The health Oriented pedagogical project (HOPP) - a controlled longitudinal school-based physical activity intervention program.

BACKGROUND: The prevalence of non-communicable diseases (NCDs) is increasing worldwide, also among children. Information about primary prevention of NCD's is increasing; however, convincing strategies among children is needed. The present paper describes the design and methods in the Health Oriented Pedagogical Project (HOPP) study. The main objective is to evaluate the effects of a school-based physical activity intervention program on cardio-metabolic risk factors. Secondary objectives include assessment of physical, psychological and academic performance variables. METHODS: The HOPP study is a 7 years longitudinal large-scale controlled intervention in seven elementary schools (n = 1545) with two control schools (n = 752); all aged 6-11 years at baseline. The school-based physical activity intervention program includes an increase in physical activity (PA) of 225 min/week as an integrated part of theoretical learning, in addition to the curriculum based 90 min/week of ordinary PA. Primary outcomes include cardio-metabolic risk factors measured as PA level, BMI status, waist circumference, muscle mass, percent fat, endurance test performance, total serum cholesterol, high-density lipoprotein (HDL), non-HDL, micro C-reactive protein (mCRP) and long-term blood sugar (HbA1c). In addition, secondary outcomes include anthropometric growth measures, physical fitness, quality of life (QoL), mental health, executive functions, diet and academic performance. DISCUSSION: HOPP will provide evidence of effects on cardio-metabolic risk factors after a long-term PA intervention program in elementary schoolchildren. School-based PA intervention programs may be an effective arena for health promotion and disease prevention. TRIAL REGISTRATION: The study is registered in Clinical trials (ClinicalTrials.gov Identifier: NCT02495714 ) as of June 20th - 2015, retrospectively registered. The collection of baseline values was initiated in mid-January 2015.

The DNA dioxygenase ALKBH2 protects Arabidopsis thaliana against methylation damage.

The Escherichia coli AlkB protein (EcAlkB) is a DNA repair enzyme which reverses methylation damage such as 1-methyladenine (1-meA) and 3-methylcytosine (3-meC). The mammalian AlkB homologues ALKBH2 and ALKBH3 display EcAlkB-like repair activity in vitro, but their substrate specificities are different, and ALKBH2 is the main DNA repair enzyme for 1-meA in vivo. The genome of the model plant Arabidopsis thaliana encodes several AlkB homologues, including the yet uncharacterized protein AT2G22260, which displays sequence similarity to both ALKBH2 and ALKBH3. We have here characterized protein AT2G22260, by us denoted ALKBH2, as both our functional studies and bioinformatics analysis suggest it to be an orthologue of mammalian ALKBH2. The Arabidopsis ALKBH2 protein displayed in vitro repair activities towards methyl and etheno adducts in DNA, and was able to complement corresponding repair deficiencies of the E. coli alkB mutant. Interestingly, alkbh2 knock-out plants were sensitive to the methylating agent methylmethanesulphonate (MMS), and seedlings from these plants developed abnormally when grown in the presence of MMS. The present study establishes ALKBH2 as an important enzyme for protecting Arabidopsis against methylation damage in DNA, and suggests its homologues in other plants to have a similar function.

Roles of Trm9- and ALKBH8-like proteins in the formation of modified wobble uridines in Arabidopsis tRNA.

Uridine at the wobble position of tRNA is usually modified, and modification is required for accurate and efficient protein translation. In eukaryotes, wobble uridines are modified into 5-methoxycarbonylmethyluridine (mcm(5)U), 5-carbamoylmethyluridine (ncm(5)U) or derivatives thereof. Here, we demonstrate, both by in vitro and in vivo studies, that the Arabidopsis thaliana methyltransferase AT1G31600, denoted by us AtTRM9, is responsible for the final step in mcm(5)U formation, thus representing a functional homologue of the Saccharomyces cerevisiae Trm9 protein. We also show that the enzymatic activity of AtTRM9 depends on either one of two closely related proteins, AtTRM112a and AtTRM112b. Moreover, we demonstrate that AT1G36310, denoted AtALKBH8, is required for hydroxylation of mcm(5)U to (S)-mchm(5)U in tRNA(Gly)(UCC), and has a function similar to the mammalian dioxygenase ALKBH8. Interestingly, atalkbh8 mutant plants displayed strongly increased levels of mcm(5)U, and also of mcm(5)Um, its 2'-O-ribose methylated derivative. This suggests that accumulated mcm(5)U is prone to further ribose methylation by a non-specialized mechanism, and may challenge the notion that the existence of mcm(5)U- and mcm(5)Um-containing forms of the selenocysteine-specific tRNA(Sec) in mammals reflects an important regulatory process. The present study reveals a role in for several hitherto uncharacterized Arabidopsis proteins in the formation of modified wobble uridines.

Organ and cell specificity of base excision repair mutants in mice.

