The Essential Role of Drosophila HIRA for De Novo Assembly of Paternal Chromatin at Fertilization

In many animal species, the sperm DNA is packaged with male germ line–specific chromosomal proteins, including protamines. At fertilization, these non-histone proteins are removed from the decondensing sperm nucleus and replaced with maternally provided histones to form the DNA replication competent male pronucleus. By studying a point mutant allele of the Drosophila Hira gene, we previously showed that HIRA, a conserved replication-independent chromatin assembly factor, was essential for the assembly of paternal chromatin at fertilization. HIRA permits the specific assembly of nucleosomes containing the histone H3.3 variant on the decondensing male pronucleus. We report here the analysis of a new mutant allele of Drosophila Hira that was generated by homologous recombination. Surprisingly, phenotypic analysis of this loss of function allele revealed that the only essential function of HIRA is the assembly of paternal chromatin during male pronucleus formation. This HIRA-dependent assembly of H3.3 nucleosomes on paternal DNA does not require the histone chaperone ASF1. Moreover, analysis of this mutant established that protamines are correctly removed at fertilization in the absence of HIRA, thus demonstrating that protamine removal and histone deposition are two functionally distinct processes. Finally, we showed that H3.3 deposition is apparently not affected in Hira mutant embryos and adults, suggesting that different chromatin assembly machineries could deposit this histone variant

Comparative Genome Analysis Provides Insights into Both the Lifestyle of Acidithiobacillus ferrivorans Strain CF27 and the Chimeric Nature of the Iron-Oxidizing Acidithiobacilli Genomes

The iron-oxidizing species Acidithiobacillus ferrivorans is one of few acidophiles able to oxidize ferrous iron and reduced inorganic sulfur compounds at low temperatures (<10°C). To complete the genome of At. ferrivorans strain CF27, new sequences were generated, and an update assembly and functional annotation were undertaken, followed by a comparative analysis with other Acidithiobacillus species whose genomes are publically available. The At. ferrivorans CF27 genome comprises a 3,409,655 bp chromosome and a 46,453 bp plasmid. At. ferrivorans CF27 possesses genes allowing its adaptation to cold, metal(loid)-rich environments, as well as others that enable it to sense environmental changes, allowing At. ferrivorans CF27 to escape hostile conditions and to move toward favorable locations. Interestingly, the genome of At. ferrivorans CF27 exhibits a large number of genomic islands (mostly containing genes of unknown function), suggesting that a large number of genes has been acquired by horizontal gene transfer over time. Furthermore, several genes specific to At. ferrivorans CF27 have been identified that could be responsible for the phenotypic differences of this strain compared to other Acidithiobacillus species. Most genes located inside At. ferrivorans CF27-specific gene clusters which have been analyzed were expressed by both ferrous iron-grown and sulfur-attached cells, indicating that they are not pseudogenes and may play a role in both situations. Analysis of the taxonomic composition of genomes of the Acidithiobacillia infers that they are chimeric in nature, supporting the premise that they belong to a particular taxonomic class, distinct to other proteobacterial subgroups

ASF1 is required to load histones on the HIRA complex in preparation of paternal chromatin assembly at fertilization

Abstract Background Anti-Silencing Factor 1 (ASF1) is a conserved H3–H4 histone chaperone involved in both Replication-Coupled and Replication-Independent (RI) nucleosome assembly pathways. At DNA replication forks, ASF1 plays an important role in regulating the supply of H3.1/2 and H4 to the CAF-1 chromatin assembly complex. ASF1 also provides H3.3–H4 dimers to HIRA and DAXX chaperones for RI nucleosome assembly. The early Drosophila embryo is an attractive system to study chromatin assembly in a developmental context. The formation of a diploid zygote begins with the unique, genome-wide RI assembly of paternal chromatin following sperm protamine eviction. Then, within the same cytoplasm, syncytial embryonic nuclei undergo a series of rapid, synchronous S and M phases to form the blastoderm embryo. Here, we have investigated the implication of ASF1 in these two distinct assembly processes. Results We show that depletion of the maternal pool of ASF1 with a specific shRNA induces a fully penetrant, maternal effect embryo lethal phenotype. Unexpectedly, despite the depletion of ASF1 protein to undetectable levels, we show that asf1 knocked-down (KD) embryos can develop to various stages, thus demonstrating that ASF1 is not absolutely required for the amplification of cleavage nuclei. Remarkably, we found that ASF1 is required for the formation of the male pronucleus, although ASF1 protein does not reside in the decondensing sperm nucleus. In asf1 KD embryos, HIRA localizes to the male nucleus but is only capable of limited and insufficient chromatin assembly. Finally, we show that the conserved HIRA B domain, which is involved in ASF1-HIRA interaction, is dispensable for female fertility. Conclusions We conclude that ASF1 is critically required to load H3.3–H4 dimers on the HIRA complex prior to histone deposition on paternal DNA. This separation of tasks could optimize the rapid assembly of paternal chromatin within the gigantic volume of the egg cell. In contrast, ASF1 is surprisingly dispensable for the amplification of cleavage nuclei, although chromatin integrity is likely compromised in KD embryos

