Transposon Elements Research Articles

Functional characterization of a cDNA encoding Piwi protein in Penaeus monodon and its potential roles in controlling transposon expression and spermatogenesis

Piwi proteins comprise a subfamily of Argonaute that plays a major role in germline development by association with a distinct class of small RNAs called Piwi interacting RNA (piRNA). Although the functions of Piwi in the development of germline cells as well as transposon regulation were reported in a number of mammalians and insects, developmental expression and function of Piwi subfamily in crustaceans is poorly known. This study is aimed at cloning and characterization of a Piwi cDNA in the black tiger shrimp, Penaeus monodon. The cDNA encoding a Piwi protein of P. monodon (PmPiwi1) was obtained by rapid amplification of cDNA ends (RACE). The PmPiwi1 coding cDNA contains 2811 nt encoding a putative protein of 936 amino acids, and was specifically expressed in testis and ovary, suggesting its possible function in gametogenesis. RNAi experiment showed that suppression of PmPiwi1 expression led to a significant up-regulation of retrotransposon gypsy2 and DNA element transposon mariner in shrimp testis. Investigation of the function of PmPiwi1 in spermatogenesis by sperm count showed significantly lower number of sperms in the spermatophore sac of PmPiwi1-knockdown shrimp compared with that in the control shrimp. Our study thus reported for the first time the cDNA encoding a Piwi protein in the shrimp P. monodon. Its roles in controlling transposons and spermatogenesis as implied by the results in this study will be important for understanding sperm development and could be useful for the improvement of reproduction in male shrimp in the future.

A Robust Transposon-Endogenizing Response from Germline Stem Cells

The heavy occupancy of transposons in the genome implies that existing organisms have survived from multiple, independent rounds of transposon invasions. However, how and which host cell types survive the initial wave of transposon invasion remain unclear. We show that the germline stem cells can initiate a robust adaptive response that rapidly endogenizes invading P element transposons by activating the DNA damage checkpoint and piRNA production. We find that temperature modulates the Pelement activity in germline stem cells, establishing a powerful tool to trigger transposon hyper-activation. Facing vigorous invasion, Drosophila first shut down oogenesis and induce selective apoptosis. Interestingly, a robust adaptive response occurs in ovarian stem cells through activation of the DNA damage checkpoint. Within 4days, the hosts amplify P element-silencing piRNAs, repair DNA damage, subdue the transposon, and reinitiate oogenesis. We propose that this robust adaptive response can bestow upon organisms the ability to survive recurrent transposon invasions throughout evolution.

First genome sequence of a blaKPC-2-carrying Citrobacter koseri isolate collected from a patient with diarrhoea.

The blaKPC gene is rarely reported in Citrobacter koseri. Here we report the first draft genome sequence of a blaKPC-2-carrying C. koseri isolate from a patient with diarrhoea. Transferability of the blaKPC-2-bearing plasmid was determined by the filter mating method. The whole genome sequence of C. koseri L168 was determined using an Illumina HiSeq platform. The genome was de novo assembled using Velvet 1.2.10. Acquired antimicrobial resistance genes and plasmid replicons were identified using ResFinder 2.1 and PlasmidFinder 1.3, respectively. Antimicrobial susceptibility testing (AST) showed that C. koseri L168 was resistant to multiple antibiotics but was susceptible to ciprofloxacin, gentamicin, tobramycin, amikacin, tigecycline and colistin. A KPC-2-harbouring plasmid was conjugative and the transconjugants conferred increased resistance to carbapenems confirmed by conjugation experiments and AST. In silico analysis revealed the presence of the β-lactam resistance genes blaKPC-2 and blaMAL-1. Additionally, plasmids of incompatibility groups IncFII and IncX4 were identified in the genome by PlasmidFinder. BLAST analysis revealed that blaKPC-2 was located on a Tn3 transposon element in C. koseri L168 with the conserved linear structure ISKpn27-blaKPC-2-ΔISKpn6-korC-klcA. To our knowledge, this is only the second report of C. koseri producing KPC-2, and we report the first draft genome sequence of a blaKPC-2-carrying C. koseri isolate from a patient with diarrhoea in China. This work may facilitate our understanding of the pathogenesis, multidrug resistance mechanisms and genomic features of this species. Further monitoring of bacteria carrying carbapenemase genes in patients' gut microbiota is warranted.

