Search

Objective Generator site pain is a relatively common phenomenon in patients undergoing spinal cord stimulation (SCS) that complicates management and effective pain relief. This pain may be managed conservatively, with repositioning of the battery and, in some cases, with explant. Here we explore our experience with management of generator site pain (“pocket pain”) in a large single-center study. Methods All SCS permanent implants and implantable pulse generator (IPG) placements over 9 years were reviewed. Of 785 cases, we identified 43 patients with pocket pain (5.5%). Demographics and treatments of the pocket pain cohort were analyzed. Results The mean age (± SEM) of the pocket pain cohort was 46.86 ± 1.06, and there were 10/33 males/females. Females were overrepresented in pocket pain cohort (76.7%) when compared with the total SCS cohort (59.0%) (X2 = 5.93, P = 0.015). Diagnosis included failed back surgery syndrome (51.2%), complex regional pain syndrome (23.3%), and chronic neuropathic pain (25.5%). No patients improved with conservative therapy. All patients either went on to revision (n = 23) or explant (n = 20). Time from initial surgery to development of pocket pain was 7.5 months (range: 0.3–88) and from pocket pain to revision surgery was 4.5 months (range: 0.4–26). In addition, significantly more pocket pain patients (65.1%) had workers’ compensation (WC) insurance compared with patients without pocket pain (24.9%) (X2 = 33.3, P Conclusion In our institutional experience, pocket pain was inadequately managed with conservative treatments. Being female and having SCS filed under WC increased risk of pocket pain. Future work will explore the nuances in device placement based on body shape and manual activity responsibilities.

Spinal cord stimulation (SCS) is a widely accepted effective treatment for managing chronic pain. SCS outcomes depend highly on accurate placement of SCS electrodes at the appropriate spine level for a desired pain relief. Intraoperative neurophysiological monitoring (IONM) under general anesthesia provides an objective real-time mapping of the dorsal columns, and has been shown to be a safe and effective tool. IONM applies stimulation to multiple electrode contacts at various intensities and monitors the triggered electromyography (EMG) responses in several muscle groups simultaneously. Therefore, it requires dynamic communication between neurosurgeon and neurophysiologist and continuous real-time annotations of the responses, which makes the procedure complex and experience-based. Here, we describe an automated data visualization tool that generates patient specific activity maps using intraoperatively collected signals. Responses were collected using a High-resolution (HR)-SCS lead with 8 columns of electrodes spanning the dorsal columns. Our JavaScript/Python based graphical user interface (GUI) provides a fast and robust visualization of EMG activity via denoising, feature extraction, normalization, and overlaying of the activity maps on body images in selected colormaps. In contrast to reviewing series of EMG signals, our user-friendly tool provides a rapid and robust analysis of stimulation effects on various muscle groups and direct comparison across subjects and/or stimulation settings. Future work includes expanding analytics capabilities and operating room implementation as a real-time processing tool that can be used in conjunction with the current IONM techniques.

Introduction: Stereotactic neurosurgical techniques are increasingly used to deliver biologics, such as cells and viruses, although standardized procedures are necessary to ensure consistency and reproducibility. Objective: We provide an instructional guide to help plan for complex image-guided trajectories; this may be of particular benefit to surgeons new to biologic trials and companies planning such trials. Methods: We show how nuclei can be segmented and multiple trajectories with multiple injection points can be created through a single or multiple burr hole(s) based on preoperative images. Screenshots similar to those shown in this article can be used for planning purposes and for quality control in clinical trials. Results: This method enables the precise definition of 3-D target structures, such as the putamen, and efficient planning trajectories for biologic injections. The technique is generalizable and largely independent of procedural format, and thus can be integrated with frame-based or frameless platforms to streamline reproducible therapeutic delivery. Conclusions: We describe an easy-to-use and generalizable protocol for intracerebral trajectory planning for stereotactic delivery of biologics. Although we highlight intracerebral stem cell delivery to the putamen using a frame-based stereotactic delivery system, similar strategies may be employed for different brain nuclei using different platforms. We anticipate this will inform future advanced and fully automated neurosurgical procedures to help unify the field and decrease inherent variability seen with manual trajectory planning.

