La neuropathie auditive est une forme de surdité caractérisée par une atteinte des cellules ciliées internes (qui détectent les ondes sonores et les transforment en message nerveux) et/ou des neurones afférents primaires (qui véhiculent les messages nerveux jusqu'au noyau cochléaire), associée à une activité normale des cellules ciliées externes (qui amplifient les ondes sonores). AUNA1 est la première neuropathie auditive héréditaire à avoir été décrite. Elle est causée par une mutation ponctuelle située dans le promoteur du gène DIAPH3, résultant en une surexpression de DIAPH3. La protéine DIAPH3, un membre de la famille des formines, est connue pour promouvoir la nucléation et l’élongation des filaments d’actine ainsi que la stabilisation des microtubules. Nous avons étudié les mécanismes d’AUNA1 à partir d’un modèle murin transgénique surexprimant le gène diap3, l’orthologue murin de DIAPH3. Les souris transgéniques développent une surdité dont les caractéristiques sont semblables à celles d’AUNA1. Cette surdité est due à une perte d’activité des cellules ciliées internes. L’activité synaptique et les courants potassiques de ces cellules ne sont pas altérés. En revanche, la microscopie électronique révèle une fusion des stéréocils (expansions cytoplasmiques qui permettent la détection des ondes sonores) et une déformation de la plaque cuticulaire (plateforme qui assure l’ancrage des stéréocils). Par la technique d’immunomarquage, nous avons mis en évidence une invasion de la plaque cuticulaire par des microtubules. Enfin, nous avons démontré que la protéine Diap3 est localisée dans la plaque cuticulaire des cellules ciliées internes, suggérant ainsi que la surexpression de diap3 provoque un remodelage du réseau de microtubule des cellules ciliées internes, à l’origine de la surdité AUNA1. / Auditory neuropathy is a type of deafness characterized by an alteration of the inner hair cells (which detect the acoustic waves and transform them into neural messages) and/or of the primary afferent neurons (which conduct the neural messages to the cochlear nucleus), associated with a normal activity of the outer hair cells (which amplify the acoustic waves).AUNA1 is the first hereditary auditory neuropathy which has been described. It is caused by a point mutation in the promoter of the DIAPH3 gene, resulting in an overexpression of DIAPH3. The DIAPH3 protein, a formin family member, is known to promote the actin filament nucleation and elongation and to stabilize the microtubules.We studied the AUNA1 mechanisms using a transgenic mouse model which overexpresses the diap3 gene, the mouse homologue of DIAPH3. Transgenic mice develop a deafness whose characteristics are similar to the ones of AUNA1. The hearing loss is due to a defect in the inner hair cell activity. The synaptic activity and the potassium currents of these cells are not altered. However, electron microscopy reveals a fusion of the stereocilia (cytoplasmic expansions which detect the acoustic waves) and a disruption of the cuticular plate (plateform which maintains stereocilia). By immunolabeling, we showed an invasion of the cuticular plate by microtubules. Eventually, we demonstrated that Diap3 is located in the inner hair cell cuticular plate, suggesting that the overexpression of diap3 provokes a remodeling of the inner hair cell microtubule network, underlying the AUNA1 deafness.

