Sirt1 Activation With Neuroheal Is Neuroprotective But Sirt2 Inhibition With Ak7 Is Detrimental For Disconnected Motoneurons

Sirtuin 1 (SIRT1) activity is neuroprotective, and we have recently demonstrated its role in the retrograde degenerative process in motoneurons (MNs) in the spinal cord of rats after peripheral nerve root avulsion (RA) injury SIRT2 has been suggested to exert effects opposite those of SIRT1, however, its roles in neurodegeneration and neuron response after nerve injury remain unclear Here we compared the neuroprotective potentials of SIRT1 activation and SIRT2 inhibition in a mouse model of hypoglossal nerve axotomy This injury induced a reduction of around half MN population within the hypoglossal nucleus by a non apoptotic neurodegenerative process triggered by endoplasmic reticulum (ER) stress that resulted in activation of the unfolded protein response mediated by IREI alpha and XBP1 by 21 days post injury Both SIRT1 activation with NeuroHeal and SIRT2 inhibition with AK7 protected NSC-34 motor neuron like cells against ER stress in vitro. In agreement with the in vitro results, NeuroHeal treatment or SIRT1 overexpression was neuroprotective of axotomized hypoglossal MNs in a transgenic mouse model In contrast, AK7 treatment or SIRT2 genetic depletion in mice inhibited damaged. MN survival To resolve the in vitro/in vivo discrepancies, we used an organotypic spinal cord culture system that preserves glial cells In this system, AK7 treatment of ER stressed organotypic cultures was detrimental for MNs and increased microglial nuclear factor-kB and the consequent transcription of cytotoxic pro inflammatory factors similarly The results highlight the importance of glial cells in determining the neuroprotective impact of any treatment

Dynamics and dispensability of variant-specific histone H1 Lys-26/Ser-27 and Thr-165 post-translational modifications

Jean-Michel Terme et al.In mammals, the linker histone H1, involved in DNA packaging into chromatin, is represented by a family of variants. H1 tails undergo post-translational modifications (PTMs) that can be detected by mass spectrometry. We developed antibodies to analyze several of these as yet unexplored PTMs including the combination of H1.4 K26 acetylation or trimethylation and S27 phosphorylation. H1.2-T165 phosphorylation was detected at S and G2/M phases of the cell cycle and was dispensable for chromatin binding and cell proliferation; while the H1.4-K26 residue was essential for proper cell cycle progression. We conclude that histone H1 PTMs are dynamic over the cell cycle and that the recognition of modified lysines may be affected by phosphorylation of adjacent residues. © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) and European Regional Development Fund (Grant BFU2011-23057 to A.J., and Grant BFU2008-00460 to P.S.), and by the Regional Government of Catalonia (Generalitat de Catalunya; Grant 2009-SGR-1222 to A.J.). J.-M.T. received a JAE-Doc contract from the Spanish National Research Council (CSIC)-MICINN; R.M. a TA contract from CSIC-MICINN; and L.M.-A. an FPU predoctoral fellowship from MICINNPeer Reviewe

Dynamics and dispensability of variant-specific histone H1 Lys-26/Ser-27 and Thr-165 post-translational modifications

Jean-Michel Terme et al.In mammals, the linker histone H1, involved in DNA packaging into chromatin, is represented by a family of variants. H1 tails undergo post-translational modifications (PTMs) that can be detected by mass spectrometry. We developed antibodies to analyze several of these as yet unexplored PTMs including the combination of H1.4 K26 acetylation or trimethylation and S27 phosphorylation. H1.2-T165 phosphorylation was detected at S and G2/M phases of the cell cycle and was dispensable for chromatin binding and cell proliferation; while the H1.4-K26 residue was essential for proper cell cycle progression. We conclude that histone H1 PTMs are dynamic over the cell cycle and that the recognition of modified lysines may be affected by phosphorylation of adjacent residues. © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) and European Regional Development Fund (Grant BFU2011-23057 to A.J., and Grant BFU2008-00460 to P.S.), and by the Regional Government of Catalonia (Generalitat de Catalunya; Grant 2009-SGR-1222 to A.J.). J.-M.T. received a JAE-Doc contract from the Spanish National Research Council (CSIC)-MICINN; R.M. a TA contract from CSIC-MICINN; and L.M.-A. an FPU predoctoral fellowship from MICINNPeer Reviewe

Advancing Key Gaps in the Knowledge of Plasmodium vivax Cryptic Infections Using Humanized Mouse Models and Organs-on-Chips

