Cypin binds to tubulin heterodimers and microtubule protofilaments and regulates microtubule spacing in developing hippocampal neurons.

Cytosolic PSD-95 interactor (cypin) is a multifunctional, guanine deaminase that plays a major role in shaping the morphology of the dendritic arbor of hippocampal and cortical neurons. Cypin catalyzes the Zn2+-dependent deamination of guanine to xanthine, which is then metabolized to uric acid by xanthine oxidase. Cypin binds to tubulin heterodimers via its carboxyl terminal region (amino acids (aa) 350-454), which contains a collapsin response mediator protein (CRMP) homology domain (aa 350-403). Moreover, this region alone is not sufficient to facilitate microtubule polymerization; therefore, additional cypin regions must be involved in this process. Here, we asked whether cypin binds to fully formed microtubules and how overexpression of cypin regulates the microtubule cytoskeleton in dendrites of cultured hippocampal neurons. Protein-protein docking strategies confirm that the cypin homodimer binds to tubulin heterodimers via amino acids within aa 350-454. Biochemical pull-down data suggest that aa 1-220 are necessary for cypin binding to soluble tubulin heterodimers and to taxol-stabilized microtubules. Molecular docking of the cypin homodimer to soluble tubulin heterodimers reveals a consistently observed docking pose using aa 47-71, 113-118, 174-178, and 411-418, which is consistent with our biochemical data. Additionally, overexpression of cypin in hippocampal neurons results in decreased spacing between microtubules. Our results suggest that several protein domains facilitate cypin-mediated polymerization of tubulin heterodimers into microtubules, possibly through a mechanism whereby cypin dimers bind to multiple tubulin heterodimers.

Finger-powered fluidic actuation and mixing via MultiJet 3D printing.

Additive manufacturing, or three-dimensional (3D) printing, has garnered significant interest in recent years towards the fabrication of sub-millimeter scale devices for an ever-widening array of chemical, biological and biomedical applications. Conventional 3D printed fluidic systems, however, still necessitate the use of non-portable, high-powered external off-chip sources of fluidic actuation, such as electro-mechanical pumps and complex pressure-driven controllers, thus limiting their scope towards point-of-need applications. This work proposes entirely 3D printed sources of human-powered fluidic actuation which can be directly incorporated into the design of any 3D printable sub-millifluidic or microfluidic system where electrical power-free operation is desired. Multiple modular, single-fluid finger-powered actuator (FPA) designs were fabricated and experimentally characterized. Furthermore, a new 3D fluidic one-way valve concept employing a dynamic bracing mechanism was developed, demonstrating a high diodicity of ∼1117.4 and significant reduction in back-flow from the state-of-the-art. As a result, fabricated FPA prototypes achieved tailorable experimental fluid flow rates from ∼100 to ∼3000 µL min-1 without the use of electricity. Moreover, a portable human-powered two-fluid pulsatile fluidic mixer, capable of generating fully-mixed fluids in 10 seconds, is presented, demonstrating the application of FPAs towards on-chip integration into more complex 3D printed fluidic networks.

3D microfluidic gradient generator for combination antimicrobial susceptibility testing.

Microfluidic concentration gradient generators (µ-CGGs) have been utilized to identify optimal drug compositions through antimicrobial susceptibility testing (AST) for the treatment of antimicrobial-resistant (AMR) infections. Conventional µ-CGGs fabricated via photolithography-based micromachining processes, however, are fundamentally limited to two-dimensional fluidic routing, such that only two distinct antimicrobial drugs can be tested at once. This work addresses this limitation by employing Multijet-3D-printed microchannel networks capable of fluidic routing in three dimensions to generate symmetric multidrug concentration gradients. The three-fluid gradient generation characteristics of the fabricated 3D µ-CGG prototype were quantified through both theoretical simulations and experimental validations. Furthermore, the antimicrobial effects of three highly clinically relevant antibiotic drugs, tetracycline, ciprofloxacin, and amikacin, were evaluated via experimental single-antibiotic minimum inhibitory concentration (MIC) and pairwise and three-way antibiotic combination drug screening (CDS) studies against model antibiotic-resistant Escherichia coli bacteria. As such, this 3D µ-CGG platform has great potential to enable expedited combination AST screening for various biomedical and diagnostic applications.

3D printed microfluidic devices for circulating tumor cells (CTCs) isolation.

