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African green monkeys (AGMs, Chlorocebus aethiops) are Old World monkeys which are used as experimental models in biomedical research. Recent technological advances in next generation sequencing are useful for unraveling the genetic mechanisms underlying senescence, aging, and age-related disease. To elucidate the normal aging mechanisms in older age, the blood transcriptomes of nine healthy, aged AGMs (15‒23 years old), were analyzed over two years. We identified 910‒1399 accumulated differentially expressed genes (DEGs) in each individual, which increased with age. Aging-related DEGs were sorted across the three time points. A major proportion of the aging-related DEGs belonged to gene ontology (GO) categories involved in translation and rRNA metabolic processes. Next, we sorted common aging-related DEGs across three time points over two years. Common aging-related DEGs belonged to GO categories involved in translation, cellular component biogenesis, rRNA metabolic processes, cellular component organization, biogenesis, and RNA metabolic processes. Furthermore, we identified 29 candidate aging genes that were upregulated across the time series analysis. These candidate aging genes were linked to protein synthesis. This study describes a changing gene expression pattern in AGMs during aging using longitudinal transcriptome sequencing. The candidate aging genes identified here may be potential targets for the treatment of aging.

Background The BLOC1S2 gene encodes the multifunctional protein BLOS2, a shared subunit of two lysosomal trafficking complexes: i) biogenesis of lysosome-related organelles complex-1 and i) BLOC-1-related complex. In our previous study, we identified an intriguing unreported transcript of the BLOC1S2 gene that has a novel exon derived from two transposable elements (TEs), MIR and AluSp. To investigate the evolutionary footprint and molecular mechanism of action of this transcript, we performed PCR and RT-PCR experiments and sequencing analyses using genomic DNA and RNA samples from humans and various non-human primates. Results The results showed that the MIR element had integrated into the genome of our common ancestor, specifically in the BLOC1S2 gene region, before the radiation of all primate lineages and that the AluSp element had integrated into the genome of our common ancestor, fortunately in the middle of the MIR sequences, after the divergence of Old World monkeys and New World monkeys. The combined MIR and AluSp sequences provide a 3′ splice site (AG) and 5′ splice site (GT), respectively, and generate the Old World monkey-specific transcripts. Moreover, branch point sequences for the intron removal process are provided by the MIR and AluSp combination. Conclusions We show for the first time that sequential integration into the same location and sequence divergence events of two different TEs generated lineage-specific transcripts through sequence collaboration during primate evolution.

Transposable elements cause alternative splicing (AS) in different ways, contributing to transcript diversification. Alternative polyadenylation (APA), one of the AS events, is related to the generation of mRNA isoforms in 70% of human genes. In this study, we tried to investigate AluYRa1s located at the terminal region of cynomolgus monkey genes, utilizing both computational analysis and molecular experimentation. We found that ten genes had AluYRa1 at their 3′ end, and nine of these AluYRa1s were sense-oriented. Furthermore, in seven genes, AluYRa1s were expected to have a similar consensus sequence for polyadenylation cleavage. Additional computational analysis using the annotation files from the UCSC database showed that AluYRa1 was more involved in polyadenylation than in open reading frame exon splicing. To examine the extent of AluYRa1 involvement in polyadenylation, RNA-seq data from 30 normal cynomolgus monkeys were analyzed using TAPAS, a recently devised software that detects all the promising polyadenylation sites including APA sites. We observed that approximately 74% of possible polyadenylation sites in the analyzed genes were provided by sense-oriented AluYRa1. In conclusion, AluYRa1 is an Old-World monkey-specific TE, and its sense-oriented insertion at the 3′UTR region tends to provide a favorable environment for polyadenylation, diversifying gene transcripts.

Background Alternative splicing (AS) generates various transcripts from a single gene and thus plays a significant role in transcriptomic diversity and proteomic complexity. Alu elements are primate-specific transposable elements (TEs) and can provide a donor or acceptor site for AS. In a study on TE-mediated AS, we recently identified a novel AluSz6-exonized ACTR8 transcript of the crab-eating monkey (Macaca fascicularis). In the present study, we sought to determine the molecular mechanism of AluSz6 exonization of the ACTR8 gene and investigate its evolutionary and functional consequences in the crab-eating monkey. Results We performed RT-PCR and genomic PCR to analyze AluSz6 exonization in the ACTR8 gene and the expression of the AluSz6-exonized transcript in nine primate samples, including prosimians, New world monkeys, Old world monkeys, and hominoids. AluSz6 integration was estimated to have occurred before the divergence of simians and prosimians. The Alu-exonized transcript obtained by AS was lineage-specific and expressed only in Old world monkeys and apes, and humans. This lineage-specific expression was caused by a single G duplication in AluSz6, which provides a new canonical 5′ splicing site. We further identified other alternative transcripts that were unaffected by the AluSz6 insertion. Finally, we observed that the alternative transcripts were transcribed into new isoforms with C-terminus deletion, and in silico analysis showed that these isoforms do not have a destructive function. Conclusions The single G duplication in the TE sequence is the source of TE exonization and AS, and this mutation may suffer a different fate of ACTR8 gene expression during primate evolution.

