Neuronal innervation regulates the secretion of neurotrophic myokines and exosomes from skeletal muscle

Myokines and exosomes, originating from skeletal muscle, are shown to play a significant role in maintaining brain homeostasis. While exercise has been reported to promote muscle secretion, little is known about the effects of neuronal innervation and activity on the yield and molecular composition of biologically active molecules from muscle. As neuromuscular diseases and disabilities associated with denervation impact muscle metabolism, we hypothesize that neuronal innervation and firing may play a pivotal role in regulating secretion activities of skeletal muscles. We examined this hypothesis using an engineered neuromuscular tissue model consisting of skeletal muscles innervated by motor neurons. The innervated muscles displayed elevated expression of mRNAs encoding neurotrophic myokines, such as interleukin-6, brain-derived neurotrophic factor, and FDNC5, as well as the mRNA of peroxisome-proliferator-activated receptor γ coactivator 1α, a key regulator of muscle metabolism. Upon glutamate stimulation, the innervated muscles secreted higher levels of irisin and exosomes containing more diverse neurotrophic microRNAs than neuron-free muscles. Consequently, biological factors secreted by innervated muscles enhanced branching, axonal transport, and, ultimately, spontaneous network activities of primary hippocampal neurons in vitro. Overall, these results reveal the importance of neuronal innervation in modulating muscle-derived factors that promote neuronal function and suggest that the engineered neuromuscular tissue model holds significant promise as a platform for producing neurotrophic molecules.

Mind In Vitro Platforms: Versatile, Scalable, Robust, and Open Solutions to Interfacing with Living Neurons

Motivated by the unexplored potential of in vitro neural systems for computing and by the corresponding need of versatile, scalable interfaces for multimodal interaction, an accurate, modular, fully customizable, and portable recording/stimulation solution that can be easily fabricated, robustly operated, and broadly disseminated is presented. This approach entails a reconfigurable platform that works across multiple industry standards and that enables a complete signal chain, from neural substrates sampled through micro-electrode arrays (MEAs) to data acquisition, downstream analysis, and cloud storage. Built-in modularity supports the seamless integration of electrical/optical stimulation and fluidic interfaces. Custom MEA fabrication leverages maskless photolithography, favoring the rapid prototyping of a variety of configurations, spatial topologies, and constitutive materials. Through a dedicated analysis and management software suite, the utility and robustness of this system are demonstrated across neural cultures and applications, including embryonic stem cell-derived and primary neurons, organotypic brain slices, 3D engineered tissue mimics, concurrent calcium imaging, and long-term recording. Overall, this technology, termed "mind in vitro" to underscore the computing inspiration, provides an end-to-end solution that can be widely deployed due to its affordable (>10× cost reduction) and open-source nature, catering to the expanding needs of both conventional and unconventional electrophysiology.

Intracerebral Nanoparticle Transport Facilitated by Alzheimer Pathology and Age

Nanoparticles have emerged as potential transporters of drugs targeting Alzheimer's disease (AD), but their design should consider the blood-brain barrier (BBB) integrity and neuroinflammation of the AD brain. This study presents that aging is a significant factor for the brain localization and retention of nanoparticles, which we engineered to bind with reactive astrocytes and activated microglia. We assembled 200 nm-diameter particles using a block copolymer of poly(lactic-co-glycolic acid) (PLGA) and CD44-binding hyaluronic acid (HA). The resulting PLGA-b-HA nanoparticles displayed increased binding to CD44-expressing reactive astrocytes and activated microglia. Upon intravascular injection, nanoparticles were localized to the hippocampi of both APP/PS1 AD model mice and their control littermates at 13-16 months of age due to enhanced transvascular transport through the leaky BBB. No particles were found in the hippocampi of young adult mice. These findings demonstrate the brain localization of nanoparticles due to aging-induced BBB breakdown regardless of AD pathology.