At present, surgical resection of primary intramedullary spinal cord tumors is the mainstay of treatment. However, given the dimensional constraints of the narrow spinal canal and dense organization of the ascending and descending tracts, intramedullary spinal cord tumor resection carries a significant risk of iatrogenic neurological injury. Intraoperative neurophysiological monitoring (IONM) and mapping techniques have been developed to evaluate the functional integrity of the essential neural pathways and optimize the surgical strategies. IONM can also inform on impending harm to at-risk structures and can correlate with postoperative functional recovery if damage has occurred. Direct waves (D-waves) will provide immediate feedback on the integrity of the lateral corticospinal tract. In the present review, we have provided an update on the utility of D-waves for spinal cord tumor resection. We have highlighted the neuroanatomical and neurophysiological insights from the use of D-wave monitoring, the technical considerations and limitations of the D-wave technique, and multimodal co-monitoring with motor-evoked potentials and somatosensory-evoked potentials. Together with motor-evoked potentials, D-waves can help to guide the extent of tumor resection and provide intraoperative warning signs and alarm criteria to direct the surgical strategy. D-waves can also serve as prognostic biomarkers for long-term recovery of postoperative motor function. We propose that the use of D-wave IONM can contribute key findings for clinical decision-making during spinal cord tumor resection.

Central neuropathic pain (CNP) affects millions worldwide, with an estimated prevalence of around 10% globally. Although there are a wide variety of treatment options available, due to the complex and multidimensional nature in which CNP arises and presents symptomatically, many patients still experience painful symptoms. Pharmaceutical, surgical, non-invasive, cognitive and combination treatment options offer a generalized starting point for alleviating symptoms; however, a more customized approach may provide greater benefit. Here, we comment on the current treatment options that exist for CNP and further suggest the need for additional research regarding the use of biomarkers to help individualize treatment options for patients.

Human elongating multi-lineage organized (EMLOC) gastruloid technology captures key aspects of trunk neurodevelopment including neural integration with cardiogenesis. We generate multi-chambered, contractile EMLOC gastruloids with integrated central and peripheral neurons using defined culture conditions and signaling factors. hiPSC colonies are primed by activating FGF and Wnt signaling pathways for co-induced lineages. EMLOC gastruloids are then initialized with primed cells in suspension culture using timed exposure to FGF2, HGF, IGF1, and Y-27632. Cardiogenesis is stimulated by FGF2, VEGF, and ascorbic acid. For complete details on the use and execution of this protocol, please refer to Olmsted and Paluh (2022).

Solitary fibrous tumors (SFTs) are rare soft tissue neoplasms that can impact the central nervous system (CNS). SFTs comprise

