Mobile element variation contributes to population-specific genome diversification, gene regulation and disease risk

Transposable elements as instructors of the immune system

Transposable elements (TEs) are mobile repetitive nucleic acid sequences that have been incorporated into the genome through spontaneous integration, accounting for almost 50% of human DNA. Even though most TEs are no longer mobile today, studies have demonstrated that they have important roles in different biological processes, such as ageing, embryonic development, and cancer. TEs influence these processes through various mechanisms, including active transposition of TEs contributing to ongoing evolution, transposon transcription generating RNA or protein, and by influencing gene regulation as enhancers. However, how TEs interact with the immune system remains a largely unexplored field. In this Perspective, we describe how TEs might influence different aspects of the immune system, such as innate immune responses, T cell activation and differentiation, and tissue adaptation. Furthermore, TEs can serve as a source of neoantigens for T cells in antitumour immunity. We suggest that TE biology is an important emerging field of immunology and discuss the potential to harness the TE network therapeutically, for example, to improve immunotherapies for cancer and autoimmune and inflammatory diseases.

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.

Impact of a horizontally transferred Helitron family on genome evolution in Xenopus laevis

BACKGROUND

Within eukaryotes, most horizontal transfer of genetic material involves mobile DNA sequences and such events are called horizontal transposable element transfer (HTT). Although thousands of HTT examples have been reported, the transfer mechanisms and their impacts on host genomes remain elusive.

RESULTS

In this work, we carefully annotated three Helitron families within several Xenopus frog genomes. One of the Helitron family, Heli1Xen1, is recurrently involved in capturing and shuffling Xenopus laevis genes required in early embryonic development. Remarkably, we found that Heli1Xen1 is seemingly expressed in X. laevis and has produced multiple genomic polymorphisms within the X. laevis population. To identify the origin of Heli1Xen1, we searched its consensus sequence against available genome assemblies. We found highly similar copies in the genomes of another 13 vertebrate species from divergent vertebrate lineages, including reptiles, ray-finned fishes and amphibians. Further phylogenetic analysis provides evidence showing that Heli1Xen1 invaded these lineages via HTT quite recently, around 0.58-10.74 million years ago.

CONCLUSIONS

The frequently Heli1Xen1-involved HTT events among reptiles, fishes and amphibians could provide insights into possible vectors for transfer, such as shared viruses across lineages. Furthermore, we propose that the Heli1Xen1 sequence could be an ideal candidate for studying the mechanism and genomic impact of Helitron transposition.

Genetic regulation of gene expression across multiple tissues in chickens

The chicken is a valuable model for understanding fundamental biology and vertebrate evolution and is a major global source of nutrient-dense and lean protein. Despite being the first non-mammalian amniote to have its genome sequenced, a systematic characterization of functional variation on the chicken genome remains lacking. Here, we integrated bulk RNA sequencing (RNA-seq) data from 7,015 samples, single-cell RNA-seq data from 127,598 cells and 2,869 whole-genome sequences to present a pilot atlas of regulatory variants across 28 chicken tissues. This atlas reveals millions of regulatory effects on primary expression (protein-coding genes, long non-coding RNA and exons) and post-transcriptional modifications (alternative splicing and 3'-untranslated region alternative polyadenylation). We highlighted distinct molecular mechanisms underlying these regulatory variants, their context-dependent behavior and their utility in interpreting genome-wide associations for 39 chicken complex traits. Finally, our comparative analyses of gene regulation between chickens and mammals demonstrate how this resource can facilitate cross-species gene mapping of complex traits.

Multi-ancestry GWAS reveals loci linked to human variation in LINE-1- and Alu-insertion numbers