Le bon fonctionnement du système nerveux dépend de la précision avec laquelle sont formées les connexions synaptiques lors du développement embryonnaire et post-natal. La navigation des cônes de croissance vers leurs cibles dépend en dernier lieu de la réorganisation dynamique du réseau d’actine et de microtubules (MTs). Historiquement considérés comme les acteurs principaux de l'élongation axonale, les MTs ont été plus récemment impliqués dans des processus d'orientation du cône de croissance et de guidage axonal, montrant ainsi le rôle capital que les protéines associées aux microtubules (MAPs) peuvent jouer dans la navigation axonale. Notre équipe s’intéresse aux protéines appartenant à un sous-groupe des protéines AAA (pour ATPases Associated with diverse cellular Activities) comprenant trois enzymes de cassure des MTs : la spastin, la katanin et la fidgetin, ainsi que deux protéines apparentées à cette dernière, les fidgetin-like 1 et 2 L’analyse fonctionnelle de fidgetin-like 1 et katanin chez le poisson zèbre a permis de montrer le rôle différentiel de ces protéines dans le guidage axonal des Neurones Moteurs Spinaux (NMS). Finalement, nous avons évalué l’impact d’une modification post-traductionnelle de la tubuline, la polyglutamylation, sur le développement axonal des NMS et l’activité de cassure des microtubules par katanin. Notre étude de deux enzymes de polyglutamylation neuronales, TTLL6 et TTLL11, a mis en évidence le rôle différentiel de ces deux enzymes dans la navigation axonale des NMS, ainsi que l’influence de la polyglutamylation par TTLL6, mais pas par TTLL11, sur l’activité de cassure des MTs par katanin dans ce processus biologique. / The formation of a functional nervous system depends on the accuracy of its network wiring during embryonic and postnatal development. Axon outgrowth and navigation ultimately rely on the reorganization of the microtubule (MT) and actin networks. Historically considered as key players in axon extension, MTs have been gradually shown to play an instructive role in axon guidance decisions, which sheds new light on the potential involvement of MT-associated proteins (MAPs) in these navigational processes. Our team program aims at deciphering the differential role and functional redundancy of a few neuronal MT-associated ATPases, including the MT-severing spastin, katanin and the newly discovered fidgetin-like 1, in SMN axon outgrowth. During my PhD, I have first participated in the functional analysis of fidgetin-like 1, which has revealed that this ATPase controls SMN axon outgrowth via the regulation of MT plus-end dynamics. My main PhD project focused on the involvement of katanin in SMN development, which has established the pivotal role of this MT-severing enzyme in SMN axon targeting. Furthermore, I have explored the potential involvement of a MT post-translational modification, the tubulin polyglutamylation, in SMN axon outgrowth and navigation, and its influence on katanin MT-severing activity. Interestingly, my analysis of two neuronal MT polyglutamylases, TTLL6 and TTLL11, shows that these two enzymes differentially affect SMN axon outgrowth and pathfinding, and reveals the exclusive impact of TTLL6-mediated polyglutamylation on katanin MT-severing activity during this developmental process.

Le virus de l’hépatite B (VHB) utilise la machinerie transcriptionnelle nucléaire pour sa réplication. Le génome viral est transporté de la périphérie cellulaire à l’enveloppe nucléaire. Généralement, ce transport intracytoplasmique rétrograde est facilité par le réseau de Mt via l’utilisation du complexe moteur de la dynéine. Nous avons montré que le transport des capsides du VHB dépend des Mt, ce qui permet l’adressage des capsides aux complexes du pore nucléaire (NPC) ; lequel est requis pour l’étape de libération du génome de la capside dans le noyau.Dans cette étude, nous avons utilisé des capsides provenant de virus récupérés dans du surnageant de HepG2.2.15, qui contiennent le génome mature partiellement double brin (capsides matures), et des capsides exprimées chez E.coli. Ces dernières sont utilisées telles quelles, capsides E.coli contenant de l’ARN, ou bien sont utilisées pour préparer des capsides vides. Après microinjection dans des ovocytes de Xenopus laevis, nous avons observé que les capsides vides et les capsides matures sont transloquées aux NPC avec une cinétique similaire. Les capsides contenant de l’ARN ne sont pas identifiées aux NPCs ce qui implique que le transport des deux autres types de capsides est actif. Cela a été confirmé par la pré-injection d’anticorps anti tubuline qui neutralisent le transport assuré par les Mt.L’attachement spécifique des capsides matures et vides aux Mt a été confirmé en utilisant des Mt polymérisés in vitro, nous avons montré que cette interaction nécessitait des protéines cytosoliques. En utilisant des expériences de coïmmunoprécipitation et de cosédimentation nous avons identifié une chaîne légère de la dynéine (DynLL1 membre de la famille Lc8) comme partenaire des capsides. Dans les expériences de microinjection, la comicroinjection d’un excès de DynLL1 avec les capsides inhibe leur transport vers les NPCs, indiquant que DynLL1 est impliquée dans le transport actif des capsides.DynLL2 qui n’interagit pas avec les capsides diffère de DynLL1 de seulement six acides aminés. Par mutagénèse dirigée de DynLL1, nous avons montré l’implication de deux acides aminés dans l’interaction directe avec les capsides. Ces deux acides aminés sont présents à la surface du dimère de DynLL1 et absents dans le sillon résultant de la dimérisation de DynLL1, sillon impliqué dans