OBJECTIVE The incidence of hemorrhage in patients who undergo deep brain stimulation (DBS) and spinal cord stimulation (SCS) is between 0.5% and 2.5%. Coagulation status is one of the factors that can predispose patients to the development of these complications. As a routine part of preoperative assessment, the authors obtain prothrombin time (PT), partial thromboplastin time (PTT), and platelet count. However, insurers often cover only PT/PTT laboratory tests if the patient is receiving warfarin/heparin. The authors aimed to examine their experience with abnormal coagulation parameters in patients who underwent neuromodulation. METHODS Patients who underwent neuromodulation (SCS, DBS, or intrathecal pump implantation) over a 9-year period and had preoperative laboratory values available were included. The authors determined abnormal values on the basis of a clinical protocol utilized at their practice, which combined the normal ranges of the laboratory tests and clinical relevance. This protocol had cutoff values of 12 seconds and 39 seconds for PT and PTT, respectively, and < 120,000 platelets/μl. The authors identified risk factors for these abnormalities and described interventions. RESULTS Of the 1767 patients who met the inclusion criteria, 136 had abnormal preoperative laboratory values. Five of these 136 patients had values that were misclassified as abnormal because they were within the normal ranges at the outside facility where they were tested. Fifty-one patients had laboratory values outside the ranges of our protocol, but the surgeons reviewed and approved these patients without further intervention. Of the remaining 80 patients, 8 had known coagulopathies and 24 were receiving warfarin/heparin. The remaining 48 patients were receiving other anticoagulant/antiplatelet medications. These included apixaban/rivaroxaban/dabigatran anticoagulants (n = 22; mean ± SD PT 13.7 ± 2.5 seconds) and aspirin/clopidogrel/other antiplatelet medications (n = 26; mean ± SD PT 14.4 ± 5.8 seconds). Eight new coagulopathies were identified and further investigated with hematological analysis. CONCLUSIONS New anticoagulants and antiplatelet medications are not monitored with PT/PTT, but they affect coagulation status and laboratory values. Although platelet function tests aid in a subset of medications, it is more difficult to assess the coagulation status of patients receiving novel anticoagulants. PT/PTT may provide value preoperatively.

Neural cell interventions in spinal cord injury (SCI) have focused predominantly on transplanted multipotent neural stem/progenitor cells (NSPCs) for animal research and clinical use due to limited information on survival of spinal neurons. However, transplanted NSPC fate is unpredictable and largely governed by injury-derived matrix and cytokine factors that are often gliogenic and inflammatory. Here, using a rat cervical hemicontusion model, we evaluate the survival and integration of hiPSC-derived spinal motor neurons (SMNs) and oligodendrocyte progenitor cells (OPCs). SMNs and OPCs were differentiated in vitro through a neuromesodermal progenitor stage to mimic the natural origin of the spinal cord. We demonstrate robust survival and engraftment without additional injury site modifiers or neuroprotective biomaterials. Ex vivo differentiated neurons achieve cervical spinal cord matched transcriptomic and proteomic profiles, meeting functional electrophysiology parameters prior to transplantation. These data establish an approach for ex vivo developmentally accurate neuronal fate specification and subsequent transplantation for a more streamlined and predictable outcome in neural cell-based therapies of SCI.

The inaccessibility of scientific discovery to human development at post-implantation, including specialization and differentiation, necessitates sophisticated heterogenous 3D in vitro models. This protocol describes the generation and self-organization of human elongating multi-lineage organized (EMLO) gastruloids in suspension without the need for supplied extracellular matrix (ECM). EMLO gastruloids can be matured to large organoid states comprised of interconnected tissue microstructures of the trunk. These include correlates of the neuromesodermal progenitor-derived central nervous system, the neural crest cell-derived peripheral nervous system, the endoderm-derived primitive gut tube, and the mesoderm-derived splanchnic mesenchyme. Herein, we provide critical details for the reproducible generation of human EMLOs in vitro.

Enhanced Recovery After Surgery (ERAS) protocols describe a standardized method of preoperative, perioperative, and postoperative care to enhance outcomes and minimize complication risks surrounding elective surgical intervention. A growing body of evidence is being generated as we learn to apply principles of ERAS standardization to neurosurgical patients. First applied in spinal surgery, ERAS protocols have been extended to cranial neuro-oncologic procedures. This review synthesizes recent findings to generate evidence-based guidelines to manage neurosurgical oncology patients with standardized systems and assess ability of these systems to coordinate multidisciplinary, patient-centric care efforts. Furthermore, we highlight the potential usefulness of multimedia, app-based communication platforms to facilitate patient education, autonomy, and team communication within each of the 3 settings.

