Microtubule length control is indispensable for cytoskeletal functions such as mitotic spindle assembly and positioning. In vivo studies have shown that kinesin motor proteins can regulate microtubule length positively and negatively. The mechanisms by which kinesins act as depolymerases and catastrophe factors are well studied. By contrast, how kinesins promote microtubule growth is unknown. The aim of this work was to elucidate the mechanism by which budding yeast kinesin Kip2 regulates microtubule dynamics, using in vitro reconstitution assays combined with total internal reflection fluorescence (TIRF) and differential interference contrast (DIC) microscopy. Kip2 was shown to increase the mean length of microtubules through length-dependent polymerase and anti-catastrophe activities, both with porcine and yeast tubulin, in the absence of accessory proteins. Using single-molecule motility assays, Kip2 was shown to translocate in a highly processive, ATP-dependent manner and to processively target tubulin oligomers to microtubule plus-ends. Mutant studies to probe Kip2 structure-function relationships revealed that the N-terminus of Kip2 is dispensable for promotion of microtubule growth, while the C-terminus is not. An effort to functionally identify a tubulin/microtubule-binding domain in the Cterminus of Kip2 remained unfruitful. Finally, the combinatorial effect of Kip2 with interaction partners Bim1 and Bik1 on microtubule dynamics was reconstituted. This microtubule plus-end tracking complex promoted microtubule growth beyond the effect of Kip2 alone. Together, this work demonstrates that a kinesin motor can act directly as a length-dependent microtubule polymerase and anti-catastrophe factor in the absence of accessory proteins. Thereby, this work provides insight into how kinesins control microtubule length.

Les agents ciblant les microtubules sont des médicaments anticancéreux efficaces. Leur utilisation dans le cadre d’un traitement combiné avec des rayonnements ionisants est également une stratégie prometteuse. Cependant, l’apparition de résistances aux produits chimiques et aux radiations nécessite de rechercher d'autres types de traitements. Nos laboratoires ont récemment décrit deux médicaments qui ciblent directement ou indirectement les microtubules. Premièrement, un analogue du 2-méthoxyestradiol, un poison de fuseau se liant à des microtubules et provoquant la formation de fuseaux mitotiques anormaux. Il s'agit du 2-éthyl-3-O-sulphamoyle-estra-1,3,5 (10) 16-tétraène (ESE-16). Deuxièmement, le 9-benzoyloxy-5,11-diméthyl-2H, 6H-pyrido [4,3-b] carbazol-1-one (LimPyr1), un nouvel inhibiteur des LIM kinases induisant indirectement la stabilisation des microtubules. Il a été démontré récemment que LimPyr1 est actif sur les modèles de cancer du sein résistants au taxol. En tant que médicaments ciblant les microtubules, les deux agents, ESE-16 et LimPyr1, induisent des défauts mitotiques. Nous émettons donc l’hypothèse qu’ils pourraient sensibiliser les cellules aux radiations. Le but de ce projet de thèse était de vérifier cette hypothèse et, plus précisément, de déterminer si de faibles doses de ESE-16 et de LimPyr1 pourraient augmenter l'apoptose et retarder la réparation nucléaire induite par le rayonnement dans les cellules du cancer du sein in vitro.Différentes lignées cellulaires cancéreuses, les cellules MCF-7, MDA-MB-231 et BT-20, ont été exposées à ESE-16 et à LimPyr1 pendant 24 heures avant un rayonnement de 8 Gy. Les effets de ces combinaisons thérapeutiques ont été comparés à ceux obtenus à partir de cellules exposées aux composés seuls ou aux seules radiations. L'activation des voies de survie et des voies apoptotiques intrinsèques a été étudiée. Les résultats ont révélé une augmentation de la signalisation de la survie et de la mort dans les cellules exposées aux traitements individuels. Les traitements combinés ont diminué la survie des cellules alors que la signalisation apoptotique augmentait, entraînant une augmentation de l'apoptose. En outre, les traitements combinés ont augmenté de manière significative la présence de micronoyaux dans les cellules BT-20, indiquant une augmentation des dommages à l'ADN. Les cellules MCF-7 et MDA-MB-231 présentent une formation de micronoyaux similaire lorsqu'elles sont exposées à la combinaison de traitements ou au rayonnement uniquement. La phosphorylation de H2AX (γH2AX) (normalement augmentée lors de dommages à l'ADN) et l'expression de Ku70 (nécessaire pour la réparation de l'ADN) étaient diminuées dans les cellules de cancer du sein prétraitées 