LINE-1 (L1) and Alu are two families of transposable elements (TEs) occupying ~17% and ~11% of the human genome, respectively. Though only a small fraction of L1 copies is able to produce the machinery to mobilize autonomously, Alu and degenerate L1s can hijack their functional machinery and mobilize in trans. The expression and subsequent mobilization of L1 and Alu can exert pathological effects on their hosts. These features have made them promising focus subjects in studies of aging where they can become active. However, mechanisms regulating TE activity are incompletely characterized, especially in diverse human populations. To address these gaps, we leveraged genomic data from the 1000 Genomes Project to carry out a trans-ethnic GWAS of L1/Alu insertion singletons. These are rare, recently acquired insertions observed in only one person and which we used as proxies for variation in L1/Alu insertion numbers. Our approach identified SNVs in genomic regions containing genes with potential and known TE regulatory properties, and it enriched for SNVs in regions containing known regulators of L1 expression. Moreover, we identified reference TE copies and structural variants that associated with L1/Alu singletons, suggesting their potential contribution to TE insertion number variation. Finally, a transcriptional analysis of lymphoblastoid cells highlighted potential cell cycle alterations in a subset of samples harboring L1/Alu singletons. Collectively, our results suggest that known TE regulatory mechanisms may be active in diverse human populations, expand the list of loci implicated in TE insertion number variability, and reinforce links between TEs and disease.

Construction of the porcine genome mobile element variations and investigation of its role in population diversity and gene expression

BACKGROUND

Mobile element variants (MEVs) have a significant and complex impact on genomic diversity and phenotypic traits. However, the quantity, distribution, and relationship with gene expression and complex traits of MEVs in the pig genome remain poorly understood.

RESULTS

We constructed the most comprehensive porcine MEV library based on high-depth whole genome sequencing (WGS) data from 747 pigs across 59 breeds worldwide. This database identified a total of 147,993 polymorphic MEVs, including 121,099 short interspersed nuclear elements (SINEs), 26,053 long interspersed nuclear elements (LINEs), 802 long terminal repeats (LTRs), and 39 other transposons, among which 54% are newly discovered. We found that MEVs are unevenly distributed across the genome and are strongly influenced by negative selection effects. Importantly, we identified 514, 530, and 584 candidate MEVs associated with population differentiation, domestication, and breed formation, respectively. For example, a significantly differentiated MEV is located in the ATRX intron between Asian and European pigs, whereas ATRX is also differentially expressed between Asian and European pigs in muscle tissue. In addition, we identified 4,169 expressed MEVs (eMEVs) significantly associated with gene expression and 6,914 splicing MEVs (sMEVs) associated with gene splicing based on RNA-seq data from 266 porcine liver tissues. These eMEVs and sMEVs explain 6.24% and 9.47%, respectively, of the observed cis-heritability and highlight the important role of MEVs in the regulation of gene expression. Finally, we provide a high-quality SNP-MEV reference haplotype panel to impute MEV genotypes from genome-wide SNPs. Notably, we identified a candidate MEV significantly associated with total teat number, demonstrating the functionality of this reference panel.

CONCLUSIONS

The present investigation demonstrated the importance of MEVs in pigs in terms of population diversity, gene expression and phenotypic traits, which may provide useful resources and theoretical support for pig genetics and breeding.

KTED: a comprehensive web-based database for transposable elements in the Korean genome

Summary

Transposable elements (TEs), commonly referred to as "mobile elements," constitute DNA segments capable of relocating within a genome. Initially disregarded as "junk DNA" devoid of specific functionality, it has become evident that TEs have diverse influences on an organism's biology and health. The impact of these elements varies according to their location, classification, and their effects on specific genes or regulatory components. Despite their significant roles, a paucity of resources concerning TEs in population-scale genome sequencing remains. Herein, we analyze whole-genome sequencing data sourced from the Korean Genome and Epidemiology Study, encompassing 2500 Korean individuals. To facilitate convenient data access and observation, we developed a web-based database, KTED. Additionally, we scrutinized the differential distributions of TEs across five distinct common disease groups: dyslipidemia, hypertension, diabetes, thyroid disease, and cancer.

Availability and implementation

https://snubh.shinyapps.io/KTED.

Cell-Specific Transposable Element and Gene Expression Analysis Across Systemic Lupus Erythematosus Phenotypes

OBJECTIVE

There is an established yet unexplained link between interferon (IFN) and systemic lupus erythematosus (SLE). The expression of sequences derived from transposable elements (TEs) may contribute to SLE phenotypes, specifically production of type I IFNs and generation of autoantibodies.