Multi-lineage development from gastruloids is enabling unprecedented opportunities to model and study human embryonic processes and is expected to accelerate

Summary To repair neural circuitry following spinal cord injury (SCI), neural stem cell (NSC) transplantation has held a primary focus; however, stochastic outcomes generate challenges driven in part by NSC differentiation and tumor formation. The recent ability to generate regionally specific neurons and their support cells now allows consideration of directed therapeutic approaches with pre-differentiated and networked spinal neural cells. Here, we form encapsulated, transplantable neuronal networks of regionally matched cervical spinal motor neurons, interneurons, and oligodendrocyte progenitor cells derived through trunk-biased neuromesodermal progenitors. We direct neurite formation in alginate-based neural ribbons to generate electrically active, synaptically connected networks, characterized by electrophysiology and calcium imaging before transplantation into rodent models of contused SCI for evaluation at 10-day and 6-week timepoints. The in vivo analyses demonstrate viability and retention of interconnected synaptic networks that readily integrate with the host parenchyma to advance goals of transplantable neural circuitry for SCI treatment., Graphical abstract, Highlights • Neuromesodermal progenitor derivation of human spinal neurons as therapeutic cells • Neural ribbons bridge in vitro network formation and in vivo host transplantation • In vivo visualization of encapsulated graft placement with magnetic resonance imaging • Six-week viability of human neuronal networks with OPCs in rat contusion SCI, Neuroscience; Bioengineering; Tissue engineering

Human stem cell technologies including self-assembling 3D tissue models provide unprecedented access to early neurodevelopment and enable fundamental insights into neuropathologies. Gastruloid models have yet to be used to investigate the developing nervous system. Here we generate elongating multi-lineage-organized (EMLO) gastruloids with trunk identity that co-develop central and peripheral nervous system (CNS, PNS) correlates. We track migrating neural crest cells that differentiate to form peripheral neurons integrated with an upstream spinal cord region. This follows initial EMLO polarization events, and is coordinated with primitive gut tube elongation and cardiomyocyte differentiation. By immunofluorescence of multi-lineage and functional biomarkers, we evaluate EMLOs over a twenty-two day period, and apply them to investigate the impact of mu opioid receptor modulation on neuronal activity. This comprehensive study demonstrates a novel combined CNS-PNS model of early organogenesis and integration events in the trunk to benefit human biomedical research.

Stem cell technologies including self-assembling 3D tissue models provide access to early human neurodevelopment and fundamental insights into neuropathologies. Gastruloid models have not been used to investigate co-developing central and peripheral neuronal systems with trunk mesendoderm which we achieve here in elongating multi-lineage organized (EMLO) gastruloids. We evaluate EMLOs over a forty-day period, applying immunofluorescence of multi-lineage and functional biomarkers, including day 16 single-cell RNA-Seq, and evaluation of ectodermal and non-ectodermal neural crest cells (NCCs). We identify NCCs that differentiate to form peripheral neurons integrated with an upstream spinal cord region after day 8. This follows initial EMLO polarization events that coordinate with endoderm differentiation and primitive gut tube formation during multicellular spatial reorganization. This combined human central-peripheral nervous system model of early organogenesis highlights developmental events of mesendoderm and neuromuscular trunk regions and enables systemic studies of tissue interactions and innervation of neuromuscular, enteric and cardiac relevance., The authors generate EMLOs (elongating multi-lineage organized gastruloids): organoids that self-organize to form compartments with characteristics of the central nervous system, peripheral nervous system, mesenchyme, and gut tube.

