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The histone variant H3.3 is encoded by two distinct genes, H3f3a and H3f3b, exhibiting identical amino-acid sequence. H3.3 is required for spermatogenesis, but the molecular mechanism of its spermatogenic function remains obscure. Here, we have studied the role of each one of H3.3A and H3.3B proteins in spermatogenesis. We have generated transgenic conditional knock-out/knock-in (cKO/KI) epitope-tagged FLAG-FLAG-HA-H3.3B (H3.3BHA) and FLAG-FLAG-HA-H3.3A (H3.3AHA) mouse lines. We show that H3.3B, but not H3.3A, is required for spermatogenesis and male fertility. Analysis of the molecular mechanism unveils that the absence of H3.3B led to alterations in the meiotic/post-meiotic transition. Genome-wide RNA-seq reveals that the depletion of H3.3B in meiotic cells is associated with increased expression of the whole sex X and Y chromosomes as well as of both RLTR10B and RLTR10B2 retrotransposons. In contrast, the absence of H3.3B resulted in down-regulation of the expression of piRNA clusters. ChIP-seq experiments uncover that RLTR10B and RLTR10B2 retrotransposons, the whole sex chromosomes and the piRNA clusters are markedly enriched of H3.3. Taken together, our data dissect the molecular mechanism of H3.3B functions during spermatogenesis and demonstrate that H3.3B, depending on its chromatin localization, is involved in either up-regulation or down-regulation of expression of defined large chromatin regions.

Platelets, anucleated megakaryocyte (MK)-derived cells, play a major role in hemostasis and arterial thrombosis. Although protein kinase casein kinase 2 (CK2) is readily detected in MKs and platelets, the impact of CK2-dependent signaling on MK/platelet (patho-)physiology has remained elusive. The present study explored the impact of the CK2 regulatory β-subunit on platelet biogenesis and activation. MK/platelet-specific genetic deletion of CK2β (ck2β-/- ) in mice resulted in a significant macrothrombocytopenia and an increased extramedullar megakaryopoiesis with an enhanced proportion of premature platelets. Although platelet life span was only mildly affected, ck2β-/- MK displayed an abnormal microtubule structure with a drastically increased fragmentation within bone marrow and a significantly reduced proplatelet formation in vivo. In ck2β-/- platelets, tubulin polymerization was disrupted, resulting in an impaired thrombopoiesis and an abrogated inositol 1,4,5-triphosphate receptor-dependent intracellular calcium (Ca2+) release. Presumably due to a blunted increase in the concentration of cytosolic Ca2+, activation-dependent increases of α and dense-granule secretion and integrin αIIbβ3 activation, and aggregation were abrogated in ck2β-/- platelets. Accordingly, thrombus formation and stabilization under high arterial shear rates were significantly diminished, and thrombotic vascular occlusion in vivo was significantly blunted in ck2β-/- mice, accompanied by a slight prolongation of bleeding time. Following transient middle cerebral artery occlusion, ck2β-/- mice displayed significantly reduced cerebral infarct volumes, developed significantly less neurological deficits, and showed significantly better outcomes after ischemic stroke than ck2βfl/fl mice. The present observations reveal CK2β as a novel powerful regulator of thrombopoiesis, Ca2+-dependent platelet activation, and arterial thrombosis in vivo.

International audience; The discoid shape of resting platelets is maintained by a peripheral, circular bundle of microtubules called marginal band. Marginal band microtubules are acetylated on lysine 40 of the alpha-tubulin subunits. We have previously shown that the deacetylase HDAC6 is responsible for tubulin deacetylation in platelets and that the hyperacetylated state of the microtubules in HDAC6KO platelets correlates with faster activation/spreading kinetics, pointing to a regulatory role of this modification. So far, the question about the reverse enzyme, responsible for tubulin acetylation in platelets, has remained unanswered. Several enzymes have been described as having tubulin acetylation activity. Here we identify αTAT1 as the enzyme responsible for the acetylation of marginal band microtubules. We show that αTAT1 deficiency has only minor consequences for platelet production and function. A residual tubulin acetylation level in αTAT1 deficient platelet lysates suggests the presence of an additional tubulin-acetylating enzyme that is unable to acetylate marginal band microtubules.