Artificial confocal microscopy for deep label-free imaging

Widefield microscopy of optically thick specimens typically features reduced contrast due to "spatial crosstalk", in which the signal at each point in the field of view is the result of a superposition from neighbouring points that are simultaneously illuminated. In 1955, Marvin Minsky proposed confocal microscopy as a solution to this problem. Today, laser scanning confocal fluorescence microscopy is broadly used due to its high depth resolution and sensitivity, but comes at the price of photobleaching, chemical, and photo-toxicity. Here, we present artificial confocal microscopy (ACM) to achieve confocal-level depth sectioning, sensitivity, and chemical specificity, on unlabeled specimens, nondestructively. We equipped a commercial laser scanning confocal instrument with a quantitative phase imaging module, which provides optical path-length maps of the specimen in the same field of view as the fluorescence channel. Using pairs of phase and fluorescence images, we trained a convolution neural network to translate the former into the latter. The training to infer a new tag is very practical as the input and ground truth data are intrinsically registered, and the data acquisition is automated. The ACM images present significantly stronger depth sectioning than the input (phase) images, enabling us to recover confocal-like tomographic volumes of microspheres, hippocampal neurons in culture, and 3D liver cancer spheroids. By training on nucleus-specific tags, ACM allows for segmenting individual nuclei within dense spheroids for both cell counting and volume measurements. In summary, ACM can provide quantitative, dynamic data, nondestructively from thick samples, while chemical specificity is recovered computationally.

Quantitative DNA-PAINT imaging of AMPA receptors in live neurons

DNA-point accumulation for imaging at nanoscale topography (DNA-PAINT) can image fixed biological specimens with nanometer resolution and absolute stoichiometry. In living systems, however, the usage of DNA-PAINT has been limited due to high salt concentration in the buffer required for specific binding of the imager to the docker attached to the target. Here, we used multiple binding motifs of the docker, from 2 to 16, to accelerate the binding speed of the imager under physiological buffer conditions without compromising spatial resolution and maintaining the basal level homeostasis during the measurement. We imaged endogenous α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in cultured neurons-critical proteins involved in nerve communication-by DNA-PAINT in 3-dimensions using a monovalent single-chain variable fragment (scFv) to the GluA1 subunit of AMPAR. We found a heterogeneous distribution of synaptic AMPARs: ≈60% are immobile, primarily in nanodomains, defined as AMPARs that are within 0.3 μm of the Homer1 protein in the postsynaptic density; the other ∼40% of AMPARs have restricted mobility and trajectory.

Homeostatic regulation of extracellular signal-regulated kinase 1/2 activity and axonal Kv7.3 expression by prolonged blockade of hippocampal neuronal activity

Homeostatic plasticity encompasses the mechanisms by which neurons stabilize their synaptic strength and excitability in response to prolonged and destabilizing changes in their network activity. Prolonged activity blockade leads to homeostatic scaling of action potential (AP) firing rate in hippocampal neurons in part by decreased activity of N-Methyl-D-Aspartate receptors and subsequent transcriptional down-regulation of potassium channel genes including KCNQ3 which encodes K_v7.3. Neuronal K_v7 channels are mostly heterotetramers of K_v7.2 and K_v7.3 subunits and are highly enriched at the axon initial segment (AIS) where their current potently inhibits repetitive and burst firing of APs. However, whether a decrease in K_v7.3 expression occurs at the AIS during homeostatic scaling of intrinsic excitability and what signaling pathway reduces KCNQ3 transcript upon prolonged activity blockade remain unknown. Here, we report that prolonged activity blockade in cultured hippocampal neurons reduces the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) followed by a decrease in the activation of brain-derived neurotrophic factor (BDNF) receptor, Tropomyosin receptor kinase B (TrkB). Furthermore, both prolonged activity blockade and prolonged pharmacological inhibition of ERK1/2 decrease KCNQ3 and BDNF transcripts as well as the density of K_v7.3 and ankyrin-G at the AIS. Collectively, our findings suggest that a reduction in the ERK1/2 activity and subsequent transcriptional down-regulation may serve as a potential signaling pathway that links prolonged activity blockade to homeostatic control of BDNF-TrkB signaling and K_v7.3 density at the AIS during homeostatic scaling of AP firing rate.

