationship between genetic and epigenetic variation while controlling for environmental factors. In this study, we have created a comprehensive resource of high-quality genomic, epigenomic, and transcriptomic data from iPSC lines and three iPSC-derived cell types (neural stem cell (NSC), motor neuron, monocyte) from three healthy donors. We find that epigenetic variation is most strongly associated with genetic variation at the iPSC stage, and that relationship weakens as epigenetic variation increases in differentiated cells. Additionally, cell type is a stronger source of epigenetic variation than genetic variation. Further, we elucidate a utility of studying epigenetic variation in iPSCs and their derivatives for identifying important loci for GWAS studies and the cell types in which they may be acting.

Unveiling the Genetic Landscape of Coronary Artery Disease Through Common and Rare Structural Variants

BACKGROUND

Genome-wide association studies have identified several hundred susceptibility single nucleotide variants for coronary artery disease (CAD). Despite single nucleotide variant-based genome-wide association studies improving our understanding of the genetics of CAD, the contribution of structural variants (SVs) to the risk of CAD remains largely unclear.

METHOD AND RESULTS

We leveraged SVs detected from high-coverage whole genome sequencing data in a diverse group of participants from the National Heart Lung and Blood Institute's Trans-Omics for Precision Medicine program. Single variant tests were performed on 58 706 SVs in a study sample of 11 556 CAD cases and 42 907 controls. Additionally, aggregate tests using sliding windows were performed to examine rare SVs. One genome-wide significant association was identified for a common biallelic intergenic duplication on chromosome 6q21 (P=1.54E-09, odds ratio=1.34). The sliding window-based aggregate tests found 1 region on chromosome 17q25.3, overlapping USP36, to be significantly associated with coronary artery disease (P=1.03E-10). USP36 is highly expressed in arterial and adipose tissues while broadly affecting several cardiometabolic traits.

CONCLUSIONS

Our results suggest that SVs, both common and rare, may influence the risk of coronary artery disease.

Long-read sequencing of 945 Han individuals identifies structural variants associated with phenotypic diversity and disease susceptibility

Genomic structural variants (SVs) are a major source of genetic diversity in humans. Here, through long-read sequencing of 945 Han Chinese genomes, we identify 111,288 SVs, including 24.56% unreported variants, many with predicted functional importance. By integrating human population-level phenotypic and multi-omics data as well as two humanized mouse models, we demonstrate the causal roles of two SVs: one SV that emerges at the common ancestor of modern humans, Neanderthals, and Denisovans in GSDMD for bone mineral density and one modern-human-specific SV in WWP2 impacting height, weight, fat, craniofacial phenotypes and immunity. Our results suggest that the GSDMD SV could serve as a rapid and cost-effective biomarker for assessing the risk of cisplatin-induced acute kidney injury. The functional conservation from human to mouse and widespread signals of positive natural selection suggest that both SVs likely influence local adaptation, phenotypic diversity, and disease susceptibility across diverse human populations.

De novo and somatic structural variant discovery with SVision-pro

Long-read-based de novo and somatic structural variant (SV) discovery remains challenging, necessitating genomic comparison between samples. We developed SVision-pro, a neural-network-based instance segmentation framework that represents genome-to-genome-level sequencing differences visually and discovers SV comparatively between genomes without any prerequisite for inference models. SVision-pro outperforms state-of-the-art approaches, in particular, the resolving of complex SVs is improved, with low Mendelian error rates, high sensitivity of low-frequency SVs and reduced false-positive rates compared with SV merging approaches.

Genomic variation responding to artificial selection on different lines of Pekin duck

