A new wave of research has been inspired by the CRISPR-Cas system with respect to their application in genome editing. The CRISPR-Cas system can not only be applied in gene knockout and insertion, but also be used in base editing, transcriptional regulation and recombination of gene clusters. However, the low efficiency of homology-directed repair (HDR) limits its application. Unlike the CRISPR-Cas system, mobile genetic elements (MGE) can insert DNA fragments into cell chromosomes without the aid of HDR. Recently, it is reported that CRISPR-related transposable elements can guide targeted DNA insertion. Their transposition mechanisms and reprogramming abilities have brought novel opportunities to the development of this field. This review summarized the research progress and application development of natural CRISPR-related transposable elements in recent years, as well as the applications of fused dCas9-transposase. It proposed the application prospects and potential challenges of CRISPR-related transposable elements in the future, which provided a reference for the development direction of gene editing tools.
DNA Transposable Elements/genetics* ; Gene Editing ; CRISPR-Cas Systems/genetics*

PiggyBac is a transposable DNA element originally discovered in the cabbage looper moth (Trichoplusia ni). The T. ni piggyBac transposon can introduce exogenous fragments into a genome, constructing a transgenic organism. Nevertheless, the comprehensive analysis of endogenous piggyBac-like elements (PLEs) is important before using piggyBac, because they may influence the genetic stability of transgenic lines. Herein, we conducted a genome-wide analysis of PLEs in the brown planthopper (BPH) Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), and identified a total of 28 PLE sequences. All N. lugens piggyBac-like elements (NlPLEs) were present as multiple copies in the genome of BPH. Among the identified NlPLEs, NlPLE25 had the highest copy number and it was distributed on five chromosomes. The full length of NlPLE25 consisted of terminal inverted repeats and sub-terminal inverted repeats at both terminals, as well as a single open reading frame transposase encoding 546 amino acids. Furthermore, NlPLE25 transposase caused precise excision and transposition in cultured insect cells and also restored the original TTAA target sequence after excision. A cross-recognition between the NlPLE25 transposon and the piggyBac transposon was also revealed in this study. These findings provide useful information for the construction of transgenic insect lines.
Amino Acid Sequence ; Animals ; Animals, Genetically Modified ; DNA Transposable Elements/genetics* ; Hemiptera/genetics* ; Transposases/genetics*

Mammalian fertilization begins with the fusion of two specialized gametes, followed by major epigenetic remodeling leading to the formation of a totipotent embryo. During the development of the pre-implantation embryo, precise reprogramming progress is a prerequisite for avoiding developmental defects or embryonic lethality, but the underlying molecular mechanisms remain elusive. For the past few years, unprecedented breakthroughs have been made in mapping the regulatory network of dynamic epigenomes during mammalian early embryo development, taking advantage of multiple advances and innovations in low-input genome-wide chromatin analysis technologies. The aim of this review is to highlight the most recent progress in understanding the mechanisms of epigenetic remodeling during early embryogenesis in mammals, including DNA methylation, histone modifications, chromatin accessibility and 3D chromatin organization.
Animals ; Chromatin Assembly and Disassembly ; DNA Methylation ; DNA Transposable Elements ; Embryo, Mammalian ; Embryonic Development/genetics* ; Epigenesis, Genetic ; Epigenome ; Female ; Fertilization/physiology* ; Gene Expression Regulation, Developmental ; Histone Code ; Histones/metabolism* ; Male ; Mice ; Oocytes/metabolism* ; Spermatozoa/metabolism*

Estrogen receptor (esr) mediates the effects of estrogen on the expression of related genes, thereby regulating the growth and reproduction of mammals. To investigate the effect of retrotransposon insertion polymorphism (RIP) of the porcine esr gene on porcine growth performance, retrotransposon insertion polymorphism of the esr gene were predicted by comparative genomics and bioinformatics, and PCR was used to verify the insertion polymorphisms in different porcine breeds. Finally, the correlation analysis between the genotypes and performance of Large White pigs was conducted. The results showed that four retrotransposon polymorphic sites were identified in the esr1 and esr2 genes, which are esr1-SINE- RIP1 located in intron 2 of the esr1 gene, esr1-LINE-RIP2 and RIP3-esr1- SINE located in intron 5 of the gene, and esr2-LINE-RIP located in intron 1 of the esr2 gene, respectively. Among them, insertion of a 287 bp of SINE into intron 2 of the esr1 gene significantly affected (P<0.05) the live back fat thickness and 100 kg body weight back fat thickness of Large White pigs. Moreover, the live back fat thickness and back fat thickness at 100 kg body weight of homozygous with insertion (SINE+/+) was significantly greater than that of heterozygous with insertion (SINE+/-) and homozygous without insertion (SINE-/-). Therefore, esr1-SINE-RIP1 could be used as a molecular marker to assist the selection of deposition traits in Large White pigs.
Animals ; Genotype ; Introns/genetics* ; Phenotype ; Polymorphism, Genetic/genetics* ; Retroelements/genetics* ; Swine/genetics*