2 heures après l'irradiation par rapport aux cellules exposées à l'irradiation uniquement. L'expression de H2AX et Ku70 est cependant significativement accrue 24 heures après irradiation des cellules prétraitées par rapport aux cellules exposées aux traitements individuels. Des expériences portant sur la réponse adaptative ont révélé que LimPyr1 diminuait le développement de la résistance aux radiations en augmentant la perméabilité transmembranaire mitochondriale et en générant des ROS, un mécanisme qui n'est pas observé dans cellules traitées par ESE-16. Nous avons également observé une communication intercellulaire entre les cellules exposées au rayonnement et les cellules non exposées via l'effet induit par le rayonnement.En conclusion, le blocage mitotique partiel induit par ESE-16 et LimPyr1 rend les chromosomes plus exposés aux dommages dus aux radiations, comme l'indique l'augmentation de la présence de micronoyaux. De plus, les deux composés diminuent la signalisation et le trafic des protéines de protection et de dommages à l'ADN. En outre, LimPyr1 empêche le développement de résistances aux radiations dans les cellules exposées aux radiations. / Microtubule targeting agents are effective anti-cancer drugs. Their use as part of a combined treatment modality with ionising radiation is also a promising strategy. However, the emergence of resistance to chemical and radiation requires searching for alternative treatments. Our laboratories have recently described two drugs that directly or indirectly target the microtubules. Firstly, an analogue of 2-methoxyestradiol, a spindle poison binding to microtubules and causing the formation of abnormal mitotic spindles. This is 2-ethyl-3-O-sulphamoyl-estra-1,3,5 (10) 16-tetraene (ESE-16). Secondly, 9-benzoyloxy-5,11-dimethyl-2H, 6H-pyrido [4,3-b] carbazol-1-one (LimPyr1), a novel inhibitor of LIM kinases indirectly inducing microtubule stabilization. It has been recently shown that LimPyr1 is active on taxol-resistant breast cancer models. As microtubule-targeting drugs, both agents, ESE-16 and LimPyr1, induce mitotic defects. We thus hypothesize that they could sensitize cells to radiation. The aim of this PhD project was to test that hypothesis and, more specifically, to investigate whether low-dose ESE-16 and LimPyr1 could increase apoptosis and delay nuclear repair induced by radiation in breast cancer cells in vitro.Various cancer cell lines, MCF-7-, MDA-MB-231- and BT-20 cells, were exposed to ESE-16 and LimPyr1 for 24-hours prior to 8 Gy radiation. The effects of these combination therapies were compared to those obtained from cells exposed to the compounds alone or only to radiation. The activation of the survival and intrinsic apoptotic pathways were investigated. Results revealed an increase in survival and -death signaling in cells exposed to the individual treatments. The combination treatments decreased the cell survival while apoptotic signaling was increased, resulting in increased apoptosis. Furthermore, the combination treatments significantly increased the presence of micronuclei in BT-20 cells, indicating an increase in DNA damage. MCF-7- and MDA-MB-231 cells displayed similar micronuclei formation when exposed to the combination treatments or radiation only. Phosphorylation of H2AX (γH2AX) (normally increased upon DNA damage) and Ku70 expression (required for DNA repair) were decreased in pretreated breast cancer cells 2 hours after irradiation compared to cells exposed to irradiation only. The expression of H2AX and Ku70, however, is significantly increased 24 hours after irradiation of the pretreated cells relative to the cells exposed to the individual treatmentsExperiments investigating the adaptive response revealed that LimPyr1 decreased radiation resistance development by increasing the permeability of the mitochondrial transmembrane (flow cytometry measuring Mitocapture™) and the generation of ROS (flow cytometry employing hydroethidine), a mechanism not observed in ESE-16 pre-treated cells. We also observed an intercellular communication between cells exposed to radiation and non-exposed cells via the radiation induced bystander effect.In conclusion, the anti-mitotic effect of ESE-16 and LimPyr1 renders the chromosomes more exposed to radiation damage, as assessed by the increased occurrence of micronuclei. Moreover, both compounds decrease the signaling and trafficking of DNA damage and repair proteins. Additionally, LimPyr1 prevented the development of radiation resistance in cells exposed to radiation.

No description available.

