Publications by authors named "Samuel Le Goff"

12 Publications

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Lactation and gestation controls on calcium isotopic compositions in a mammalian model.

Metallomics 2021 Apr 21. Epub 2021 Apr 21.

Univ Lyon, ENSL, Univ Lyon 1, CNRS, LGL-TPE, F-69007 Lyon, France.

Lactation and gestation are among the physiological events that trigger the most intense changes in body calcium (Ca) fluxes. Along with the composition of the animal diet, these events are suspected to impact the Ca isotopic composition of Ca body reservoirs but their dynamics are poorly understood. In this study, we monitored a group of domestic sows across a full reproduction cycle. We collected tissues and fluids (blood, urine, milk, colostrum, umbilical blood, adult and piglet bones) at different steps of gestation and lactation, and analyzed their Ca isotopic compositions (i.e. δ44/42Ca) by mean of MC-ICP-MS. Among other results, we report the first observations of Ca isotopic fractionation between maternal and umbilical blood (Δ44/42Caumbilical blood- sow blood = -0.18 ± 0.11 ‰, n = 3). Our data also highlight that gestation and lactation periods are characterized by small diet-bone Ca isotopic offsets (Δ44/42Cabone-diet = -0.28 ± 0.11 ‰, n = 3), with 44Ca-enriched blood compositions during nursing (Δ44/42Canursing blood-gestation blood = $+ 0.42{\rm{\ }}_{ - 0.12}^{ + 0.11}\ $‰, n = 3). Under the light of an up-to-date mammalian box model, we explored different scenarios of gestation and lactation Ca fluxes experienced by a sow-like animal. These simulations suggest that gestation changes on body δ44/42Ca values may result from the intensification of Ca absorption by the animal, whereas the production of 44Ca-depleted milk is the main driver for the 44Ca enrichment in blood during lactation. In addition, our results also support that bone mineralization could be associated with a more restricted Ca isotopic fractionation than previously envisioned. Together, these results refine the framework of Ca isotope applications, notably regarding the monitoring of human bone balance and the study of species and ecosystems from the present and the past.
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http://dx.doi.org/10.1093/mtomcs/mfab019DOI Listing
April 2021

Determination of magnesium isotopic ratios of biological reference materials via multi-collector inductively coupled plasma mass spectrometry.

Rapid Commun Mass Spectrom 2021 May;35(10):e9074

ENS de Lyon, Univ Lyon 1, Lyon, France.

Rationale: Despite a wide range of potential applications, magnesium (Mg) isotope composition has been so far sparsely measured in reference materials with a biological matrix, which is important for the quality control of the results. We describe a method enabling the chemical separation of Mg in geological and biological materials and the determination of its stable isotope composition.

Methods: Different geological (BHVO-1, BHVO-2, BCR-1, and IAPSO) and biological (SRM-1577c, BCR-383, BCR380R, ERM-CE464, DORM-2, DORM-4, TORT-3, and FBS) reference materials were used to test the performance of a new sample preparation procedure for Mg isotopic analysis. The procedure consisted of a simple three-stage elution method to separate Mg from the matrix. Mg isotopic analyses were performed in two different laboratories and with three different multi-collector inductively coupled plasma mass spectrometry instruments.

Results: The biological reference materials show a wide range of δ Mg values (relative to DSM3 standard), spanning over 2‰, from 0.52 ± 0.29‰ (2SD, n = 7) in bovine liver (SRM-1577c) to -1.45 ± 0.20‰ (2SD, n = 5) in tuna fish (ERM-CE464), with an external precision of 0.03‰ (2SD, n = 85).

Conclusions: This study indicates that isotopic measurements of Mg in biological reference materials show good performance, with the results being within the accepted range. We confirmed that δ Mg values in liver are the most positive of all biological materials reported so far.
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http://dx.doi.org/10.1002/rcm.9074DOI Listing
May 2021

A new chemical separation procedure for the determination of rare earth elements and yttrium abundances in carbonates by ICP-MS.

Talanta 2020 Nov 13;219:121244. Epub 2020 Jun 13.

LaTIM (INSERM UMR 1101) Université de Bretagne Occidentale, 22, Avenue C. Desmoulins, 29238, Brest Cedex 3, France.