Pet ownership has been shown to decrease morbidity and mortality in several aspects of health but has not been studied in chronic pain patients. We evaluate whether subjects who underwent spinal cord stimulation (SCS) and own a pet have improved outcomes compared to non-pet owners.After obtaining IRB approval, we re-contacted 38 subjects who underwent SCS surgery with preoperative and 1-year postoperative data on Numerical Rating Scale (NRS), McGill Pain Questionnaire (MPQ), Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), and Pain Catastrophizing scale (PCS). We examined influence of pets and pet ownership-specific behaviors on improvement in SCS outcomes.Patients included 24 males/14 females with a mean age of 59.9 ± 11.5 years. At mean follow-up of 12.2 months (range 10-14), there were improvements in NRS, ODI, BDI, PCS and MPQ. Twenty subjects owned pets and 18 did not; all believed pet ownership could improve health. Pet owners improved more on NRS-right now (p = 0.05) and BDI (p = 0.05), and were more satisfied with SCS (p = 0.04). No significant improvement was seen in ODI, MPQ, or PCS. However, PCS did improve in pet owners who exercised their pet (PCS-total, p 0.01; PCS-helplessness, p 0.01; PCS-rumination, p = 0.05; PCS-magnification, p = 0.02).We provide preliminary evidence that pet ownership is associated with improved pain, depression and SCS satisfaction. Exercising with a pet also appears to be beneficial in limiting pain catastrophizing. Pets show promise as a novel means to improve patient SCS outcomes.

Improved human stem cell interventions to treat CNS trauma requires continued expansion of in vitro models and delivery platforms to fill gaps in analysis and treatment. Transplanted neural stem cells (NSCs) face unique, multi-faceted challenges beyond survival that include differentiation, maturation, and integration into a complex cytokine-releasing microenvironment that impinges on a multipotent cell type. Alternate strategies to transplant neurons and neuronal networks deserve reevaluation, particularly since novel differentiation protocols mimicking region-specific developmental and positional cues have recently emerged. To investigate transplantation of neurons and their early networks, we generate in vitro neural ribbons containing spinal neurons and support cells anatomically matched for cervical spinal cord injury (SCI). These glutamate-responsive, electrically-active neural ribbons apply a new hiPSC differentiation strategy transiting through neuromesodermal progenitors (NMps) to derive developmentally relevant spinal motor neurons (SMNs), interneurons (INs), and oligodendrocyte progenitor cells (OPCs). Bioinformatic profiling validates region-specific identities. Neurons and neuronal networks are functionally evaluated for action potential firing, calcium signaling, population activity, and synaptogenesis. NMp-derived neurons survive in vivo within the subacute phase hemi-contusion injury cavity when delivered either as free suspension or as encapsulated networks of pre-formed CNS cytoarchitectures. Delivery as encapsulated networks further supports survival of lower cell numbers and rapid graft penetration into host tissue. Neural network ribbons therefore provide a novel intermediary approach between cell suspensions and complex organoids for investigating network formation and early transplantation events with hiPSC-derived neurons, providing flexibility to rapidly tune cell type(s), cell ratios, and traceable biomarkers.Significance StatementIn the two decades since human stem cell technologies have emerged, the challenge has remained to improve the developmentally relevant derivation of therapeutic cells. The ability to now generate anatomically matched neurons for SCI necessitates a re-evaluation of these cells and their networks in vitro and in vivo. In this study, we apply developmental cues via neuromesodermal progenitors to generate spinal neurons from hiPSCs. Genetic and functional evaluation of these cells as in vitro neuronal networks, due to their capacity to survive and graft effectively within the rat subacute contusion cavity, offer novel approaches for customizing SCI transplantation. This work demonstrates a strategy to develop transplantable, chemically-responsive networks linking in vitro models with injury customization towards improved in vivo outcomes.

Cell therapy for the injured spinal cord will rely on combined advances in human stem cell technologies and delivery strategies. Here we encapsulate homotypic spinal cord neural stem cells (scNSCs) in an alginate-based neural ribbon delivery platform. We perform a comprehensive in vitro analysis and qualitatively demonstrate graft survival and injury site retention using a rat C4 hemi-contusion model. Pre-configured neural ribbons are transport-stable modules that enable site-ready injection, and can support scNSC survival and retention in vivo. Neural ribbons offer multifunctionality in vitro including co-encapsulation of the injury site extracellular matrix modifier chondroitinase ABC (chABC), tested here in glial scar models, and ability of cervically-patterned scNSCs to differentiate within neural ribbons and project axons for integration with 3-D external matrices. This is the first extensive in vitro characterization of neural ribbon technology, and constitutes a plausible method for reproducible delivery, placement, and retention of viable neural cells in vivo.

