Tubulin Post-translational Modifications Research Articles

Acetylated Microtubules Are Preferentially Bundled Leading to Enhanced Kinesin-1 Motility

The motor proteins kinesin and dynein transport organelles, mRNA, proteins, and signaling molecules along the microtubule cytoskeleton. In addition to serving as tracks for transport, the microtubule cytoskeleton directs intracellular trafficking by regulating the activity of motor proteins through the organization of the filament network, microtubule-associated proteins, and tubulin posttranslational modifications. However, it is not well understood how these factors influence motor motility, and in vitro assays and live cell observations often produce disparate results. To systematically examine the factors that contribute to cytoskeleton-based regulation of motor protein motility, we extracted intact microtubule networks from cells and tracked the motility of single fluorescently labeled motor proteins on these cytoskeletons. We find that tubulin acetylation alone does not directly affect kinesin-1 motility. However, acetylated microtubules are predominantly bundled, and bundling enhances kinesin run lengths and provides a greater number of available kinesin binding sites. The neuronal MAP tau is also not sensitive to tubulin acetylation, but enriches preferentially on highly curved regions of microtubules where it strongly inhibits kinesin motility. Taken together, these results suggest that the organization of the microtubule network is a key contributor to the regulation of motor-based transport.

Tubulin acetylation accompanies autophagy development induced by different abiotic stimuli in Arabidopsis thaliana.

Microtubules (MTs) play an important role in the regulation of autophagy development in yeast and animal as well as in plant cells. MTs participate in maturation and traffic of autophagosomes through their dynamic state changes and post-translational modifications of tubulin, namely acetylation. We subjected Arabidopsis thaliana seedlings to metabolic-, salt-, osmotic stresses as well as irradiation of ultraviolet B and investigated the involvement of plant MTs in the development of stress-induced autophagy via tubulin acetylation. For this purpose Arabidopsis thaliana line expressing autophagy-related protein 8 h (atg8h)-GFP was generated to investigate autophagy, applying the level of free GFP as an indicator of autophagy development. Using autophagosome confocal imaging and Western blot analysis of Atg8 post-translational lipidation and synchronous GFP release it was shown that all examined stressful stimuli led to pronounced development of autophagy, particularly in different root tissues. Moreover, autophagy development was accompanied by α-tubulin acetylation under all stressful conditions. Presented data indicate the possible role of the post-translational acetylation of α-tubulin in the mediation of plant stress-induced autophagy.

Stabilization of dynamic microtubules by mDia1 drives Tau-dependent Aβ1-42 synaptotoxicity.

Oligomeric Amyloid β1-42 (Aβ) plays a crucial synaptotoxic role in Alzheimer's disease, and hyperphosphorylated tau facilitates Aβ toxicity. The link between Aβ and tau, however, remains controversial. In this study, we find that in hippocampal neurons, Aβ acutely induces tubulin posttranslational modifications (PTMs) and stabilizes dynamic microtubules (MTs) by reducing their catastrophe frequency. Silencing or acute inhibition of the formin mDia1 suppresses these activities and corrects the synaptotoxicity and deficits of axonal transport induced by Aβ. We explored the mechanism of rescue and found that stabilization of dynamic MTs promotes tau-dependent loss of dendritic spines and tau hyperphosphorylation. Collectively, these results uncover a novel role for mDia1 in Aβ-mediated synaptotoxicity and demonstrate that inhibition of MT dynamics and accumulation of PTMs are driving factors for the induction of tau-mediated neuronal damage.

Differential Expression of Tubulin Acetylase and Deacetylase Between the Damaged Central and Peripheral Branch of Dorsal Root Ganglion Neurons.