Summary Recently discovered histone lysine acylation marks increase the functional diversity of nucleosomes well beyond acetylation. Here, we focus on histone butyrylation in the context of sperm cell differentiation. Specifically, we investigate the butyrylation of histone H4 lysine 5 and 8 at gene promoters where acetylation guides the binding of Brdt, a bromodomain-containing protein, thereby mediating stage-specific gene expression programs and post-meiotic chromatin reorganization. Genome-wide mapping data show that highly active Brdt-bound gene promoters systematically harbor competing histone acetylation and butyrylation marks at H4 K5 and H4 K8. Despite acting as a direct stimulator of transcription, histone butyrylation competes with acetylation, especially at H4 K5, to prevent Brdt binding. Additionally, H4 K5K8 butyrylation also marks retarded histone removal during late spermatogenesis. Hence, alternating H4 acetylation and butyrylation, while sustaining direct gene activation and dynamic bromodomain binding, could impact the final male epigenome features., Graphical Abstract, Highlights • Active gene TSSs are marked by competing H4 K5K8 acetylation and butyrylation • Histone butyrylation directly stimulates transcription • H4K5 butyrylation prevents binding of the testis specific gene expression-driver Brdt • H4K5K8 butyrylation is associated with delayed histone removal in spermatogenic cells, Histone butyrylation stimulates gene transcription while competing with acetylation at H4K5 to control Brdt bromodomain binding. Differential chromatin labeling with interchangeable H4 acylations is an important epigenetic regulatory mechanism controlling gene expression and chromatin reorganization.

Background Altering the biochemical makeup of chromatin by the incorporation of histone variants during development represents a key mechanism in regulating gene expression. The histone variant H2A.B, H2A.B.3 in mice, appeared late in evolution and is most highly expressed in the testis. In the mouse, it is encoded by three different genes. H2A.B expression is spatially and temporally regulated during spermatogenesis being most highly expressed in the haploid round spermatid stage. Active genes gain H2A.B where it directly interacts with polymerase II and RNA processing factors within splicing speckles. However, the importance of H2A.B for gene expression and fertility are unknown. Results Here, we report the first mouse knockout of this histone variant and its effects on fertility, nuclear organization, and gene expression. In view of the controversy related to the generation of off-target mutations by gene editing approaches, we test the specificity of TALENs by disrupting the H2A.B multi-copy gene family using only one pair of TALENs. We show that TALENs do display a high level of specificity since no off-target mutations are detected by bioinformatics analyses of exome sequences obtained from three consecutive generations of knockout mice and by Sanger DNA sequencing. Male H2A.B.3 knockout mice are subfertile and display an increase in the proportion of abnormal sperm and clogged seminiferous tubules. Significantly, a loss of proper RNA Pol II targeting to distinct transcription–splicing territories and changes to pre-mRNA splicing are observed. Conclusion We have produced the first H2A.B knockout mouse using the TALEN approach. Electronic supplementary material The online version of this article (10.1186/s13059-019-1633-3) contains supplementary material, which is available to authorized users.