Adenosine/metabolism* ; Animals ; Chromatin/metabolism* ; DNA Transposable Elements ; Epigenesis, Genetic ; RNA, Messenger/metabolism*

The dynamic activity of transposable elements (TEs) contributes to the vast diversity of genome size and architecture among plants. Here, we examined the genomic distribution and transposition activity of long terminal repeat retrotransposons (LTR-RTs) in Arabidopsis thaliana (Ath) and three of its relatives, Arabidopsis lyrata (Aly), Eutrema salsugineum (Esa), and Schrenkiella parvula (Spa), in Brassicaceae. Our analyses revealed the distinct evolutionary dynamics of Gypsyretrotransposons, which reflects the different patterns of genome size changes of the four species over the past million years. The rate of Gypsy transposition in Aly is approximately five times more rapid than that of Ath and Esa, suggesting an expanding Aly genome. Gypsy insertions in Esa are strictly confined to pericentromeric heterochromatin and associated with dramatic centromere expansion. In contrast, Gypsy insertions in Spa have been largely suppressed over the last million years, likely as a result of a combination of an inherent molecular mechanism of preferential DNA removal and purifying selection at Gypsy elements. Additionally, species-specific clades of Gypsy elements shaped the distinct genome architectures of Aly and Esa.
Brassicaceae/genetics* ; Evolution, Molecular ; Genome Size ; Genome, Plant ; Genomics ; Phylogeny ; Retroelements ; Species Specificity

PURPOSE: Helicobacter pylori infection induces phenotype-stabilizing methylation and promotes gastric mucosal atrophy that can inhibit CpG-island methylation. Relationship between the progression of gastric mucosal atrophy and the initiation of CpG-island methylation was analyzed to delineate epigenetic period for neoplastic transformation. MATERIALS AND METHODS: Normal-appearing gastric mucosa was biopsied from 110 H. pylori–positive controls, 95 H. pylori–negative controls, 99 gastric cancer patients, and 118 gastric dysplasia patients. Gastric atrophy was assessed using endoscopic-atrophic-border score. Methylation-variable sites of eight CpG-island genes adjacent to Alu (CDH1, ARRDC4, PPARG, and TRAPPC2L) or LTR (MMP2, CDKN2A, RUNX2, and RUNX3) retroelements and stomach-specific TFF3 gene were analyzed using radioisotope-labeled methylation-specific polymerase chain reaction. RESULTS: Mean ages of H. pylori–positive controls with mild, moderate, and severe atrophy were 51, 54, and 65 years and those of H. pylori–associated TFF3 overmethylation at the three atrophic levels (51, 58, and 63 years) tended to be periodic. Alu-adjacent overmethylation (50 years) was earlier than TFF3 overmethylation (58 years) in H. pylori–positive controls with moderate atrophy. Cancer patients with moderate atrophy showed late Alu-adjacent (58 years) overmethylation and frequent LTR-adjacent overmethylation. LTR-adjacent overmethylation was frequent in cancer (66 years) and dysplasia (68 years) patients with severe atrophy. CONCLUSION: Atrophic progression is associated with gastric cancer at moderate level by impeding the initiation of Alu-adjacent methylation. LTR-adjacent methylation is increased in cancer patients and subsequently in dysplasia patients.
Atrophy* ; DNA Methylation ; Epigenomics ; Gastric Mucosa ; Gastritis, Atrophic ; Genes, Essential* ; Helicobacter pylori ; Housekeeping* ; Humans ; Methylation* ; Polymerase Chain Reaction ; Retroelements ; Stomach Neoplasms*