BackgroundThe differences between the peripheral and central branches of the dorsal root ganglion (DRG) have not been fully elucidated. This study aimed to explore the expression of tubulin post-translational modifications (acetylation and deacetylation) between damaged peripheral and central branches of DRG neurons.Material/MethodsFifty Sprague-Dawley rats were randomly assigned to five groups with 10 rats in each group. These five groups consisted of spinal nerve ligation (SNL) at 24 hour and 48 hour, and cauda equina compression (CEC) at 24 hour and 48 hour, and a sham group. SNL injury in rats was induced by ligating L5 and L6 spinal nerves with 1-0 silk thread outboard the DRGs. CEC injury in rats was induced by a piece of silicone (10×1×1 mm) placed under the laminae of the L5–6 vertebra. Sham-operated rats underwent a simple laminectomy in L4, but silicone was not implanted. The expression profile of acetylase and deacetylase was examined by real-time PCR, Western blotting, and immunohistochemistry.ResultsIn the experimental groups, rats presented increased expression of acetylase (NAT1 and MEC-17) and decreased expression of deacetylase (Sirt2 and HDAC6) levels. Additionally, the expression of NAT1 and MEC-17 was gradually increased in DRG neurons following peripheral axonal injury compared to central axonal injury in a time-dependent manner. Conversely, the expression of Sirt2 and HDAC6 was gradually decreased in DRG neurons following peripheral axonal injury compared to central axonal injury in a time-dependent manner.ConclusionsOur study indicated that insufficiency of acetylase and upregulation of deacetylase in DRG neurons after central axonal injury may contribute to the pathogenesis of cauda equine syndrome.

Tubulin glycylation controls primary cilia length.

As essential components of the eukaryotic cytoskeleton, microtubules fulfill a variety of functions that can be temporally and spatially controlled by tubulin posttranslational modifications. Tubulin glycylation has so far been mostly found on motile cilia and flagella, where it is involved in the stabilization of the axoneme. In contrast, barely anything is known about the role of glycylation in primary cilia because of limitations in detecting this modification in these organelles. We thus developed novel glycylation-specific antibodies with which we detected glycylation in many primary cilia. Glycylation accumulates in primary cilia in a length-dependent manner, and depletion or overexpression of glycylating enzymes modulates the length of primary cilia in cultured cells. This strongly suggests that glycylation is essential for the homeostasis of primary cilia, which has important implications for human disorders related to primary cilia dysfunctions, such as ciliopathies and certain types of cancer.

Molecular interactions between tubulin tails and glutamylases reveal determinants of glutamylation patterns.

Posttranslational modifications of tubulin currently emerge as key regulators of microtubule functions. Polyglutamylation generates a variety of modification patterns that are essential for controlling microtubule functions in different cell types and organelles, and deregulation of these patterns has been linked to ciliopathies, cancer and neurodegeneration. How the different glutamylating enzymes determine precise modification patterns has so far remained elusive. Using computational modelling, molecular dynamics simulations and mutational analyses we now show how the carboxy-terminal tails of tubulin bind into the active sites of glutamylases. Our models suggest that the glutamylation sites on α- and β-tubulins are determined by the positioning of the tails within the catalytic pocket. Moreover, we found that the binding modes of α- and β-tubulin tails are highly similar, implying that most enzymes could potentially modify both, α- and β-tubulin. This supports a model in which the binding of the enzymes to the entire microtubule lattice, but not the specificity of the C-terminal tubulin tails to their active sites, determines the catalytic specificities of glutamylases.

Tubulin acetylation protects long-lived microtubules against mechanical ageing

Introductory ParagraphLong-lived microtubules endow the eukaryotic cell with long-range transport abilities. While long-lived microtubules are acetylated on lysine 40 of α-tubulin (αK40), acetylation takes place after stabilization1 and does not protect against depolymerization2. Instead, αK40 acetylation has been proposed to mechanically stabilize microtubules3. Yet how modification of αK40, a residue exposed to the microtubule lumen and inaccessible from MAPs and motors1,4, could affect microtubule mechanics remains an open question. Here we develop FRET-based assays that report on the lateral interactions between protofilaments and find that αK40 acetylation directly weakens inter-protofilament interactions. Congruently, αK40 acetylation affects two processes largely governed by inter-protofilament interactions, reducing the nucleation frequency and accelerating the shrinkage rate. Most relevant to the biological function of acetylation, microfluidics manipulations demonstrate that αK40 acetylation enhances flexibility and confers resilience against repeated mechanical stresses. Thus, unlike deacetylated microtubules that accumulate damages when subjected to repeated stresses, long-lived microtubules are protected from mechanical aging through their acquisition of αK40 acetylation. Thus, unlike other tubulin post-translational modifications that act through MAPs, motors and severing enzymes, intraluminal acetylation directly tunes the compliance and resilience of microtubules.

Mechanisms of Chromosome Congression during Mitosis.