Heterozygous Deletion of Epilepsy Gene KCNQ2 Has Negligible Effects on Learning and Memory

Neuronal Kv7/Potassium Voltage-Gated Channel Subfamily Q (KCNQ) potassium channels underlie M-current that potently suppresses repetitive and burst firing of action potentials (APs). They are mostly heterotetramers of Kv7.2 and Kv7.3 subunits in the hippocampus and cortex, the brain regions important for cognition and behavior. Underscoring their critical roles in inhibiting neuronal excitability, autosomal dominantly inherited mutations in Potassium Voltage-Gated Channel Subfamily Q Member 2 (KCNQ2) and Potassium Voltage-Gated Channel Subfamily Q Member 3 (KCNQ3) genes are associated with benign familial neonatal epilepsy (BFNE) in which most seizures spontaneously remit within months without cognitive deficits. De novo mutations in KCNQ2 also cause epileptic encephalopathy (EE), which is characterized by persistent seizures that are often drug refractory, neurodevelopmental delay, and intellectual disability. Heterozygous expression of EE variants of KCNQ2 is recently shown to induce spontaneous seizures and cognitive deficit in mice, although it is unclear whether this cognitive deficit is caused directly by Kv7 disruption or by persistent seizures in the developing brain as a consequence of Kv7 disruption. In this study, we examined the role of Kv7 channels in learning and memory by behavioral phenotyping of the KCNQ2+/− mice, which lack a single copy of KCNQ2 but dos not display spontaneous seizures. We found that both KCNQ2+/− and wild-type (WT) mice showed comparable nociception in the tail-flick assay and fear-induced learning and memory during a passive inhibitory avoidance (IA) test and contextual fear conditioning (CFC). Both genotypes displayed similar object location and recognition memory. These findings together provide evidence that heterozygous loss of KCNQ2 has minimal effects on learning or memory in mice in the absence of spontaneous seizures.

Pharmacological inhibition of STriatal-Enriched protein tyrosine Phosphatase by TC-2153 reduces hippocampal excitability and seizure propensity

OBJECTIVE

STriatal-Enriched protein tyrosine Phosphatase (STEP) is a brain-specific tyrosine phosphatase. Membrane-bound STEP61 is the only isoform expressed in hippocampus and cortex. Genetic deletion of STEP enhances excitatory synaptic currents and long-term potentiation in the hippocampus. However, whether STEP61 affects seizure susceptibility is unclear. Here we investigated the effects of STEP inhibitor TC-2153 on seizure propensity in a murine model displaying kainic acid (KA)-induced status epilepticus and its effect on hippocampal excitability.

METHODS

Adult male and female C57BL/6J mice received intraperitoneal injection of either vehicle (2.8% dimethylsulfoxide [DMSO] in saline) or TC-2153 (10 mg/kg) and then either saline or KA (30 mg/kg) 3 h later before being monitored for behavioral seizures. A subset of female mice was ovariectomized (OVX). Acute hippocampal slices from Thy1-GCaMP6s mice were treated with either DMSO or TC-2153 (10 μM) for 1 h, and then incubated in artificial cerebrospinal fluid (ACSF) and potassium chloride (15 mM) for 2 min prior to live calcium imaging. Pyramidal neurons in dissociated rat hippocampal culture (DIV 8-10) were pre-treated with DMSO or TC-2153 (10 µM) for 1 h before whole-cell patch-clamp recording.

RESULTS

TC-2153 treatment significantly reduced KA-induced seizure severity, with greater trend seen in female mice. OVX abolished this TC-2153-induced decrease in seizure severity in female mice. TC-2153 application significantly decreased overall excitability of acute hippocampal slices from both sexes. Surprisingly, TC-2153 treatment hyperpolarized resting membrane potential and decreased firing rate, sag voltage, and hyperpolarization-induced current (Ih ) of cultured hippocampal pyramidal neurons.

SIGNIFICANCE

This study is the first to demonstrate that pharmacological inhibition of STEP with TC-2153 decreases seizure severity and hippocampal activity in both sexes, and dampens hippocampal neuronal excitability and Ih . We propose that the antiseizure effects of TC-2153 are mediated by its unexpected action on suppressing neuronal intrinsic excitability.

Unstable Non-isthmic Spondylolisthesis Following Unilateral Biportal Endoscopy Assisted Unilateral Laminotomy for Bilateral Decompression: A Case Report

Lumbar decompressive laminectomy is a standard treatment for degenerative lumbar spinal stenosis, but in some cases, can lead to iatrogenic spondylolysis and delayed segmental instability. Iatrogenic spondylolysis occurs in most cases in pars interarticularis, but rare cases have also been reported, pediculolysis in pedicle and laminolysis in lamina. Minimally invasive spine surgery (MIS) is known to have a low risk of developing these iatrogenic spondylolyses, and unilateral biportal endoscopy is the MIS that has been drawing attention. We present a case of a 72-year-old female who was diagnosed with L4-5 unstable non-isthmic spondylolisthesis and severe right central disc extrusion 10 weeks after UBE assisted unilateral laminotomy for bilateral decompression (ULBD) at the consecutive segments of L3-4 and L4-5. Pre-operative imaging studies revealed severe central stenosis without spondylolisthesis at L3-L4 and L4-L5 along with L4-L5 facet tropism. She was managed by anterior lumbar interbody fusion and cement augmented pedicle screw fixation, which resulted in the complete resolution of her clinical and neurologic symptoms.