The determination of rare earth elements (REEs) and Y in carbonates can be complicated by low REE abundances and the presence of significant amounts of Ba resulting in problematic interferences when analysed by ICP-MS. We describe here a novel ion-exchange method using the DGA resin (TODGA), combined with addition of a Tm spike, which allows the separation of the REEs+Y as a whole prior to analysis using an Element XR ICP-MS. This method was validated with results obtained on three different reference carbonate materials (CAL-S, JLs-1 and BEAN, an in-house standard), yielding reproducibility levels better than 3% (RSD) in most cases. This new separation scheme is particularly well suited for carbonate samples having very low REE contents, but could be equally applied to various rock types and organic-rich sample matrices whenever quantitative Ba removal is required.
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http://dx.doi.org/10.1016/j.talanta.2020.121244DOI Listing
November 2020

The H3 histone chaperone NASP escorts CenH3 in Arabidopsis.

Plant J 2020 01 14;101(1):71-86. Epub 2019 Oct 14.

Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Corrensstrasse 3, D-06466, Seeland, Germany.

Centromeres define the chromosomal position where kinetochores form to link the chromosome to microtubules during mitosis and meiosis. Centromere identity is determined by incorporation of a specific histone H3 variant termed CenH3. As for other histones, escort and deposition of CenH3 must be ensured by histone chaperones, which handle the non-nucleosomal CenH3 pool and replenish CenH3 chromatin in dividing cells. Here, we show that the Arabidopsis orthologue of the mammalian NUCLEAR AUTOANTIGENIC SPERM PROTEIN (NASP) and Schizosaccharomyces pombe histone chaperone Sim3 is a soluble nuclear protein that binds the histone variant CenH3 and affects its abundance at the centromeres. NASP is co-expressed with Arabidopsis CenH3 in dividing cells and binds directly to both the N-terminal tail and the histone fold domain of non-nucleosomal CenH3. Reduced NASP expression negatively affects CenH3 deposition, identifying NASP as a CenH3 histone chaperone.
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http://dx.doi.org/10.1111/tpj.14518DOI Listing
January 2020

Compound-specific recording of gadolinium pollution in coastal waters by great scallops.

Sci Rep 2019 05 29;9(1):8015. Epub 2019 May 29.

LaTIM (INSERM UMR 1101) Université de Bretagne Occidentale. 22, avenue C. Desmoulins, 29238, Brest Cedex 3, France.

Gadolinium-based contrast agents (GBCAs), routinely used in magnetic resonance imaging (MRI), end up directly in coastal seawaters where gadolinium concentrations are now increasing. Because many aquatic species could be sensitive to this new pollution, we have evaluated the possibility of using shellfish to assess its importance. Gadolinium excesses recorded by scallop shells collected in Bay of Brest (Brittany, France) for more than 30 years do not reflect the overall consumption in GBCAs, but are largely controlled by one of them, the gadopentetate dimeglumine. Although its use has been greatly reduced in Europe over the last ten years, gadolinium excesses are still measured in shells. Thus, some gadolinium derived from other GBCAs is bioavailable and could have an impact on marine wildlife.
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http://dx.doi.org/10.1038/s41598-019-44539-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6541655PMC
May 2019

Replication-coupled histone H3.1 deposition determines nucleosome composition and heterochromatin dynamics during Arabidopsis seedling development.

New Phytol 2019 01 13;221(1):385-398. Epub 2018 Jun 13.

GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001, Clermont-Ferrand, France.

Developmental phase transitions are often characterized by changes in the chromatin landscape and heterochromatin reorganization. In Arabidopsis, clustering of repetitive heterochromatic loci into so-called chromocenters is an important determinant of chromosome organization in nuclear space. Here, we investigated the molecular mechanisms involved in chromocenter formation during the switch from a heterotrophic to a photosynthetically competent state during early seedling development. We characterized the spatial organization and chromatin features at centromeric and pericentromeric repeats and identified mutant contexts with impaired chromocenter formation. We find that clustering of repetitive DNA loci into chromocenters takes place in a precise temporal window and results in reinforced transcriptional repression. Although repetitive sequences are enriched in H3K9me2 and linker histone H1 before repeat clustering, chromocenter formation involves increasing enrichment in H3.1 as well as H2A.W histone variants, hallmarks of heterochromatin. These processes are severely affected in mutants impaired in replication-coupled histone assembly mediated by CHROMATIN ASSEMBLY FACTOR 1 (CAF-1). We further reveal that histone deposition by CAF-1 is required for efficient H3K9me2 enrichment at repetitive sequences during chromocenter formation. Taken together, we show that chromocenter assembly during post-germination development requires dynamic changes in nucleosome composition and histone post-translational modifications orchestrated by the replication-coupled H3.1 deposition machinery.
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http://dx.doi.org/10.1111/nph.15248DOI Listing
January 2019

Genetic and epigenetic variation in 5S ribosomal RNA genes reveals genome dynamics in Arabidopsis thaliana.

Nucleic Acids Res 2018 04;46(6):3019-3033

GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France.