As a renewable source of progenitor and mature cell types, human iPSCs offer promise to replace or restore impaired neural circuits in the injured nervous system. CNS delivery of neural stem cell suspensions lacking pre-connected networks requires their differentiation, maturation, and connectivity in vivo. By contrast, integrating specified neural networks and their support cells with biomaterials allows the advancement of tailored transplantation strategies. Here, we demonstrate encapsulated 3D electrically-active and glutamate-responsive neural ribbon networks using differentiated hiPSC-derived spinal motor neurons and oligodendrocyte progenitor support cells. We apply comprehensive multi-parameter analysis in vitro to interrogate synaptogenesis, myotube innervation, action potential firing and relevant bioinformatics profiles. As proof-of-principle for spinal cord delivery, we inject neural ribbons within the contused injury cavity in rat and qualitatively demonstrate cell viability. Neural ribbons therefore constitute a tunable method to deliver pre-configured, physiologically-matched functional cytoarchitectures to the CNS.

In pluripotent stem cell differentiation, embryoid bodies (EBs) provide a three-dimensional [3D] multicellular precursor in lineage specification. The internal structure of EBs is not well characterized yet is predicted to be an important parameter to differentiation. Here, we use custom SU-8 molds to generate transparent lithography-templated arrays of polydimethylsiloxane (LTA-PDMS) for high throughput analysis of human embryonic stem cell (hESC) EB formation and internal architecture. EBs formed in 200 and 500 μm diameter microarray wells by use of single cells, 2D clusters, or 3D early aggregates were compared. We observe that 200 μm EBs are monocystic versus 500 μm multicystic EBs that contain macro, meso and microsized cysts. In adherent differentiation of 500 μm EBs, the multicystic character impairs the 3D to 2D transition creating non-uniform monolayers. Our findings reveal that EB core structure has a size-dependent character that influences its architecture and cell population uniformity during early differentiation.

Summary Microtubule-organizing centers such as the γ-tubulin ring complex (γ-TuRC) act as a template for polarized growth and regulation of microtubules that are essential for diverse cellular structures and processes in eukaryotes. New structural models of the budding yeast γ-tubulin small complex (γ-TuSC) of the γ-TuRC combined with functional studies done in multiple eukaryotes are revealing the first mechanistic clues into control of microtubule nucleation and organization. Cross-species studies of human and budding yeast γ-TuSC proteins in fission yeast revealed conserved and divergent structural and functional features of the γ-TuSC. We show genetically that GCP3/Spc98 function is fully conserved with Alp6 across species but that functional differences exist between GCP2/Spc97 and Alp4. By further analysis of human γ-TuSC proteins, we found that GCP3 assembles normally into the >2000 kDa fission yeast γ-TuRC and that the GCP3 gene replaces fission yeast alp6. Interestingly, human GCP2 replaces the essential alp4 gene but is unable to rescue a normally recessive G1 defect of the alp4-1891 allele that results in loss of γ-TuRC from poles in subsequent cell cycles. Biochemically, GCP2 incorporation into fission yeast γ-TuRC is limited in the presence of Alp4; instead, the bulk of GCP2 fractionates as smaller complexes. By generating a functional Alp4–GCP2 chimeric protein we determined that the GCP2 N-terminal domain limits its ability to fully displace or compete with Alp4 during γ-TuRC assembly. Our findings have broad importance for understanding the essential domains of γ-TuSC proteins in the γ-TuRC mechanism.