Spontaneous seizure and memory loss in mice expressing an epileptic encephalopathy variant in the calmodulin-binding domain of Kv7.2

Epileptic encephalopathy (EE) is characterized by seizures that respond poorly to antiseizure drugs, psychomotor delay, and cognitive and behavioral impairments. One of the frequently mutated genes in EE is KCNQ2, which encodes the Kv7.2 subunit of voltage-gated Kv7 potassium channels. Kv7 channels composed of Kv7.2 and Kv7.3 are enriched at the axonal surface, where they potently suppress neuronal excitability. Previously, we reported that the de novo dominant EE mutation M546V in human Kv7.2 blocks calmodulin binding to Kv7.2 and axonal surface expression of Kv7 channels via their intracellular retention. However, whether these pathogenic mechanisms underlie epileptic seizures and behavioral comorbidities remains unknown. Here, we report conditional transgenic cKcnq2+/M547V mice, in which expression of mouse Kv7.2-M547V (equivalent to human Kv7.2-M546V) is induced in forebrain excitatory pyramidal neurons and astrocytes. These mice display early mortality, spontaneous seizures, enhanced seizure susceptibility, memory impairment, and repetitive behaviors. Furthermore, hippocampal pathology shows widespread neurodegeneration and reactive astrocytes. This study demonstrates that the impairment in axonal surface expression of Kv7 channels is associated with epileptic seizures, cognitive and behavioral deficits, and neuronal loss in KCNQ2-related EE.

Waist circumference and the risk of lumbar and femur fractures: a nationwide population-based cohort study

Although obesity is known to have an influence on fracture, the relationship between lumbar and femur fractures and weight or waist circumference is controversial. We investigated the incidence of fracture with regards to waist circumference using the customised database of the Korean National Health Insurance Service (NHIS). Among 8,922,940 adults who participated at least twice in the NHIS National Health Check-up Program in South Korea between 2009 and 2011, 1,556,751 subjects (780,074 men and 776,677 women) were extracted. Over a mean follow-up of 6.5 years, multivariate-adjusted logistic regression analysis demonstrated that higher waist circumference was associated with an increased risk of femur fractures in both males and females. Moreover, the incidence of lumbar fractures was also positively associated with an increased waist circumference in males and females. An increased waist circumference showed a positive linear relationship with the risk of lumbar and femur fractures in both males and females.

Visit-to-visit changes in fasting blood sugar and the risk for cardiovascular disease and mortality in the Korean population: a nationwide population-based cohort study

OBJECTIVE

The importance of continuous monitoring of fasting blood sugar (FBS) levels of diabetic patients has been established.

MATERIALS AND METHODS

An observational prospective study was conducted. Our analysis included 1,700,796 individuals from the nationwide South Korean National Health Insurance System cohort. FBS variability was measured by standard deviation (SD).

RESULTS

Kaplan-Meier curves demonstrated elevated disease probability in the higher FBS fluctuation group compared with the lower FBS fluctuation group. After adjusting for confounding variables, Cox proportional hazards analysis showed that the hazard ratios of 411 individuals in the highest quartile of SD variation of FBS were 1.77 (95% confidence interval 1.37-2.28, p<0.001) compared with the lowest quartile of SD variation of FBS. The impact of FBS fluctuation on the risk of cardiovascular diseases (CVDs), cerebrovascular diseases, CVD mortality and all-cause mortality in the highest quartiles of diabetic and non-diabetic individuals was statistically significant.

CONCLUSIONS

Visit-to-visit FBS variability has prognostic value for predicting micro- and macrovascular disease, cardiovascular mortality, and all-cause mortality.