Chromosome congression during prometaphase culminates with the establishment of a metaphase plate, a hallmark of mitosis in metazoans. Classical views resulting from more than 100 years of research on this topic have attempted to explain chromosome congression based on the balance between opposing pulling and/or pushing forces that reach an equilibrium near the spindle equator. However, in mammalian cells, chromosome bi-orientation and force balance at kinetochores are not required for chromosome congression, whereas the mechanisms of chromosome congression are not necessarily involved in the maintenance of chromosome alignment after congression. Thus, chromosome congression and maintenance of alignment are determined by different principles. Moreover, it is now clear that not all chromosomes use the same mechanism for congressing to the spindle equator. Those chromosomes that are favorably positioned between both poles when the nuclear envelope breaks down use the so-called “direct congression” pathway in which chromosomes align after bi-orientation and the establishment of end-on kinetochore-microtubule attachments. This favors the balanced action of kinetochore pulling forces and polar ejection forces along chromosome arms that drive chromosome oscillatory movements during and after congression. The other pathway, which we call “peripheral congression”, is independent of end-on kinetochore microtubule-attachments and relies on the dominant and coordinated action of the kinetochore motors Dynein and Centromere Protein E (CENP-E) that mediate the lateral transport of peripheral chromosomes along microtubules, first towards the poles and subsequently towards the equator. How the opposite polarities of kinetochore motors are regulated in space and time to drive congression of peripheral chromosomes only now starts to be understood. This appears to be regulated by position-dependent phosphorylation of both Dynein and CENP-E and by spindle microtubule diversity by means of tubulin post-translational modifications. This so-called “tubulin code” might work as a navigation system that selectively guides kinetochore motors with opposite polarities along specific spindle microtubule populations, ultimately leading to the congression of peripheral chromosomes. We propose an integrated model of chromosome congression in mammalian cells that depends essentially on the following parameters: (1) chromosome position relative to the spindle poles after nuclear envelope breakdown; (2) establishment of stable end-on kinetochore-microtubule attachments and bi-orientation; (3) coordination between kinetochore- and arm-associated motors; and (4) spatial signatures associated with post-translational modifications of specific spindle microtubule populations. The physiological consequences of abnormal chromosome congression, as well as the therapeutic potential of inhibiting chromosome congression are also discussed.

Microtubule-regulating proteins and cAMP-dependent signaling in neuroblastoma differentiation.

Neurons are highly differentiated cells responsible for the conduction and transmission of information in the nervous system. The proper function of a neuron relies on the compartmentalization of their intracellular domains. Differentiated neuroblastoma cells have been extensively used to study and understand the physiology and cell biology of neuronal cells. Here, we show that differentiation of N1E-115 neuroblastoma cells is more pronounced upon exposure of a chemical analog of cyclic AMP (cAMP), db-cAMP. We next analysed the expression of key microtubule-regulating proteins in differentiated cells and the expression and activation of key cAMP players such as EPAC, PKA and AKAP79/150. Most of the microtubule-promoting factors were up regulated during differentiation of N1E-115 cells, while microtubule-destabilizing proteins were down regulated. We observed an increase in tubulin post-translational modifications related to microtubule stability. As expected, db-cAMP increased PKA- and EPAC-dependent signalling. Consistently, pharmacological modulation of EPAC activity instructed cell differentiation, number of neurites, and neurite length in N1E-115 cells. Moreover, disruption of the PKA-AKAP interaction reduced these morphometric parameters. Interestingly, PKA and EPAC act synergistically to induce neuronal differentiation in N1E-115. Altogether these results show that the changes observed in the differentiation of N1E-115 cells proceed by regulating several microtubule-stabilizing factors, and the acquisition of a neuronal phenotype is a process involving concerted although independent functions of EPAC and PKA.

Readout of the Tubulin Code by Cellular Effectors: Graded Control of Microtubule Severing by Tubulin Glutamylation

Microtubule-severing enzymes are critical for the biogenesis and maintenance of complex microtubule arrays in axons, spindles and cilia where tubulin detyrosination, acetylation and glutamylation are abundant. These modifications exhibit stereotyped patterns suggesting spatial and temporal control of microtubule functions. Using human engineered and differentially modified microtubules we find that glutamylation is the main regulator of the hereditary spastic paraplegia microtubule severing enzyme spastin and that neither detyrosination nor acetylation regulate spastin activity. Glutamylation acts as a rheostat and tunes microtubule severing as a function of glutamate number added per tubulin. Unexpectedly, glutamylation is a non-linear biphasic tuner and becomes inhibitory beyond a threshold. Furthermore, the inhibitory effect of localized glutamylation propagates across neighboring microtubules, modulating severing in trans. Our work provides the first quantitative evidence for a graded, spatially controlled response to a tubulin posttranslational modification and constitutes an essential step towards understanding how the cell interprets the tubulin code. Furthermore, it provides a biochemical link between tubulin glutamylation and complex architectures of microtubule arrays such as those in neurons where spastin deficiency causes disease.