Platelets, anucleated megakaryocyte (MK)-derived cells, play a major role in hemostasis and arterial thrombosis. Although protein kinase casein kinase 2 (CK2) is readily detected in MKs and platelets, the impact of CK2-dependent signaling on MK/platelet (patho-)physiology has remained elusive. The present study explored the impact of the CK2 regulatory β-subunit on platelet biogenesis and activation. MK/platelet-specific genetic deletion of CK2β (

International audience; Histone replacement by transition proteins (TPs) and protamines (Prms) constitutes an essential step for the successful production of functional male gametes, yet nothing is known on the underlying functional interplay between histones, TPs, and Prms. Here, by studying spermatogenesis in the absence of a spermatid-specific histone variant, H2A.L.2, we discover a fundamental mechanism involved in the transformation of nucleosomes into nucleoprotamines. H2A.L.2 is synthesized at the same time as TPs and enables their loading onto the nucleosomes. TPs do not displace histones but rather drive the recruitment and processing of Prms, which are themselves responsible for histone eviction. Altogether, the incorporation of H2A.L.2 initiates and orchestrates a series of successive transitional states that ultimately shift to the fully compacted genome of the mature spermatozoa. Hence, the current view of histone-to-nucleoprotamine transition should be revisited and include an additional step with H2A.L.2 assembly prior to the action of TPs and Prms.

S100A1 and S100B are induced by the SOX trio transcription factors (SOX9, SOX5, and SOX6) in chondrocytes, and inhibit their hypertrophic differentiation in culture. However, functional roles of S100A1 and S100B during in vivo skeletal development are yet to be determined. Here we show that mice deficient of both the S100a1 and S100b genes displayed normal skeletal growth from embryonic stage to adulthood. Although no compensatory upregulation of other S100 family members was observed in S100a1/S100b double mutants, the related S100a2, S100a4, S100a10, and S100a11 were expressed at similarly high levels to S100a1 and S100b in mouse primary chondrocytes. Furthermore, overexpression of these other S100 members suppressed the hypertrophic differentiation of chondrocytes in vitro as efficiently as S100A1 and S100B. Taken together, the present study demonstrates that S100A1 and S100B are dispensable for endochondral ossification during skeletal development, most likely because their deficiency may be masked by other S100 proteins which have similar functions to those of S100A1 and S100B.

SummaryWe report the identification of 67 previously undescribed histone modifications, increasing the current number of known histone marks by about 70%. We further investigated one of the marks, lysine crotonylation (Kcr), confirming that it represents an evolutionarily-conserved histone posttranslational modification. The unique structure and genomic localization of histone Kcr suggest that it is mechanistically and functionally different from histone lysine acetylation (Kac). Specifically, in both human somatic and mouse male germ cell genomes, histone Kcr marks either active promoters or potential enhancers. In male germinal cells immediately following meiosis, Kcr is enriched on sex chromosomes and specifically marks testis-specific genes, including a significant proportion of X-linked genes that escape sex chromosome inactivation in haploid cells. These results therefore dramatically extend the repertoire of histone PTM sites and designate Kcr as a specific mark of active sex chromosome-linked genes in postmeiotic male germ cells.

La perte des mécanismes de contrôle de la progression du cycle de division cellulaire ou du déclenchement des processus d’apoptose permet aux cellules d’acquérir des propriétés décisives pour leur transformation tumorale. Plusieurs protéine kinases participent à la transduction de signaux qui neutralisent des composants de la machinerie apoptotique. Dans ce contexte, la protéine kinase CK2 (caséine kinase 2), dont la structure vient d’être élucidée, apparaît comme un régulateur déterminant pour la viabilité cellulaire. Il est concevable que la surexpression de la CK2 observée dans les cancers puisse conduire à la formation de signaux de survie contribuant à la tumorigenèse., Protein kinase CK2 (formerly known as casein kinase 2) was among the first protein kinases to be identified and characterized. Surprisingly, in spite of intense efforts, the regulation and cellular functions of CK2 remain obscure. However, recent data on its molecular structure, its signal-mediated intracellular dynamic localization and its unexpected function in cell survival have raised new interest in this enzyme. These studies reveal unique features of CK2 and highlight its importance in the transduction of survival signals.