Plasmodium vivax is the most widely distributed human malaria parasite representing 36.3% of disease burden in the South-East Asia region and the most predominant species in the region of the Americas. Recent estimates indicate that 3.3 billion of people are under risk of infection with circa 7 million clinical cases reported each year. This burden is certainly underestimated as the vast majority of chronic infections are asymptomatic. For centuries, it has been widely accepted that the only source of cryptic parasites is the liver dormant stages known as hypnozoites. However, recent evidence indicates that niches outside the liver, in particular in the spleen and the bone marrow, can represent a major source of cryptic chronic erythrocytic infections. The origin of such chronic infections is highly controversial as many key knowledge gaps remain unanswered. Yet, as parasites in these niches seem to be sheltered from immune response and antimalarial drugs, research on this area should be reinforced if elimination of malaria is to be achieved. Due to ethical and technical considerations, working with the liver, bone marrow and spleen from natural infections is very difficult. Recent advances in the development of humanized mouse models and organs-on-a-chip models, offer novel technological frontiers to study human diseases, vaccine validation and drug discovery. Here, we review current data of these frontier technologies in malaria, highlighting major challenges ahead to study P. vivax cryptic niches, which perpetuate transmission and burden

Chromatin regulation by Histone H4 acetylation at Lysine 16 during cell death and differentiation in the myeloid compartment

Histone H4 acetylation at Lysine 16 (H4K16ac) is a key epigenetic mark involved in gene regulation, DNA repair and chromatin remodeling, and though it is known to be essential for embryonic development, its role during adult life is still poorly understood. Here we show that this lysine is massively hyperacetylated in peripheral neutrophils. Genome-wide mapping of H4K16ac in terminally differentiated blood cells, along with functional experiments, supported a role for this histone post-translational modification in the regulation of cell differentiation and apoptosis in the hematopoietic system. Furthermore, in neutrophils, H4K16ac was enriched at specific DNA repeats. These DNA regions presented an accessible chromatin conformation and were associated with the cleavage sites that generate the 50 kb DNA fragments during the first stages of programmed cell death. Our results thus suggest that H4K16ac plays a dual role in myeloid cells as it not only regulates differentiation and apoptosis, but it also exhibits a non-canonical structural role in poising chromatin for cleavage at an early stage of neutrophil cell death