Understanding the genomic variation in Pekin duck under artificial selection is important for improving the utilization of duck genetic resources. Here, the genomic changes in Pekin duck were analyzed by using the genome resequencing data from 96 individual samples, including 2 conservation populations and 4 breeding populations with different breeding backgrounds. The population structure, runs of homozygosity (ROH), effective population number (Ne), and other genetic parameters were analyzed. The breeding populations showed lower genetic diversity compared to the conservation populations. Maple Leaf duck and Cherry Valley duck retained low genetic diversity compared to other breeding populations, with Cherry Valley duck showing the lowest diversity and the highest inbreeding coefficient. This suggested that Cherry Valley and Maple Leaf ducks have undergone intensive selection compared to other breeding populations. By the analysis of runs of homozygosity (ROHs), some genes (e.g., IGF1R) associated with growth traits were identified. By the analysis of the selection signal, strong selection characteristics in certain genomic regions during the breeding of Peking duck across different selected lines were observed. In addition, copy number variations (CNVs) in Pekin duck populations were analyzed. Six regions of interest were identified, containing RPA1, DOT1L, SLC25A42, RALYL, TRPA1, and IGFBP2. Furthermore, the allele frequency distribution of these genes showed significant differences between breeding populations and conservation populations, indicating that these candidate genes could have undergone strong selection pressure during long-term selection for improved production. These findings contribute to a deeper understanding of the distinct evolutionary processes in Pekin ducks under artificial selection and provide valuable insights for future breeding strategies.

Genome sequencing and assembly of feral chickens in the wild of Sulawesi, Indonesia

The feralization of domestic chicken makes the conservation and management of red jungle fowl (Gallus gallus) more complicated and challenging. We collected two Sulawesi feral chickens, located east of the Wallace Line, for whole-genome sequencing and de novo genome assembly. Phylogenetic and f4-statistics analyses indicated that the Sulawesi feralized domestic chickens (G. g. domesticus) received gene flow from G. g. gallus. We integrated ~45× ultra-long Oxford Nanopore Technology reads and ~28× PacBio HiFi reads to generate a de novo genome assembly of a female Sulawesi feral chicken (GGsula) with a contig N50 of 19.88 Mbp. We characterized structural variations in GGsula, and found some were related to nervous system. Our study provides the first genome assembly of feral chickens, which is a unique genomic resource to explore the process of chicken domestication and feralization.

The rate and spectrum of new mutations in mice inferred by long-read sequencing

All forms of genetic variation originate from new mutations, making it crucial to understand their rates and mechanisms. Here, we use long-read sequencing from Pacific Biosciences (PacBio) to investigate de novo mutations that accumulated in 12 inbred mouse lines derived from three commonly used inbred strains (C3H, C57BL/6, and FVB) maintained for 8 to 15 generations in a mutation accumulation (MA) experiment. We built chromosome-level genome assemblies based on the MA line founders' genomes and then employed a combination of read and assembly-based methods to call the complete spectrum of new mutations. On average, there are about 45 mutations per haploid genome per generation, about half of which (54%) are insertions and deletions shorter than 50 bp (indels). The remainder are single-nucleotide mutations (SNMs; 44%) and large structural mutations (SMs; 2%). We found that the degree of DNA repetitiveness is positively correlated with SNM and indel rates and that a substantial fraction of SMs can be explained by homology-dependent mechanisms associated with repeat sequences. Most (90%) indels can be attributed to microsatellite contractions and expansions, and there is a marked bias toward 4 bp indels. Among the different types of SMs, tandem repeat mutations have the highest mutation rate, followed by insertions of transposable elements (TEs). We uncover a rich landscape of active TEs, notable differences in their spectrum among MA lines and strains, and a high rate of gene retroposition. Our study offers novel insights into mammalian genome evolution and highlights the importance of repetitive elements in shaping genomic diversity.

Mapping the chromothripsis landscape in urothelial carcinoma unravels great intratumoral and intertumoral heterogeneity

Chromothripsis, a hallmark of cancer, is characterized by extensive and localized DNA rearrangements involving one or a few chromosomes. However, its genome-wide frequency and characteristics in urothelial carcinoma (UC) remain largely unknown. Here, by analyzing single-regional and multi-regional whole-genome sequencing (WGS), we present the chromothripsis blueprint in 488 UC patients. Chromothripsis events exhibit significant intertumoral heterogeneity, being detected in 41% of UC patients, with an increase from 30% in non-muscle-invasive disease (Ta/1) to 53% in muscle-invasive disease (T2-4). The presence of chromothripsis correlates with an unstable cancer genome and poor clinical outcomes. Analysis of multi-regional WGS data from 52 patients revealed pronounced intratumoral heterogeneity with chromothripsis events detectable only in specific tumor regions rather than uniformly across all areas. Chromothripsis events evolve under positive selection and contribute to tumor dissemination. This study presents a comprehensive genome-wide chromothripsis landscape in UC, highlighting the significance of chromothripsis in UC development.