Vascular endothelial–cadherin (VE–cadherin) is exclusively expressed in endothelial cells and is strictly located at cell-to-cell junctions. As the other members of the cadherin family, VE–cadherin is able to mediate a homotypic type of cellular interaction in a Ca 2+ -dependent manner. In the mouse embryo, VE–cadherin transcripts are detected at the earliest stages of vascular development. To ascertain if VE–cadherin expression is required for the assembly of endothelial cells into vascular structures, we generated VE–cadherin -negative mouse embryonic stem cells ( VE–cadherin −/− ES cells) by gene targeting and examined the consequences on vascular development of ES-derived embryoid bodies (EBs). In contrast to wild-type EBs, we observed that endothelial cells remained dispersed and failed to organize a vessel-like pattern in VE–cadherin −/− ES-derived EBs. However, dispersed VE–cadherin −/− ES-derived endothelial cells expressed a large range of other endothelial markers. Moreover, the targeted null-mutation in the VE–cadherin locus did not interfere with the hematopoietic differentiation potential of ES cells. These in vitro experiments are consistent with a pivotal role of VE–cadherin in vascular structure assembly.

International audience; The conversion of male germ cell chromatin to a nucleoprotamine structure is fundamental to the life cycle, yet the underlying molecular details remain obscure. Here we show that an essential step is the genome-wide incorporation of TH2B, a histone H2B variant of hitherto unknown function. Using mouse models in which TH2B is depleted or C-terminally modified, we show that TH2B directs the final transformation of dissociating nucleosomes into protamine-packed structures. Depletion of TH2B induces compensatory mechanisms that permit histone removal by up-regulating H2B and programming nucleosome instability through targeted histone modifications, including lysine crotonylation and arginine methylation. Furthermore, after fertilization, TH2B reassembles onto the male genome during protamine-to-histone exchange. Thus, TH2B is a unique histone variant that plays a key role in the histone-to-protamine packing of the male genome and guides genome-wide chromatin transitions that both precede and follow transmission of the male genome to the egg.

HDAC6, a major cytoplasmic deacetylase, is shown here to fine-tune the kinetics of platelet activation, a process that must be precisely regulated to ensure hemostasis after blood vessel injury while preventing pathologic thrombus formation. The discoid shape of resting platelets in the circulation is maintained by several highly acetylated microtubules organized in a marginal band. During platelet activation, microtubules undergo major reorganizations, which contribute to the shape change of activating platelets. We show that, during these activation-induced shape changes, a dramatic HDAC6-mediated tubulin deacetylation takes place, followed by microtubule reacetylation in spread platelets. In addition, although HDAC6-controlled tubulin deacetylation is not required for platelet activation, the capacity of HDAC6 to prevent tubulin hyperacetylation influences the speed of platelet spreading. These results are particularly important in view of HDAC6 inhibitors being currently used in clinical trials and represent the first example of cell signaling by lysine acetylation in platelet biology.

International audience; Male germ cell differentiation is a highly regulated multistep process initiated by the commitment of progenitor cells into meiosis and characterized by major chromatin reorganizations in haploid spermatids. We report here that a single member of the double bromodomain BET factors, Brdt, is a master regulator of both meiotic divisions and post-meiotic genome repackaging. Upon its activation at the onset of meiosis, Brdt drives and determines the developmental timing of a testis-specific gene expression program. In meiotic and post-meiotic cells, Brdt initiates a genuine histone acetylation-guided programming of the genome by activating essential genes and repressing a ‘progenitor cells’ gene expression program. At post-meiotic stages, a global chromatin hyperacetylation gives the signal for Brdt's first bromodomain to direct the genome-wide replacement of histones by transition proteins. Brdt is therefore a unique and essential regulator of male germ cell differentiation, which, by using various domains in a developmentally controlled manner, first drives a specific spermatogenic gene expression program, and later controls the tight packaging of the male genome.