Isolation of circulating tumor cells (CTCs) from blood samples has important prognostic and therapeutic implications for cancer treatments, but the process is very challenging due to the low concentration of CTCs. In this study, we report a novel 3D printed microfluidic device functionalized with anti-EpCAM (epithelial cell adhesion molecule) antibodies to isolate CTCs from human blood samples. A 3D printing technology was utilized with specially designed interior structures to fabricate a microfluidic device with high surface area and fluid flow manipulation, increasing capture efficiency of tumor cells. These devices with the optimal flow rate (1 mL/h) and channel length (2 cm) were demonstrated to test three kinds of EpCAM positive cancer cell lines (MCF-7 breast cancer, SW480 colon cancer, and PC3 prostate cancer), and one kind of EpCAM negative cancer cell line (293T kidney cancer). Experimentally, the capture efficiency higher than 90% has been achieved, and the isolation of MCF-7 tumor cells from spiked human blood samples has also been demonstrated. Combined with DNA-based detection (e.g. polymerase chain reaction or DNA sequencing), the detection and analysis of released DNAs from captured tumor cells could be another future direction for clinical diagnosis and cancer treatment.

Autophagy protein NRBF2 has reduced expression in Alzheimer's brains and modulates memory and amyloid-beta homeostasis in mice.

BACKGROUND: Dysfunctional autophagy is implicated in Alzheimer's Disease (AD) pathogenesis. The alterations in the expression of many autophagy related genes (ATGs) have been reported in AD brains; however, the disparity of the changes confounds the role of autophagy in AD. METHODS: To further understand the autophagy alteration in AD brains, we analyzed transcriptomic (RNAseq) datasets of several brain regions (BA10, BA22, BA36 and BA44 in 223 patients compared to 59 healthy controls) and measured the expression of 130 ATGs. We used autophagy-deficient mouse models to assess the impact of the identified ATGs depletion on memory, autophagic activity and amyloid-ß (Aß) production. RESULTS: We observed significant downregulation of multiple components of two autophagy kinase complexes BECN1-PIK3C3 and ULK1/2-FIP200 specifically in the parahippocampal gyrus (BA36). Most importantly, we demonstrated that deletion of NRBF2, a component of the BECN1-PIK3C3 complex, which also associates with ULK1/2-FIP200 complex, impairs memory in mice, alters long-term potentiation (LTP), reduces autophagy in mouse hippocampus, and promotes Aß accumulation. Furthermore, AAV-mediated NRBF2 overexpression in the hippocampus not only rescues the impaired autophagy and memory deficits in NRBF2-depleted mice, but also reduces ß-amyloid levels and improves memory in an AD mouse model. CONCLUSIONS: Our data not only implicates NRBF2 deficiency as a risk factor for cognitive impairment associated with AD, but also support the idea of NRBF2 as a potential therapeutic target for AD.

CSF-1 controls cerebellar microglia and is required for motor function and social interaction.

Microglia, the brain resident macrophages, critically shape forebrain neuronal circuits. However, their precise function in the cerebellum is unknown. Here we show that human and mouse cerebellar microglia express a unique molecular program distinct from forebrain microglia. Cerebellar microglial identity was driven by the CSF-1R ligand CSF-1, independently of the alternate CSF-1R ligand, IL-34. Accordingly, CSF-1 depletion from Nestin+ cells led to severe depletion and transcriptional alterations of cerebellar microglia, while microglia in the forebrain remained intact. Strikingly, CSF-1 deficiency and alteration of cerebellar microglia were associated with reduced Purkinje cells, altered neuronal function, and defects in motor learning and social novelty interactions. These findings reveal a novel CSF-1-CSF-1R signaling-mediated mechanism that contributes to motor function and social behavior.

Cypin: A novel target for traumatic brain injury.

Cytosolic PSD-95 interactor (cypin), the primary guanine deaminase in the brain, plays key roles in shaping neuronal circuits and regulating neuronal survival. Despite this pervasive role in neuronal function, the ability for cypin activity to affect recovery from acute brain injury is unknown. A key barrier in identifying the role of cypin in neurological recovery is the absence of pharmacological tools to manipulate cypin activity in vivo. Here, we use a small molecule screen to identify two activators and one inhibitor of cypin's guanine deaminase activity. The primary screen identified compounds that change the initial rate of guanine deamination using a colorimetric assay, and secondary screens included the ability of the compounds to protect neurons from NMDA-induced injury and NMDA-induced decreases in frequency and amplitude of miniature excitatory postsynaptic currents. Hippocampal neurons pretreated with activators preserved electrophysiological function and survival after NMDA-induced injury in vitro, while pretreatment with the inhibitor did not. The effects of the activators were abolished when cypin was knocked down. Administering either cypin activator directly into the brain one hour after traumatic brain injury significantly reduced fear conditioning deficits 5 days after injury, while delivering the cypin inhibitor did not improve outcome after TBI. Together, these data demonstrate that cypin activation is a novel approach for improving outcome after TBI and may provide a new pathway for reducing the deficits associated with TBI in patients.