Abstract 5183: Using transposon elements to elucidate the genetic mechanisms of HCC-associated lung metastases

Abstract Metastases account for most cancer-related deaths as a result of primary cancer spreading to distant sites. Amongst human hepatocellular carcinoma (HCC), there is a drastic decrease in the survival rate observed in patients with early stage localized HCC to late stage metastasis-associated HCC. Importantly, the genetic mechanisms associated with metastasis-associated HCC remains elusive. Therefore, a forward genetic screen in mice using Sleeping Beauty (SB) insertional mutagenesis system was developed to identify genes associated with metastasis-associated HCC. Truncated version of the epidermal growth factor receptor (Egfr) gene was frequently detected in both mouse primary liver tumors and lung metastases, which was confirmed by DNA sequencing and RNA sequencing. This indicates the importance of Egfr mutations for liver tumorigenesis and the metastasis process. More importantly, additional candidate genes involved in the metastasis process were also identified by our forward genetic screen and showed to be relevant in human HCC patients at the M1 cancer metastasis stage. Taken together, our study shows that the SB screen yields a high fraction of relevant events in human liver cancer and can provide valuable information on the evolution of metastasis-associated HCC. The authors declare that they have no competing interests. Citation Format: Lilian H. Lo, Amy P. Chiu, Xiao-Xiao Li, Barbara R. Tschida, Dewi K. Rowlands, David A. Largaespada, Vincent W. Keng. Using transposon elements to elucidate the genetic mechanisms of HCC-associated lung metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5183.

Abstract 3017: Identifying drivers for advanced prostate cancer by a transposon-based genetic screen

Abstract Prostate cancer remains the second leading cause of cancer death in men in the United States. Androgen-deprivation therapy (ADT) often leads to progression to castration-resistant prostate cancer (CRPC), which is more aggressive and frequently associated with metastasis and poor prognosis. Despite the significance of CRPC in the clinic, the molecular mechanism driving the emergence of advanced prostate cancer is still not well understood. Identifying novel drivers is particularly important for developing therapeutic targets that lead to improved treatment outcome. We sought to explore drivers for advanced prostate cancer by utilizing the Sleeping Beauty (SB) system, a murine transposition-based forward mutagenesis screening approach. We generated mouse strain in which the SB transposase expression is under the control of a tamoxifen-inducible Cre allele driven by the prostate specific Nkx3.1 promoter. After crossing this strain to transgenic strain for the transposon element (T2/Onc2), as well as strain with floxed alleles for Pten and Trp53, we obtained a mouse model allowing mutagenesis screening in mouse prostate on a Pten and Trp53 null background (SB mice). Mice with only conditional deletion of Pten and Trp53 were generated as controls. Prostate tumor tissue from moribund mice were collected for sequencing and histopathologic analysis. Kaplan-Meier survival analysis was performed to examine the disease progression. Linker-mediated PCR was performed to amplify genomic loci containing SB transposon insertions. Barcoded sequencing library was generated and sequenced on an Illumina HiSeq4000. Sequencing reads and common insertion sites (CIS) were analyzed by published TAPDANCE pipeline. Survival analysis revealed that the SB mice (n=28) have a significantly shorter time to death than the controls (n=65) (log-rank p<0.0001). Interestingly, histologic analysis revealed frequent detection (11/28) of features associated with human neuroendocrine prostate cancer (NEPC), including presence of small round cells with prominent nuclei and scant cytoplasm that stain positively for neuroendocrine markers such as synaptophysin, but negatively for androgen receptor. Frequent detection of NEPC features in SB mice but not in control mice (1/53) suggests that SB-mediated mutagenesis drives NEPC development. CIS analysis revealed more than 200 insertion sites with statistical significance (integrated p<0.05), which require further validation in human tumors. In conclusion, we have implemented the SB genetic screen system in our existing CRPC mouse model. Our data show that SB mice present with accelerated disease progression and higher incidence of NEPC tumor features, consistent with a lethal and aggressive subtype of human CRPC. CIS analysis have identified hundreds of insertion sites, which are likely to include novel candidate drivers of aggressive prostate cancer. Citation Format: Min Zou, Alessandro Vasciaveo, Andrea Califano, Cory Abate-Shen. Identifying drivers for advanced prostate cancer by a transposon-based genetic screen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3017.