International audience; Genetic programs that govern neural stem/progenitor cell (NSC) proliferation and differentiation are dependent on extracellular cues and a network of transcription factors, which can be regulated posttranslationally by phosphorylation. However, little is known about the kinase-dependent pathways regulating NSC maintenance and oligodendrocyte development. We used a conditional knockout approach to target the murine regulatory subunit (beta) of protein kinase casein kinase 2 (CK2beta) in embryonic neural progenitors. Loss of CK2beta leads to defects in proliferation and differentiation of embryonic NSCs. We establish CK2beta as a key positive regulator for the development of oligodendrocyte precursor cells (OPCs), both in vivo and in vitro. We show that CK2beta directly interacts with the basic helix-loop-helix (bHLH) transcription factor Olig2, a critical modulator of OPC development, and activates the CK2-dependent phosphorylation of its serine-threonine-rich (STR) domain. Finally, we reveal that the CK2-targeted STR domain is required for the oligodendroglial function of Olig2. These findings suggest that CK2 may control oligodendrogenesis, in part, by regulating the activity of the lineage-specific transcription factor Olig2. Thus, CK2beta appears to play an essential and uncompensated role in central nervous system development.

The release of Agrin by motoneurons activates the muscle-specific receptor tyrosine kinase (MuSK) as the main organizer of subsynaptic specializations at the neuromuscular junction. MuSK downstream signaling is largely undefined. Here we show that protein kinase CK2 interacts and colocalizes with MuSK at post-synaptic specializations. We observed CK2-mediated phosphorylation of serine residues within the kinase insert (KI) of MuSK. Inhibition or knockdown of CK2, or exchange of phosphorylatable serines by alanines within the KI of MuSK, impaired acetylcholine receptor (AChR) clustering, whereas their substitution by residues that imitate constitutive phosphorylation led to aggregation of AChRs even in the presence of CK2 inhibitors. Impairment of AChR cluster formation after replacement of MuSK KI with KIs of other receptor tyrosine kinases correlates with potential CK2-dependent serine phosphorylation within KIs. MuSK activity was unchanged but AChR stability decreased in the presence of CK2 inhibitors. Muscle-specific CK2β knockout mice develop a myasthenic phenotype due to impaired muscle endplate structure and function. This is the first description of a regulatory cross-talk between MuSK and CK2 and of a role for the KI of the receptor tyrosine kinase MuSK for the development of subsynaptic specializations.

Protein kinase CK2 (formerly known as casein kinase 2) was among the first protein kinases to be identified and characterized. Surprisingly, in spite of intense efforts, the regulation and cellular functions of CK2 remain obscure. However, recent data on its molecular structure, its signal-mediated intracellular dynamic localization and its unexpected function in cell survival have raised new interest in this enzyme. These studies reveal unique features of CK2 and highlight its importance in the transduction of survival signals.

Udgivelsesdato: 2003-Feb Protein kinase CK2 is a ubiquitous protein kinase implicated in proliferation and cell survival. Its regulatory beta subunit, CK2beta, which is encoded by a single gene in mammals, has been suspected of regulating other protein kinases. In this work, we show that knockout of the CK2beta gene in mice leads to postimplantation lethality. Mutant embryos were reduced in size at embryonic day 6.5 (E6.5). They did not exhibit signs of apoptosis but did show reduced cell proliferation. Mutant embryos were resorbed at E7.5. In vitro, CK2beta(-/-) morula development stopped after the blastocyst stage. Attempts to generate homozygous embryonic stem (ES) cells failed. By using a conditional knockout approach, we show that lack of CK2beta is deleterious for mouse ES cells and primary embryonic fibroblasts. This is in contrast to what occurs with yeast cells, which can survive without functional CK2beta. Thus, our study demonstrates that in mammals, CK2beta is essential for viability at the cellular level, possibly because it acquired new functions during evolution.