Paper de SirT2 en el control epigenètic de la mitosi

La cromatina és una estructura nucleoproteica, dinàmica i jeràrquicament organitzada dins del nucli cel•Iular. La seva estructura, organització i funció està controlada al llarg del cicle cel.lular, per processos epigenètics que produeixen canvis heretables que no afecten la seqüència de DNA. Entre aquests canvis es troben la metilació del DNA, les modificacions postraduccionals de les histones i desplegament de la cromatina orquestrat pels complexes remodeladors i proteïnes estructurals. Les modificacions postraduccionals de les histones es donen principalment de forma dinàmica i regulada a l'extrem N-terminal, canviant la seva càrrega i funció. Entre les diferents modificacions descrites, l'acetilació i la metilació de les histones H3 i H4, semblen tenir una importància especial sobre l'estructura i estat de la cromatina. En particular, l'acetilació de la lisina 16 de la histona H4 (H4K16Ac) per se impedeix la formació d'estructures compactes de cromatina. D'aquesta manera, s'associa l'estat desacetilat d'aquest residu a zones d'heterocromatina i transcripcionalment inactives, mentre que la hiperacetilació d'H4K16 està estretament vinculada a zones eucromàtiques i transcripcionalmentactives. La dinàmica d'acetilació-desacetiIació d' H 4K 16 està controlada principalment per l'equilibri de les activitats acetiltransferasa de MOF i desacetilasa de Si rT1 i Si rT2. Per tant, aquests dos grups d'enzims són essencials per el control de l'expressió gènica i de l'arquitectura de la cromatina dins del nucli, regulant la transició entre l'estat transcripcionalment actiu i inactiu de la cromatina. MOF és crucial per el desenvolupament embrionari , I a reparació del DNA i la progressió del cicle cel .lular, i la seva pèrdua està associada a l'augment de les aberracions cromosòmiques, a l'aturada del cicle cel.lular en G2/M i a l'augment de la inestabilitat genòmica. SirT1 i Si rT2 pertanyen a la classe III de desacetilases d'histones (HDACs), conegudes com sirtuïnes, i són crucials per el manteniment de la integritat genòmica, l'adaptació a l'entorn i l'envelliment, entre altres funcions. No obstant, dels set membres de sirtuïnes presents a mamífers, només Si rT2 i en menor mesura SirT1, han estat vinculades amb el control del cicle cel.lular. Concretament, Si rT2, tot i ser principalment citoplasmàtica, és transportada al nucli durant I a transició G2/M , moment en el que a través de la desacetilació d'H4K16 permet la monometilació d'H4K20 per PR-SET7 (la monometiI transferasa d'H4K20), determinant els nivells d'H4K2Ome2,3 en la resta del cicle cel.lular. Com a conseqüència, SirT2 està implicat en processos estrictament associat a aquestes modificacions, com la compactació dels cromosomes metafàsics, Ia progressió a través de mitosi, la replicació i reparació del DNA o la formació de l'heterocromatina. Fins al moment el paper de Si rT2 en el control de I a progressió a través de la mitosi ha estat atribuït a la regulació de diferents substrats. En particular, el control d'H4K2Ome1 dependent de SirT2 ha estat relacionat amb l'activació del checkpoint de G2/M en resposta a estrès, tot i que els mecanismes involucrats en l'aturada del cicle cel.lular eren del tot desconeguts. En aquest treball hem volgut indagar sobre com Si rT2 regula la transició G2/M i la seva coordinació amb la maquinària regulatória del checkpoint. Les nostres dades semblen indicar que SirT2 condueix a l'activació del checkpoint de G2/M a través de la regulació d' H4K 1 6Ac, H4K2Ome1 i el control de I a transcripció de gens relacionats amb el cicle cel.lular. Es descriu per primera vegada, com SirT2 controla H4K16Ac a través de la regulació de l'activitat i de l'estabilitat proteica de MOF durant G2/M. Concretament, SirT2 desacetila MOF durant G2/M i en promou la sortida de la cromatina, la inactivació i degradació, afavorint l'estat desacetilat d'H4K16 i la monometilació d'H4K20. En concordança, hem vist que MOF controla negativament la presència de PR-SET7 a la cromatina, mantenint així uns nivells adequats d'H4K2Omel abans d'entrar a mitosi i evitant la condensació prematura dels cromosomes. El nostre estudi suggereix que la interconnexió entre SirT2 i MOF està directament implicada en el control epigenètic del cicle cel.lular, contribuint al manteniment de l'estabilitat genòmica.Chromatin is a dynamical structure hierarchically organized to fit inside the nucleus. The structure, organization and function of chromatin are tightly controlled throughout the cell cycle by different epigenetic mechanisms, including DNA methylation and histone modifications. The histone post-translational modifications occur mainly in their N-terminal tail, and give rise to changes in the charge and function of the protein. Among the different histone modifications, lysine acetylation (K) is one of the best characterized. Acetylation of lysine 16 of histone H4 is the most frequently acetylated residue in eukaryotes and is a key regulator of high orders of chromatin structure. Thus, the deacetylated state of this residue is associated with heterochromatic and transcriptional inactive regions, whereas the acetylated form is found in euchromatic and transcriptional active regions. The dynamics of this histone mark is mainly governed by the acetyltransferase MOF and the NAD±-dependent deacetylases SirT1 and SirT2, which makes both groups of enzymes essential for the regulation of the gene expression and the control of chromatin organization. MOF is crucial in embryogenesis, DNA repair and the cell cycle progression. In fact, loss of MOF has been shown to induce cell cycle arrest during G2/M transition, increased chromosomal aberrations and genome instability. SirT 1 and SirT2 belong to Class III of histone deacetylases (HDACs), commonly referred as sirtuins. They play a key role in stress response, and in particular in protecting genome integrity. Among the seven mammalian sirtuins (SirT1-7), only SirT2 and to a lesser extend SirT1, have been linked with cell cycle regulation. In particular, SirT2, which mainly localizes to the cytoplasm during most of the cell cycle, shuttles to the nucleus in G2/M transition, where deacetylates H4K16Ac driving, among other things, H4K2Omel deposition by the histone methyltransferase PR-SETT. The control of H4K2Omel deposition determines the levels of H4K2Ome2,3 in the next cell cycle, which links SirT2 to the regulation of DNA replication and repair, as well as heterochromatin formation. Work from our group and others have shown that SirT2 plays a role in the control of mitosis progression. In particular, SirT2 is required for the cell cycle arrest in the G2/M checkpoint during stress response, process that has been related to SirT2-dependent regulation of H4K2Omel. However, the mechanisms behind the cell cycle arrest are still undefined. In the present work we aimed to elucidate the function of SirT2 in G2/M transition and its coordination with the checkpoint regulatory machinery. Our results seem indicate that SirT2 drives the G2/M checkpoint activation through the regulation of H4K16Ac, H4K2Omel and the control of the expression of cell cycle related genes. We also describe for the first time, a complementary mechanism whereby SirT2 regulates the levels of H4K16Ac during mitosis. We observe that SirT2 not only deacetylates MOF during G2/M, suppressing its acetyltransferase activity, but also induces both chromatin eviction and degradation of MOF. This in turn, results in H4K16 hypoacetylation and subsequent monomethylation of H4K20. Additionally, we show that MOF inhibits PR-SETT chromatin localization, maintaining the appropriate levels of H4K2Omel before entering mitosis and avoiding premature chromosome condensation. Our study suggests that the crosstalk between MOF and SirT2 is directly involved in the epigenetic control of the cell cycle, contributing to the maintenance of genome stability