Background: Alternative splicing (AS) generate various transcripts from a single gene and thus plays a significant role in transcriptomic diversity and proteomic complexity. Alu elements are primate-specific transposable elements (TEs) and can provide a donor or acceptor site for AS. In a study on TE-mediated AS, we recently identified a novel Alu Sz6-exonized ACTR8 transcript of a crab-eating monkey ( Macaca fascicularis ). In the present study, we sought to analyse the molecular mechanism of Alu Sz6-derived exonization in ACTR8 gene.Results: We performed RT-PCR and genomic PCR using the tissue RNA and DNA samples from the crab-eating monkey and various other primates, including humans, to study Alu Sz6-derived exonization in ACTR8 gene and transcript variants expression. Alu Sz6 integration was estimated to have occurred before the divergence of simians and prosimians. The novel transcript was expressed only in Old world monkeys and apes, and humans. Lineage-specific expression of ACTR8 gene was due to a ‘G’ duplication in the Alu Sz6 sequences of Old world monkey and ape lineages. Six alternative transcripts (TV1-TV6) generated by various AS mechanisms were newly identified. Based on in-silico analysis, the alternative transcripts were transcribed into new isoforms with C-terminus deletion.Conclusion: ‘G’ duplication together with TE exonization and AS via various mechanisms resulted in a different fate of ACTR8 gene expression during primate evolution.

Background The characterization of genomic or epigenomic variation in human and animal models could provide important insight into pathophysiological mechanisms of various diseases, and lead to new developments in disease diagnosis and clinical intervention. The African green monkey (AGM; Chlorocebus aethiops) and cynomolgus monkey (CM; Macaca fascicularis) have long been considered important animal models in biomedical research. However, non-human primate-specific methods applicable to epigenomic analyses in AGM and CM are lacking. The recent development of methyl-capture sequencing (MC-seq) has an unprecedented advantage of cost-effectiveness, and further allows for extending the methylome coverage compared to conventional sequencing approaches. Results Here, we used a human probe-designed MC-seq method to assay DNA methylation in DNA obtained from 13 CM and three AGM blood samples. To effectively adapt the human probe-designed target region for methylome analysis in non-human primates, we redefined the target regions, focusing on regulatory regions and intragenic regions with consideration of interspecific sequence homology and promoter region variation. Methyl-capture efficiency was controlled by the sequence identity between the captured probes based on the human reference genome and the AGM and CM genome sequences, respectively. Using reasonable guidelines, 56 and 62% of the human-based capture probes could be effectively mapped for DNA methylome profiling in the AGM and CM genome, respectively, according to numeric global statistics. In particular, our method could cover up to 89 and 87% of the regulatory regions of the AGM and CM genome, respectively. Conclusions Use of human-based MC-seq methods provides an attractive, cost-effective approach for the methylome profiling of non-human primates at the single-base resolution level. Electronic supplementary material The online version of this article (10.1186/s12864-018-4666-1) contains supplementary material, which is available to authorized users.