Steroid hormones produce a response in target cells by binding to hormone-specific soluble receptors, which undergo a transformational change, leading to their interaction with chromatin and to modified gene expression. In a previous paper, we described a monoclonal antibody, BF4, that specifically recognizes and binds the non-transformed '8S' form of chicken oviduct progesterone receptor (8S-PR). We now show that BF4 does not form an immune complex with the 4S transformed form of 3H-progestin-labelled progesterone receptor, but does interact with the 8S non-transformed forms of the oestrogen, androgen and glucocorticosteroid receptors. Our results suggest that the antigenic determinant recognized by BF4 is present on a non-hormone binding unit, which we identify as a polypeptide of molecular weight (MW) 90,000 in the case of the progesterone receptor, and that this unit is common to other 8S non-transformed chicken steroid receptors.

A monoclonal antibody, AC7, directed against the RGD (Arg-Gly-Asp) binding site on the GpIIIa subunit of the platelet fibrinogen receptor, interacts only with activated platelet. In order to identify the regions of AC7 that interact with the receptor, cDNA sequences of AC7 immunoglobulin heavy and light chain variable regions were determined. Among the six complementarity-determining regions (CDRS) of AC7, the CDR3 heavy chain (H3) contains homology to the RGDF sequence within fibrinogen. A synthetic peptide encompassing the H3 region (H3, RQMIRGYFDV) inhibited platelet aggregation and fibrinogen binding to platelet (IC50 = 700μM). The inhibitory potencies of modified H3 peptides suggest that the RGYF sequence within the H3 peptide mimic the receptor recognition sequence in fibrinogen.

Summary Protamines confer a compact structure to the genome of male gametes. Here, we find that somatic cells can be remodeled by transient expression of protamine 1 (Prm1). Ectopically expressed Prm1 forms scattered foci in the nuclei of fibroblasts, which coalescence into spermatid-like structures, concomitant with a loss of histones and a reprogramming barrier, H3 lysine 9 methylation. Protaminized nuclei injected into enucleated oocytes efficiently underwent protamine to maternal histone TH2B exchange and developed into normal blastocyst stage embryos in vitro. Altogether, our findings present a model to study male-specific chromatin remodeling, which can be exploited for the improvement of somatic cell nuclear transfer., Graphical Abstract, Highlights • In vitro protaminization of somatic cell nuclei • Conversion of interphase somatic nuclei into “spermatid-like” structures • Protaminization of somatic nuclei that is reversed upon injection into enucleated oocytes • A simplified model of nuclear remodeling and reprogramming in vitro, Iuso et al. find that exogenous expression of human protamine 1 remodels interphase fibroblast nuclei into spermatid-like structures. The process is reversible upon nuclear transfer into enucleated oocytes. This finding could be exploited as a simplified model for investigating protamine-induced genome compaction and may also boost somatic cell nuclear transfer efficiency.

A 110kDa component of the chick oviduct progesterone receptor (PR) has been purified to homogeneity according to electrophoretic criteria and specific activity (assuming one progestagen-binding site/110kDa). The procedure involved affinity chromatography of 0.3 M-KCl-prepared cytosol, followed by DEAE-Sephacel chromatography (elution at 0.2 M-KCl). The final yield was about 12% in terms of binding activity. Properties of the 110kDa component indicate that it is identical with the ‘B’ subunit described previously [Stokes radius approximately 6.1 nm; sedimentation coefficient, (S20, w) approximately 4S; frictional ratio approximately 1.77]. It reacted with the IgG-G3 polyclonal antibody, but not with BF4 monoclonal antibody raised against the 8S molybdate-stabilized chick oviduct PR and reacting with its 90kDa component. Another progesterone-binding component, corresponding to the ‘A’ subunit, also previously described, was eluted from the DEAE-Sephacel column at approximately 0.08 M-KCl, and contained a peptide of molecular mass approx. 75-80kDa, which had S20, w approximately 4S in a sucrose gradient. This component was also recognized by IgG-G3, but not by BF4; it was very unstable in terms of hormone-binding activity.