Abstract 2185: Multiple region whole-genome sequencing reveals intratumor heterogeneity and branching clonal architecture of non-clear-cell renal cell carcinoma

Abstract Limited knowledge about the intratumor heterogeneity (ITH) of non-clear-cell renal cell carcinoma (nccRCC) hinders therapeutic efficacy. We performed multi-region whole-genome sequencing, genome-wide methylation profiling and deep targeted sequencing of both primary and paired metastatic tumors in 124 samples from 29 subjects with papillary renal cell carcinoma type 1, papillary renal cell carcinoma type 2 and collecting duct kidney tumors. Samples were taken from the tumors' center to the periphery at ~1.5cm from each other. We conducted integrative ITH analysis of single nucleotide variants, somatic copy number alterations, structural variants, transposon element insertions, telomere length and DNA methylation, and inferred their respective evolutionary history. We also analyzed the concordance between physical and lineage phylogenetic evolution, and inferred the regions from which the metastases likely originated. ITH varied significantly across tumors and histological subtypes. For example, the average number of structural variants per tumor was 1.2 in papillary RCC type 1 vs. 23.6 in papillary RCC type 2. In papillary tumors, ITH was lowest for copy number alterations (~5% subclonal changes across all tumor types), intermediate for single nucleotide variants (~32%), and highest for structural variants (~60%), suggesting a tumor molecular evolution along these steps. Lineage trees commonly showed branching evolutions with a dominant subclone. Focal deletion of the CDKN2A gene characterized the collecting duct tumors. Methylation ITH was highest in the enhancer regions. Metastatic and primary tumors shared similar mutation signatures. Telomere length was generally longer in normal vs. tumor samples and was similar in physically adjacent samples. In summary, our study characterized ITH of nccRCC with unprecedented details for multiple types of somatic alterations, and delineated the branching architecture of clonal evolution, including the metastatic phase. Citation Format: Bin Zhu*, Luana Poeta*, Manuela Costantini*, Tongwu Zhang*, Steno Sentinelli, Jianxin Shi, Kevin Brown, Xing Hua, Meredith Yeager, Mingyi Wang, Belynda Hicks, Stephen Chanock*, Michele Gallucci*, Vito Fazio*, Maria Teresa Landi*. Multiple region whole-genome sequencing reveals intratumor heterogeneity and branching clonal architecture of non-clear-cell renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2185.

Embryonic defects induced by maternal obesity in mice derive from Stella insufficiency in oocytes.

Maternal obesity can impair embryo development and offspring health, yet the mechanisms responsible remain poorly understood. In a high-fat diet (HFD)-based female mouse model of obesity, we identified a marked reduction of Stella (also known as DPPA3 or PGC7) protein in oocytes. Starting with this clue, we found that the establishment of pronuclear epigenetic asymmetry in zygotes from obese mice was severely disrupted,inducing the accumulation of maternal 5-hydroxymethylcytosine modifications and DNA lesions. Furthermore, methylome-wide sequencing analysis detected global hypomethylation across the zygote genome in HFD-fed mice, with a specific enrichment in transposon elements and unique regions. Notably, overexpression of Stella in the oocytes of HFD-fed mice not only restored the epigenetic remodeling in zygotes but also partly ameliorated the maternal-obesity-associated developmental defects in early embryos and fetal growth. Thus, Stella insufficiency in oocytes may represent a critical mechanism that mediates the phenotypic effects of maternal obesity in embryos and offspring.

Botulinum Neurotoxins: Still a Privilege of Clostridia?

Botulinum neurotoxins (BoNTs) are potent bacterial toxins mostly produced by genetically diverse clostridial strains. Recently, BoNT variants have been reported in non-clostridial strains. In this issue of Cell Host & Microbe, Zhang etal. (2018) describe a novel BoNT in Entecoccus faecium.