Additional file 1: Table S1. List of primers used in this study. Figure S1 Multiple sequence alignment of the AluSz6 insertion region in the ACTR8 gene in various primates. Sequences obtained from the genomic PCR product (Fig. 1b). Black lined boxes indicate exons, and sequences between boxes are intron regions. Two forward slashes indicate the region of omitted intron sequence for good-quality data. The sky-blue region represents the full length of AluSz6. 3′ Splice sites and 5′ splice sites in the AluSz6 region are not in sky blue. The black-shaded region indicates the branch point site, and New world monkeys and prosimians have a deletion in this branch point region. Figure S2 Multiple sequence alignment of the region from exon 2 to exon 4 in the ACTR8 gene in various primates. Genomic sequences from the NCBI database were aligned in various primates. The donor splice site (5′ splice site) and acceptor splice site (3′ splice site) are indicated as blue and red dotted line boxes, respectively. Figure S3 Multiple sequence alignment of the RT-PCR products using the validation primer. The RT-PCR products were sequenced, and these sequences were analyzed by multiple nucleotide alignment. The sky-blue region indicates the AluSz6-derived exon region. The red lined box represents the premature termination codon (PTC). Figure S4 Multiple sequence alignment of AluSz6 of the ACTR8 gene. AluSz6 sequences of various primates were searched using online resources (UCSC Genome browser). In this figure, the AluSz6 sequences are shown in the forward direction (5′ to 3′), whereas the main figure is shown in the reverse direction as inserted into the genome. The blue lined box indicates the point mentioned as a G duplication. AluSz6 of RTL could not be analyzed, but we confirmed the AluSz6 sequence of RTL through the experiment. Figure S5 Analysis of the ACTR8 gene PCR band intensity. (A) Green lanes (1–5) were PCR-positive bands by the V1 primer from Fig. 2b. Vision-capt software selected five bands and generated peaks of the corresponding PCR band. The PCR band intensity was generated from these peaks. (B) Vision-capt software measured the volume based on height and area of the positive bands, respectively.

Infrastructure in animal husbandry refers to fundamental facilities and services necessary for better living conditions of animals and its economy to function through better productivity. Mainly, infrastructure can be divided into two categories: hard infrastructure and soft infrastructure. Physical infrastructure, such as buildings, roads, and water supplying systems, belongs to hard infrastructure. Soft infrastructure includes services which are required to maintain economic, health, cultural and social standards of animal husbandry. Therefore, the proper management of infrastructure in animal husbandry is necessary for animal welfare and its economy. Among various technologies to improve the quality of infrastructure, non-thermal plasma (NTP) technology is an effectively applicable technology in different stages of animal husbandry. NTP is mainly helpful in maintaining better health conditions of animals in several ways via decontamination from microorganisms present in air, water, food, instruments and surfaces of animal farming systems. Furthermore, NTP is used in the treatment of waste water, vaccine production, wound healing in animals, odor-free ventilation, and packaging of animal food or animal products. This review summarizes the recent studies of NTP which can be related to the infrastructure in animal husbandry.

Additional file 1: Table S1. Primer list for genomic PCR and RT-PCR. Figure S1. Alignment of reported BLOC1S2 m-RNA sequences for crab-eating monkey, rhesus monkey and human. Figure S2. Multiple sequence alignment of the integrated MIR and AluSp region in the BLOC1S2 gene. Figure S3. Structural analysis of gDNA PCR products of 10 primates. Figure S4. RT-PCR amplification for validation of the MIR_AluSp-derived V1 transcript. The 5′- and 3′-ends of MIR_AluSp-derived exon were validated using Validation Primers 1 and 2. A) 531 bp product and 389 bp product of the V1 transcript were detected in the crab-eating monkey, rhesus monkey, and African green monkey. For the African green monkey, a 506 bp product of a different 5′-end transcript (V2) was detected. B) The 531 bp product and 389 bp product of the V1 transcript were not detected in the human, chimpanzee, and gibbon samples. Figure S5. RT-PCR amplification for validation of the V2 transcript using Primer 3. A 239 bp product of the V2 transcript was detected in the crab-eating monkey, rhesus monkey, and African green monkey and was not detected in human, chimpanzee, and gibbon samples. Figure S6. RT-PCR amplification for expression pattern of V2 transcript (239 bp) in the crab-eating monkey (A), rhesus monkey (B), and human (C). The experiments were performed with 35 cycles of 94 °C for 30 s, 59 °C for 30 s, and 72 °C for 30 s because 30 cycles of V2 PCR amplification in Fig. 4 doesn’t show clear target bands. Figure S7. Multiple alignment of the amino acid sequences of the reference transcript, V1, and V2 transcripts of BLOC1S2. Lysine (K), Leucine (L) in green rectangular part are equivalent to the last part of the 4th exon nucleotide sequences of BLOC1S2 transcript and see Fig. 5 for more details. Table S2. Calculation of MIR_AluSp combination throughout the genome.