The chicken lysozyme gene can be induced in oviduct cells by four classes of steroid hormones, including glucocorticosteroids and progestins. The glucocorticosteroid receptor of rat liver and the progesterone receptor of rabbit uterus both bind, although with different relative affinities, to two sites in the promoter region of the chicken lysozyme gene located, respectively, between 50 and 80 and between 160 and 200 base pairs upstream of the transcription start point. Now we show that the purified progesterone binding unit of the chicken oviduct progesterone receptor (Mr 110,000, or so-called B subunit) generates a DNase I protection pattern ("footprint") in the promoter-distal site that is longer than the footprint generated by the glucocorticosteroid receptor. Methylation protection studies within the promoter-distal binding site identify four contact points for the chicken progesterone receptor and three contact points for the glucocorticosteroid receptor, of which only one is shared by both receptors. Computer graphics models allow one to envisage a different interaction of each receptor with the B form of the DNA double helix.

The protein kinase CK2 is a dynamic molecular complex of 2 catalytic subunits α and of a dimer of regulatory subunit β. Cristallographic structure of the CK2β dimer suggests the existence of functional domains involved in the regulating function of the dimer towards the catalytic subunits, as well as in interactions with various protein partners. The CK2β dimer would represent a molecular platform, linking the protein to the center of signalling pathway networks.The knockout of the murin CK2β gene results in a defect of embryonic stem cell viability. We studied the in vitro function of different functional domains with the use of a “death-rescue” cellular model of by additional transgenesis of mutants CK2β. This cellular system is based on a conditional CK2β gene knockout strategy using murin embryonic stem cells (ES cells). The abolition of the endogenous gene expression is lethal for ES cells and the exogenous expression of the wild-type protein CK2β rescues their viability. This “death-rescue” model allows us to study the involvement of various domains of CK2β in the survival, the proliferation and the differentiation of embryonic stem cells.In parallel, the conditional targeted knockout in murin neural precursors demonstrated that CK2β is a key element in signalling pathways that control oligodendrogenesis. The differentiation of nullizygotes ES cells expressing the wild-type exogenous protein reveals that wild-type CK2β rescues the oligodendrocyte lineage. We also showed that some CK2β domains, linked to dimer regulatory functions, are crucial structural determinants for the proliferation of neural stem cells and their progression into the oligodendrocyte lineage., La protéine kinase CK2 est un complexe moléculaire dynamique composé de 2 sous-unités catalytiques α et d'un dimère de sous-unités régulatrices β. La structure cristallographique du dimère de CK2β suggère qu'il représente une plate-forme moléculaire, plaçant la protéine au cœur d'un réseau de voies de signalisation.L'invalidation du gène CK2β chez la souris conduit à un défaut de viabilité des cellules souches embryonnaires (ES). Nous avons pu étudier la fonction de différents domaines fonctionnels in vitro dans un modèle cellulaire reposant sur une stratégie d'invalidation conditionnelle du gène CK2β dans les cellules ES murines. L'abolition de l'expression du gène endogène est létale pour les cellules ES et leur viabilité est restaurée par l'expression exogène de la protéine CK2β sauvage. Ce modèle nous permet d'étudier l'implication de divers domaines de CK2β dans la survie, la prolifération et la différenciation des cellules souches embryonnaires, en remplaçant la protéine endogène par diverses formes mutées de la protéine. Parallèlement, l'invalidation conditionnelle du gène chez la souris ciblée dans les précurseurs neuraux a montré que CK2β est un élément clef dans les voies de signalisation qui contrôlent l'oligodendrogenèse. La différenciation des cellules ES nullizygotes exprimant la protéine exogène sauvage nous a permis de montrer que celle-ci restaure la lignée oligodendrocytaire. Nous avons aussi montré que certains domaines de CK2β, impliqués dans la fonction régulatrice du dimère, sont des déterminants structuraux cruciaux pour la prolifération des cellules souches neurales et leur progression dans la lignée oligodendrocytaire.