Infantile amnesia reflects a developmental critical period for hippocampal learning.

Episodic memories formed during the first postnatal period are rapidly forgotten, a phenomenon known as 'infantile amnesia'. In spite of this memory loss, early experiences influence adult behavior, raising the question of which mechanisms underlie infantile memories and amnesia. Here we show that in rats an experience learned during the infantile amnesia period is stored as a latent memory trace for a long time; indeed, a later reminder reinstates a robust, context-specific and long-lasting memory. The formation and storage of this latent memory requires the hippocampus, follows a sharp temporal boundary and occurs through mechanisms typical of developmental critical periods, including the expression switch of the NMDA receptor subunits from 2B to 2A, which is dependent on brain-derived neurotrophic factor (BDNF) and metabotropic glutamate receptor 5 (mGluR5). Activating BDNF or mGluR5 after training rescues the infantile amnesia. Thus, early episodic memories are not lost but remain stored long term. These data suggest that the hippocampus undergoes a developmental critical period to become functionally competent.

The Parkinson's Disease-Associated Mutation LRRK2-G2019S Impairs Synaptic Plasticity in Mouse Hippocampus.

Parkinson's disease (PD) is a major movement disorder characterized by the loss of dopamine neurons and formation of Lewy bodies. Clinical and pathological evidence indicates that multiple brain regions are affected in PD in a spatiotemporal manner and are associated with a variety of motor and nonmotor symptoms, including disturbances in mood, executive function, and memory. The common PD-associated gene for leucine-rich repeat kinase, leucine-rich repeat kinase 2 (LRRK2), is highly expressed in brain regions that are involved with nonmotor functions, including the neocortex and hippocampus, but whether mutant LRRK2 contributes to neuronal dysfunction in these regions is unknown. Here, we use bacterial artificial chromosome transgenic mouse models of LRRK2 to explore potential nonmotor mechanisms of PD. Through electrophysiological analysis of the Schaffer collateral-CA1 synapse in dorsal hippocampus, we find that overexpression of LRRK2-G2019S increases basal synaptic efficiency through a postsynaptic mechanism, and disrupts long-term depression. Furthermore, these effects of the G2019S mutation are age dependent and can be normalized by acute inhibition of LRRK2 kinase activity. In contrast, overexpression of wild-type LRRK2 has no effect under the same conditions, suggesting a specific phenotype for the G2019S mutation. These results identify a pathogenic function of LRRK2 in the hippocampus that may contribute to nonmotor symptoms of PD. SIGNIFICANCE STATEMENT: Parkinson's disease (PD) is among the most common neurological diseases and is best known for its adverse effects on brain regions that control motor function, resulting in tremor, rigidity, and gait abnormalities. Less well appreciated are the psychiatric symptoms experienced by many PD patients, including depression and memory loss, which do not respond well to currently available treatments for PD. Here, we describe functional effects of a common PD-linked mutation of leucine-rich repeat kinase 2 in the mouse hippocampus, an area of the brain that is responsible for encoding and retaining memories. By providing a potential mechanism for some of the cognitive symptoms produced by this mutation, our findings may lead to novel approaches for the treatment of nonmotor symptoms of PD.

Parental THC exposure leads to compulsive heroin-seeking and altered striatal synaptic plasticity in the subsequent generation.

Recent attention has been focused on the long-term impact of cannabis exposure, for which experimental animal studies have validated causal relationships between neurobiological and behavioral alterations during the individual's lifetime. Here, we show that adolescent exposure to Δ(9)-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, results in behavioral and neurobiological abnormalities in the subsequent generation of rats as a consequence of parental germline exposure to the drug. Adult F1 offspring that were themselves unexposed to THC displayed increased work effort to self-administer heroin, with enhanced stereotyped behaviors during the period of acute heroin withdrawal. On the molecular level, parental THC exposure was associated with changes in the mRNA expression of cannabinoid, dopamine, and glutamatergic receptor genes in the striatum, a key component of the neuronal circuitry mediating compulsive behaviors and reward sensitivity. Specifically, decreased mRNA and protein levels, as well as NMDA receptor binding were observed in the dorsal striatum of adult offspring as a consequence of germline THC exposure. Electrophysiologically, plasticity was altered at excitatory synapses of the striatal circuitry that is known to mediate compulsive and goal-directed behaviors. These findings demonstrate that parental history of germline THC exposure affects the molecular characteristics of the striatum, can impact offspring phenotype, and could possibly confer enhanced risk for psychiatric disorders in the subsequent generation.