The realization of personalized medicine through human induced pluripotent stem cell (iPSC) technology can be advanced by transcriptomics, epigenomics, and bioinformatics that inform on genetic pathways directing tissue development and function. When possible, population diversity should be included in new studies as resources become available. Previously we derived replicate iPSC lines of African American, Hispanic-Latino and Asian self-designated ethnically diverse (ED) origins with normal karyotype, verified teratoma formation, pluripotency biomarkers, and tri-lineage in vitro commitment. Here we perform bioinformatics of RNA-Seq and ChIP-seq pluripotency data sets for two replicate Asian and Hispanic-Latino ED-iPSC lines that reveal differences in generation of contractile cardiomyocytes but similar and robust differentiation to multiple neural, pancreatic, and smooth muscle cell types. We identify shared and distinct genes and contributing pathways in the replicate ED-iPSC lines to enhance our ability to understand how reprogramming to iPSC impacts genes and pathways contributing to cardiomyocyte contractility potential.

In pluripotent stem cell differentiation, embryoid bodies (EBs) provide a three-dimensional [3D] multicellular precursor in lineage specification. The internal structure of EBs is not well characterized yet is predicted to be an important parameter to differentiation. Here, we use custom SU-8 molds to generate transparent lithography-templated arrays of polydimethylsiloxane (LTA-PDMS) for high throughput analysis of human embryonic stem cell (hESC) EB formation and internal architecture. EBs formed in 200 and 500 μm diameter microarray wells by use of single cells, 2D clusters, or 3D early aggregates were compared. We observe that 200 μm EBs are monocystic versus 500 μm multicystic EBs that contain macro, meso and microsized cysts. In adherent differentiation of 500 μm EBs, the multicystic character impairs the 3D to 2D transition creating non-uniform monolayers. Our findings reveal that EB core structure has a size-dependent character that influences its architecture and cell population uniformity during early differentiation.

Bipolar spindle assembly is a critical control point for initiation of mitosis through nucleation and organization of spindle microtubules and is regulated by kinesin-like proteins. In fission yeast, the kinesin-14 Pkl1 binds the γ-tubulin ring complex (γ-TuRC) microtubule-organizing centre at spindle poles and can alter its structure and function. Here we show that kinesin-14 blocks microtubule nucleation in yeast and reveal that this inhibition is countered by the kinesin-5 protein, Cut7. Furthermore, we demonstrate that Cut7 binding to γ-TuRC and the Cut7 BimC domain are both required for inhibition of Pkl1. We also demonstrate that a yeast kinesin-14 peptide blocks microtubule nucleation in two human breast cancer cell lines, suggesting that this mechanism is evolutionarily conserved. In conclusion, using genetic, biochemical and cell biology approaches we uncover antagonistic control of microtubule nucleation at γ-TuRC by two kinesin-like proteins, which may represent an attractive anti-mitotic target for cancer therapies., Mitotic spindle assembly requires strict control of microtubule nucleation by γ-tubulin ring complexes. Olmsted et al. report that the kinesin-like proteins Pkl1 and Cut7 antagonistically regulate nucleation in fission yeast, and show that a Pkl1 peptide blocks spindle assembly in human cancer cells.