METHODS

We profiled cell-sorted RNA-sequencing data (CD4+ T cells, CD14+ monocytes, CD19+ B cells, and natural killer cells) from peripheral blood mononuclear cells of 120 patients with SLE and quantified TE expression identifying 27,135 TEs. We tested for differential TE expression across 10 SLE phenotypes, including autoantibody production and disease activity.

RESULTS

We found 731 differentially expressed (DE) TEs across all SLE phenotypes that were mostly cell specific and phenotype specific. DE TEs were enriched for specific families and open reading frames of viral genes encoded in TE sequences. Increased expression of DE TEs was associated with genes involved in antiviral activity, such as LY6E, ISG15, and TRIM22, and pathways such as IFN signaling.

CONCLUSION

These findings suggest that expression of TEs contributes to activation of SLE-related mechanisms in a cell-specific manner, which can impact disease diagnostics and therapeutics.

Update on the Pathogenesis of Keloid Formation

Keloids are abnormal skin growths occurring in a significant portion of the global population. Despite their pervasiveness, the underlying pathophysiology of this scarring process is yet to be fully understood. In this review article, we delve into the current literature on the pathophysiological mechanisms of keloids. We take a top-down approach, first looking at host factors such as genetics and endocrine factors and then taking a more granular approach describing specific control factors such as germline keloid predisposition variants, epigenetics and transcriptomics, inflammatory and immune dysregulation, and the role of profibrotic and angiogenic cell signaling pathways. We then discuss current knowledge gaps, propose further research avenues, and explore potential future treatment options considering our increased understanding of keloid pathogenesis.

A unified framework to analyze transposable element insertion polymorphisms using graph genomes

Transposable elements are ubiquitous mobile DNA sequences generating insertion polymorphisms, contributing to genomic diversity. We present GraffiTE, a flexible pipeline to analyze polymorphic mobile elements insertions. By integrating state-of-the-art structural variant detection algorithms and graph genomes, GraffiTE identifies polymorphic mobile elements from genomic assemblies or long-read sequencing data, and genotypes these variants using short or long read sets. Benchmarking on simulated and real datasets reports high precision and recall rates. GraffiTE is designed to allow non-expert users to perform comprehensive analyses, including in models with limited transposable element knowledge and is compatible with various sequencing technologies. Here, we demonstrate the versatility of GraffiTE by analyzing human, Drosophila melanogaster, maize, and Cannabis sativa pangenome data. These analyses reveal the landscapes of polymorphic mobile elements and their frequency variations across individuals, strains, and cultivars.

MEHunter: transformer-based mobile element variant detection from long reads

SUMMARY

Mobile genetic elements (MEs) are heritable mutagens that significantly contribute to genetic diseases. The advent of long-read sequencing technologies, capable of resolving large DNA fragments, offers promising prospects for the comprehensive detection of ME variants (MEVs). However, achieving high precision while maintaining recall performance remains challenging mainly brought by the variable length and similar content of MEV signatures, which are often obscured by the noise in long reads. Here, we propose MEHunter, a high-performance MEV detection approach utilizing a fine-tuned transformer model adept at identifying potential MEVs with fragmented features. Benchmark experiments on both simulated and real datasets demonstrate that MEHunter consistently achieves higher accuracy and sensitivity than the state-of-the-art tools. Furthermore, it is capable of detecting novel potentially individual-specific MEVs that have been overlooked in published population projects.

AVAILABILITY AND IMPLEMENTATION

MEHunter is available from https://github.com/120L021101/MEHunter.

Targeting transposable elements in cancer: developments and opportunities

Transposable elements (TEs), comprising nearly 50% of the human genome, have transitioned from being perceived as "genomic junk" to key players in cancer progression. Contemporary research links TE regulatory disruptions with cancer development, underscoring their therapeutic potential. Advances in long-read sequencing, computational analytics, single-cell sequencing, proteomics, and CRISPR-Cas9 technologies have enriched our understanding of TEs' clinical implications, notably their impact on genome architecture, gene regulation, and evolutionary processes. In cancer, TEs, including long interspersed element-1 (LINE-1), Alus, and long terminal repeat (LTR) elements, demonstrate altered patterns, influencing both tumorigenic and tumor-suppressive mechanisms. TE-derived nucleic acids and tumor antigens play critical roles in tumor immunity, bridging innate and adaptive responses. Given their central role in oncology, TE-targeted therapies, particularly through reverse transcriptase inhibitors and epigenetic modulators, represent a novel avenue in cancer treatment. Combining these TE-focused strategies with existing chemotherapy or immunotherapy regimens could enhance efficacy and offer a new dimension in cancer treatment. This review delves into recent TE detection advancements, explores their multifaceted roles in tumorigenesis and immune regulation, discusses emerging diagnostic and therapeutic approaches centered on TEs, and anticipates future directions in cancer research.