Organized in tandem repeat arrays in most eukaryotes and transcribed by RNA polymerase III, expression of 5S rRNA genes is under epigenetic control. To unveil mechanisms of transcriptional regulation, we obtained here in depth sequence information on 5S rRNA genes from the Arabidopsis thaliana genome and identified differential enrichment in epigenetic marks between the three 5S rDNA loci situated on chromosomes 3, 4 and 5. We reveal the chromosome 5 locus as the major source of an atypical, long 5S rRNA transcript characteristic of an open chromatin structure. 5S rRNA genes from this locus translocated in the Landsberg erecta ecotype as shown by linkage mapping and chromosome-specific FISH analysis. These variations in 5S rDNA locus organization cause changes in the spatial arrangement of chromosomes in the nucleus. Furthermore, 5S rRNA gene arrangements are highly dynamic with alterations in chromosomal positions through translocations in certain mutants of the RNA-directed DNA methylation pathway and important copy number variations among ecotypes. Finally, variations in 5S rRNA gene sequence, chromatin organization and transcripts indicate differential usage of 5S rDNA loci in distinct ecotypes. We suggest that both the usage of existing and new 5S rDNA loci resulting from translocations may impact neighboring chromatin organization.
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http://dx.doi.org/10.1093/nar/gky163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5887818PMC
April 2018

Arabidopsis ATRX Modulates H3.3 Occupancy and Fine-Tunes Gene Expression.

Plant Cell 2017 Jul 6;29(7):1773-1793. Epub 2017 Jul 6.

GReD, Université Clermont Auvergne, CNRS, INSERM, 63001 Clermont-Ferrand, France

Histones are essential components of the nucleosome, the major chromatin subunit that structures linear DNA molecules and regulates access of other proteins to DNA. Specific histone chaperone complexes control the correct deposition of canonical histones and their variants to modulate nucleosome structure and stability. In this study, we characterize the Alpha Thalassemia-mental Retardation X-linked (ATRX) ortholog and show that ATRX is involved in histone H3 deposition. Arabidopsis ATRX mutant alleles are viable, but show developmental defects and reduced fertility. Their combination with mutants of the histone H3.3 chaperone HIRA (Histone Regulator A) results in impaired plant survival, suggesting that HIRA and ATRX function in complementary histone deposition pathways. Indeed, ATRX loss of function alters cellular histone H3.3 pools and in consequence modulates the H3.1/H3.3 balance in the cell. H3.3 levels are affected especially at genes characterized by elevated H3.3 occupancy, including the 45S ribosomal DNA (45S rDNA) loci, where loss of ATRX results in altered expression of specific 45S rDNA sequence variants. At the genome-wide scale, our data indicate that ATRX modifies gene expression concomitantly to H3.3 deposition at a set of genes characterized both by elevated H3.3 occupancy and high expression. Together, our results show that ATRX is involved in H3.3 deposition and emphasize the role of histone chaperones in adjusting genome expression.
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http://dx.doi.org/10.1105/tpc.16.00877DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5559740PMC
July 2017

The histone chaperone complex HIR maintains nucleosome occupancy and counterbalances impaired histone deposition in CAF-1 complex mutants.

Plant J 2015 Mar;81(5):707-22

Génétique, Reproduction et Développement, CNRS UMR 6293, Clermont Université, INSERM U1103, 24 Avenue des Landais, BP 80026, Aubière Cedex, 63171, France.

Chromatin organization is essential for coordinated gene expression, genome stability, and inheritance of epigenetic information. The main components involved in chromatin assembly are specific complexes such as Chromatin Assembly Factor 1 (CAF-1) and Histone Regulator (HIR), which deposit histones in a DNA synthesis-dependent or -independent manner, respectively. Here, we characterize the role of the plant orthologs Histone Regulator A (HIRA), Ubinuclein (UBN) and Calcineurin Binding protein 1 (CABIN1), which constitute the HIR complex. Arabidopsis loss-of-function mutants for the various subunits of the complex are viable, but hira mutants show reduced fertility. We show that loss of HIRA reduces extractable histone H3 protein levels and decreases nucleosome occupancy at both actively transcribed genes and heterochromatic regions. Concomitantly, HIRA contributes to maintenance of silencing of pericentromeric repeats and certain transposons. A genetic analysis based on crosses between mutants deficient in subunits of the CAF-1 and HIR complexes showed that simultaneous loss of both the CAF-1 and HIR histone H3 chaperone complexes severely affects plant survival, growth and reproductive development. Our results suggest that HIRA partially rescues impaired histone deposition in fas mutants to preserve nucleosome occupancy, implying plasticity in histone variant interaction and deposition.
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http://dx.doi.org/10.1111/tpj.12758DOI Listing
March 2015

Gene targeting in maize by somatic ectopic recombination.