Semiautomated analysis of dendrite morphology in cell culture.

Quantifying dendrite morphology is a method for determining the effect of biochemical pathways and extracellular agents on neuronal development and differentiation. Quantification can be performed using Sholl analysis, dendrite counting, and length quantification. These procedures can be performed on dendrite-forming cell lines or primary neurons grown in culture. In this protocol, we describe the use of a set of computer programs to assist in quantifying many aspects of dendrite morphology, including changes in total and localized arbor complexity.

Caffeine decreases systemic urea in elite soccer players during intermittent exercise.

PURPOSE: We investigated the effects of caffeine on the ammonia and amino acid metabolism of elite soccer players. METHODS: In this double-blind randomized study, athletes (n = 19) received 5 mg·kg caffeine or lactose (LEx, control) and performed 45 min of intermittent exercise followed by an intermittent recovery test (Yo-Yo IR2) until exhaustion. The caffeine-supplemented athletes were divided into two groups (CEx and SCEx) depending on their serum caffeine levels (<900% and >10,000%, respectively). Data were analyzed by ANOVA and Tukey post hoc test (P < 0.05 was considered to be statistically significant). RESULTS: Caffeine supplementation did not significantly affect the performance (LEx = 12.3 ± 0.3 km·h, 1449 ± 378 m; CEx = 12.2 ± 0.5 km·h, 1540 ± 630 m; SCEx = 12.3 ± 0.5 km·h, 1367 ± 330 m). Exercise changed the blood concentrations of several amino acids and increased the serum concentrations of ammonia, glucose, lactate, and insulin. The LEx group showed an exercise-induced increase in valine (∼29%), which was inhibited by caffeine. Higher serum caffeine levels abolished the exercise-induced increase (∼24%-27%) in glutamine but did not affect the exercise-induced increase in alanine (∼110%-160%) and glutamate (42%-61%). In response to exercise, the SCEx subjects did not exhibit an increase in uremia and showed a significantly lower increase in their serum arginine (15%), citrulline (16%), and ornithine (ND) concentrations. CONCLUSIONS: Our data suggest that caffeine might decrease systemic urea by decreasing the glutamine serum concentration, which decreases the transportation of ammonia to the liver and thus urea synthesis.

To branch or not to branch: How PSD-95 regulates dendrites and spines.

PSD-95, a synaptic scaffolding protein, plays important roles in the regulation of dendritic spine morphology and glutamate receptor signaling. We have recently shown that PSD-95 also plays an extrasynaptic role during development. PSD-95 shapes dendrite branching patterns in cultured rat hippocampal neurons by altering microtubule dynamics via an association with the microtubule end-binding protein-3 (EB3). We discovered that PSD-95 interacts directly with EB3 and that the result of this interaction decreases EB3 binding to and EB3 comet lifetime on microtubules. This decrease in lifetime also correlates to decreased dendrite branching. Here we present an additional effect of PSD-95 overexpression on microtubules. Neurons that overexpress PSD-95 show increased distance between microtubules in a manner that is not fully dependent on the interaction between PSD-95 and EB3. We discuss these new data in the context of the role of PSD-95 in shaping the dendritic arbor, and we extend our findings to include a discussion of how PSD-95 may guide neurons toward a more mature and synapse-oriented growth stage.

PSD-95 alters microtubule dynamics via an association with EB3.

Little is known about how the neuronal cytoskeleton is regulated when a dendrite decides whether to branch or not. Previously, we reported that postsynaptic density protein 95 (PSD-95) acts as a stop signal for dendrite branching. It is yet to be elucidated how PSD-95 affects the cytoskeleton and how this regulation relates to the dendritic arbor. Here, we show that the SH3 (src homology 3) domain of PSD-95 interacts with a proline-rich region within the microtubule end-binding protein EB3. Overexpression of PSD-95 or mutant EB3 results in a decreased lifetime of EB3 comets in dendrites. In line with these data, transfected rat neurons show that overexpression of PSD-95 results in less organized microtubules at dendritic branch points and decreased dendritogensis. The interaction between PSD-95 and EB3 elucidates a function for a novel region of EB3 and provides a new and important mechanism for the regulation of microtubules in determining dendritic morphology.