TSEN54encodes a subunit of the tRNA-splicing endonuclease complex, which catalyzes the identification and cleavage of introns from precursor tRNAs. Previously, we identified anAluSx-derived alternative transcript inTSEN54of cynomolgus monkey. Reverse transcription-polymerase chain reaction (RT-PCR) amplification andTSEN54sequence analysis of primate and human samples identified five novel alternative transcripts, including theAluSxexonized transcript. Additionally, we performed comparative expression analysis via RT-qPCR in various cynomolgus, rhesus monkey, and human tissues. RT-qPCR amplification revealed differential expression patterns. Furthermore, genomic PCR amplification and sequencing of primate and human DNA samples revealed thatAluSxelements were integrated in human and all of the primate samples tested. Intriguingly, in langur genomic DNA, an additionalAluYelement was inserted intoAluSxof intron eight ofTSEN54. The newAluYelement showed polymorphic insertion. Using standardized nomenclature forAlurepeats, the polymorphicAluYof the langurTSEN54was designated as being of theAluYl17subfamily. Our results suggest that integration of theAluSxelement inTSEN54contributed to diversity in transcripts and induced lineage- or species-specific evolutionary events such as alternative splicing and polymorphic insertion during primate evolution.

Epidermal growth factor (EGF)-like (EGFL) domain, a common structural module in numerous secreted or transmembrane proteins, is generally involved in protein-protein interactions. To date, several EGFL proteins have been identified and characterized, but little is known about EGFL domain 8 (EGFL8). The present study reported the molecular characterization and expression analysis of EGFL8 in mice. Mouse EGFL8 amplified using a reverse transcription-polymerase chain reaction approach was sequenced and characterized. Mouse EGFL8 encodes a protein of 293 amino acids with two EGFL domains, an Emilin-like domain and a Ca(2+)-binding EGFL domain, which has a molecular mass of 32 kDa. The coding sequence has a high degree of amino acid sequence identity across species, and the EGFL domain has been highly conserved in various species during evolutionary radiation. A phylogenetic tree calculated using the neighbor-joining method revealed that EGFL8 and EGFL7 are more closely associated with each other than either is to EGFL3, and they cluster with EGFL6. It was found that mouse EGFL8 protein was highly expressed in diverse mouse tissue types, including the thymus, lymph nodes, testis, ovaries, epididymis, ductus deferens, ileum, colon, stomach, esophagus, lung, uterus, urinary bladder, skin, spleen, adrenal glands and penis. These results are of great use in understanding the biological roles of mouse EGFL8 for further study.

// Chae Hwa Kwon 1,* , Hye Ji Park 1,* , Jin Hwa Choi 1 , Ja Rang Lee 1 , Hye Kyung Kim 1 , Hong-jae Jo 2 , Hyun Sung Kim 2 , Nahmgun Oh 2 , Geun Am Song 3 and Do Youn Park 1 1 Department of Pathology, Pusan National University Hospital and Pusan National University School of Medicine, and BioMedical Research Institute, Pusan National University Hospital, Seo-Gu, Busan, Korea 2 Department of Surgery, Pusan National University Hospital and Pusan National University School of Medicine, and BioMedical Research Institute, Pusan National University Hospital, Seo-Gu, Busan, Korea 3 Department of Internal Medicine, Pusan National University Hospital and Pusan National University School of Medicine, and BioMedical Research Institute, Pusan National University Hospital, Seo-Gu, Busan, Korea * These authors have contributed equally to this work Correspondence to: Do Youn Park, email: // Keywords : colorectal cancer, snail, serpinA1, prognosis, fibronectin Received : December 16, 2014 Accepted : April 10, 2015 Published : April 29, 2015 Abstract The role of Snail and serpin peptidase inhibitor clade A member 1 (serpinA1) in tumorigenesis has been previously identified. However, the exact role and mechanism of these proteins in progression of colorectal cancer (CRC) are controversial. In this study, we investigated the role of Snail and serpinA1 in colorectal cancer (CRC) and examined the mechanisms through which these proteins mediate CRC progression. Immunohistochemical analysis of 528 samples from patients with CRC showed that elevated expression of Snail or serpinA1 was correlated with advanced stage, lymph node metastasis, and poor prognosis. Moreover, we detected a correlation between Snail and serpinA1 expression. Functional studies performed using the CRC cell lines DLD-1 and SW-480 showed that overexpression of Snail or serpinA1 significantly increased CRC cell invasion and migration. Conversely, knockdown of Snail or serpinA1 expression suppressed CRC cell invasion and migration. ChIP analysis revealed that Snail regulated serpinA1 by binding to its promoter. In addition, fibronectin mediated Snail and serpinA1 signaling was involved in CRC cell invasion and migration. Taken together, our data showed that Snail and serpinA1 promoted CRC progression through fibronectin. These findings suggested that Snail and serpinA1 were novel prognostic biomarkers and candidate therapeutic targets in CRC.