Plant Biotechnol J 2013 Apr 24;11(3):305-14. Epub 2012 Oct 24.

Biogemma, Centre de Recherche de Chappes, Chappes, France.

Low transformation efficiency and high background of non-targeted events are major constraints to gene targeting in plants. We demonstrate here applicability in maize of a system that reduces the constraint from transformation efficiency. The system requires regenerable transformants in which all of the following elements are stably integrated in the genome: (i) donor DNA with the gene of interest adjacent to sequence for repair of a defective selectable marker, (ii) sequence encoding a rare-cutting endonuclease such as I-SceI, (iii) a target locus (TL) comprising the defective selectable marker and I-SceI cleavage site. Typically, this requires additional markers for the integration of the donor and target sequences, which may be assembled through cross-pollination of separate transformants. Inducible expression of I-SceI then cleaves the TL and facilitates homologous recombination, which is assayed by selection for the repaired marker. We used bar and gfp markers to identify assembled transformants, a dexamethasone-inducible I-SceI::GR protein, and selection for recombination events that restored an intact nptII. Applying this strategy to callus permitted the selection of recombination into the TL at a frequency of 0.085% per extracted immature embryo (29% of recombinants). Our results also indicate that excision of the donor locus (DL) through the use of flanking I-SceI cleavage sites may be unnecessary, and a source of unwanted repair events at the DL. The system allows production, from each assembled transformant, of many cells that subsequently can be treated to induce gene targeting. This may facilitate gene targeting in plant species for which transformation efficiencies are otherwise limiting.
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http://dx.doi.org/10.1111/pbi.12014DOI Listing
April 2013

The nuclear genome of a Drosophila mutant strain increases the frequency of rearranged mitochondrial DNA molecules.

Curr Genet 2002 Feb 25;40(5):345-54. Epub 2002 Jan 25.

Equipe Génome Mitochondrial, UMR CNRS 6547, Université Blaise-Pascal, Clermont 2, 63177 Aubière Cedex, France.

We studied a mutant strain of Drosophila subobscura, in which 80% of the mitochondrial genomes (mtDNA) have lost over 30% of the coding region. The mutation is stable and is transmitted identically to offspring. The putative role of the mutant nuclear genome in the production of rearranged mtDNA was investigated using reciprocal crosses, to place the mitochondria of the wild strain in a mutant nuclear context. Nested PCR was used to screen for rearrangements in different regions of mtDNA; and rearrangements were detected in some individuals from the F6 generation. The frequency of these deleted mtDNAs then increased progressively in the population; and they were present in nearly all individuals in the F11 generation. They were not transmissible. Direct repeats were present at the deletion boundaries. These mutated genomes disappeared on reversion to a wild-type nuclear genome. Deletions were detected in a very small fraction of the wild population (0.7% of individuals). The mutant nuclear genome therefore does not promote a particular deletion but increases the frequency of different mtDNA rearrangements. The potential involvement of different candidate nuclear genes is discussed.
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http://dx.doi.org/10.1007/s00294-001-0265-8DOI Listing
February 2002

The nuclear genome is involved in heteroplasmy control in a mitochondrial mutant strain of Drosophila subobscura.

Eur J Biochem 2002 Feb;269(3):998-1005

Equipe Génome Mitochondrial, UMR CNRS 6547, Université Blaise Pascal-Clermont II, Aubière, France.

Most (78%) mitochondrial genomes in the studied mutant strain of Drosophila subobscura have undergone a large-scale deletion (5 kb) in the coding region. This mutation is stable, and is transmitted intact to the offspring. This animal model of major rearrangements of mitochondrial genomes can be used to analyse the involvement of the nuclear genome in the production and maintenance of these rearrangements. Successive backcrosses between mutant strain females and wild-type males yield a biphasic change in heteroplasmy level: (a) a 5% decrease in mutated genomes per generation (from 78 to 55%), until the nuclear genome is virtually replaced by the wild-type genome (seven to eight crosses); and (b) a continuous decrease of 0.5% per generation when the nuclear context is completely wild-type. In parallel with these changes, NADH dehydrogenase activity, which is halved in the mutant strain (five subunits of this complex are affected by the mutation), gradually increases and stabilizes near the wild-type activity. A return to a nuclear context is accompanied by the opposite phenomena: progressive increase in heteroplasmy level and stabilization at the value seen in the wild-type strain and a decrease in the activity of complex I. These results indicate that the nuclear genome plays an important role in the control of heteroplasmy level and probably in the production of rearranged genomes.
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http://dx.doi.org/10.1046/j.0014-2956.2001.02737.xDOI Listing
February 2002