The Effects of Guizhi Gancao Decoction on Pressure Overload-Induced Heart Failure and Posttranslational Modifications of Tubulin in Mice.

Guizhi Gancao Decoction (GGD), a traditional Chinese medical recipe, has been widely used in the treatment of cardiovascular diseases in China for centuries. The present study was carried out to determine whether GGD exerts direct protective effects against pressure overload-induced heart failure. Moreover, we investigated whether GGD affects tubulin expression and posttranslational modifications. We demonstrated that GGD ameliorated TAC caused cardiac hypertrophy by gravimetric and echocardiography analysis in C57BL/6 mice. We found that GGD abrogated TAC-induced myocardium fibrosis by Masson's staining and collagen volume fraction (CVF) analysis. By using pressure-volume hemodynamic measurements, we found that GGD prevented TAC-induced cardiac systolic and diastolic dysfunction. Immunoblotting and immunofluorescent analysis revealed that GGD abrogated TAC-induced detyrosination and acetylation abnormalities on microtubules. Our present study demonstrated potential therapeutic effects of GGD against pressure overload-induced heart failure.

The tubulin code at a glance.

Microtubules are key cytoskeletal elements of all eukaryotic cells and are assembled of evolutionarily conserved α-tubulin-β-tubulin heterodimers. Despite their uniform structure, microtubules fulfill a large diversity of functions. A regulatory mechanism to control the specialization of the microtubule cytoskeleton is the 'tubulin code', which is generated by (i) expression of different α- and β-tubulin isotypes, and by (ii) post-translational modifications of tubulin. In this Cell Science at a Glance article and the accompanying poster, we provide a comprehensive overview of the molecular components of the tubulin code, and discuss the mechanisms by which these components contribute to the generation of functionally specialized microtubules.

Cellular and Molecular Mechanisms of Centromere Drive.

The asymmetric outcome of female meiosis I, whereby an entire set of chromosomes are discarded into a polar body, presents an opportunity for selfish genetic elements to cheat the process and disproportionately segregate to the egg. Centromeres, the chromosomal loci that connect to spindle microtubules, could potentially act as selfish elements and “drive” in meiosis. We review the current understanding of the genetic and epigenetic contributions to centromere identity and describe recent progress in a powerful model system to study centromere drive in mice. The progress includes mechanistic findings regarding two main requirements for a centromere to exploit the asymmetric outcome of female meiosis. The first is an asymmetry between centromeres of homologous chromosomes, and we found this is accomplished through massive changes in the abundance of the repetitive DNA underlying centromeric chromatin. The second requirement is an asymmetry in the meiotic spindle, which is achieved through signaling from the oocyte cortex that leads to asymmetry in a posttranslational modification of tubulin, tyrosination. Together, these two asymmetries culminate in the biased segregation of expanded centromeres to the egg, and we describe a mechanistic framework to understand this process.

Posttranslational Modifications of Tubulin and Cilia.

Tubulin undergoes several highly conserved posttranslational modifications (PTMs) including acetylation, detyrosination, glutamylation, and glycylation. These PTMs accumulate on a subset of microtubules that are long-lived, including those in the basal bodies and axonemes. Tubulin PTMs are distributed nonuniformly. In the outer doublet microtubules of the axoneme, the B-tubules are highly enriched in the detyrosinated, polyglutamylated, and polyglycylated tubulin, whereas the A-tubules contain mostly unmodified tubulin. The nonuniform patterns of tubulin PTMs may functionalize microtubules in a position-dependent manner. Recent studies indicate that tubulin PTMs contribute to the assembly, disassembly, maintenance, and motility of cilia. In particular, tubulin glutamylation has emerged as a key PTM that affects ciliary motility through regulation of axonemal dynein arms and controls the stability and length of the axoneme.