l’interaction avec la DynIC. Nous avons partiellement reconstitué le complexe DynIC, DynLL1 et capsides vides qui doit en partie refléter la situation in vivo. / Hepatitis B virus (HBV) needs the nuclear transcription machinery for replication. The virus thus depends on the transport of its genome from the cell periphery to the nuclear envelope. In general this retrograde intracytoplasmic trafficking is facilitated along Mt (MT) using motor protein complexes of the dynein family. As we showed earlier HBV capsid transport also depends upon intact MT in order to allow their arrival at the nuclear pores, which in turn is required for genome liberation from the capsid.In the analysis we used virus-derived HBV capsids obtained from the supernatant of HepG2.2.15, which contain the mature partially double-stranded DNA genome (mature capsids) and capsids expressed in E. coli. The latter were applied in two forms: as unspecific E. coli RNA- containing capsids and as empty capsids. Upon microinjection into Xenopus laevis oocytes we observed that mature and empty capsids were translocated to the nuclear pores with a similar kinetic. RNA-containing capsids failed to arrive at the pores implying that transport of the two other capsid types was active. Active translocation was confirmed by pre-injecting anti tubulin antibodies which interfere with MT-mediated translocation.In vitro reconstitution assays confirmed the specific attachment of mature and empty capsids to MTs and showed the need of further cytosolic proteins. Using pull-down and co-sedimentation experiments we identified one dynein light chain (DYNLL1, member of the Lc8 family) as interaction partner of the capsids. Injecting an excess of recombinant DYNLL1 with empty capsids into Xenopus laevis oocytes inhibited capsid transport to the nuclear pores indicating that DYNLL1 was only functional interaction partner implied in active transport.DNYLL2 did not interact with the capsids although differing from DYNLL1 by just six amino acids. Site directed mutagenesis of DYNLL1 revealed that two amino acids were critical for a direct interaction with the capsids. Both localized at the exterior of the DYNLL1 dimer and not in the groove of DYNLL1, which interacts with the dynein intermediate chain. Accordingly we could reconstitute a complex consisting of empty capsids, DYNLL1 and dynein intermediate chain as it should be in the in vivo situation.

Microtubules (MTs) are highly dynamic structures essential for the spatio-temporal intracellular organization and transport, signal propagation, cell differentiation, motility and division. To perform these roles, MTs create arrangements capable of fast and precise adaptation to various signals. MTs are under the control of many factors regulating MT nucleation, stability and dynamics. Bone marrow-derived mast cells (BMMCs) are important immune system cells, which can cause serious diseases if their functions are deregulated. Although MT reorganization during BMMC activation is well established, the molecular mechanisms that control their remodelling are largely unknown. In the presented thesis we functionally characterised GIT1/βPIX signalling proteins, PAK1 kinase, and Ca2+ signalling in the regulation of MT nucleation in BMMCs and other cell types. We also elucidated the function of miltefosine (hexadecylphosphocholine), a promising candidate for the treatment of mast cell-driven diseases. We found that GIT1/βPIX signalling proteins are γ-tubulin-interacting proteins associating with centrosomes in BMMCs. MT nucleation is positively regulated by GIT1 and Ca2+ , whereas βPIX is a negative regulator of MT nucleation in BMMCs. Cytosolic Ca2+ affects γ-tubulin properties and stimulates the...

Microtubules are a part of the cell cytoskeleton that performs different functions, such as providing the mechanical support for the shape of a cell, acting as tracks along which the motor protein move organelles from one part of the cell to another, or the forming mitotic spindle during the cell division. The microtubules are dynamic structures, namely they can grow and shrink. The phase of microtubule growth alternates with the phase of shrinkage that results in the dynamic microtubule network in the cell. However, to form stable and spatially well-defined structures, such as a mitotic spindle, the cell needs to control this stochastic process. This is done by microtubule-associated proteins (MAPs). One class of MAPs is the proteins of XMAP216/Dis1 family, which are microtubule polymerases. The founding member of this family is X. laevis XMAP215. XMAP215 is a processive polymerase acting on the microtubule plus end. XMAP215 binds either directly or reaches the microtubule plus end by the diffusion along the microtubule lattice. Being at the microtubule plus-end XMAP215 stays there transiently and helps to incorporate up to 25 tubulin dimers into microtubule lattice before it dissociates and, therefore, it processively tracks the growing microtubule end during polymerization. There are two hypothesis of microtubule assembly promotion: (i) XMAP215 repeatedly releases an associated tubulin dimer into the microtubule growing plus end or (ii) structurally stabilizes a polymerized tubulin intermediate at the growing plus end and, therefore, preventing depolymerization events. The first way results into the increase of on-rate of tubulin dimers at the microtubule end, whereas the second way results into the decrease of off-rate of tubulin dimers at the microtubule end. Here, I show the study of the mechanism of microtubule growth acceleration by XMAP215 and the dependence of XMAP215 polymerization activity on