Table S4. On-targeted reads and average depth with accumulative depth coverage on CG sites. (DOCX 31 kb)

Table S2. CG site distribution according to the genomic region in the redefined target region. (DOCX 28 kb)

Table S3. Summary of alignment statistics about sequenced reads. (DOCX 28 kb)

Table S5. Average methylation level on CG sites for each genomic regions (meanâ Âąâ s.d.). (DOCX 27 kb)

Table S1.The length (Mb) of aligned homologous probe region according to identities and e-value. (DOCX 27 kb)

Athletic performance is an important criteria used for the selection of superior horses. However, little is known about exercise-related epigenetic processes in the horse. DNA methylation is a key mechanism for regulating gene expression in response to environmental changes. We carried out comparative genomic analysis of genome-wide DNA methylation profiles in the blood samples of two different thoroughbred horses before and after exercise by methylated-DNA immunoprecipitation sequencing (MeDIP-Seq). Differentially methylated regions (DMRs) in the pre-and post-exercise blood samples of superior and inferior horses were identified. Exercise altered the methylation patterns. After 30 min of exercise, 596 genes were hypomethylated and 715 genes were hypermethylated in the superior horse, whereas in the inferior horse, 868 genes were hypomethylated and 794 genes were hypermethylated. These genes were analyzed based on gene ontology (GO) annotations and the exercise-related pathway patterns in the two horses were compared. After exercise, gene regions related to cell division and adhesion were hypermethylated in the superior horse, whereas regions related to cell signaling and transport were hypermethylated in the inferior horse. Analysis of the distribution of methylated CpG islands confirmed the hypomethylation in the gene-body methylation regions after exercise. The methylation patterns of transposable elements also changed after exercise. Long interspersed nuclear elements (LINEs) showed abundance of DMRs. Collectively, our results serve as a basis to study exercise-based reprogramming of epigenetic traits.

Tyrosinase is a copper-containing enzyme that regulates melanin biosynthesis and is encoded by the tyrosinase (TYR) gene. Previous studies demonstrated that mutations in TYR could lead to oculocutaneous albinism type 1 (OCA1) owing to the failure of melanin formation. Although a previous study found that albinism in the rhesus monkey was derived from a mutation in TYR, the identification and characterization of this gene in non-human primates has not been achieved thus far. Thus, using the rapid amplification of cDNA ends (RACE) and internal reverse transcription PCR (RT-PCR) we identified the full-length sequence of TYR in the crab-eating macaque, and two different transcript variants (TYR_1 and TYR_2). While TYR_1 comprised five exons and its coding sequence was highly similar to that of humans, TYR_2 comprised four exons and was generated by a third-exon-skipping event. Interestingly, these two transcripts were also present in the African green monkey (Old World monkey) and the common marmoset (New World monkey). Deduced amino acid sequence analyses revealed that TYR_2 had a shorter C-terminal region than TYR_1 owing to the exon-skipping event. Thus, the present study is the first to identify and characterize a full-length TYR gene in a non-human primate, while the further validation of the third-exon-skipping in TYR indicates that this event is well conserved in the primate lineage. Therefore, this study provides useful and important information for the study of albinism using non-human primate models.

Long interspersed elements (LINEs or L1 s) are an abundant class of autonomous retrotransposons in the human genome. Full-length L1 elements have two transcriptional regulatory regions: an internal sense promoter and an antisense promoter (ASP). The ASP of L1 elements can generate chimeric RNAs via direct transcription of adjacent genomic sequences. Chimeric transcripts derived from the L1ASP are highly represented, but the extent to which this occurs is largely unknown. Using a genome-wide L1 chimera display (LCD) technique, we have isolated 4 L1 chimeric transcripts (LCTs) in the lung cancer genome. Then, we analyzed the structural characteristics of the 4 LCTs using bioinformatics tool. Expression patterns of the 4 LCTs were analyzed by reverse transcription polymerase chain reaction using normal and lung cancer tissues. LCT24 and LCT25 showed higher expression in lung cancer tissue than in normal tissue. These results suggest that the genome-wide LCD technique could be of great use for further study to find cancer markers via cancer-associated LCTs and to understand cancer biology.