Escaping the immune system by DNA repair and recombination in African trypanosomes

International audienceAfrican trypanosomes escape the mammalian immune response by antigenic variation-the periodic exchange of one surface coat protein, in Trypanosoma brucei the variant surface glycoprotein (VSG), for an immunologically distinct one. VSG transcription is monoallelic, with only one VSG being expressed at a time from a specialized locus, known as an expression site. VSG switching is a predominantly recombination-driven process that allows VSG sequences to be recombined into the active expression site either replacing the currently active VSG or generating a 'new' VSG by segmental gene conversion. In this review, we describe what is known about the factors that influence this process, focusing specifically on DNA repair and recombination

SHERLOCK4HAT: A CRISPR-based tool kit for diagnosis of Human African Trypanosomiasis

International audienceBackgroundTo achieve elimination of Human African Trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense (gHAT), the development of highly sensitive diagnostics is needed. We have developed a CRISPR based diagnostic for HAT using SHERLOCK (Specific High-sensitivity Enzymatic Reporter unLOCKing) that is readily adaptable to a field-based setting.MethodsWe adapted SHERLOCK for the detection of T. brucei species. We targeted 7SLRNA, TgSGP and SRA genes and tested SHERLOCK against RNA from blood, buffy coat, dried blood spots (DBS), and clinical samples.FindingsThe pan-Trypanozoon 7SLRNA and T. b. gambiense-specific TgSGP SHERLOCK assays had a sensitivity of 0.1 parasite/μL and a limit of detection 100 molecules/μL. T. b. rhodesiense-specific SRA had a sensitivity of 0.1 parasite/μL and a limit of detection of 10 molecules/μL. TgSGP SHERLOCK and SRA SHERLOCK detected 100% of the field isolated strains. Using clinical specimens from the WHO HAT cryobank, the 7SLRNA SHERLOCK detected trypanosomes in gHAT samples with 56.1%, 95% CI [46.25–65.53] sensitivity and 98.4%, 95% CI [91.41–99.92] specificity, and rHAT samples with 100%, 95% CI [83.18–100] sensitivity and 94.1%, 95% CI [80.91–98.95] specificity. The species-specific TgSGP and SRA SHERLOCK discriminated between the gambiense/rhodesiense HAT infections with 100% accuracy.InterpretationThe 7SLRNA, TgSGP and SRA SHERLOCK discriminate between gHAT and rHAT infections, and could be used for epidemiological surveillance and diagnosis of HAT in the field after further technical development

Sirt1 Activation With Neuroheal Is Neuroprotective But Sirt2 Inhibition With Ak7 Is Detrimental For Disconnected Motoneurons

Sirtuin 1 (SIRT1) activity is neuroprotective, and we have recently demonstrated its role in the retrograde degenerative process in motoneurons (MNs) in the spinal cord of rats after peripheral nerve root avulsion (RA) injury SIRT2 has been suggested to exert effects opposite those of SIRT1, however, its roles in neurodegeneration and neuron response after nerve injury remain unclear Here we compared the neuroprotective potentials of SIRT1 activation and SIRT2 inhibition in a mouse model of hypoglossal nerve axotomy This injury induced a reduction of around half MN population within the hypoglossal nucleus by a non apoptotic neurodegenerative process triggered by endoplasmic reticulum (ER) stress that resulted in activation of the unfolded protein response mediated by IREI alpha and XBP1 by 21 days post injury Both SIRT1 activation with NeuroHeal and SIRT2 inhibition with AK7 protected NSC-34 motor neuron like cells against ER stress in vitro. In agreement with the in vitro results, NeuroHeal treatment or SIRT1 overexpression was neuroprotective of axotomized hypoglossal MNs in a transgenic mouse model In contrast, AK7 treatment or SIRT2 genetic depletion in mice inhibited damaged. MN survival To resolve the in vitro/in vivo discrepancies, we used an organotypic spinal cord culture system that preserves glial cells In this system, AK7 treatment of ER stressed organotypic cultures was detrimental for MNs and increased microglial nuclear factor-kB and the consequent transcription of cytotoxic pro inflammatory factors similarly The results highlight the importance of glial cells in determining the neuroprotective impact of any treatment