Multiscale Assay of Unlabeled Neurite Dynamics Using Phase Imaging with Computational Specificity

Primary neuronal cultures have been widely used to study neuronal morphology, neurophysiology, neurodegenerative processes, and molecular mechanism of synaptic plasticity underlying learning and memory. However, the unique behavioral properties of neurons make them challenging to study, with phenotypic differences expressed as subtle changes in neuronal arborization rather than easy-to-assay features such as cell count. The need to analyze morphology, growth, and intracellular transport has motivated the development of increasingly sophisticated microscopes and image analysis techniques. Due to its high-contrast, high-specificity output, many assays rely on confocal fluorescence microscopy, genetic methods, or antibody staining techniques. These approaches often limit the ability to measure quantitatively dynamic activity such as intracellular transport and growth. In this work, we describe a method for label-free live-cell cell imaging with antibody staining specificity by estimating the associated fluorescence signals via quantitative phase imaging and deep convolutional neural networks. This computationally inferred fluorescence image is then used to generate a semantic segmentation map, annotating subcellular compartments of live unlabeled neural cultures. These synthetic fluorescence maps were further applied to study the time-lapse development of hippocampal neurons, highlighting the relationships between the cellular dry mass production and the dynamic transport activity within the nucleus and neurites. Our implementation provides a high-throughput strategy to analyze neural network arborization dynamically, with high specificity and without the typical phototoxicity and photobleaching limitations associated with fluorescent markers.

An epilepsy-causing mutation leads to co-translational misfolding of the Kv7.2 channel

Background

The amino acid sequence of proteins generally carries all the necessary information for acquisition of native conformations, but the vectorial nature of translation can additionally determine the folding outcome. Such consideration is particularly relevant in human diseases associated to inherited mutations leading to structural instability, aggregation, and degradation. Mutations in the KCNQ2 gene associated with human epilepsy have been suggested to cause misfolding of the encoded Kv7.2 channel. Although the effect on folding of mutations in some domains has been studied, little is known of the way pathogenic variants located in the calcium responsive domain (CRD) affect folding. Here, we explore how a Kv7.2 mutation (W344R) located in helix A of the CRD and associated with hereditary epilepsy interferes with channel function.

Results

We report that the epilepsy W344R mutation within the IQ motif of CRD decreases channel function, but contrary to other mutations at this site, it does not impair the interaction with Calmodulin (CaM) in vitro, as monitored by multiple in vitro binding assays. We find negligible impact of the mutation on the structure of the complex by molecular dynamic computations. In silico studies revealed two orientations of the side chain, which are differentially populated by WT and W344R variants. Binding to CaM is impaired when the mutated protein is produced in cellulo but not in vitro, suggesting that this mutation impedes proper folding during translation within the cell by forcing the nascent chain to follow a folding route that leads to a non-native configuration, and thereby generating non-functional ion channels that fail to traffic to proper neuronal compartments.

Conclusions

Our data suggest that the key pathogenic mechanism of Kv7.2 W344R mutation involves the failure to adopt a configuration that can be recognized by CaM in vivo but not in vitro.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01040-1.

Subjective Perception of Individuals with Physical Disabilities Regarding Exercise Equipment Use

Rehabilitation exercise is effective for improving the health of persons with physical disabilities. However, there are limited studies on their perception of exercise equipment use. The purpose of this study was to investigate the subjectivity to understand the types of perceptions of individuals with physical disabilities regarding the use of exercise equipment in South Korea. This study used Q-methodology. A literature review and focus group interviews with individuals with physical disabilities were conducted to construct Q-Population. Q-statements were selected from the Q-population, after which Q-sorting was executed by P-sample. The results indicated 4 perception types: (1) "Independent user," (2) "Practical user," (3) "Motivational user," and (4) "Convenience user." Recommendations were provided for developing exercise equipment for use by individuals with physical disabilities. This study revealed 4 perception categories and the findings have strong potential to contribute to the development of proper services and the effective utilization of exercise equipment for individuals with physical disabilities.

Development of the Parental Questionnaire for Cerebral Visual Impairment in Children Younger than 72 Months

Background and Purpose

Cerebral visual impairment (CVI) is an underdiagnosed condition in children, and its assessment tools have focused on older children. We aimed to develop a parental questionnaire for cerebral visual impairment (PQCVI) for screening CVI in young children.