Single-cell chromatin accessibility and transposable element landscapes reveal shared features of tissue-residing immune cells

Tissue adaptation is required for regulatory T (Treg) cell function within organs. Whether this program shares aspects with other tissue-localized immune populations is unclear. Here, we analyzed single-cell chromatin accessibility data, including the transposable element (TE) landscape of CD45+ immune cells from colon, skin, adipose tissue, and spleen. We identified features of organ-specific tissue adaptation across different immune cells. Focusing on tissue Treg cells, we found conservation of the Treg tissue adaptation program in other tissue-localized immune cells, such as amphiregulin-producing T helper (Th)17 cells. Accessible TEs can act as regulatory elements, but their contribution to tissue adaptation is not understood. TE landscape analysis revealed an enrichment of specific transcription factor binding motifs in TE regions within accessible chromatin peaks. TEs, specifically from the LTR family, were located in enhancer regions and associated with tissue adaptation. These findings broaden our understanding of immune tissue residency and provide an important step toward organ-specific immune interventions.

A sequence of SVA retrotransposon insertions in ASIP shaped human pigmentation

Retrotransposons comprise about 45% of the human genome1, but their contributions to human trait variation and evolution are only beginning to be explored2,3. Here, we find that a sequence of SVA retrotransposon insertions in an early intron of the ASIP (agouti signaling protein) gene has probably shaped human pigmentation several times. In the UK Biobank (n = 169,641), a recent 3.3-kb SVA insertion polymorphism associated strongly with lighter skin pigmentation (0.22 [0.21-0.23] s.d.; P = 2.8 × 10-351) and increased skin cancer risk (odds ratio = 1.23 [1.18-1.27]; P = 1.3 × 10-28), appearing to underlie one of the strongest common genetic influences on these phenotypes within European populations4-6. ASIP expression in skin displayed the same association pattern, with the SVA insertion allele exhibiting 2.2-fold (1.9-2.6) increased expression. This effect had an unusual apparent mechanism: an earlier, nonpolymorphic, human-specific SVA retrotransposon 3.9 kb upstream appeared to have caused ASIP hypofunction by nonproductive splicing, which the new (polymorphic) SVA insertion largely eliminated. Extended haplotype homozygosity indicated that the insertion allele has risen to allele frequencies up to 11% in European populations over the past several thousand years. These results indicate that a sequence of retrotransposon insertions contributed to a species-wide increase, then a local decrease, of human pigmentation.

Identification of transposable element families from pangenome polymorphisms

BACKGROUND

Transposable Elements (TEs) are segments of DNA, typically a few hundred base pairs up to several tens of thousands bases long, that have the ability to generate new copies of themselves in the genome. Most existing methods used to identify TEs in a newly sequenced genome are based on their repetitive character, together with detection based on homology and structural features. As new high quality assemblies become more common, including the availability of multiple independent assemblies from the same species, an alternative strategy for identification of TE families becomes possible in which we focus on the polymorphism at insertion sites caused by TE mobility.

RESULTS

We develop the idea of using the structural polymorphisms found in pangenomes to create a library of the TE families recently active in a species, or in a closely related group of species. We present a tool, pantera, that achieves this task, and illustrate its use both on species with well-curated libraries, and on new assemblies.

CONCLUSIONS

Our results show that pantera is sensitive and accurate, tending to correctly identify complete elements with precise boundaries, and is particularly well suited to detect larger, low copy number TEs that are often undetected with existing de novo methods.