Neurotoxic mechanisms of paclitaxel are local to the distal axon and independent of transport defects

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting side effect of paclitaxel and other chemotherapeutic agents. Paclitaxel binds and stabilizes microtubules, but the cellular mechanisms that underlie paclitaxel's neurotoxic effects are not well understood. We therefore used primary cultures of adult murine dorsal root ganglion neurons, the cell type affected in patients, to examine leading hypotheses to explain paclitaxel neurotoxicity. We address the role of microtubule hyperstabilization and its downstream effects. Paclitaxel administered at 10–50nM for 1–3days induced retraction bulbs at the tips of axons and arrested axon growth without triggering axon fragmentation or cell death. By correlating the toxic effects and microtubule stabilizing activity of structurally different microtubule stabilizing compounds, we confirmed that microtubule hyperstabilization, rather than an off-target effect, is the likely primary cause of paclitaxel neurotoxicity. We examined potential downstream consequences of microtubule hyperstabilization and found that changes in levels of tubulin posttranslational modifications, although present after paclitaxel exposure, are not implicated in the paclitaxel neurotoxicity we observed in the cultures. Additionally, defects in axonal transport were not implicated as an early, causative mechanism of paclitaxel's toxic effects on dorsal root ganglion neurons. By using microfluidic chambers to selectively treat different parts of the axon with paclitaxel, we found that the distal axon was primarily vulnerable to paclitaxel, indicating that paclitaxel acts directly on the distal axon to induce degenerative effects. Together, our findings point to local effects of microtubule hyperstabilization on the distal-most portion of the axon as an early mediator of paclitaxel neurotoxicity. Because sensory neurons have a unique and ongoing requirement for distal growth in order to reinnervate the epidermis as it turns over, we propose that the ability of paclitaxel to arrest their growth accounts for the selective vulnerability of sensory neurons to paclitaxel neurotoxicity.

Dual Chromatin and Cytoskeletal Remodeling by SETD2

Posttranslational modifications (PTMs) of tubulin specify microtubules for specialized cellular functions and comprise what is termed a "tubulin code." PTMs of histones comprise an analogous "histone code," although the "readers, writers, and erasers" of thecytoskeleton and epigenome have heretofore been distinct. We show that methylation is a PTM ofdynamic microtubules and that the histone methyltransferase SET-domain-containing 2 (SETD2), which is responsible for H3 lysine 36 trimethylation (H3K36me3) of histones, also methylates α-tubulin at lysine 40, the same lysine that is marked by acetylation on microtubules. Methylation of microtubules occurs during mitosis and cytokinesis and can be ablated by SETD2 deletion, which causes mitotic spindle and cytokinesis defects, micronuclei, and polyploidy. These data now identify SETD2 as a dual-function methyltransferase for both chromatin and the cytoskeleton and show a requirement for methylation in maintenance of genomic stability and the integrity of both the tubulin and histone codes.

Abstract 2932: Impaired taxane binding to MT pore sites mediates intrinsic drug resistance in diffuse gastric cancer

Abstract Successful clinical application of taxanes (microtubule-stabilizers) is limited due to intrinsic or acquired drug resistance. Thus, it is critical to unveil the molecular mechanisms of taxane resistance to significantly improve clinical outcomes. Retrospective analysis of the TAX-325 gastric cancer (GC) trial revealed that the addition of docetaxel (DTX) to cisplatin/fluorouracil increased progression-free plus overall survival, in intestinal (INT) but not in diffuse (DIF) GC subtypes. Our preclinical data confirmed that DIF GC cell lines are intrinsically resistant to taxanes. The incidence of DTX resistance in DIF GC cell lines was 2.5 times higher than INT GC cell lines. Drug efflux, tubulin posttranslational modification and differential β-tubulin isotype expression were ruled out as potential mechanisms of intrinsic taxane resistance. Thus, a new molecular mechanism must underlie the intrinsic taxane resistance in DIF GC. To quantify the kinetics of taxol binding to cellular MTs, we treated both DIF and INT groups of GC lines with the fluorescein-conjugated paclitaxel analog, Flutax-2. The Flutax-2 staining intensity of cellular MTs was assessed by live-cell confocal microscopy at different time points. Following a 3h incubation, there was less than 20% decrease in Flutax-2 intensity in the sensitive cell lines, compared to 59∼89% decrease in the resistant cell lines. These data suggested different binding kinetics between sensitive and resistant cells. We added 1μM Flutax-2 to sensitive/resistant cells’ native cytoskeletons for 0∼60 seconds to determine the association rate (kon) of Flutax-2 binding to MTs. The kon of Flutax-2 in the sensitive cell lines was significantly higher in sensitive (5.8×104M−1s−1) versus resistant cells (0.3∼2.6×104M−1s−1). Next, we measured the dissociation rates (koff) by competing the pre-bound Flutax-2 with DTX (0∼600 seconds). Although 20∼40% faster koff was observed in resistant cells, it appeared that the association rate of Flutax-2 was the dominant factor of differential taxane binding to MTs in GC cells. The binding mode of taxanes to MTs involves 1) binding to MT pores and 2) internalization to the high-affinity binding site at the MT lumen. To differentiate between the two, we used hexaflutax, which binds exclusively to the MT pores. We observed hexaflutax decorating radial MT arrays in sensitive but not in the resistant cells. As tubulin mutations around the high-affinity taxane binding site or tubulin posttranslational modifications/differential expression of β-tubulin isotype is not the case in DIF GC cell lines, our data suggest that modifications of the MT pore conformation or occlusion of the pore site is responsible for the intrinsic taxane resistance in DIF GC. Determining the origin of the defect at the pores will help design better MT-stabilizing drugs to overcome chemo-resistance, the major obstacle hindering overall survival of patients. Citation Format: Katsuhiro Kita, Giuseppe Galletti, Kyle Cleveland, Chao Zhang, Isabel Barasoain, J. Fernando Díaz, Doron Betel, Manish A. Shah, Paraskevi Giannakakou. Impaired taxane binding to MT pore sites mediates intrinsic drug resistance in diffuse gastric cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2932.