A genome for gnetophytes and early evolution of seed plants

Gnetophytes are an enigmatic gymnosperm lineage comprising three genera, Gnetum, Welwitschia and Ephedra, which are morphologically distinct from all other seed plants. Their distinctiveness has triggered much debate as to their origin, evolution and phylogenetic placement among seed plants. To increase our understanding of the evolution of gnetophytes, and their relation to other seed plants, we report here a high-quality draft genome sequence for Gnetum montanum, the first for any gnetophyte. By using a novel genome assembly strategy to deal with high levels of heterozygosity, we assembled >4 Gb of sequence encoding 27,491 protein-coding genes. Comparative analysis of the G. montanum genome with other gymnosperm genomes unveiled some remarkable and distinctive genomic features, such as a diverse assemblage of retrotransposons with evidence for elevated frequencies of elimination rather than accumulation, considerable differences in intron architecture, including both length distribution and proportions of (retro) transposon elements, and distinctive patterns of proliferation of functional protein domains. Furthermore, a few gene families showed Gnetum-specific copy number expansions (for example, cellulose synthase) or contractions (for example, Late Embryogenesis Abundant protein), which could be connected with Gnetum’s distinctive morphological innovations associated with their adaptation to warm, mesic environments. Overall, the G. montanum genome enables a better resolution of ancestral genomic features within seed plants, and the identification of genomic characters that distinguish Gnetum from other gymnosperms.

Update on fosfomycin-modified genes in Enterobacteriaceae.

The long-used antibiotic fosfomycin has recently been re-evaluated as a potential regimen for treating extended-spectrum β-lactamases (ESBLs) and carbapenem-resistant Enterobacteriaceae (CRE). Fosfomycin is known for its robust bactericidal effect against ESBL-producing Enterobacteriaceae and CRE. However, fosfomycin-modified genes have been reported in transposon elements and conjugative plasmids, resulting in fosfomycin resistance in parts of East Asia. Here we review reports of fosfomycin-modified (fos) genes in Enterobacteriaceae and assess the efficacy of fosfomycin against multidrug-resistant Enterobacteriaceae infections. At least 10 kinds of fos genes have been identified in the past decade; of these, fosA (and fosA subtypes) and fosC2 are primarily found in Enterobacteriaceae. All fosA subtypes except fosA2 are found in plasmids and transposons, nearby insertion sequence elements, or integrons, indicating that mobilizing elements also play an important role in plasmid-mediated fos genes in Enterobacteriaceae. fosA3, which is prevalent in East Asia, has been transmitted (mostly by animals) within and across continents via IS26 mobile elements. The acquisition of multiple antibiotic resistance genes via plasmids and mobile elements has resulted in a need for combined treatments for Enterobacteriaceae cases. The combination of fosfomycin and carbapenem has been the focus of many invitro studies, but there is a clear need for additional invivo investigations involving pharmacokinetics.

CGmapTools improves the precision of heterozygous SNV calls and supports allele-specific methylation detection and visualization in bisulfite-sequencing data

DNA methylation is important for gene silencing and imprinting in both plants and animals. Recent advances in bisulfite sequencing allow detection of single nucleotide variations (SNVs) achieving high sensitivity, but accurately identifying heterozygous SNVs from partially C-to-T converted sequences remains challenging. We designed two methods, BayesWC and BinomWC, that substantially improved the precision of heterozygous SNV calls from ∼80% to 99% while retaining comparable recalls. With these SNV calls, we provided functions for allele-specific DNA methylation (ASM) analysis and visualizing the methylation status on reads. Applying ASM analysis to a previous dataset, we found that an average of 1.5% of investigated regions showed allelic methylation, which were significantly enriched in transposon elements and likely to be shared by the same cell-type. A dynamic fragment strategy was utilized for DMR analysis in low-coverage data and was able to find differentially methylated regions (DMRs) related to key genes involved in tumorigenesis using a public cancer dataset. Finally, we integrated 40 applications into the software package CGmapTools to analyze DNA methylomes. This package uses CGmap as the format interface, and designs binary formats to reduce the file size and support fast data retrieval, and can be applied for context-wise, gene-wise, bin-wise, region-wise and sample-wise analyses and visualizations. The CGmapTools software is freely available at https://cgmaptools.github.io/. guoweilong@cau.edu.cn. Supplementary data are available at Bioinformatics online.