Porcine endogenous retroviruses (PERVs) integrate into germline DNA as proviral genome that enables vertical transmission from parents to their offspring. The provirus usually survives as part of the host genome rather than as an infectious agent, but may become pathogenic if it crosses species barriers. Therefore, replication-competent PERV should be controlled through selective breeding or knockout technologies. Two microRNAs (miRNAs), dual LTR1 and LTR2, were selected to inhibit the expression of PERV in primary porcine kidney cells. The inhibition efficiency of the miRNAs was compared based on their inhibition of different PERV regions, specifically long terminal repeats (LTRs), gag, pol, and env. Gene expression was quantified using real-time polymerase chain reaction and the C-type reverse transcriptase (RT) activity was determined. The messenger RNA (mRNA) expression of the PERV LTR and env regions was determined in HeLa cells co-cultured with primary porcine kidney cells. The mRNA expression of the LTR, gag, pol, and env regions of PERV was dramatically inhibited by dual miRNA from 24 to 144 h after transfection, with the highest inhibition observed for the LTR and pol regions at 120 h. Additionally, the RT activity of PERV in the co-culture experiment of porcine and human cells was reduced by 84.4% at the sixth passage. The dual LTR 1+2 miRNA efficiently silences PERV in primary porcine kidney cells.
Coculture Techniques ; DNA ; Endogenous Retroviruses ; Gene Expression ; Genome ; HeLa Cells ; Humans ; Kidney ; MicroRNAs ; Parents ; Proviruses ; Real-Time Polymerase Chain Reaction ; RNA, Messenger ; RNA-Directed DNA Polymerase ; Selective Breeding ; Terminal Repeat Sequences ; Transfection

To develop more active LTR retrotransposons in Phyllostachys edulis, a Ph. edulis LTR retrotransposon (Ph-LTR2) was identified, and the expression pattern of the transposon under stress was systematically analyzed. Ph-LTR2 transposon is 6 030 bp in length and belongs to the Reina subfamily in the Ty3-Gypsy family. With the similarity of 96.41% of both LTR sequences, the Ph-LTR2 transposon inserted the moso bamboo genome about 61.92 thousand years ago. There are 5 copies identified in the genome. The Ph-LTR2 transposon domain includes GAG (gag protein) protein domain, PR (Proteases) protein domain, RT (Reverse transcriptase) protein domain, RH (Ribonuclease H) protein domain, INT (Integrase) protein domain and CHR (Chromatin organization modifier) protein domain. The expression patterns of INT, RT and RH were detected by real-time quantitative PCR. The three domains were found to have specific expression patterns at different tissues of the bamboo. Under the conditions of low/high temperature, methylation inhibitors treatments, irradiation and high salt stress, transcription levels of the three domains of the Ph-LTR2 transposon increased with different degrees. Specifically, after treatment with low/high temperature and methylation inhibitors, the transcription level was up-regulated; after low dose radiation treatment and low concentration of salt solution treatment, the transcription level was also increased, but the expression level decreased with increasing dose of radiation and concentration of salt solution. These results indicate that the expression pattern of the Ph-LTR2 transposon responds to the changes of the external environment, but the exact mechanism is not yet known. The results of this study laid a certain theoretical foundation for the development of the genetic tool based on Ph-LTR2 transposons.
Genome ; Phylogeny ; Poaceae ; Retroelements

Ralstonia solanacearum strain PRS-84 used in this study was isolated from diseased Pogostemon cablin plants in our previous study.The competent cells of R.solanacearum strain PRS-84 were transformed by electroporation with Tn5 transposon and then were plated on TTC agar plates containing kanamycin to select for kanamycin-resistant colonies.The detection of kanamycin-resistant gene in kanamycin-resistant colonies was performed by PCR.Further,the flanking fragments of Tn5 transposon insertion site in the mutants were amplified by inverse PCR,and the flanking fragments were sequenced and analyzed.The results indicated that the kanamycin-resistant colonies were obtained in the transformation experiment of R.solanacearum strain PRS-84 by electroporation with Tn5 transposon.A specific band of approximately 700 bp was amplified by PCR from kanamycin-resistant colonies.The flanking sequences of Tn5 transposon insertion site in the transformants were obtained by inverse PCR.After sequencing and sequence analysis of Tn5 transposon insertion site in mutants,we preliminarily speculated that the Tn5 transposon inserted in the typ A gene,rec O gene and gid A gene in three mutants,respectively.A random mutagenesis system of R.solanacearum strain PRS-84 by electroporation with Tn5 transposon has been established,and the Tn5 insertion mutants have been obtained.This study might facilitate the creation of mutant library and the discovery of the virulence gene of R.solanacearum isolated from P.cablin.
DNA Transposable Elements ; Electroporation ; Genes, Bacterial ; Mutagenesis, Insertional ; Pogostemon ; microbiology ; Ralstonia solanacearum ; genetics ; Virulence