ORCID Profile
0000-0002-2207-2473
Current Organisation
Babraham Institute
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Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243795
Abstract: Context. The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, α , through measurements along the line of sight of a bright quasar with a precision of 1.36 ppm at 1 σ level. This imposes new constraints on cosmological models with a varying α . We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of α with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. Aims. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. Methods. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. Results. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a ΛCDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound. Conclusions. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of α as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of α resulting mostly from the strong MICROSCOPE limits.
Publisher: Oxford University Press (OUP)
Date: 23-06-2022
DOI: 10.1093/GBE/EVAC094
Abstract: Genomic imprinting is found in marsupial and eutherian mammals, but not in monotremes. While the primary regulator of genomic imprinting in eutherians is differential DNA methylation between parental alleles, conserved imprinted genes in marsupials tend to lack DNA methylation at their promoters. DNA methylation at eutherian imprinted genes is mainly catalyzed by a DNA methyltransferase (DNMT) enzyme, DNMT3A. There are two isoforms of eutherian DNMT3A: DNMT3A and DNMT3A2. DNMT3A2 is the primary isoform for establishing DNA methylation at eutherian imprinted genes and is essential for eutherian genomic imprinting. In this study, we investigated whether DNMT3A2 is also present in the two other mammalian lineages, marsupials and monotremes. We identified DNMT3A2 in both marsupials and monotremes, although imprinting has not been identified in monotremes. By analyzing genomic sequences and transcriptome data across vertebrates, we concluded that the evolution of DNMT3A2 occurred in the common ancestor of mammals. In addition, DNMT3A/3A2 gene and protein expression during gametogenesis showed distinct sexual dimorphisms in a marsupial, the tammar wallaby, and this pattern coincided with the sex-specific DNA methylation reprogramming in this species as it does in mice. Our results show that DNMT3A2 is present in all mammalian groups and suggests that the basic DNMT3A/3A2-based DNA methylation mechanism is conserved at least in therian mammals.
Publisher: The Royal Society
Date: 17-10-2022
Abstract: The evolution of a placenta requires several steps including changing the timing of reproductive events, facilitating nutrient exchange, and the capacity for maternal–fetal communication. To understand the evolution of maternal–fetal communication, we used ligand-receptor gene expression as a proxy for the potential for cross-talk in a live-bearing lizard ( Pseudemoia entrecasteauxii ) and homologous tissues in a related egg-laying lizard ( L ropholis guichenot i ). Approximately 70% of expressed ligand/receptor genes were shared by both species. Gene ontology (GO) analysis showed that there was no GO-enrichment in the fetal membranes of the egg-laying species, but live-bearing fetal tissues were significantly enriched for 50 GO-terms. Differences in enrichment suggest that the evolution of viviparity involved reinforcing specific signalling pathways, perhaps to support fetal control of placentation. One identified change was in transforming growth factor beta signalling. Using immunohistochemistry, we show the production of the signalling molecule inhibin beta B (INHBB) occurs in viviparous fetal membranes but was absent in closely related egg-laying tissues, suggesting that the evolution of viviparity may have involved changes to signalling via this pathway. We argue that maternal–fetal signalling evolved through co-opting expressed signalling molecules and recruiting new signalling molecules to support the complex developmental changes required to support a fetus in utero . This article is part of the theme issue ‘Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom’.
Publisher: Frontiers Media SA
Date: 10-03-2022
DOI: 10.3389/FCELL.2022.838684
Abstract: Genomic imprinting, parent-of-origin-specific gene expression, is controlled by differential epigenetic status of the parental chromosomes. While DNA methylation and suppressive histone modifications established during gametogenesis suppress imprinted genes on the inactive allele, how and when the expressed allele gains its active status is not clear. In this study, we asked whether the active histone-3 lysine-4 trimethylation (H3K4me3) marks remain at paternally expressed genes (PEGs) in sperm and embryos before and after fertilization using published data. Here we show that mouse sperm had the active H3K4me3 at more than half of known PEGs, and these genes were present even after fertilization. Using reciprocal cross data, we identified 13 new transient PEGs during zygotic genome activation. Next, we confirmed that the 12 out of the 13 new transient PEGs were associated with the paternal H3K4me3 in sperm. Nine out of the 12 genes were associated with the paternal H3K4me3 in zygotes. Our results show that paternal H3K4me3 marks escape inactivation during the histone-to-protamine transition that occurs during sperm maturation and are present in embryos from early zygotic stages up to implantation.