the applied force. To answer these questions, I investigated the addition of tubulin dimers to the plus end of the microtubule by XMAP215 and how this addition depends on the applied force. XMAP215 remains at the microtubule end for several rounds of tubulin addition surfing both growing and shrinking microtubule ends. Therefore, if one could track the position of the XMAP215 molecules at the very tip of a microtubule with sufficient resolution, it would provide the information about the dynamics of the microtubule end. The technique, which can detect the position of the object of interest with high spatial and temporal resolution in addition to being able to exert a force, is an optical trap. A calibrated optical trap not only provides a good measure of displacement but also enables force measurements. To monitor the position of the molecules of interest, the molecules of interest are usually attached to a microsphere. Hence, I tethered XMAP215 to a microsphere held by an optical trap, and used XMAP215 as a handle to interact with the microtubule tip. When the microtubule grows, the XMAP215 coated microsphere will move in the optical trap and this movement can be detected with high temporal and spatial resolution. My work demonstrates that cooperatively working XMAP215 molecules can not only polymerize microtubule but also harness the energy of microtubule polymerization or depolymerization to transport some cargo. There is an evidence that orthologues of XMAP215 in budding yeasts, fission yeasts and Drosophila localize on the kinetochores. Therefore, the ability of the bearing some load during microtubule polymerization could be potentially important for the XMAP215 functioning during cell division. I also showed the influence of external force applied to the XMAP215 molecules. Pointing toward microtubule growth, a force of 0.5 pN applied to the microtubule tip-coupled XMAP215-coated microsphere increases XMAP215 polymerization activity. However, the force of the same magnitude but applied against microtubule growth does not affect XMAP215 polymerization activity. This result can be explained by the fact, that the force acting in the direction of microtubule growth constrains XMAP215 to be at the very microtubule tip. Hence, XMAP215 can not diffuse away from plus-end and there is higher chance to incorporate tubulin dimers into the microtubule plus-end. The on- and off-rate of tubulin dimers at the microtubule end are both decreased when the external force applied either in direction of microtubule growth or opposite to it. The external force affects the off-rate slightly stronger than on-rate of tubulin dimer. Taking together, my study gives new insights into the mechanism of microtubule polymerization by XMAP215 and shows some novel properties of this protein.

Microtubules are a part of the cell cytoskeleton that performs different functions, such as providing the mechanical support for the shape of a cell, acting as tracks along which the motor protein move organelles from one part of the cell to another, or the forming mitotic spindle during the cell division. The microtubules are dynamic structures, namely they can grow and shrink. The phase of microtubule growth alternates with the phase of shrinkage that results in the dynamic microtubule network in the cell. However, to form stable and spatially well-defined structures, such as a mitotic spindle, the cell needs to control this stochastic process. This is done by microtubule-associated proteins (MAPs). One class of MAPs is the proteins of XMAP216/Dis1 family, which are microtubule polymerases. The founding member of this family is X. laevis XMAP215. XMAP215 is a processive polymerase acting on the microtubule plus end. XMAP215 binds either directly or reaches the microtubule plus end by the diffusion along the microtubule lattice. Being at the microtubule plus-end XMAP215 stays there transiently and helps to incorporate up to 25 tubulin dimers into microtubule lattice before it dissociates and, therefore, it processively tracks the growing microtubule end during polymerization. There are two hypothesis of microtubule assembly promotion: (i) XMAP215 repeatedly releases an associated tubulin dimer into the microtubule growing plus end or (ii) structurally stabilizes a polymerized tubulin intermediate at the growing plus end and, therefore, preventing depolymerization events. The first way results into the increase of on-rate of tubulin dimers at the microtubule end, whereas the second way results into the decrease of off-rate of tubulin dimers at the microtubule end. Here, I show the study of the mechanism of microtubule growth acceleration by XMAP215 and the dependence of XMAP215 polymerization activity on the applied force. To answer these questions, I investigated the addition of tubulin dimers to the plus end of the microtubule by XMAP215 and how this addition depends on the applied force. XMAP215 remains at the microtubule end for several rounds of tubulin addition surfing both growing and shrinking microtubule ends. Therefore, if one could track the position of the XMAP215 molecules at the very tip of a microtubule with sufficient resolution, it would provide the information about the dynamics of the microtubule end. The technique, which can detect the position of the object of interest with high spatial and temporal resolution in addition to being able to exert a force, is an optical trap. A calibrated optical trap not only provides a good measure of displacement but also enables force measurements. To monitor the position of the molecules of interest, the molecules of interest are usually attached to a