The Biomechanical Effect of Arm Mass on Long Jump Performance: A Case Study of a Paralympic Upper Limb Amputee

Epub 2013 Aug 28BACKGROUND: The role of arm motion during the long jump has been well studied. The aim of this study was to quantify the effect of forearm mass on impulse and the kinematics of the flight phase in an upper limb amputee.CASE DESCRIPTION AND METHODS: A world-record paralympic long jumper carried out jumps in three conditions: wearing his usual forearm prosthesis and with 0.3 and 0.4 kg added mass. A motion capture system including force plates was used to record the jump.FINDINGS AND OUTCOME: At take-off, the addition of 0.4 kg to the prosthesis decreased the vertical velocity of the centre of mass but increased horizontal velocity. These modifications were associated with an increase in landing distance and an improvement of the synchronization between arms.CONCLUSION: Increasing forearm mass appears to improve long jump performance. Further studies need to evaluate the optimal prosthetic mass for both training and competition.CLINICAL RELEVANCE: This biomechanical analysis of the long jump highlighted the effects of changing prosthesis mass on performance. This methodological approach may be useful in the context of sport and performance research

Beyond RF: the terahertz radiation and its applications

National audienc

Beyond RF: the terahertz radiation and its applications

National audienc

Influence of oxidative stress biomarkers on cognitive decline

International audienceBACKGROUND: Abnormal oxidative stress is an established feature of Alzheimer's disease (AD). Markers of lipoperoxidation and deficits in serum antioxidants could have a predictive value for identifying subjects at risk of dementia and to predict cognitive decline. OBJECTIVE: Search for relationships between the levels of some oxidative stress biomarkers and cognitive function decline that would help predict this decline. METHODS: The study solicited and included 97 patients aged 63 to 93 years with various suspected neurodegenerative diseases (35 with AD). They were followed up at six-month intervals over two years (2010-2012). The study: i) assessed the blood levels of glutathione peroxidase, glutathione, and malondialdehyde; ii) performed the Mini-Mental Status Examination (MMSE), the Clock Drawing test, the free/cued recall task with 16-item lists, the cue percentage; and the Trail Making Test; and iii) acquired brain magnetic resonance imaging or tomodensitometry. The primary outcome measure was the MMSE score. RESULTS: The MMSE score was correlated with the score of each neuropsychological test, the age at baseline, and the glutathione level. On average, the decline in the MMSE score was 1.63 points per six months. A 100 International Unit increase in glutathione peroxidase was associated with an average loss of 1.19 MMSE points per six months (p = 0.002). A 100 mumol/L increase in glutathione was associated with an average loss of 1.80 MMSE points per six months (p = 0.014). CONCLUSION: Oxidative stress biomarkers, especially glutathione peroxidase and glutathione, may predict the course of cognitive decline in patients with AD or other neurodegenerative disorders

MOESM5 of ASF1 is required to load histones on the HIRA complex in preparation of paternal chromatin assembly at fertilization

Additional file 5: Fig. S4. ASF1::V5 is not detected in the decondensing male pronucleus. a: An egg in metaphase of meiosis II from a g-asf1::V5 transgenic female stained with anti-V5 antibodies. Scale bar: 50 μm. b: Pronuclear migration. Scale bar: 10 μm. c: ASF1::V5 is incorporated in both pronuclei at the onset of DNA replication. Scale bar: 10 μm. d: Pronuclei stained with anti-V5 antibodies during apposition. Scale bar: 10 μm

The Male Nucleus Does Not Recondense in <i>Hira ; sra</i> Double Mutant Eggs

<div><p>(A) In <i>sra^A108/Df(3R)sbd45</i> mutant eggs, the female meiosis arrests in anaphase of the first meiotic division (MI). The male nucleus (arrowhead and bottom panels) appears condensed but irregular in shape and stains with anti-acetylated histone H4 antibodies (bottom right panel). Note that the DNA positive dots that are visible in this egg are <i>Wolbachia</i> bacteria that naturally infect the stock.</p><p>(B) In <i>Hira^ssm ; sra^A108/Df(3R)sbd45</i> Double Mutant Eggs, the Male Nucleus Is Round and Does Not Stain with Anti-Histone Antibodies. Bars: 2 μm.</p></div