Automated Sholl analysis of digitized neuronal morphology at multiple scales: Whole cell Sholl analysis versus Sholl analysis of arbor subregions.

The morphology of dendrites and the axon determines how a neuron processes and transmits information. Neurite morphology is frequently analyzed by Sholl analysis or by counting the total number of neurites and branch tips. However, the time and resources required to perform such analysis by hand is prohibitive for the processing of large data sets and introduces problems with data auditing and reproducibility. Furthermore, analyses performed by hand or using course-grained morphometric data extraction tools can obscure subtle differences in data sets because they do not store the data in a form that facilitates the application of multiple analytical tools. To address these shortcomings, we have developed a program (titled "Bonfire") to facilitate digitization of neurite morphology and subsequent Sholl analysis. Our program builds upon other available open-source morphological analysis tools by performing Sholl analysis on subregions of the neuritic arbor, enabling the detection of local level changes in dendrite and axon branching behavior. To validate this new tool, we applied Bonfire analysis to images of hippocampal neurons treated with 25 ng/ml brain-derived neurotrophic factor (BDNF) and untreated control neurons. Consistent with prior findings, conventional Sholl analysis revealed that global exposure to BDNF increases the number of neuritic intersections proximal to the soma. Bonfire analysis additionally uncovers that BDNF treatment affects both root processes and terminal processes with no effect on intermediate neurites. Taken together, our data suggest that global exposure of hippocampal neurons to BDNF results in a reorganization of neuritic segments within their arbors, but not necessarily a change in their number or length. These findings were only made possible by the neurite-specific Sholl data returned by Bonfire analysis.

Identification of small molecule compounds with higher binding affinity to guanine deaminase (cypin) than guanine.

Guanine deaminase (GDA; cypin) is an important metalloenzyme that processes the first step in purine catabolism, converting guanine to xanthine by hydrolytic deamination. In higher eukaryotes, GDA also plays an important role in the development of neuronal morphology by regulating dendritic arborization. In addition to its role in the maturing brain, GDA is thought to be involved in proper liver function since increased levels of GDA activity have been correlated with liver disease and transplant rejection. Although mammalian GDA is an attractive and potential drug target for treatment of both liver diseases and cognitive disorders, prospective novel inhibitors and/or activators of this enzyme have not been actively pursued. In this study, we employed the combination of protein structure analysis and experimental kinetic studies to seek novel potential ligands for human guanine deaminase. Using virtual screening and biochemical analysis, we identified common small molecule compounds that demonstrate a higher binding affinity to GDA than does guanine. In vitro analysis demonstrates that these compounds inhibit guanine deamination, and more surprisingly, affect GDA (cypin)-mediated microtubule assembly. The results in this study provide evidence that an in silico drug discovery strategy coupled with in vitro validation assays can be successfully implemented to discover compounds that may possess therapeutic value for the treatment of diseases and disorders where GDA activity is abnormal.

The yin-yang of dendrite morphology: unity of actin and microtubules.

Actin and microtubules (MT) are targets of numerous molecular pathways that control neurite outgrowth. To generate a neuronal protrusion, coordinated structural changes of the actin and MT cytoskeletons must occur. Neurite formation occurs when actin filaments (F-actin) are destabilized, filopodia are extended, and MTs invade filopodia. This process results in either axon or dendrite formation. Axonal branching involves interplay between F-actin and MTs, with F-actin and MTs influencing polymerization, stabilization, and maintenance of each other. Our knowledge of the mechanisms regulating development of the axon, however, far eclipses our understanding of dendritic development and branching. The two classes of neurites, while fundamentally similar in their ability to elongate and branch, dramatically differ in growth rate, orientation of polarized MT bundles, and mechanisms that initiate branching. In this review, we focus on how F-actin, MTs, and proteins that link the two cytoskeletons coordinate to specifically initiate dendritic events.

Neuronal polarization: old cells can learn new tricks.

Regeneration was once thought to be exclusive to young neurons. Now, a new study shows that functional and interconnected hippocampal neurons have the potential to quickly recover from losing an axon. They do so by signaling a dendrite to change its specification and replace the missing axon by rearranging the microtubule cytoskeleton.

Severe tongue injury in an adolescent with epilepsy: a case report.

Epilepsy and other neurological disorders can have profound social, physical and psychological consequences, especially when they begin in childhood. Moreover, seizure episodes may cause fractures, burns, head injuries and oral injuries. This report presents a case history of an adolescent with a severe tongue injury related to epileptic seizures and outlines the proposed treatment, which included use of a maxillary silicone bite guard that allowed healing of the tongue injury within a few months.