Investigating mobile element variations by statistical genetics

The integration of structural variations (SVs) in statistical genetics provides an opportunity to understand the genetic factors influencing complex human traits and disease. Recent advances in long-read technology and variant calling methods for short reads have improved the accurate discovery and genotyping of SVs, enabling their use in expression quantitative trait loci (eQTL) analysis and genome-wide association studies (GWAS). Mobile elements are DNA sequences that insert themselves into various genome locations. Insertional polymorphisms of mobile elements between humans, called mobile element variations (MEVs), contribute to approximately 25% of human SVs. We recently developed a variant caller that can accurately identify and genotype MEVs from biobank-scale short-read whole-genome sequencing (WGS) datasets and integrate them into statistical genetics. The use of MEVs in eQTL analysis and GWAS has a minimal impact on the discovery of genome loci associated with gene expression and disease; most disease-associated haplotypes can be identified by single nucleotide variations (SNVs). On the other hand, it helps make hypotheses about causal variants or effector variants. Focusing on MEVs, we identified multiple MEVs that contribute to differential gene expression and one of them is a potential cause of skin disease, emphasizing the importance of the integration of MEVs in medical genetics. Here, I will provide an overview of MEVs, MEV calling from WGS, and the integration of MEVs in statistical genetics. Finally, I will discuss the unanswered questions about MEVs, such as rare variants.

Mapping and functional characterization of structural variation in 1060 pig genomes

BACKGROUND

Structural variations (SVs) have significant impacts on complex phenotypes by rearranging large amounts of DNA sequence.

RESULTS

We present a comprehensive SV catalog based on the whole-genome sequence of 1060 pigs (Sus scrofa) representing 101 breeds, covering 9.6% of the pig genome. This catalog includes 42,487 deletions, 37,913 mobile element insertions, 3308 duplications, 1664 inversions, and 45,184 break ends. Estimates of breed ancestry and hybridization using genotyped SVs align well with those from single nucleotide polymorphisms. Geographically stratified deletions are observed, along with known duplications of the KIT gene, responsible for white coat color in European pigs. Additionally, we identify a recent SINE element insertion in MYO5A transcripts of European pigs, potentially influencing alternative splicing patterns and coat color alterations. Furthermore, a Yorkshire-specific copy number gain within ABCG2 is found, impacting chromatin interactions and gene expression across multiple tissues over a stretch of genomic region of ~200 kb. Preliminary investigations into SV's impact on gene expression and traits using the Pig Genotype-Tissue Expression (PigGTEx) data reveal SV associations with regulatory variants and gene-trait pairs. For instance, a 51-bp deletion is linked to the lead eQTL of the lipid metabolism regulating gene FADS3, whose expression in embryo may affect loin muscle area, as revealed by our transcriptome-wide association studies.

CONCLUSIONS

This SV catalog serves as a valuable resource for studying diversity, evolutionary history, and functional shaping of the pig genome by processes like domestication, trait-based breeding, and adaptive evolution.

Functional variants in a TTTG microsatellite on 15q26.1 cause familial nonautoimmune thyroid abnormalities

Insufficient thyroid hormone production in newborns is referred to as congenital hypothyroidism. Multinodular goiter (MNG), characterized by an enlarged thyroid gland with multiple nodules, is usually seen in adults and is recognized as a separate disorder from congenital hypothyroidism. Here we performed a linkage analysis of a family with both nongoitrous congenital hypothyroidism and MNG and identified a signal at 15q26.1. Follow-up analyses with whole-genome sequencing and genetic screening in congenital hypothyroidism and MNG cohorts showed that changes in a noncoding TTTG microsatellite on 15q26.1 were frequently observed in congenital hypothyroidism (137 in 989) and MNG (3 in 33) compared with controls (3 in 38,722). Characterization of the noncoding variants with epigenomic data and in vitro experiments suggested that the microsatellite is located in a thyroid-specific transcriptional repressor, and its activity is disrupted by the variants. Collectively, we presented genetic evidence linking nongoitrous congenital hypothyroidism and MNG, providing unique insights into thyroid abnormalities.