Novel Plasmid-Mediated Colistin Resistance Gene mcr-3 in Escherichia coli.

ABSTRACTThe mobile colistin resistance gene mcr-1 has attracted global attention, as it heralds the breach of polymyxins, one of the last-resort antibiotics for the treatment of severe clinical infections caused by multidrug-resistant Gram-negative bacteria. To date, six slightly different variants of mcr-1, and a second mobile colistin resistance gene, mcr-2, have been reported or annotated in the GenBank database. Here, we characterized a third mobile colistin resistance gene, mcr-3. The gene coexisted with 18 additional resistance determinants in the 261-kb IncHI2-type plasmid pWJ1 from porcine Escherichia coli. mcr-3 showed 45.0% and 47.0% nucleotide sequence identity to mcr-1 and mcr-2, respectively, while the deduced amino acid sequence of MCR-3 showed 99.8 to 100% and 75.6 to 94.8% identity to phosphoethanolamine transferases found in other Enterobacteriaceae species and in 10 Aeromonas species, respectively. pWJ1 was mobilized to an E. coli recipient by conjugation and contained a plasmid backbone similar to those of other mcr-1-carrying plasmids, such as pHNSHP45-2 from the original mcr-1-harboring E. coli strain. Moreover, a truncated transposon element, TnAs2, which was characterized only in Aeromonas salmonicida, was located upstream of mcr-3 in pWJ1. This ΔTnAs2-mcr-3 element was also identified in a shotgun genome sequence of a porcine E. coli isolate from Malaysia, a human Klebsiella pneumoniae isolate from Thailand, and a human Salmonella enterica serovar Typhimurium isolate from the United States. These results suggest the likelihood of a wide dissemination of the novel mobile colistin resistance gene mcr-3 among Enterobacteriaceae and aeromonads; the latter may act as a potential reservoir for mcr-3.

Genome-wide mapping and characterization of microsatellites in the swamp eel genome

We described genome-wide screening and characterization of microsatellites in the swamp eel genome. A total of 99,293 microsatellite loci were identified in the genome with an overall density of 179 microsatellites per megabase of genomic sequences. The dinucleotide microsatellites were the most abundant type representing 71% of the total microsatellite loci and the AC-rich motifs were the most recurrent in all repeat types. Microsatellite frequency decreased as numbers of repeat units increased, which was more obvious in long than short microsatellite motifs. Most of microsatellites were located in non-coding regions, whereas only approximately 1% of the microsatellites were detected in coding regions. Trinucleotide repeats were most abundant microsatellites in the coding regions, which represented amino acid repeats in proteins. There was a chromosome-biased distribution of microsatellites in non-coding regions, with the highest density of 203.95/Mb on chromosome 8 and the least on chromosome 7 (164.06/Mb). The most abundant dinucleotides (AC)n was mainly located on chromosome 8. Notably, genomic mapping showed that there was a chromosome-biased association of genomic distributions between microsatellites and transposon elements. Thus, the novel dataset of microsatellites in swamp eel provides a valuable resource for further studies on QTL-based selection breeding, genetic resource conservation and evolutionary genetics.

Pln24NT: a web resource for plant 24-nt siRNA producing loci.

In plants, 24 nucleotide small interfering RNAs (24-nt siRNAs) account for a large percentage of the total siRNA pool, and they play an important role in guiding plant-specific RNA-directed DNA methylation (RdDM), which transcriptionally silences transposon elements, transgenes, repetitive sequences and some endogenous genes. Several loci in plant genomes produce clusters of 24-nt RNAs, and these loci are receiving increasing attention from the research community. However, at present there is no bioinformatics resource dedicated to 24-nt siRNA loci and their derived 24-nt siRNAs. Thus, in this study, Pln24NT, a freely available web resource, was created to centralize 24-nt siRNA loci and 24-nt siRNA information, including fundamental locus information, expression profiles and annotation of transposon elements, from next-generation sequencing (NGS) data for 10 popular plant species. An intuitive web interface was also developed for convenient searching and browsing, and analytical tools were included to help users flexibly analyze their own siRNA NGS data. Pln24NT will help the plant research community to discover and characterize 24-nt siRNAs, and may prove useful for studying the roles of siRNA in RNA-directed DNA methylation in plants. http://bioinformatics.caf.ac.cn/Pln24NT . suxh@caf.ac.cn. Supplementary data are available at Bioinformatics online.