Publisher: Bioscientifica
Date: 03-03-2023
DOI: 10.1530/REP-22-0286
Abstract: Apart from mice, meiosis initiation factors and their transcriptional regulation mechanisms are largely unknown in mammals. This study suggests that STRA8 and MEIOSIN are both meiosis initiation factors in mammals, but their transcription is epigenetically regulated differently from each other. In the mouse, the timing of meiosis onset differs between sexes due to the sex-specific regulation of the meiosis initiation factors, STRA8 and MEIOSIN. Before the initiation of meiotic prophase I, the Stra8 promoter loses suppressive histone-3-lysine-27 trimethylation (H3K27me3) in both sexes, suggesting that H3K27me3-associated chromatin remodelling may be responsible for activating STRA8 and its co-factor MEIOSIN . Here we examined MEIOSIN and STRA8 expression in a eutherian (the mouse), two marsupials (the grey short-tailed opossum and the tammar wallaby) and two monotremes (the platypus and the short-beaked echidna) to ask whether this pathway is conserved between all mammals. The conserved expression of both genes in all three mammalian groups and of MEIOSIN and STRA8 protein in therian mammals suggests that they are the meiosis initiation factors in all mammals. Analyses of published DNase-seq and chromatin-immunoprecipitation sequencing (ChIP-seq) data sets confirmed that H3K27me3-associated chromatin remodelling occurred at the STRA8, but not the MEIOSIN, promoter in therian mammals. Furthermore, culturing tammar ovaries with an inhibitor of H3K27me3 demethylation before meiotic prophase I affected STRA8 but not MEIOSIN transcriptional levels. Our data suggest that H3K27me3-associated chromatin remodelling is an ancestral mechanism that allows STRA8 expression in mammalian pre-meiotic germ cells.
Publisher: Pensoft Publishers
Date: 25-02-2019
DOI: 10.3897/JHR.68.30372
Abstract: Woodwasps (Hymenoptera: Siricidae) are saproxylic insects and a common forest pest. Siricid woodwasps are classified into two subfamilies: Siricinae and Tremecinae. All known symbiotic fungi of Siricinae are in the genus Amylostereum Boidin while some species of Tremecinae have been observed to have a relationship with the fungus Cerrenaunicolor (Bull.) Murrill. Previous studies about the host searching behavior of woodwasps and their parasitoids have focused primarily on the subfamily Siricinae. We analyzed the role of C.unicolor volatiles on the host searching behavior of Tremexapicalis Matsumura (Hymenoptera: Siricidae: Tremecinae) and its parasitoid Ibalia (Tremibalia) japonica Matsumura (Hymenoptera: Ibaliidae). The results of an olfactory response experiment indicated that the females of T.apicalis and its parasitoid find their respective hosts using volatiles from C.unicolor . Using DNA barcode, we identified basidiocarps on the trees infested with T.apicalis. The basidiocarps were all white-rot fungi that cause sapwood decay, including C.unicolor . Two additional species that we identified belonged to genera closely related to C.unicolor . Woodwasp species are known to carry symbiotic fungi in a pair of specialized sacs called mycangia. Notably we found that mycangia-like structures were absent in the abdomens of T.apicalis females. To the best of our knowledge, Xerisspectrum (Linnaeus) (Hymenoptera: Siricidae) is the only reported ex le of woodwasp species that do not contain symbiotic fungi in their bodies. Our results suggested that: (1) T.apicalis females search for host wood that is already infected with sapwood decaying fungus using volatile compounds (2) T.apicalis ’ female parasitoid also uses volatile compounds from fungus to locate wood that is infested with its potential host.