A Murine Database of Structural Variants Enables the Genetic Architecture of a Spontaneous Murine Lymphoma to be Characterized

A more complete map of the pattern of genetic variation among inbred mouse strains is essential for characterizing the genetic architecture of the many available mouse genetic models of important biomedical traits. Although structural variants (SVs) are a major component of genetic variation, they have not been adequately characterized among inbred strains due to methodological limitations. To address this, we generated high-quality long-read sequencing data for 40 inbred strains; and designed a pipeline to optimally identify and validate different types of SVs. This generated a database for 40 inbred strains with 573,191SVs, which included 10,815 duplications and 2,115 inversions, that also has 70 million SNPs and 7.5 million insertions/deletions. Analysis of this SV database led to the discovery of a novel bi-genic model for susceptibility to a B cell lymphoma that spontaneously develops in SJL mice, which was initially described 55 years ago. The first genetic factor is a previously identified endogenous retrovirus encoded protein that stimulates CD4 T cells to produce the cytokines required for lymphoma growth. The second genetic factor is a newly found deletion SV, which ablates a protein whose promotes B lymphoma development in SJL mice. Characterizing the genetic architecture of SJL lymphoma susceptibility could provide new insight into the pathogenesis of a human lymphoma that has similarities with this murine lymphoma.

GDBr: genomic signature interpretation tool for DNA double-strand break repair mechanisms

Large genetic variants can be generated via homologous recombination (HR), such as polymerase theta-mediated end joining (TMEJ) or single-strand annealing (SSA). Given that these HR-based mechanisms leave specific genomic signatures, we developed GDBr, a genomic signature interpretation tool for DNA double-strand break repair mechanisms using high-quality genome assemblies. We applied GDBr to a draft human pangenome reference. We found that 78.1% of non-repetitive insertions and deletions and 11.0% of non-repetitive complex substitutions contained specific signatures. Of these, we interpreted that 98.7% and 1.3% of the insertions and deletions were generated via TMEJ and SSA, respectively, and all complex substitutions via TMEJ. Since population-level pangenome datasets are being dramatically accumulated, GDBr can provide mechanistic insights into how variants are formed. GDBr is available on GitHub at https://github.com/Chemical118/GDBr.

Highly accurate Korean draft genomes reveal structural variation highlighting human telomere evolution

Given the presence of highly repetitive genomic regions such as subtelomeric regions, understanding human genomic evolution remains challenging. Recently, long-read sequencing technology has facilitated the identification of complex genetic variants, including structural variants (SVs), at the single-nucleotide level. Here, we resolved SVs and their underlying DNA damage-repair mechanisms in subtelomeric regions, which are among the most uncharted genomic regions. We generated ∼20 × high-fidelity long-read sequencing data from three Korean individuals and their partially phased high-quality de novo genome assemblies (contig N50: 6.3-58.2 Mb). We identified 131 138 deletion and 121 461 insertion SVs, 41.6% of which were prevalent in the East Asian population. The commonality of the SVs identified among the Korean population was examined by short-read sequencing data from 103 Korean individuals, providing the first comprehensive SV set representing the population based on the long-read assemblies. Manual investigation of 19 large subtelomeric SVs (≥5 kb) and their associated repair signatures revealed the potential repair mechanisms leading to the formation of these SVs. Our study provides mechanistic insight into human telomere evolution and can facilitate our understanding of human SV formation.

Atypical free sialic acid storage disorder associated with tissue specific mosaicism of SLC17A5