High-Level Heat Resistance of Spores of Bacillus amyloliquefaciens and Bacillus licheniformis Results from the Presence of a spoVA Operon in a Tn1546 Transposon.

Bacterial endospore formers can produce spores that are resistant to many food processing conditions, including heat. Some spores may survive heating processes aimed at production of commercially sterile foods. Recently, it was shown that a spoVA operon, designated spoVA2mob, present on a Tn1546 transposon in Bacillus subtilis, leads to profoundly increased wet heat resistance of B. subtilis spores. Such Tn1546 transposon elements including the spoVA2mob operon were also found in several strains of Bacillus amyloliquefaciens and Bacillus licheniformis, and these strains were shown to produce spores with significantly higher resistances to wet heat than their counterparts lacking this transposon. In this study, the locations and compositions of Tn1546 transposons encompassing the spoVA2mob operons in B. amyloliquefaciens and B. licheniformis were analyzed. Introduction of these spoVA2mob operons into B. subtilis 168 (producing spores that are not highly heat resistant) rendered mutant 168 strains that produced high-level heat resistant spores, demonstrating that these elements in B. amyloliquefaciens and B. licheniformis are responsible for high level heat resistance of spores. Assessment of growth of the nine strains of each species between 5.2°C and 57.7°C showed some differences between strains, especially at lower temperatures, but all strains were able to grow at 57.7°C. Strains of B. amyloliquefaciens and B. licheniformis that contain the Tn1546 elements (and produce high-level heat resistant spores) grew at temperatures similar to those of their Tn1546-negative counterparts that produce low-level heat resistant spores. The findings presented in this study allow for detection of B. amyloliquefaciens and B. licheniformis strains that produce highly heat resistant spores in the food chain.

Global DNA methylation variations after short-term heat shock treatment in cultured microspores of Brassica napus cv. Topas

Heat stress can induce the cultured microspores into embryogenesis. In this study, whole genome bisulphite sequencing was employed to study global DNA methylation variations after short-term heat shock (STHS) treatments in cultured microspores of Brassica napus cv. Topas. Our results indicated that treatment on cultured Topas microspores at 32 °C for 6 h triggered DNA hypomethylation, particularly in the CG and CHG contexts. And the total number of T32 (Topas 32 °C for 6 h) vs. T0 (Topas 0 h) differentially methylated region-related genes (DRGs) was approximately two-fold higher than that of T18 (Topas 18 °C for 6 h) vs. T0 DRGs, which suggested that 32 °C might be a more intense external stimulus than 18 °C resulting in more changes in the DNA methylation status of cultured microspores. Additionally, 32 °C treatment for 6 h led to increased CHG differential methylations of transposons (DMTs), which were mainly constituted by overlaps between the hypomethylated differentially methylated regions (hypo-DMRs) and transposon elements (TEs). Further analysis demonstrated that the DRGs and their paralogs exhibited differential methylated/demethylated patterns. To summarize, the present study is the first methylome analysis of cultured microspores in response to STHS and may provide valuable information on the roles of DNA methylation in heat response.

Mammalian non-CG methylations are conserved and cell-type specific and may have been involved in the evolution of transposon elements.

Although non-CG methylations are abundant in several mammalian cell types, their biological significance is sparsely characterized. We gathered 51 human and mouse DNA methylomes from brain neurons, embryonic stem cells and induced pluripotent stem cells, primordial germ cells and oocytes. We utilized an unbiased sub-motif prediction method and reported CW as the representative non-CG methylation context, which is distinct from CC methylation in terms of sequence context and genomic distribution. A two-dimensional comparison of non-CG methylations across cell types and species was performed. Unambiguous studies of sequence preferences and genomic region enrichment showed that CW methylation is cell-type specific and is also conserved between humans and mice. In brain neurons, it was found that active long interspersed nuclear element-1 (LINE-1) lacked CW methylations but not CG methylations. Coincidentally, both human Alu and mouse B1 elements preferred high CW methylations at specific loci during their respective evolutionary development. Last, the strand-specific distributions of CW methylations in introns and long interspersed nuclear elements are also cell-type specific and conserved. In summary, our results illustrate that CW methylations are highly conserved among species, are dynamically regulated in each cell type, and are potentially involved in the evolution of transposon elements.