Genetically modified mouse models are a powerful approach to study the relation of a single gene-deletion to processes such as mutagenesis and carcinogenesis. The generation of base excision repair (BER) deficient mouse models has resulted in a re-examination of the cellular defence mechanisms that exist to counteract DNA base damage. This review discusses novel insights into the relation between specific gene-deletions and the organ and cell specificity of visible and molecular phenotypes, including accumulation of base lesions in genomic DNA and carcinogenesis. Although promising models exist, there is still a need for new models. These models should comprise combined deficiencies of DNA glycosylases which initiate the BER pathway, to elaborate on the repair redundancy, as well as conditional models of the intermediate steps of BER.

Tolerated wobble mutations in siRNAs decrease specificity, but can enhance activity in vivo.

RNA interference (RNAi) has become an invaluable tool for functional genomics. A critical use of this tool depends on an understanding of the factors that determine the specificity and activity of the active agent, small interfering RNA (siRNA). Several studies have concluded that tolerance of mutations can be considerable and hence lead to off-target effects. In this study, we have investigated in vivo the toleration of wobble (G:U) mutations in high activity siRNAs against Flap Endonuclease 1 (Fen1) and Aquaporin-4 (Aqp4). Mutations in the central part of the antisense strand caused a pronounced decrease in activity, while mutations in the 5' and 3'ends were tolerated very well. Furthermore, based on analysis of nine different mutated siRNAs with widely differing intrinsic activities, we conclude that siRNA activity can be significantly enhanced by wobble mutations (relative to mRNA), in the 5' terminal of the antisense strand. These findings should facilitate design of active siRNAs where the target mRNA offers limited choice of siRNA positions.

Ten members of the Arabidopsis gene family encoding methyl-CpG-binding domain proteins are transcriptionally active and at least one, AtMBD11, is crucial for normal development.

Animal proteins that contain a methyl-CpG-binding domain (MBD) are suggested to provide a link between DNA methylation, chromatin remodelling and gene silencing. However, some MBD proteins reside in chromatin remodelling complexes, but do not have specific affinity for methylated DNA. It has recently been shown that the Arabidopsis genome contains 12 putative genes encoding proteins with domains similar to MBD, of which at least three bind symmetrically methylated DNA. Using a bioinformatics approach, we have identified additional domains in a number of these proteins and, on this basis and extended sequence similarity, divided the proteins into subgroups. Using RT-PCR we show that 10 of the AtMBD genes are active and differentially expressed in diverse tissues. To investigate the biological significance of AtMBD proteins, we have transformed Arabidopsis with a construct aimed at RNA interference with expression of the AtMBD11 gene, normally active in most tissues. The resulting 35S::AtMBD11-RNAi plants displayed a variety of phenotypic effects, including aerial rosettes, serrated leaves, abnormal position of flowers, fertility problems and late flowering. Arabidopsis lines with reduced expression of genes involved in chromatin remodelling and transgene silencing show similar phenotypes. Our results suggest an important role for AtMBD proteins in plant development.

Analyses of single-copy Arabidopsis T-DNA-transformed lines show that the presence of vector backbone sequences, short inverted repeats and DNA methylation is not sufficient or necessary for the induction of transgene silencing.

In genetically transformed plants, transgene silencing has been correlated with multiple and complex insertions of foreign DNA, e.g. T-DNA and vector backbone sequences. Occasionally, single-copy transgenes also suffer transgene silencing. We have compared integration patterns and T-DNA/plant DNA junctions in a collection of 37 single-copy T-DNA-transformed Arabidopsis lines, of which 13 displayed silencing. Vector sequences were found integrated in five lines, but only one of these displayed silencing. Truncated T-DNA copies, positioned in inverse orientation to an intact T-DNA copy, were discovered in three lines. The whole nptII gene with pnos promoter was present in the truncated copy of one such line in which heavy silencing has been observed. In the two other lines no silencing has been observed over five generations. Thus, vector sequences and short additional T-DNA sequences are not sufficient or necessary to induce transgene silencing. DNA methylation of selected restriction endonuclease sites could not be correlated with silencing. Our collection of T-DNA/plant DNA junctions has also been used to evaluate current models of T-DNA integration. Data for some of our lines are compatible with T-DNA integration in double-strand breaks, while for others initial invasion of plant DNA by the left or by the right T-DNA end seem important.

Human ALKBH4 interacts with proteins associated with transcription.