Free sialic acid storage disorder (FSASD) is a rare autosomal recessive lysosomal storage disease caused by pathogenic SLC17A5 variants with variable disease severity. We performed a multidisciplinary evaluation of an adolescent female with suspected lysosomal storage disease and conducted comprehensive studies to uncover the molecular etiology. The proband exhibited intellectual disability, a storage disease gestalt, and mildly elevated urine free sialic acid levels. Skin electron micrographs showed prominent cytoplasmic vacuolation. Clinical exome and genome sequencing identified a maternally-inherited SLC17A5 variant: c.533delC;p.Thr178Asnfs*34. RNASeq of proband skin fibroblasts revealed exon 3 skipping, which was not detected in RNA from proband blood or parental fibroblasts. Targeted deep sequencing of proband fibroblast DNA revealed a 184 bp deletion in ∼15 % of reads, encompassing the 3' end of exon 3. Illumina Complete Long Read sequencing confirmed the deletion was in the paternally-inherited allele and found in a mosaic state in proband fibroblasts and muscle but not in blood or buccal cells. Functional studies, including SLC17A5 knockout cells and transient transfections of mutated SLC17A5 demonstrated pathogenicity of the identified variants. We report an adolescent female with atypical FSASD with tissue-specific mosaicism for an intragenic deletion in SLC17A5, explaining the atypical clinical course, mild biochemical abnormalities, and long diagnostic process.

Pan-genome bridges wheat structural variations with habitat and breeding

Wheat is the second largest food crop with a very good breeding system and pedigree record in China. Investigating the genomic footprints of wheat cultivars will unveil potential avenues for future breeding efforts1,2. Here we report chromosome-level genome assemblies of 17 wheat cultivars that chronicle the breeding history of China. Comparative genomic analysis uncovered a wealth of structural rearrangements, identifying 249,976 structural variations with 49.03% (122,567) longer than 5 kb. Cultivars developed in 1980s displayed significant accumulations of structural variations, a pattern linked to the extensive incorporation of European and American varieties into breeding programmes of that era. We further proved that structural variations in the centromere-proximal regions are associated with a reduction of crossover events. We showed that common wheat evolved from spring to winter types via mutations and duplications of the VRN-A1 gene as an adaptation strategy to a changing environment. We confirmed shifts in wheat cultivars linked to dietary preferences, migration and cultural integration in Northwest China. We identified large presence or absence variations of pSc200 tandem repeats on the 1RS terminal, suggesting its own rapid evolution in the wheat genome. The high-quality genome assemblies of 17 representatives developed and their good complementarity to the 10+ pan-genomes offer a robust platform for future genomics-assisted breeding in wheat.

Identification of candidate genes related to hybrid sterility by genomic structural variation and transcriptome analyses in cattle-yak

Hybrids between closely related but genetically incompatible species are often inviable or sterile. Cattle-yak, an interspecific hybrid of yak and cattle, exhibits male-specific sterility, which limits the fixation of its desired traits and prevents genetic improvement in yak through crossbreeding. Transcriptome profiles of testicular tissues have been generated in cattle, yak, and cattle-yak; however, the genetic variations underlying differential gene expression associated with hybrid sterility have yet to be elucidated. We detected differences in the cellular composition and gene expression of testes from yak and cattle-yak at 3 mo of age, 10 mo of age, and adulthood. Histological analysis revealed that the most advanced germ cells were gonocytes (prospermatogonia) at 3 mo and spermatocytes at 10 mo. Complete spermatogenesis occurred in the seminiferous tubules of adult yak, whereas only spermatogonia and a limited number of spermatocytes were detected in the testis of adult cattle-yak. Transcriptome analysis revealed 180, 6,310, and 6,112 differentially expressed genes (DEG) in yak and cattle-yak at each stage, respectively. Next, we examined the spermatogenic cell types in the backcross generation (BC1) and detected the appearance of round spermatids, indicating the partial recovery of spermatogenesis in these animals. Compared with those in cattle-yak, 272 DEG were identified in the testes of BC1 animals. Notably, we discovered that the expression of X chromosome-linked genes was upregulated in the testis of cattle-yak compared with yak, suggesting a possible abnormality in the process of meiotic sex chromosome inactivation in hybrid animals. We next screened DEG harboring structural variations (SV) and identified a list of SV genes associated with spermatogonial development, meiotic recombination, and double-strand break repair. Furthermore, we found that the SV genes ESCO2 (establishment of sister chromatid cohesion N-acetyltransferase 2) and BRDT (bromodomain testis associated) may be involved in meiotic arrest of cattle-yak spermatocytes. Overall, our research provides a valuable database for identifying structural variant loci that contribute to hybrid sterility.