Publisher: Oxford University Press (OUP)
Date: 07-12-2018
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.IBMB.2017.08.008
Abstract: Insect cellular immune reactions differ depending on the target species. Phagocytosis is activated to scavenge microorganisms such as bacteria and fungi. On the other hand, larger invaders such as parasitoid wasps are eliminated by activation of encapsulation. In this study, we hypothesized that novel determinants regulate cellular immunities independent of surface molecular pattern recognition involving pattern recognition receptors (PRRs). Immune-related genes differentially expressed depending on the treated material size were screened in larval hemocytes of the rice armyworm, Mythimna separata. Consequently, we identified a novel C-type lectin gene up-regulated by injection of large beads but not small beads of identical material. Examination of in vitro effect of the recombinant protein on the immune reactions clarified that the protein activated encapsulation reaction, while it suppressed phagocytosis. These results suggest that this novel C-type lectin designated "encapsulation promoting lectin (EPL)" regulates cellular immunity by a novel immune target size-recognition mechanism.
Publisher: Springer Science and Business Media LLC
Date: 27-08-2022
DOI: 10.1186/S13072-022-00465-4
Abstract: The eutherian IGF2R imprinted domain is regulated by an antisense long non-coding RNA, Airn , which is expressed from a differentially methylated region (DMR) in mice. Airn silences two neighbouring genes, Solute carrier family 22 member 2 ( Slc22a2) and Slc22a3 , to establish the Igf2r imprinted domain in the mouse placenta. Marsupials also have an antisense non-coding RNA, ALID , expressed from a DMR, although the exact function of ALID is currently unknown. The eutherian IGF2R DMR is located in intron 2, while the marsupial IGF2R DMR is located in intron 12, but it is not yet known whether the adjacent genes SLC22A2 and/or SLC22A3 are also imprinted in the marsupial lineage. In this study, the imprinting status of marsupial SLC22A2 and SLC22A3 in the IGF2R imprinted domain in the chorio-vitelline placenta was examined in a marsupial, the tammar wallaby. In the tammar placenta, SLC22A3 but not SLC22A2 was imprinted. Tammar SLC22A3 imprinting was evident in placental tissues but not in the other tissues examined in this study. A putative promoter of SLC22A3 lacked DNA methylation, suggesting that this gene is not directly silenced by a DMR on its promoter as seen in the mouse. Based on immunofluorescence, we confirmed that the tammar SLC22A3 is localised in the endodermal cell layer of the tammar placenta where nutrient trafficking occurs. Since SLC22A3 is imprinted in the tammar placenta, we conclude that this placental imprinting of SLC22A3 has been positively selected after the marsupial and eutherian split because of the differences in the DMR location. Since SLC22A3 is known to act as a transporter molecule for nutrient transfer in the eutherian placenta, we suggest it was strongly selected to control the balance between supply and demand of nutrients in marsupial as it does in eutherian placentas.
Publisher: Bioscientifica
Date: 03-2021
DOI: 10.1530/REP-20-0634
Abstract: Male germ cells undergo two consecutive processes – pre-spermatogenesis and spermatogenesis – to generate mature sperm. In eutherian mammals, epigenetic information such as DNA methylation is dynamically reprogrammed during pre-spermatogenesis, before and during mitotic arrest. In mice, by the time germ cells resume mitosis, the majority of DNA methylation is reprogrammed. The tammar wallaby has a similar pattern of germ cell global DNA methylation reprogramming to that of the mouse during early pre-spermatogenesis. However, early male germline development in the tammar or in any marsupial has not been described previously, so it is unknown whether this is a general feature regulating male germline development or a more recent phenomenon in mammalian evolutionary history. To answer this, we examined germ cell nuclear morphology and mitotic arrest during male germline development in the tammar wallaby ( Macropus eugenii ), a marsupial that erged from mice and humans around 160 million years ago. Tammar pro-spermatogonia proliferated after birth and entered mitotic arrest after day 30 postpartum (pp). At this time, they began moving towards the periphery of the testis cords and their nuclear size increased. Germ cells increased in number after day 100 pp which is the time that DNA methylation is known to be re-established in the tammar. This is similar to the pattern observed in the mouse, suggesting that resumption of germ cell mitosis and the timing of DNA methylation reprogramming are correlated and conserved across mammals and over long evolutionary timescales.
Publisher: Pensoft Publishers
Date: 28-10-2016
DOI: 10.3897/JHR.52.10060
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Teruhito Ishihara.