microsphere. Hence, I tethered XMAP215 to a microsphere held by an optical trap, and used XMAP215 as a handle to interact with the microtubule tip. When the microtubule grows, the XMAP215 coated microsphere will move in the optical trap and this movement can be detected with high temporal and spatial resolution. My work demonstrates that cooperatively working XMAP215 molecules can not only polymerize microtubule but also harness the energy of microtubule polymerization or depolymerization to transport some cargo. There is an evidence that orthologues of XMAP215 in budding yeasts, fission yeasts and Drosophila localize on the kinetochores. Therefore, the ability of the bearing some load during microtubule polymerization could be potentially important for the XMAP215 functioning during cell division. I also showed the influence of external force applied to the XMAP215 molecules. Pointing toward microtubule growth, a force of 0.5 pN applied to the microtubule tip-coupled XMAP215-coated microsphere increases XMAP215 polymerization activity. However, the force of the same magnitude but applied against microtubule growth does not affect XMAP215 polymerization activity. This result can be explained by the fact, that the force acting in the direction of microtubule growth constrains XMAP215 to be at the very microtubule tip. Hence, XMAP215 can not diffuse away from plus-end and there is higher chance to incorporate tubulin dimers into the microtubule plus-end. The on- and off-rate of tubulin dimers at the microtubule end are both decreased when the external force applied either in direction of microtubule growth or opposite to it. The external force affects the off-rate slightly stronger than on-rate of tubulin dimer. Taking together, my study gives new insights into the mechanism of microtubule polymerization by XMAP215 and shows some novel properties of this protein.

<p> </p><p>In previous studies the carboxyl-terminus of microtubule-associated protein 1S was shown to interact with the <em>N</em>-methyl-D-aspartate receptor subunit NR3A (Eriksson <em>et. al.</em>)¹.  In this study, interactions between three truncations of the microtubule-associated proteins 1B and one truncation of the microtubule-associated protein 1S carboxyl-terminus and the <em>N</em>-methyl-D-aspartate receptor subunits NR1 and NR3A were examined. The study showed that an interaction occurred between amino acids 2167 to 2365 of the microtubule-associated protein 1B and NR3A.  That region of microtubule associated protein 1B corresponds to a microtubule-binding region in the light chain. It has been shown in earlier studies (Reviewed in Halpain S. <em>et a1²</em>, Riederer, BM<em>.  et.al³</em>.) that the light chain is a active part of the protein that have been post translational cleaved. The MAP 1 proteins are present in all tissue but has higher concentrations in the Post Synaptic Density of neurons in the central nervous system.  The <em>N</em>-methyl-D-aspartate receptors are present in glial cells and in the dendritic shafts of the central nervous system neurons (Eriksson <em>et. al.</em>)¹. The diseases were these proteins may play a part is mainly memory destructive diseases such as Alzheimers disease and in muscular dystrophy, but these assumptions are still being speculated.</p><p> </p>

Senile plaques (Aβ) and neurofibrillary tangles (tau) are pathological hallmarks of Alzheimer’s disease (AD). If and how the formation of these deposits are mechanistically linked remains mainly unknown. In recent years, the focus has shifted from insoluble protein deposits to soluble aggregates of Aβ and tau. Protofibrils are large soluble Aβ oligomers which were linked to AD by the discovery of the Arctic AβPP mutation. Treatment of young tg-ArcSwe mice with an Aβ protofibril-selective antibody, mAb158, cleared protofibrils, prevented amyloid plaque deposition and protected cultured cells from protofibril-mediated toxicity. This suggests that Aβ protofibrils are necessary for the formation of Aβ deposits. Functional assessment of tg-ArcSwe mice in IntelliCage demonstrated hippocampal-dependent behavioral deficits such as memory/learning impairments, hyperactivity and perseverance behavior. Learning impairments did not correlate to Aβ-measures but to calbindin, which might be a good marker for Aβ-mediated neuronal dysfunction. Splicing of exon 10 in the tau gene differs between human and mouse brain. Exon 10 is part of the microtubule-binding domains which helps to maintain microtubule stability and axonal transport, functions vital to neuronal viability. Axonal transport dysfunction has been proposed as a common pathway of Aβ and tau pathogenesis in AD. Generation of a novel tau mouse model with absence of exon 10 led to age-dependent sensorimotor impairments which may relate to dysfunctions in cerebellum. No tau pathology was evident suggesting that a trigger of tau fibrillization e.g. a human Aβ or tau aggregate is needed. Generation of AβPPxE10 bitransgenic mice with no exon 10 showed lower Aβ plaque burden. Possibly changes in microtubule function lead to altered intracellular AβPP transport and Aβ production. Initiation of tau pathology in AβPPxE10 mice might require a certain type of Aβ-aggregates which is not produced or exist at too low concentration in transgenic mouse brain. In summary, the Aβ protofibril-selective antibody was found to be a promising treatment for AD. The IntelliCage system was proven to be useful for functional evaluation of AβPP mice. Exon 10 in tau was shown to affect sensorimotor functions and Aβ pathology in bitransgenic mice by mechanisms that deserve further investigation.