Transcriptomic and genetic profiling in a spontaneous non-human primate model of hypertrophic cardiomyopathy and sudden cardiac death

Hypertrophic cardiomyopathy (HCM) afflicts humans, cats, pigs, and rhesus macaques. Disease sequelae include congestive heart failure, thromboembolism, and sudden cardiac death (SCD). Sarcomeric mutations explain some human and cat cases, however, the molecular basis in rhesus macaques remains unknown. RNA-Seq of the LV tissues of five HCM-affected and seven healthy control rhesus macaques was employed for differential transcriptomic analyses. DNA from 15 severely HCM-affected and 21 healthy geriatric rhesus macaques were selected for whole-genome sequencing. A genome-wide association study (GWAS) of disease status and SCD outcome was performed. 614 down- and 1,065 upregulated differentially expressed genes (DEGs) were identified between groups. The top DEG (MAFF) was overexpressed in affected animals (log2FoldChange = 4.71; PAdjusted-value = 1.14E-133). Channelopathy-associated enriched terms were identified in ~ 57% of downregulated DEGs providing transcriptomic evidence of hypertrophic and arrhythmic disease processes. For GWAS, no putative variant withstood segregation. Polygenic modeling analysis resulted in poor prediction power and burden testing could not explain HCM by an association of multiple variants in any gene. Neither single nor compound genetic variant(s), or identified polygenic profile, suggest complex genotype-phenotype interactions in rhesus macaques. Brought forth is an established dataset of robustly phenotyped rhesus macaques as an open-access resource for future cardiovascular disease genetic studies.

Genome-Wide Structural Variation Analysis and Breed Comparison of Local Domestic Ducks in Shandong Province, China

Structural variations in the duck genome significantly impact the environmental adaptability and phenotypic diversity of duck populations. Characterizing these SVs in local domestic duck breeds from Shandong province offers valuable insights for breed selection and the development of new breeds. This study aimed to profile the genomic SVs in three local duck breeds (Matahu duck, Weishan partridge duck, and Wendeng black duck) and explore their differential distributions. A total of 21,673 SVs were detected using LUMPY (v0.2.13) and DELLY (v1.0.3) software, with 46% located in intergenic regions, 33% in intronic regions, and frameshift deletions being the most prevalent in exonic regions (3%). SVs distribution showed a decreasing trend with shorter chromosome lengths. Population structure analysis revealed distinct genetic profiles, with Matahu and Weishan partridge ducks showing closer affinities and the Wendeng black duck having a more homogeneous genetic background, likely due to geographic isolation. Functional annotation identified genes related to nervous system development, mitosis, spindle assembly, and energy metabolism. Notable genes included PLXNA4, NRP2, SEMA3A, PTEN, MYBL2, ADK, and COX4I1. Additionally, genes such as PRKG1, GABRA2, and FSHR were linked to energy metabolism and reproductive activity. The study provides a comprehensive analysis of SVs, revealing significant genetic differentiation and identifying genes associated with economically important traits, offering valuable resources for the genetic improvement and breeding of local duck breeds.

Revealing genes related teat number traits via genetic variation in Yorkshire pigs based on whole-genome sequencing

BACKGROUND

Teat number is one of the most important indicators to evaluate the lactation performance of sows, and increasing the teat number has become an important method to improve the economic efficiency of farms. Therefore, it is particularly important to deeply analyze the genetic mechanism of teat number traits in pigs. In this study, we detected Single Nucleotide Ploymorphism (SNP), Insertion-Deletion (InDel) and Structural variant (SV) by high-coverage whole-genome resequencing data, and selected teat number at birth and functional teat number as two types of teat number traits for genome-wide association study (GWAS) to reveal candidate genes associated with pig teat number traits.

RESULTS

In this study, we used whole genome resequencing data from 560 Yorkshire sows to detect SNPs, InDels and SVs, and performed GWAS for the traits of born teat number and functional teat number, and detected a total of 85 significant variants and screened 214 candidate genes, including HEG1, XYLT1, SULF1, MUC13, VRTN, RAP1A and NPVF. Among them, HEG1 and XYLT1 were the new candidate genes in this study. The co-screening and population validation of multiple traits suggested that HEG1 may have a critical effect on the born teat number.

CONCLUSION

Our study shows that more candidate genes associated with pig teat number traits can be identified by GWAS with different variant types. Through large population validation, we found that HEG1 may be a new key candidate gene affecting pig teat number traits. In conclusion, the results of this study provide new information for exploring the genetic mechanisms affecting pig teat number traits and genetic improvement of pigs.