Working dogs serve as military watch dogs, search dogs, rescue dogs, and guide dogs with un-come-at-able character. They are drafted by in-training examination including concentration, capacity for locomotion, boldness and earthly desires. In this study, genetic diversity and relationships among two groups of working dogs (pass and fail group in-training examination) were assessed based on 15 microsatellite markers in 25 individuals of working dogs (military watch dogs and Korean search dogs). For the 15 microsatellite markers, the values of allelic richness (AR) ranged from 2.21 (pass group) to 1.60 (fail group) in military watch dogs, while AR ranged from 2.79 (pass group) to 2.72 (fail group) in Korean search dogs. Among 52 different alleles of military watch dogs, 22 alleles were detected in pass group only, while 8 alleles in fail group only. In case of Korean search dogs, 3 alleles were observed in pass group only, while 13 alleles in fail group only. These group-specific unique alleles reflect good biomarker for selecting working dogs (military watch dogs and Korean search dogs), indicating that those group specific microsatellite alleles could separate working dogs to be pass or fail group in out-training dog population. Taken together, this study demonstrates the feasibility of microsatellite analyses for the selection of superior working dogs objectively. Furthermore, this approach could be used for the proper selection of working dogs in combination with in-training examination.

Cathepsin F, which is encoded by CTSF, is a cysteine proteinase ubiquitously expressed in several tissues. In a previous study, novel transcripts of the CTSF gene were identified in the crab-eating monkey deriving from the integration of an Alu element–AluYRa1. The occurrence of AluYRa1-derived alternative transcripts and the mechanism of exonization events in the CTSF gene of human, rhesus monkey, and crab-eating monkey were investigated using PCR and reverse transcription PCR on the genomic DNA and cDNA isolated from several tissues. Results demonstrated that AluYRa1 was only integrated into the genome of Macaca species and this lineage-specific integration led to exonization events by producing a conserved 3′ splice site. Six transcript variants (V1–V6) were generated by alternative splicing (AS) events, including intron retention and alternative 5′ splice sites in the 5′ and 3′ flanking regions of CTSF_AluYRa1. Among them, V3–V5 transcripts were ubiquitously expressed in all tissues of rhesus monkey and crab-eating monkey, whereas AluYRa1-exonized V1 was dominantly expressed in the testis of the crab-eating monkey, and V2 was only expressed in the testis of the two monkeys. These five transcript variants also had different amino acid sequences in the C-terminal region of CTSF, as compared to reference sequences. Thus, species-specific Alu-derived exonization by lineage-specific integration of Alu elements and AS events seems to have played an important role during primate evolution by producing transcript variants and gene diversification.

Transposable elements (TEs) are repetitive sequences dispersed throughout mammalian genomes, and they occupy important genetic positions. TEs have been shown to have both harmful and beneficial effects such as exonization, polyadenylation, and/or altering transcription rates in various vertebrate genomes. However, to the best of our knowledge, no study has yet considered the relationship between TEs and horse genes. In this study, we examined the contribution of TEs to the horse genome by collecting TEs inserted within mRNA genes. By screening the abundance, distribution, and orientation of TEs, we found that the majority of TE insertions belong to retroelements and DNA elements, most of which exist in the coding sequences of horse genes. In addition, the MIR, L1, L2, ERVL, and ERVL-MaLR subfamilies were found to be the most abundant in both non-LTR and LTR elements. Retroelements (LTRs, LINEs, and SINEs) among the TEs inserted in the coding sequences showed a preference for antisense orientation. The most pronounced imbalance in insertional orientation was observed in LINEs, which represent 40 % of all TEs in antisense orientation. Through these analyses, we identified that a total of 1310 TEs have been integrated into horse mRNA genes and small fractions of them have been exonized into coding sequences.

Eukaryotic genomes comprise numerous retroelements that have a major impact on the structure and regulation of gene function. Retroelements are regulated by epigenetic controls, and they generate multiple miRNAs that are involved in the induction and progression of genomic instability. Elucidation of the biological roles of retroelements deserves continuous investigation to better understand their evolutionary features and implications for disease.

Ionizing radiation induces numerous biological events in mammalian cells, including cell death, mutagenesis, and genomic instability via changes in genomic structure, epigenetic regulation, and gene expression. Retroelements can also alter genomic structure based on their ability to mobilize, and their abundance and sequence similarity have been implicated in the pathogenesis of several human diseases. Here, we summarize the current knowledge on the mobilization, genomic rearrangement, epigenetic state, and transcriptional activation of retroelements in response to radiation. We further discuss the potential effects of their activation in radiation-induced genomic instability.