Methods

The PQCVI comprised 23 questions based on a modified version of Houliston and Dutton's questionnaire for older children. The PQCVI with neurocognitive function tests was applied to 201 child-parent pairs with typically developing children younger than 72 months (age 32.4±20.1 months, mean±standard deviation). The children were classified into six age groups. The normative data, cutoff scores, and internal reliability were assessed and item analysis was performed. We referred to the total score for all questions as the cerebral visual function (CVF) score.

Results

The normative data showed that the CVF score and the scores corresponding to ventral-stream and dorsal-stream visual functions plausibly increased with age. The scores rapidly reached 90% of their maximum values up to the age of 36 months, after which they increased slowly. Cronbach's alpha for all questions across all age groups was 0.97, showing excellent consistency. The item difficulty and item discrimination coefficients showed that the questions were generally adequate for this age stage.

Conclusions

The PQCVI items produced reliable responses in children younger than 72 months. The rapid increase in scores before the age of 3 years supports the importance of early identification of CVI. Following additional clinical verification, the PQCVI may be useful for CVI screening.

Development of the Korean Developmental Screening Test for Infants and Children (K-DST)

BACKGROUND

Most developmental screening tools in Korea are adopted from foreign tests. To ensure efficient screening of infants and children in Korea, a nationwide screening tool with high reliability and validity is needed.

PURPOSE

This study aimed to independently develop, standardize, and validate the Korean Developmental Screening Test for Infants and Children (K-DST) for screening infants and children for neurodevelopmental disorders in Korea.

METHODS

The standardization and validation conducted in 2012-2014 of 3,284 subjects (4-71 months of age) resulted in the first edition of the K-DST. The restandardization and revalidation performed in 2015-2016 of 3.06 million attendees of the National Health Screening Program for Infants and Children resulted in the revised K-DST. We analyzed inter-item consistency and test-retest reliability for the reliability analysis. Regarding the validation of K-DST, we examined the construct validity, sensitivity and specificity, receiver operating characteristic curve analysis, and a criterion-related validity analysis.

RESULTS

We ultimately selected 8 questions in 6 developmental domains. For most age groups and each domain, internal consistency was 0.73-0.93 and test-retest reliability was 0.77-0.88. The revised K-DST had high discriminatory ability with a sensitivity of 0.833 and specificity of 0.979. The test supported construct validity by distinguishing between normal and neurodevelopmentally delayed groups. The language and cognition domain of the revised K-DST was highly correlated with the K-Bayley Scales of Infant Development-II's Mental Age Quotient (r=0.766, 0.739), while the gross and fine motor domains were highly correlated with Motor Age Quotient (r=0.695, 0.668), respectively. The Verbal Intelligence Quotient of Korean Wechsler Preschool and Primary Scales of Intelligence was highly correlated with the K-DST cognition and language domains (r=0.701, 0.770), as was the performance intelligence quotient with the fine motor domain (r=0.700).

CONCLUSION

The K-DST is reliable and valid, suggesting its good potential as an effective screening tool for infants and children with neurodevelopmental disorders in Korea.

The Role of Kv7 Channels in Neural Plasticity and Behavior

Activity-dependent persistent changes in neuronal intrinsic excitability and synaptic strength are widely thought to underlie learning and memory. Voltage-gated KCNQ/K_v7 potassium channels have been of great interest as the potential targets for memory disorders due to the beneficial effects of their antagonists in cognition. Importantly, de novo dominant mutations in their neuronal subunits KCNQ2/K_v7.2 and KCNQ3/K_v7.3 are associated with epilepsy and neurodevelopmental disorder characterized by developmental delay and intellectual disability. The role of K_v7 channels in neuronal excitability and epilepsy has been extensively studied. However, their functional significance in neural plasticity, learning, and memory remains largely unknown. Here, we review recent studies that support the emerging roles of K_v7 channels in intrinsic and synaptic plasticity, and their contributions to cognition and behavior.