Both Structural Variant and Single Nucleotide Polymorphism Load Impact Lifetime Fitness in a Threatened Bird Species

The field of conservation genomics is becoming increasingly interested in whether, and how, structural variant (SV) genotype information can be leveraged in the management of threatened species. The functional consequences of SVs are more complex than for single nucleotide polymorphisms (SNPs), as SVs typically impact a larger proportion of the genome due to their size and thus may be more likely to contribute to load. While the impacts of SV-specific genetic load may be less consequential for large populations, the interplay between weakened selection and stochastic processes means that smaller populations, such as those of the threatened Aotearoa hihi/New Zealand stitchbird (Notiomystis cincta), may harbour a high SV load. Hihi were once confined to a single remnant population, but have been reestablished into six sanctuaries and reserves, often via secondary bottlenecks, resulting in low genetic diversity, low adaptive potential, and inbreeding depression. In this study, we use whole genome resequencing of 30 individuals from the Tiritiri Matangi population to identify the nature and distribution of both SNPs and SVs within this small avian population. We find that SNP and SV individual mutation load is only moderately correlated, likely because SVs arise in regions of high recombination and that are less evolutionarily conserved. Finally, we leverage a long-term monitoring dataset of pedigree and fitness data to assess the impact of SNP and SV mutation loads on individual fitness, and find that SNP and SV realised load had similar negative correlations with lifetime fitness. However, of the masked load metrics, only SVs had a positive significant correlation with lifetime fitness, indicating that masking of deleterious alleles may be more important for SVs than for SNPs. The results of this study indicate that only examining SNPs neglects important aspects of intra-specific variation and that studying SVs has direct implications for linking genetic diversity and genomic health to inform management decisions.

Mapping the genetic landscape of treatable inherited metabolic disorders in a large Middle Eastern biobank

PURPOSE

To date, approximately 1400 inherited metabolic disorders (IMDs) have been described, some of which are treatable. It is estimated that 2% to 3% of live births worldwide are affected by treatable IMDs. Roughly 80% of IMDs are autosomal recessive, leading to a potentially higher incidence in regions with high consanguinity.

METHODOLOGY

The study utilized genome sequencing data from 14,060 adult Qatari participants who were recruited by the Qatar Biobank and sequenced by the Qatar Genome Program. The genome sequencing data were analyzed for 125 nuclear genes known to be associated with 115 treatable IMDs.

RESULTS

Our study identified 253 pathogenic/likely pathogenic single-nucleotide variations associated with 69 treatable IMDs, including 211 known and 42 novel predicted loss-of-function variants. We estimated that approximately 1 in 13 unrelated individuals (8%) carry a heterozygous pathogenic variant for at least 1 of 46 treatable IMDs. Notably, phenylketonuria/hyperphenylalaninemia and homocystinuria had among the highest carrier frequencies (1 in 68 and 1 in 85, respectively).

CONCLUSION

Population-based studies of treatable IMDs, particularly in globally under-studied populations, can identify high-frequency alleles segregating in the community and inform public health policies, including carrier and newborn screening.

Genome-wide characterization of structure variations in the Xiang pig for genetic resistance to African swine fever

African swine fever (ASF) is a rapidly fatal viral haemorrhagic fever in Chinese domestic pigs. Although very high mortality is observed in pig farms after an ASF outbreak, clinically healthy and antibody-positive pigs are found in those farms, and viral detection is rare from these pigs. The ability of pigs to resist ASF viral infection may be modulated by host genetic variations. However, the genetic basis of the resistance of domestic pigs against ASF remains unclear. We generated a comprehensive set of structural variations (SVs) in a Chinese indigenous Xiang pig with ASF-resistant (Xiang-R) and ASF-susceptible (Xiang-S) phenotypes using whole-genome resequencing method. A total of 53,589 nonredundant SVs were identified, with an average of 25,656 SVs per individual in the Xiang pig genome, including insertion, deletion, inversion and duplication variations. The Xiang-R group harboured more SVs than the Xiang-S group. The F-statistics (FST) was carried out to reveal genetic differences between two populations using the resequencing data at each SV locus. We identified 2,414 population-stratified SVs and annotated 1,152 Ensembl genes (including 986 protein-coding genes), in which 1,326 SVs might disturb the structure and expression of the Ensembl genes. Those protein-coding genes were mainly enriched in the Wnt, Hippo, and calcium signalling pathways. Other important pathways associated with the ASF viral infection were also identified, such as the endocytosis, apoptosis, focal adhesion, Fc gamma R-mediated phagocytosis, junction, NOD-like receptor, PI3K-Akt, and c-type lectin receptor signalling pathways. Finally, we identified 135 candidate adaptive genes overlapping 166 SVs that were involved in the virus entry and virus-host cell interactions. The fact that some of population-stratified SVs regions detected as selective sweep signals gave another support for the genetic variations affecting pig resistance against ASF. The research indicates that SVs play an important role in the evolutionary processes of Xiang pig adaptation to ASF infection.