Mitotic spindle assembly is a critical control point in eukaryotic chromosome segregation. In fission yeast conserved mitotic kinesin-like proteins (Klps) Kinesin-14 and Kinesin-5 are emerging as novel regulators of the γ-tubulin ring complex (γ-TuRC) MTOC. While these Klps typically participate in microtubule roles for spindle assembly, alternatively in fission yeast they localize to γ-TuRC and when co-deleted a bipolar spindle forms. Our analysis by genetics, biochemistry, cell biology and nanotechnology provides new knowledge on mitotic mechanisms in S. pombe. Previous work from our lab and others uncovered a novel functional relationship between Kinesin-14 Pkl1 and all proteins of the γ-tubulin small complex (γ-TuSC). We demonstrated that Pkl1 binds γ-TuRC through Motor and Tail interactions to directly regulate its function. A Pkl1 Tail peptide is sufficient in vitro and disrupts γ-TuRC structure by removal of γ-tubulin subunits (Cell Cycle 2013), an action that is reversible. New data from our lab indicates that the essential Kinesin-5 Cut7 is actually dispensable in the absence of Pkl1 with which it shares an important antagonistic MTOC regulatory relationship. Cut-7 associates with FPLC purified γ-TuRC and binds to γ-tubulin similarly as Pkl1. We demonstrate in vivo that Pkl1 blocks microtubule nucleation from γ-TuRC and additionally influences spindle microtubule numbers and microtubule overlap. Kinetochore-based microtubule motors Klp5 and Klp6 may facilitate spindle organization, since triple mutants of Pkl1, Cut7 and either Kinesin-6 Klp9 or Kinesin-14 Klp2 are viable. Previously we showed in vivo that human Kinesin-14 HSET, but not Drosophila Ncd, functionally replaces Pkl1 and more recently that human γ-TuSC proteins GCP2 and GCP3 replace fission yeast Alp4 and Alp6 (JCS 2013). Our research highlights conserved in vivo functions of γ-TuSC and provides a new model of spindle assembly in S. pombe.

The γ-tubulin ring complex (γ-TuRC) is a key part of microtubule-organizing centers (MTOCs) that control microtubule polarity, organization and dynamics in eukaryotes. Understanding regulatory mechanisms of γ-TuRC function is of fundamental importance, as this complex is central to many cellular processes, including chromosome segregation, fertility, neural development, T-cell cytotoxicity and respiration. The fission yeast microtubule motor kinesin-14 Pkl1 regulates mitosis by binding to the γ-tubulin small complex (γ-TuSC), a subunit of γ-TuRC. Here we investigate the binding mechanism of Pkl1 to γ-TuSC and its functional consequences using genetics, biochemistry, peptide assays and cell biology approaches in vivo and in vitro. We identify two critical elements in the Tail domain of Pkl1 that mediate γ-TuSC binding and trigger release of γ-tubulin from γ-TuRC. Such action disrupts the MTOC and results in failed mitotic spindle assembly. This study is the first demonstration that a motor protein directly affects the structural composition of the γ-TuRC, and we provide details of this mechanism that may be of broad biological importance.

Mitotic spindle formation into a bipolar structure suitable for chromosome segregation requires reorganization of the interphase microtubule cytoskeleton. A multi-protein complex at spindle poles acts as a microtubule organizing center (MTOC). Microtubules are assembled from this site through the addition of α/β-tubulin heterodimers onto a template complex containing γ-tubulin (γ-TuSC) imbedded into a larger macromolecular ring (γ-TuRC). Our goal is to apply insights on patterning biological polymers in vivo to development of hybrid biosynthetic systems capable of utilizing microtubules in self-assembling metamorphic patterns including parquet deformation behavior. Dynamic patterning has applications in biosensing, materials design and new nanomanufacturing paradigms. Building off of recent structural insights into γ-TuSC and GCP4 with our own detailed genetic analysis, site-directed mutagenesis, cross-species functional studies and biochemical purification and nucleation assays we provide novel insights on MTOC structural requirements to nucleation. Additionally we have identified an associated regulatory mechanism utilized by a subset of Kinesin-14 members for targeting and regulatory interference at poles (TRIP) distinct from microtubule targeting elements found in other Kinesin-14 members such as Drosophila Ncd. Our in vivo analysis supports application of the recent Kollman-Agard structure as a general eukaryotic model however with species-specific protein and domain constraints as well as contact sites for Kinesin-14 regulation of γ-TuRC. Our findings have broad application towards a general understanding of cellular MTOC machinery and reiterates the flexibility of Klps to localize to multiple spindle compartments and participate in a diversity of cellular roles. Natural cellular machines provide tools and inspiration for biomimicry and for resolution of societal grand challenges through redirected applications. Using tools available through the semiconductor industry and materials science we are generating artificial centrosomes (ACENs) from nanoparticles to act as simplified nucleation centers for use in synthetic self-assembly paradigms.