Dans cette thèse, des méthodes de la physique statistique hors équilibre sont utilisées pour décrire deux processus intracellulaires. Le transport bidirectionnel sur les microtubules est décrit à l'aide d'un gaz sur réseau stochastique quasi-unidimensionnel. Deux espèces de particules sautent dans des directions opposées en interagissant par exclusion. La présence habituelle d'accumulations de particules peut être supprimée en rajoutant la dynamique du réseau, c'est-à-dire de la microtubule. Un modèle simplifié pour la dynamique du réseau produit une transition de phase vers un état homogène avec un transport très efficace dans les deux directions. Dans la limite thermodynamique, une propriété de l'état stationnaire limite la longueur maximale des accumulations. La formation de voies peut être causée par des interactions entre particules. Néanmoins, ces mécanismes s'avèrent peu robustes face à une variation des paramètres du modèle. Dans presque tous les cas, la dynamique du réseau a un effet positif et bien plus important sur le transport que la formation de voies. Par conséquent, la dynamique du réseau semble un point-clé pour comprendre la régulation du transport intracellulaire. La dernière partie introduit un modèle pour la dynamique d'une microtubule sous l'action d'une protéine qui favorise les sauvetages. Des phénomènes intéressants de vieillissement apparaissent alors, et devraient être observables dans des expériences. / This thesis uses methods and models from non-equilibrium statistical physics to describe intracellular processes. Bidirectional microtubule-based transport within axons is modeled as a quasi-one-dimensional stochastic lattice gas with two particle species moving in opposite directions under mutual exclusion interaction. Generically occurring clusters of particles in current models for intracellular transport can be dissolved by additionally considering the dynamics of the transport lattice, i.e., the microtubule. An idealized model for the lattice dynamics is used to create a phase transition toward a homogenous state with efficient transport in both directions. In the thermodynamic limit, a steady state property of the dynamic lattice limits the maximal size of clusters. Lane formation mechanisms which are due to specific particle-particle interactions turn out to be very sensitive to the model assumptions. Furthermore, even if some particle-particle interaction is considered, taking the lattice dynamics into account almost always improves transport. Thus the lattice dynamics seems to be the key aspect in understanding how nature regulates intracellular traffic. The last part introduces a model for the dynamics of a microtubule which is limited in its growth by the cell boundary. The action of a rescue-enhancing protein which is added to the growing tip of a microtubule and then slowly dissociates leads to interesting aging effects which should be experimentally observable.

Gastrulation, literally “formation of the gut” is ultimately an inadequate term to describe one of the most dynamic periods during vertebrate developmental biology. During gastrulation coordinated cell movements reshape the non-descript blastula into the structured gastrula and simultaneously specify the three germ layers: endoderm, mesoderm and ectoderm. The morphogenetic movements of gastrulation are highly conserved between species, but the links between their genetic and biomechanical regulation are poorly understood. The zebrafish embryo – externally hatched, optically clear and amenable to genetic manipulation – is an ideal vertebrate model in which to study both morphogenetic movements and their genetic control. This thesis provides a detailed analysis of the zebrafish Mix-type homeobox transcription factor, Mtx2, both in terms of its role in gastrulation and the molecular mechanisms regulated by Mtx2. This approach involved detailed examination of the Mtx2 loss-of-function phenotype and, subsequently, use of this phenotype as the basis for a microarray screen to identify and investigate Mtx2-dependent genes. One specific Mtx2-dependent gene, katanin-like 1 was investigated further by loss-of-function studies. Prior to this study the mtx2 gene was identified by homology, within its homeodomain, to other Mix-family transcription factors, but both its function and transcriptional targets remained unknown. Using a morpholino knockdown approach, this thesis demonstrates that Mtx2 is essential for vegetal movement (epiboly), but not specification, of the embryonic germ layers and extra-embryonic tissues during zebrafish gastrulation. The recruitment of filamentous actin (F-actin) to a punctate band at the blastoderm margin, was previously shown to be responsible for progression of epiboly. However, formation of this structure is demonstrated to be Mtx2-dependent. Microarray expression profiling of the Mtx2 loss-of-function phenotype was performed to screen for novel genes with roles in gastrulation. This approach identified Mtx2-dependent genes with roles in cytoskeletal dynamics, cell-cell adhesion and