A transposon present in specific strains of Bacillus subtilis negatively affects nutrient‐ and dodecylamine‐induced spore germination

Spore germination shows a large inter-strain variability. Spores of certain Bacillus subtilis strains, including isolates from spoiled food products, exhibit different germination behavior from spores of the well-studied model organism Bacillus subtilis 168, often for unknown reasons. In this study, we analyzed spore germination efficiencies and kinetics of seventeen B. subtilis strains with previously sequenced genomes. A subsequent gene-trait matching analysis revealed a correlation between a slow germination phenotype and the presence of a mobile genetic element, i.e., a Tn1546-like transposon. A detailed investigation of the transposon elements showed an essential role of a specific operon (spoVA2mob ) in inhibiting spore germination with nutrients and with the cationic surfactant dodecylamine. Our results indicate that this operon negatively influences release of Ca-DPA by the SpoVA channel and may additionally alter earlier germination events, potentially by affecting proteins in the spore inner membrane. The spoVA2mob operon is an important factor that contributes to inter-strain differences in spore germination. Screening for its genomic presence can be applied for identification of spores that exhibit specific properties that impede spore eradication by industrial processes.

Principal components analysis--K-means transposon element based foxtail millet core collection selection method.

BackgroundCore collections are important tools in genetic resources research and administration. At present, most core collection selection criteria are based on one of the following item characteristics: passport data, genetic markers, or morphological traits, which may lead to inadequate representations of variability in the complete collection. The development of a comprehensive methodology that includes as much element data as possible has been explored poorly. Using a collection of (Setaria italica sbsp. italica (L.) P. Beauv.) as a model, we developed a method for core collection construction based on genotype data and numerical representations of agromorphological traits, thereby improving the selection process.ResultsPrincipal component analysis allows the selection of the most informative discriminators among the various elements evaluated, regardless of whether they are genetic or morphological, thereby providing an adequate criterion for further K-mean clustering. Overall, the core collections of S. italica constructed using only genotype data demonstrated overall better validation scores than other core collections that we generated. However, core collection based on both genotype and agromorphological characteristics represented the overall diversity adequately.ConclusionsThe inclusion of both genotype and agromorphological characteristics as a comprehensive dataset in this methodology ensures that agricultural traits are considered in the core collection construction. This approach will be beneficial for genetic resources management and research activities for S. italica as well as other genetic resources.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0343-z) contains supplementary material, which is available to authorized users.

PiggyBac as a novel vector in cancer gene therapy: current perspective.

Selection of suitable delivery system is one of the crucial aspects in gene therapy that determines the efficiency of gene therapy. The past two decades have witnessed extensive efforts for finding safe and efficient vectors to overcome the limitations of viral vectors. The utilization of DNA transposon-based vectors for gene therapy has emerged as a promising non-viral alternative. DNA 'cut-and-paste' is one of the main mechanisms of genome engineering by transposon elements. However, the lack of an efficient transposition system has limited the utilization of transposon vectors in mice and mammalian systems. PiggyBac (PB) is known as a highly efficient DNA transposon originally isolated from Trichoplusia ni as an alternative to Sleeping Beauty (SB). It has been shown that PB can be functional in various species including mammalian systems. This vector could overcome some limitations of other vectors in cancer gene therapy. Some advantages of PB include the capacity for integration into the genome and providing a stable expression, capacity to harbor 10 and 9.1 kb of foreign DNA into the host genome, without a significant reduction in their transposition activity and display non-overlapping targeting preferences. However, to advance PB to clinical applications, some obstacles still require to be overcome to improve its safety and efficiency. Hence, it seems that this vector could open new horizons in gene and cancer therapy.