The 1000 Chinese Indigenous Pig Genomes Project provides insights into the genomic architecture of pigs

Pigs play a central role in human livelihoods in China, but a lack of systematic large-scale whole-genome sequencing of Chinese domestic pigs has hindered genetic studies. Here, we present the 1000 Chinese Indigenous Pig Genomes Project sequencing dataset, comprising 1011 indigenous individuals from 50 pig populations covering approximately two-thirds of China's administrative divisions. Based on the deep sequencing (~25.95×) of these pigs, we identify 63.62 million genomic variants, and provide a population-specific reference panel to improve the imputation performance of Chinese domestic pig populations. Using a combination of methods, we detect an ancient admixture event related to a human immigration climax in the 13th century, which may have contributed to the formation of southeast-central Chinese pig populations. Analyzing the haplotypes of the Y chromosome shows that the indigenous populations residing around the Taihu Lake Basin exhibit a unique haplotype. Furthermore, we find a 13 kb region in the THSD7A gene that may relate to high-altitude adaptation, and a 0.47 Mb region on chromosome 7 that is significantly associated with body size traits. These results highlight the value of our genomic resource in facilitating genomic architecture and complex traits studies in pigs.

Telomere-to-telomere genome assembly of a male goat reveals variants associated with cashmere traits

A complete goat (Capra hircus) reference genome enhances analyses of genetic variation, thus providing insights into domestication and selection in goats and related species. Here, we assemble a telomere-to-telomere (T2T) gap-free genome (2.86 Gb) from a cashmere goat (T2T-goat1.0), including a Y chromosome of 20.96 Mb. With a base accuracy of >99.999%, T2T-goat1.0 corrects numerous genome-wide structural and base errors in previous assemblies and adds 288.5 Mb of previously unresolved regions and 446 newly assembled genes to the reference genome. We sequence the genomes of five representative goat breeds for PacBio reads, and use T2T-goat1.0 as a reference to identify a total of 63,417 structural variations (SVs) with up to 4711 (7.42%) in the previously unresolved regions. T2T-goat1.0 was applied in population analyses of global wild and domestic goats, which revealed 32,419 SVs and 25,397,794 SNPs, including 870 SVs and 545,026 SNPs in the previously unresolved regions. Also, our analyses reveal a set of selective variants and genes associated with domestication (e.g., NKG2D and ABCC4) and cashmere traits (e.g., ABCC4 and ASIP).

The landscape of structural variation in aye-ayes (Daubentonia madagascariensis)

Aye-ayes (Daubentonia madagascariensis) are one of the 25 most critically endangered primate species in the world. Endemic to Madagascar, their small and highly fragmented populations make them particularly vulnerable to both genetic disease and anthropogenic environmental changes. Over the past decade, conservation genomic efforts have largely focused on inferring and monitoring population structure based on single nucleotide variants to identify and protect critical areas of genetic diversity. However, the recent release of a highly contiguous genome assembly allows, for the first time, for the study of structural genomic variation (deletions, duplications, insertions, and inversions) which are likely to impact a substantial proportion of the species' genome. Based on whole-genome, short-read sequencing data from 14 individuals, >1,000 high-confidence autosomal structural variants were detected, affecting ~240 kb of the aye-aye genome. The majority of these variants (>85%) were deletions shorter than 200 bp, consistent with the notion that longer structural mutations are often associated with strongly deleterious fitness effects. For example, two deletions longer than 850 bp located within disease-linked genes were predicted to impose substantial fitness deficits owing to a resulting frameshift and gene fusion, respectively; whereas several other major effect variants outside of coding regions are likely to impact gene regulatory landscapes. Taken together, this first glimpse into the landscape of structural variation in aye-ayes will enable future opportunities to advance our understanding of the traits impacting the fitness of this endangered species, as well as allow for enhanced evolutionary comparisons across the full primate clade.