endocytosis and vesicular trafficking – processes known to be involved in morphogenetic movements. Many Mtx2-dependent genes are co-expressed with mtx2 in the extra-embryonic yolk syncytial layer (YSL), the teleost functional equivalent of mammalian visceral endoderm. The subset of Mtx2-dependent genes co-expressed with mtx2 and that contain Mtx2-binding sites within their 2kb proximal promoter represent the genes with the greatest likelihood of being direct Mtx2 transcriptional targets. A novel homologue of the microtubule severing protein Katanin, known as katanin-like 1 (katnal1) met all these conditions. Morpholino knockdown of Katnal1 demonstrates that like Mtx2, Katnal1 is essential for gastrulation in zebrafish. A cloned Katnal1mCherry fusion construct was observed to associate with microtubules, and demonstrated bi-directional trafficking around transfected mammalian cells. Analysis of the microtubule network in wild-type and morpholino injected zebrafish embryos demonstrated that remodelling of the extensive microtubule network found in the YSL and yolk cytoplasmic layer (YCL) is Katnal1-dependent. Nuclear division within the YSL and F-actin recruitment to the blastoderm margin are also Katnal1-dependent. This thesis therefore demonstrates, for the first time directly, the multiple, specific roles played by the microtubule network of the YSL/YCL. Katnal1 is highly conserved from Drosophila to mammals and is dynamically expressed during mouse gastrulation. The Mtx2 binding motif in the katnal1 2kb proximal promoter can be bound by both Mtx2 and its putative mouse homologue Mixl1. This suggests that katnal1 may also be a direct target of Mtx2. At the technical level, these results demonstrate the validity of screening for novel developmentally important genes using a zebrafish microarray-based approach, the potential of such an approach to, ab initio, identify a candidate list of transcription factor targets and confirm the utility of the zebrafish as a developmental model. At the biological level, this work collectively suggests that Mtx2 is a central regulator of the morphogenetic movement of epiboly and that Katnal1-dependent microtubule remodelling drives multiple aspects of gastrulation, potentially from Drosophila through to humans.

The amino acid proline is unique – within a polypeptide chain, proline adopts either a cis or trans peptide bond conformation while all other amino acids are sterically bound primarily in the trans configuration. In proteins, the isomeric state of a single proline can have dramatic consequences on structure and function. Consequently, cis-trans interconversion confers both barrier and opportunity – on one hand, isomerization is a rate limiting step in de novo protein folding and on the other can be utilized as a post-translational regulatory switch. Peptidyl-prolyl isomerases (PPIs) are a ubiquitous superfamily that catalyzes the interconversion between conformers. Although pervasive, the functions and substrates of most PPIs are unknown. The two largest subfamilies, FKBPs and cyclophilins, are the intracellular receptors of clinically relevant immunosuppressant drugs that also show promise in the treatment of neurodegenerative disorders and cancer. Therefore, narrowing the knowledge gap has significant potential to benefit human health. FKBP25 is a high-affinity binder of the PPI inhibitor rapamycin and is one of few nuclear-localized isomerases. While it has been shown to bind DNA and associate with chromatin, its function has remained largely uncharacterized. I hypothesized that FKBP25 targets prolines in nuclear proteins to regulate chromatin-templated processes. To explore this, I performed high-throughput transcriptomic and proteomic studies followed by detailed molecular characterizations of FKBP25’s function. Here, I discover that FKBP25 is a multifunctional protein required for the maintenance of genomic stability. In Chapter 2, I characterize the unique N-terminal Basic Tilted Helical Bundle (BTHB) domain of FKBP25 as a novel dsRNA binding module that recruits FKBP25’s prolyl isomerase activity to pre-ribosomal particles in the nucleolus. In Chapter 3, I show for the first time that FKBP25 associates with the mitotic spindle apparatus and acts to stabilize the microtubule cytoskeleton. In this chapter, I also present evidence that this function influences the stress response, cell cycle, and chromosomal stability. Additionally, I characterize the regulation of FKBP25’s localization and nucleic acid binding activity throughout the cell cycle. Finally, in Chapter 4, I uncover a role for FKBP25 in the repair of DNA double-stranded breaks. Importantly, this function requires FKBP25’s catalytic activity, identifying for the first time a functional requirement for cis-trans prolyl isomerization by FKBP25. Collectively, this work identifies FBKP25 as a multifunctional protein that is required for the maintenance of genomic stability. The knowledge gained contributes to the exploration of PPIs as important drug targets. / Graduate

No description available.