In search of critical dsRNA targets of ADAR1

Recent studies have underscored the pivotal role of adenosine-to-inosine RNA editing, catalyzed by ADAR1, in suppressing innate immune interferon responses triggered by cellular double-stranded RNA (dsRNA). However, the specific ADAR1 editing targets crucial for this regulatory function remain elusive. We review analyses of transcriptome-wide ADAR1 editing patterns and their evolutionary dynamics, which offer valuable insights into this unresolved query. The growing appreciation of the significance of immunogenic dsRNAs and their editing in inflammatory and autoimmune diseases and cancer calls for a more comprehensive understanding of dsRNA immunogenicity, which may promote our understanding of these diseases and open doors to therapeutic avenues.

The role of transposable elements in human evolution and methods for their functional analysis: current status and future perspectives

Transposable elements (TEs) are mobile DNA sequences that can insert themselves into various locations within the genome, causing mutations that may provide advantages or disadvantages to individuals and species. The insertion of TEs can result in genetic variation that may affect a wide range of human traits including genetic disorders. Understanding the role of TEs in human biology is crucial for both evolutionary and medical research. This review discusses the involvement of TEs in human traits and disease susceptibility, as well as methods for functional analysis of TEs.

Retrotransposon-derived transcripts and their functions in immunity and disease

Retrotransposons, which account for approximately 42% of the human genome, have been increasingly recognized as "non-self" pathogen-associated molecular patterns (PAMPs) due to their virus-like sequences. In abnormal conditions such as cancer and viral infections, retrotransposons that are aberrantly expressed due to impaired epigenetic suppression display PAMPs, leading to their recognition by pattern recognition receptors (PRRs) of the innate immune system and triggering inflammation. This viral mimicry mechanism has been observed in various human diseases, including aging and autoimmune disorders. However, recent evidence suggests that retrotransposons possess highly regulated immune reactivity and play important roles in the development and function of the immune system. In this review, I discuss a wide range of retrotransposon-derived transcripts, their role as targets in immune recognition, and the diseases associated with retrotransposon activity. Furthermore, I explore the implications of chimeric transcripts formed between retrotransposons and known gene mRNAs, which have been previously underestimated, for the increase of immune-related gene isoforms and their influence on immune function. Retrotransposon-derived transcripts have profound and multifaceted effects on immune system function. The aim of this comprehensive review is to provide a better understanding of the complex relationship between retrotransposon transcripts and immune defense.

Cell-Specific Transposable Element Gene Expression Analysis Identifies Associations with Systemic Lupus Erythematosus Phenotypes

There is an established yet unexplained link between interferon (IFN) and systemic lupus erythematosus (SLE). The expression of sequences derived from transposable elements (TEs) may contribute to production of type I IFNs and generation of autoantibodies. We profiled cell-sorted RNA-seq data (CD4+ T cells, CD14+ monocytes, CD19+ B cells, and NK cells) from PBMCs of 120 SLE patients and quantified TE expression identifying 27,135 TEs. We tested for differential TE expression across 10 SLE phenotypes including autoantibody production and disease activity and discovered 731 differentially expressed (DE) TEs whose effects were mostly cell-specific and phenotype-specific. DE TEs were enriched for specific families and viral genes encoded in TE sequences. Increased expression of DE TEs was associated with genes involved in antiviral activity such as LY6E, ISG15, TRIM22 and pathways such as interferon signaling. These findings suggest that expression of TEs contributes to activation of SLE-related mechanisms in a cell-specific manner, which can impact disease diagnostics and therapeutics.

Taming transposable elements in livestock and poultry: a review of their roles and applications

Livestock and poultry play a significant role in human nutrition by converting agricultural by-products into high-quality proteins. To meet the growing demand for safe animal protein, genetic improvement of livestock must be done sustainably while minimizing negative environmental impacts. Transposable elements (TE) are important components of livestock and poultry genomes, contributing to their genetic diversity, chromatin states, gene regulatory networks, and complex traits of economic value. However, compared to other species, research on TE in livestock and poultry is still in its early stages. In this review, we analyze 72 studies published in the past 20 years, summarize the TE composition in livestock and poultry genomes, and focus on their potential roles in functional genomics. We also discuss bioinformatic tools and strategies for integrating multi-omics data with TE, and explore future directions, feasibility, and challenges of TE research in livestock and poultry. In addition, we suggest strategies to apply TE in basic biological research and animal breeding. Our goal is to provide a new perspective on the importance of TE in livestock and poultry genomes.