Drosophila Toxicogenomics: genetic variation and sexual dimorphism in susceptibility to 4-Methylimidazole

BACKGROUND

4-methylimidazole is a ubiquitous and potentially carcinogenic environmental toxicant. Genetic factors that contribute to variation in susceptibility to its toxic effects are challenging to assess in human populations. We used the Drosophila melanogaster Genetic Reference Panel (DGRP), a living library of natural genetic variation, to identify genes with human orthologs associated with variation in susceptibility to 4-methylimidazole.

RESULTS

We screened 204 DGRP lines for survival following 24-hour exposure to 4-methylimidazole. We found extensive genetic variation for survival, with a broad sense heritability of 0.82; as well as genetic variation in sexual dimorphism, with a cross-sex genetic correlation of 0.59. Genome-wide association analyses identified a total of 241 candidate molecular polymorphisms in or near 273 unique genes associated with survival. These polymorphisms had either sex-specific or sex-antagonistic effects, and most had putative regulatory effects. We generated interaction networks using these candidate genes as inputs and computationally recruited genes with known physical or genetic interactions. The network genes were significantly over-represented for gene ontology terms involving all aspects of development (including nervous system development) and cellular and organismal functions as well as canonical signaling pathways, and most had human orthologs.

CONCLUSIONS

The genetic basis of variation in sensitivity to acute exposure to 4-methylimidazole in Drosophila is attributable to variation in genes and networks of genes known for their effects on multiple developmental and cellular processes, including possible neurotoxicity. Given evolutionary conservation of the underlying genes and pathways, these insights may be applicable to humans.

Fc gamma receptors: Their evolution, genomic architecture, genetic variation, and impact on human disease

Fc gamma receptors (FcγRs) are a family of receptors that bind IgG antibodies and interface at the junction of humoral and innate immunity. Precise regulation of receptor expression provides the necessary balance to achieve healthy immune homeostasis by establishing an appropriate immune threshold to limit autoimmunity but respond effectively to infection. The underlying genetics of the FCGR gene family are central to achieving this immune threshold by regulating affinity for IgG, signaling efficacy, and receptor expression. The FCGR gene locus was duplicated during evolution, retaining very high homology and resulting in a genomic region that is technically difficult to study. Here, we review the recent evolution of the gene family in mammals, its complexity and variation through copy number variation and single-nucleotide polymorphism, and impact of these on disease incidence, resolution, and therapeutic antibody efficacy. We also discuss the progress and limitations of current approaches to study the region and emphasize how new genomics technologies will likely resolve much of the current confusion in the field. This will lead to definitive conclusions on the impact of genetic variation within the FCGR gene locus on immune function and disease.

Convergence and divergence of diploid and tetraploid cotton genomes

Polyploidy is an important driving force in speciation and evolution; however, the genomic basis for parallel selection of a particular trait between polyploids and ancestral diploids remains unexplored. Here we construct graph-based pan-genomes for diploid (A2) and allotetraploid (AD1) cotton species, enabled by an assembly of 50 genomes of genetically diverse accessions. We delineate a mosaic genome map of tetraploid cultivars that illustrates genomic contributions from semi-wild forms into modern cultivars. Pan-genome comparisons identify syntenic and hyper-divergent regions of continued variation between diploid and tetraploid cottons, and suggest an ongoing process of sequence evolution potentially linked to the contrasting genome size change in two subgenomes. We highlight 43% of genetic regulatory relationships for gene expression in diploid encompassing sequence divergence after polyploidy, and specifically characterize six underexplored convergent genetic loci contributing to parallel selection of fiber quality. This study offers a framework for pan-genomic dissection of genetic regulatory components underlying parallel selection of desirable traits in organisms.