Stochastic Particle Approach Electrochemistry (SPAE): Estimating Size, Drift Velocity, and Electric Force of Insulating Particles

Stochastic particle impact electrochemistry (SPIE) is considered one of the most important electro-analytical methods to understand the physicochemical properties of single entities. SPIE of individual insulating particles (IPs) has been particularly crucial for analyses of bioparticles. In this article, we introduce stochastic particle approach electrochemistry (SPAE) for electrochemical analyses of IPs, which is the advanced version of SPIE; SPAE is analogous to SPIE but focuses on deciphering a sudden current drop (SCD) by an IP-approach toward the edge of an ultramicroelectrode (UME). Polystyrene particles (PSPs) with and without different surface functionalities (-COOH and - NH₃) as well as fixed human platelets (F-HPs) were used as model IPs. From theory based on finite element analysis, a sudden current drop (SCD) induced by an IP during electro-oxidation (or reduction) of a redox mediator on a UME can represent the rapid approach of an IP toward an edge of a UME, where a strong electric field is generated. It is also found that the amount of current drop, i_drop, of an SCD depends strongly on both the size of an IP and the concentration of redox electrolyte. From simulations based on the SPAE model that fit the experimentally obtained SCDs of three types of PSPs or F-HP dispersed in solutions with two redox electrolytes, their size distribution histograms are estimated, from which their average radii determined by SPAE are compared to those from scanning electron microscopic images. In addition, the drift velocity and corresponding electric force of the PSPs and F-HPs during their approach toward an edge of a Pt UME are estimated, which cannot be addressed currently with SPIE. We further learned that the estimated drift velocity and the corresponding electric force could provide a relative order of the number of excess surface charges on the IPs.

Optimizing Quantum Dot Probe Size for Single-Receptor Imaging

Quantum dots (QDs) are nanocrystals with bright fluorescence and long-term photostability, attributes particularly beneficial for single-molecule imaging and molecular counting in the life sciences. The size of a QD nanocrystal determines its physicochemical and photophysical properties, both of which dictate the success of imaging applications. Larger nanocrystals typically have better optical properties, with higher brightness, red-shifted emission, reduced blinking, and greater stability. However, larger nanocrystals introduce molecular-labeling biases due to steric hindrance and nonspecific binding. Here, we systematically analyze the impact of nanocrystal size on receptor labeling in live and fixed cells. We designed three (core)shell QDs with red emission (600-700 nm) and crystalline sizes of 3.2, 5.5, and 8.3 nm. After coating with the same multidentate polymer, hydrodynamic sizes were 9.2 nm (QD9.2), 13.3 nm (QD13.3), and 17.4 nm (QD17.4), respectively. The QDs were conjugated to streptavidin and applied as probes for biotinylated neurotransmitter receptors. QD9.2 exhibited the highest labeling specificity for receptors in the narrow synaptic cleft (∼20-30 nm) in living neurons. However, for dense receptor labeling for molecular counting in live and fixed HeLa cells, QD13.3 yielded the highest counts. Nonspecific binding rose sharply for hydrodynamic sizes larger than 13.3 nm, with QD17.4 exhibiting particularly diminished specificity. Our comparisons further highlight needs to continue engineering the smallest QDs to increase single-molecule intensity, suppress blinking frequency, and inhibit nonspecific labeling in fixed and permeabilized cells. These results lay a foundation for designing QD probes with further reduced sizes to achieve unbiased labeling for quantitative and single-molecule imaging.

Long-term cognitive, executive, and behavioral outcomes of moderate and late preterm at school age

BACKGROUND

There is increasing concern that moderate preterm (32-33 weeks' gestation) and late preterm (34-36 weeks' gestation) birth may be associated with minor neurodevelopmental problems affecting poor school performance.

PURPOSE

We explored the cognitive function, cognitive visual function, executive function, and behavioral problems at school age in moderate to late preterm infants.

METHODS

Children aged 7-10 years who were born at 32+0 to 36+6 weeks of gestation and admitted to the neonatal intensive care unit from August 2006 to July 2011 at the National Health Insurance Service Ilsan Hospital were included. We excluded children with severe neurologic impairments, congenital malformations, or chromosomal abnormalities. Neuropsychological assessments consisted of 5 neuropsychological tests and 3 questionnaires.

RESULTS

A total of 37 children (mean age, 9.1±1.2 years) participated. The mean gestational age at birth was 34.6±7.5 weeks, while the mean birth weight was 2,229.2±472.8 g. The mean full-scale intelligence quotient was 92.89±11.90; 24.3% scored between 70 and 85 (borderline intelligence functioning). An abnormal score was noted for at least one of the variables on the attention deficit hyperactivity disorder diagnostic system for 65% of the children. Scores below borderline function for executive quotient and memory quotient were 32.4% and 24.3%, respectively. Borderline or clinically relevant internalizing problems were noted in 13.5% on the Child Behavior Check List. There were no significant associations between perinatal factors or socioeconomic status and cognitive, visual perception, executive function, or behavior outcomes.