Le cancer du sein touche une femme sur neuf dans le monde et constitue un problème majeur de santé publique. L’identification de nouveaux biomarqueurs pour un traitement personnalisé pour les tumeurs du sein de plus mauvais pronostic, dites « triple-négatives », est extrêmement urgent. ATIP3, le produit majeur du gène candidat suppresseur de tumeurs MTUS1, a été identifié par l’équipe comme étant un biomarqueur des tumeurs du sein les plus agressives. De plus, ATIP3 inhibe la prolifération et la migration in vitro, ainsi que la progression tumorale et la formation de métastases in vivo et constitue une cible thérapeutique. ATIP3 est une protéine associée aux microtubules (MT) en interphase et au fuseau mitotique durant la mitose. Mon projet de thèse a pour objectif principal d’identifier les partenaires d’interaction d’ATIP3 impliqués dans ses mécanismes d’action antitumoraux. Dans une première partie, j’ai montré qu’ATIP3 interagit avec EB1, une protéine majeure de la dynamique du MT. L’interaction ATIP3-EB1 diminue l’accumulation d’EB1 à l’extrémité croissante du MT. Un nouveau mécanisme a été proposé dans lequel l’interaction ATIP3-EB1 réduit indirectement la vitesse d’échange d’EB1 à son site de liaison au bout plus du MT, ayant pour conséquence une diminution de la dynamique du MT. Dans une deuxième partie, j’ai montré qu’une déplétion d’ATIP3 induit une réduction de la taille du fuseau mitotique. Une analyse protéomique a permis d’identifier la kinésine Kif2A comme partenaire d’interaction d’ATIP3. ATIP3 forme un complexe avec Kif2A et Dda3 qui est dépendant d’une phosphorylation par Aurora kinase A. ATIP3 maintient la taille du fuseau en diminuant le recrutement de Kif2A et Dda3 au pôle de façon dépendante d’AurKA. ATIP3 régule donc négativement ses partenaires d’interaction. Enfin, dans une troisième partie, la relevance clinique du couple ATIP3-EB1 a été évaluée et j’ai montré que l’expression combinée des deux biomarqueurs ATIP3 et EB1 était associée à l’agressivité de la tumeur et à une survie diminuée. Ainsi, l’ensemble de mes travaux a permis de mettre en évidence de nouvelles cibles thérapeutiques afin de mettre en place des traitements personnalisés / Breast cancer is a leading cause of death by malignancy in women worldwide. The identification of new molecular markers for personalized treatment of poor prognosis breast tumors, such as those of the triple negative subtype, is urgently needed. Our team is leader in the study of ATIP3 protein, encoded by candidate tumor suppressor gene MTUS1. ATIP3 is down-regulated in 85% of triple negative breast tumors, and low levels of ATIP3 are associated with poor survival of the patients. We have shown that ATIP3 reduces proliferation and migration in vitro, and tumor growth and metastasis formation in vivo. ATIP3 localizes along the microtubule (MT) in interphase and on the mitotic spindle and spindle poles during mitosis. My PhD project aimed at identifying ATIP3 partners involved in its anti-tumoral effects. In the first part, I will present data showing that ATIP3 interacts with EB1, a major regulator of MT dynamics. ATIP3-EB1 interaction prevents EB1 accumulation at MT growing ends. I proposed a novel mechanism by which ATIP3-EB1 indirectly reduces EB1 turnover at its binding site at MT plus end, which consequently reduces MT dynamics. In the second part of my thesis, I showed that ATIP3 silencing induces reduced spindle length. In parallel, I identified the MT-depolymerizing kinesin Kif2A as an ATIP3 partner by proteomic analysis. ATIP3 forms a complex with Kif2A and Dda3 in an AurKA-dependent manner. I showed that ATIP3 maintains mitotic spindle size by inhibiting Kif2A and Dda3 recruitment at the spindle pole. My study also revealed a recriprocal regulation between ATIP3 and AurKA. Thus, ATIP3 negatively regulates its binding partners. Finally, in a third part, clinical relevance of ATIP3-EB1 in breast cancer has been evaluated and I showed that combinatorial expression of ATIP3 and EB1 is associated with tumor agressiveness and reduced patient survival. Altogether, this work highlighted new therapeutic targets to propose personalized treatments.