The Tubulin Code: A Navigation System for Chromosomes during Mitosis.

Before chromosomes segregate during mitosis in metazoans, they align at the cell equator by a process known as chromosome congression. This is in part mediated by the coordinated activities of kinetochore motors with opposite directional preferences that transport peripheral chromosomes along distinct spindle microtubule populations. Because spindle microtubules are all made from the same α/β-tubulin heterodimers, a critical longstanding question has been how chromosomes are guided to specific locations during mitosis. This implies the existence of spatial cues/signals on specific spindle microtubules that are read by kinetochore motors on chromosomes and ultimately indicate the way towards the equator. Here, we discuss the emerging concept that tubulin post-translational modifications (PTMs), as part of the so-called tubulin code, work as a navigation system for kinetochore-based chromosome motility during early mitosis.

Microtubule and microtubule associated protein anomalies in psychiatric disease.

Anomalies in neuronal cell architecture, in particular dendritic complexity and synaptic density changes, are widely observed in the brains of subjects with schizophrenia or mood disorders. The concept that a disturbed microtubule cytoskeleton underlies these abnormalities and disrupts synaptic connectivity is supported by evidence from clinical studies and animal models. Prominent changes in tubulin expression levels are commonly found in disease specific regions such as the hippocampus and prefrontal cortex of psychiatric patients. Genetic linkage studies associate tubulin-binding proteins such as the dihydropyrimidinase family with an increased risk to develop schizophrenia and bipolar disorder. For many years, altered immunoreactivity of microtubule associated protein-2 has been a hallmark found in the brains of individuals with schizophrenia. In this review, we present a growing body of evidence that connects a dysfunctional microtubule cytoskeleton with neuropsychiatric illnesses. Findings from animal models are discussed together with clinical data with a particular focus on tubulin post-translational modifications and on microtubule-binding proteins. © 2016 Wiley Periodicals, Inc.

The emerging role of the tubulin code: From the tubulin molecule to neuronal function and disease.

Across different cell types and tissues, microtubules are assembled from highly conserved dimers of α- and β-tubulin. Despite their highly similar structures, microtubules have functional heterogeneity, generated either by the expression of different tubulin genes, encoding distinct isotypes, or by posttranslational modifications of tubulin. This genetically encoded and posttranslational generated heterogeneity of tubulin-the "tubulin code"-has the potential to modulate microtubule structure, dynamics, and interactions with associated proteins. The tubulin code is therefore believed to regulate microtubule functions on a cellular and sub-cellular level. This review highlights the importance of the tubulin code for tubulin structure, as well as on microtubule dynamics and functions in neurons. It further summarizes recent developments in the understanding of mutations in tubulin genes, and how they are linked to neurodegenerative and neurodevelopmental disorders. The current advances in the knowledge of the tubulin code on the molecular and the functional level will certainly lead to a better understanding of how complex signaling events control microtubule functions, especially in cells of the nervous system. © 2016 Wiley Periodicals, Inc.