At the onset of cell division microtubules growing from spindle pole bodies (SPB) interact with each other to form the mitotic spindle enabling proper chromosome positioning and segregation. However, the exact mechanism of microtubule dynamics and microtubule associated proteins (MAPs) underlying spindle assembly is still not well understood. We developed an in vivo method to observe spindle assembly in the fission yeast Schizosaccharomyces pombe by inducing depolymerization of already formed and grown spindles by subjecting the cells to low temperatures, followed by subsequent repolymerization at a permissive temperature. We observed that microtubules pivot, i.e., perform angular movement around the SPB in a random manner, exploring the intranuclear space. Eventually microtubules extending from opposite SPBs come into contact and establish an antiparallel connection thus reassembling the spindle. Mutant approaches revealed that deletion of ase1 and klp5 did not prevent spindle reassembly, however introduced aberrations during the spindle formation. Amazingly, cut7p showed direct colocalization with microtubule overlap during spindle reassembly. Abrogation of cut7p led to inability to form a functional spindle. Thus, cut7p is the main regulator of spindle formation in fission yeast. None of the mutant strains affected microtubule pivoting, confirming that microtubule pivoting is a random movement unrelated to MAPs.

Cell-type specific dendritic morphologies emerge via complex growth mechanisms modulated by intrinsic and extrinsic signaling coupled with activity-dependent regulation. Combined, these processes converge on cytoskeletal effectors to direct dendritic arbor development, stabilize mature architecture, and facilitate structural plasticity. Transcription factors (TFs) function as essential cell intrinsic regulators of dendritogenesis involving both combinatorial and cell-type specific effects, however the molecular mechanisms via which these TFs govern arbor development and dynamics remain poorly understood. Studies in Drosophila dendritic arborization (da) sensory neurons have revealed combinatorial roles of the TFs Cut and Knot in modulating dendritic morphology, however putative convergent nodal points of Cut/Knot cytoskeletal regulation remain elusive. Here we use a combined neurogenomic, bioinformatic, and genetic approach to identify and molecularly characterize downstream effectors of these TFs. From these analyses, we identified Formin3 (Form3) as a convergent transcriptional target of both Cut and Knot. We demonstrate that Form3 functions cell-autonomously in class IV (CIV) da neurons to stabilize distal higher order branching along the proximal-distal axis of dendritic arbors. Furthermore, live confocal imaging of multi-fluor cytoskeletal reporters and IHC analyses reveal that form3 mutants exhibit a specific collapse of the dendritic microtubule (MT) cytoskeleton, the functional consequences of which include defective dendritic trafficking of mitochondria and satellite Golgi. Biochemical analyses reveal Form3 directly interacts with MTs via the FH1/FH2 domains. Form3 is predicted to interact with two alpha-tubulin N-acetyltransferases (ATAT1) suggesting it may promote MT stabilization via acetylation. Analyses of acetylated dendritic MTs supports this hypothesis as defects in form3 lead to reductions, whereas overexpression promotes increases in MT acetylation. Neurologically, mutations in Inverted Formin 2 (INF2; the human ortholog of form3) have been causally linked to dominant intermediate Charcot-Marie-Tooth (CMT) disease E. CMT sensory neuropathies lead to distal sensory loss resulting in a reduced ability to sense heat, cold, and pain. Intriguingly, disruption of form3 function in CIV nociceptive neurons results in a severe impairment in nocifensive behavior in response to noxious heat, which can be rescued by expression of INF2 revealing shared primordial functions in regulating nociception and providing novel mechanistic insights into the potential etiological bases of CMT sensory neuropathies.