La mise en conformation de l’α et β tubulines en hétérodimeres polymérisables nécessite l’intervention de cinq protéines « Tubulin Binding Cofactors » (TBCA a TBCE) dont TBCC qui joue un rôle indispensable. Dans des cellules humaines d’adénocarcinome mammaire, nous avons modifié le niveau d’expression de TBCC et nous avons montre que ceci avait un impact sur le contenu des fractions de tubuline, la dynamique des microtubules ainsi que sur le phénotype et chimiosensibilité des cellules. La distribution en cycle cellulaire et les durées de la mitose et de la phase S ont été altérées. La modification de TBCC avait un faible effet sur la vitesse de prolifération in vitro par contre les cellules présentaient des différences significatives de croissance tumorale in vivo. Les réponses aux agents antimicrotubulaires et à la gemcitabine ont montrées une chimiosensibilité dépendante de la distribution en cycle cellulaire. Tous ces résultats montrent l’importance de la régulation du contenu en tubulines et l’impact de ceci sur le comportement de la cellule en général et vis-à-vis des traitements / The proper folding pathway of α and β-tubulin into the α/β-tubulin heterodimers involve five Tubulin Binding Cofactors (TBCA to TBCE). TBCC plays a crucial role in the formation of polymerization-competent the α/β-tubulin heterodimers. To evaluate the impact of microtubule mass and dynamics on the phenotype and chemosensitivity of breast cancer cells, we targeted TBCC in human breast adenocarcinoma and developed variants of breast cancer cells with modified content of TBCC. We have shown that the modifications in TBCC expression level influenced tubulin fraction distribution and microtubule dynamics. Cell cycle distribution and the durations of mitosis and S-phase were altered. The proliferation rate in vitro was slightly modified whereas in vivo the TBCC variants presented major differences in tumor growth capacity. Chemosensitivity to antimicrotubule agents (paclitaxel and vinorelbine) as well as to gemcitabine was observed to be dependent on the cell cycle distribution of the TBCC variants. These results underline the essential role of fine tuned regulation of tubulin content in tumor cells and the major impact of dysregulation of tubulin dimer content on tumor cell phenotype, cell cycle progression and response to chemotherapy. A better understanding of how the microtubule cytoskeleton is dysregulated in cancer cells would greatly contribute to a better understanding of tumor cell biology and characterization of resistant phenotypes

Des mutations hétérozygotes faux-sens dans le gène de la tubuline gamma TUBG1, ont été identifiées dans le contexte des malformations du développement cortical, associées à une déficience intellectuelle et à l'épilepsie. Ici, nous avons étudié par la technique d’électroporation in-utero et par des études in vivo, l’effet de quatre de ces variantes sur le développement cortical. Nous montrons que les mutations dans TUBG1 affectent le positionnement neuronal dans la plaque corticale, en perturbant la locomotion des neurones nouvellement nés, mais sans affecter la neurogenèse. Nous proposons que la γ-tubuline mutante affecte le fonctionnement global de ses complexes, et en particulier leur rôle dans la régulation de la dynamique des microtubules. De plus, nous avons développé un modèle de souris knock-in Tubg1Y92C/+ et évalué les conséquences de la mutation sur le développement cortical, les caractéristiques neuroanatomiques et le comportement. Les souris mutantes présentent une microcéphalie globale, des anomalies du néocortex et de l'hippocampe, des altérations du comportement et une susceptibilité épileptique. Ainsi, nous montrons que les souris Tubg1Y92C/+ miment au moins partiellement le phénotype humain et représentent donc un modèle pertinent pour d'autres investigations de la physiopathologie des malformations du développement cortical. / Missense heterozygous variants in the gamma tubulin gene TUBG1 have been linked to malformations of cortical development, associated with intellectual disability and epilepsy. Here, we investigated through in-utero electroporation and in-vivo studies, how four of these variants affect cortical development. We show that TUBG1 mutants affect neuronal positioning within the cortical wall, by a disrupting the locomotion of newly born neurons but without affecting neurogenesis. We propose that mutant γ-tubulin affects overall functioning of γ-tubulin complexes, and in particular their role in the regulation of microtubule dynamics. Additionally, we developed a knock-in Tubg1Y92C/+ model and assessed consequences of the mutation on cortical development, neuroanatomical features and behaviour. Mutant mice present with global microcephaly, neocortical and hippocampal abnormalities, behavioural alterations and epileptic susceptibility. Thus, we show that Tubg1Y92C/+ mice partially mimic the human phenotype and therefore represent a relevant model for further investigations of the physiopathology of malformations of cortical development.