The Fe(II)- and 2-oxoglutarate (2OG)-dependent dioxygenase AlkB from E. coli is a demethylase which repairs alkyl lesions in DNA, as well as RNA, through a direct reversal mechanism. Humans possess nine AlkB homologs (ALKBH1-8 and FTO). ALKBH2 and ALKBH3 display demethylase activities corresponding to that of AlkB, and both ALKBH8 and FTO are RNA modification enzymes. The biochemical functions of the rest of the homologs are still unknown. To increase our knowledge on the functions of ALKBH4 and ALKBH7 we have here performed yeast two-hybrid screens to identify interaction partners of the two proteins. While no high-confidence hits were detected in the case of ALKBH7, several proteins associated with chromatin and/or involved in transcription were found to interact with ALKBH4. For all interaction partners, the regions mediating binding to ALKBH4 comprised domains previously reported to be involved in interaction with DNA or chromatin. Furthermore, some of these partners showed nuclear co-localization with ALKBH4. However, the global gene expression pattern was only marginally altered upon ALKBH4 over-expression, and larger effects were observed in the case of ALKBH7. Although the molecular function of both proteins remains to be revealed, our findings suggest a role for ALKBH4 in regulation of gene expression or chromatin state.

Early-onset lymphoma and extensive embryonic apoptosis in two domain-specific Fen1 mice mutants.

Flap endonuclease 1 (FEN1) processes Okazaki fragments in lagging strand DNA synthesis, and FEN1 is involved in several DNA repair pathways. The interaction of FEN1 with the proliferating cell nuclear antigen (PCNA) processivity factor is central to the function of FEN1 in both DNA replication and repair. Here we present two gene-targeted mice with mutations in FEN1. The first mutant mouse carries a single amino acid point mutation in the active site of the nuclease domain of FEN1 (Fen1(E160D/E160D)), and the second mutant mouse contains two amino acid substitutions in the highly conserved PCNA interaction domain of FEN1 (Fen1(DeltaPCNA/DeltaPCNA)). Fen1(E160D/E160D) mice develop a considerably elevated incidence of B-cell lymphomas beginning at 6 months of age, particularly in females. By 16 months of age, more than 90% of the Fen1(E160D/E160D) females have tumors, primarily lymphomas. By contrast, Fen1(DeltaPCNA/DeltaPCNA) mouse embryos show extensive apoptosis in the forebrain and vertebrae area and die around stage E9.5 to E11.5.

An inverted repeat transgene with a structure that cannot generate double-stranded RNA, suffers silencing independent of DNA methylation.

Transgene silencing in plants is most often dependent on homologous sequences, e.g. tandemly repeated T-DNAs. We have identified an Arabidopsis line (ex2-4 line 4) displaying silencing of the T-DNA-born nptII gene. This line contains a truncated copy of the T-DNA encompassing the nptII gene with its nos promoter adjacent to an intact T-DNA copy. The orientation of the intact and the truncated copies preclude the generation of a double-stranded nptII transcript. Therefore, we have investigated the genomic landscape surrounding T-DNA insertion in the silenced ex2-4 line 4 and five single-copy ex2-4 lines without silencing in search of features that might explain the silencing phenomenon. GC content, putative matrix-attachment regions and transcriptional interference from neighbouring genes could all be ruled out as major causes of silencing. Bisulphite sequencing revealed de novo methylation of the nos promoter both in non-silenced and silenced plants of this line, thus silencing was not correlated to DNA methylation level. Also, the methylation pattern deviated from that characteristic for RNA-mediated DNA methylation and silencing. Our data therefore suggest that ex2-4 line 4 represents a case where silencing is due to DNA-DNA pairing, i.e. pairing between the intact T-DNA and the adjacent truncated, inverted T-DNA copy.

Seed 1-cysteine peroxiredoxin antioxidants are not involved in dormancy, but contribute to inhibition of germination during stress.

Peroxiredoxins (Prx) are thiol-dependent antioxidants containing one (1-cysteine [-Cys]) or two (2-Cys) conserved Cys residues that protect lipids, enzymes, and DNA against reactive oxygen species. In plants, the 1-Cys Prxs are highly expressed during late seed development, and the expression pattern is dormancy related in mature seeds. We have expressed the Arabidopsis 1-Cys Prx AtPER1 in Escherichia coli and show that this protein has antioxidant activity in vitro and protects E. coli in vivo against the toxic oxidant cumene hydroperoxide. Although some 1-Cys Prxs are targeted to the nucleus, a green fluorescent protein-AtPER1 fusion protein was also localized to the cytoplasm in an onion epidermis subcellular localization assay. It has been proposed that seed Prxs are involved in maintenance of dormancy and/or protect the embryo and aleurone layer surviving desiccation against damage caused by reactive oxygen species. These hypotheses were tested using transgenic Arabidopsis lines overexpressing the barley (Hordeum vulgare) 1-Cys PER1 protein and lines with reduced levels of AtPER1 due to antisensing or RNA interference. We found no correlation between Prx levels and the duration of the after-ripening period required before germination. Thus, Prxs are unlikely to contribute to maintenance of dormancy. RNA interference lines almost devoid of AtPER1 protein developed and germinated normally under standard growth room conditions. However, seeds from lines overexpressing PER1 were less inclined to germinate than wild-type seeds in the presence of NaCl, mannitol, and methyl viologen, suggesting that Prx can sense harsh environmental surroundings and play a part in the inhibition of germination under unfavorable conditions.