CONCLUSION

Moderate to late preterm infants are at risk of developing borderline intelligence functioning and attention problems at early school age. Cognitive and executive functions that are important for academic performance must be carefully monitored and continuously followed up in moderate to late preterm infants.

A sensitive and specific nanosensor for monitoring extracellular potassium levels in the brain

Extracellular potassium concentration affects the membrane potential of neurons, and, thus, neuronal activity. Indeed, alterations of potassium levels can be related to neurological disorders, such as epilepsy and Alzheimer's disease, and, therefore, selectively detecting extracellular potassium would allow the monitoring of disease. However, currently available optical reporters are not capable of detecting small changes in potassium, in particular, in freely moving animals. Furthermore, they are susceptible to interference from sodium ions. Here, we report a highly sensitive and specific potassium nanosensor that can monitor potassium changes in the brain of freely moving mice undergoing epileptic seizures. An optical potassium indicator is embedded in mesoporous silica nanoparticles, which are shielded by an ultrathin layer of a potassium-permeable membrane, which prevents diffusion of other cations and allows the specific capturing of potassium ions. The shielded nanosensor enables the spatial mapping of potassium ion release in the hippocampus of freely moving mice.

Identifying mutation hotspots reveals pathogenetic mechanisms of KCNQ2 epileptic encephalopathy

Kv7 channels are enriched at the axonal plasma membrane where their voltage-dependent potassium currents suppress neuronal excitability. Mutations in Kv7.2 and Kv7.3 subunits cause epileptic encephalopathy (EE), yet the underlying pathogenetic mechanism is unclear. Here, we used novel statistical algorithms and structural modeling to identify EE mutation hotspots in key functional domains of Kv7.2 including voltage sensing S4, the pore loop and S6 in the pore domain, and intracellular calmodulin-binding helix B and helix B-C linker. Characterization of selected EE mutations from these hotspots revealed that L203P at S4 induces a large depolarizing shift in voltage dependence of Kv7.2 channels and L268F at the pore decreases their current densities. While L268F severely reduces expression of heteromeric channels in hippocampal neurons without affecting internalization, K552T and R553L mutations at distal helix B decrease calmodulin-binding and axonal enrichment. Importantly, L268F, K552T, and R553L mutations disrupt current potentiation by increasing phosphatidylinositol 4,5-bisphosphate (PIP2), and our molecular dynamics simulation suggests PIP2 interaction with these residues. Together, these findings demonstrate that each EE variant causes a unique combination of defects in Kv7 channel function and neuronal expression, and suggest a critical need for both prediction algorithms and experimental interrogations to understand pathophysiology of Kv7-associated EE.

Performance Evaluation of the QXDx BCR-ABL %IS Droplet Digital PCR Assay

Accurate detection of BCR-ABL fusion transcripts at and below molecular response (MR) 4 (0.01% International Scale [IS]) is required for disease monitoring in patients with chronic myeloid leukemia (CML). We evaluated the analytical performance of the QXDx BCR-ABL %IS (Bio-Rad, Hercules, CA, USA) droplet digital PCR (ddPCR) assay, which is the first commercially available ddPCR-based in vitro diagnostics product. In precision analysis, the %CV was 9.3% and 3.0%, with mean values of 0.031% IS and 9.4% IS, respectively. The assay was linear in the first order, ranging from 0.032% IS to 20% IS. The manufacturer-claimed limit of blank, limit of detection, and limit of quantification were verified successfully. There was a very strong correlation between the results of the QXDx BCR-ABL %IS ddPCR assay and the ipsogen BCR-ABL1 Mbcr IS-MMR (Qiagen, Hilden, Germany) real-time quantitative PCR assay (r=0.996). In conclusion, the QXDx BCR-ABL %IS ddPCR assay can provide reliable results for CML patients.

Polycystin 2 is increased in disease to protect against stress-induced cell death

Polycystin 2 (PC2 or TRPP1, formerly TRPP2) is a calcium-permeant Transient Receptor Potential (TRP) cation channel expressed primarily on the endoplasmic reticulum (ER) membrane and primary cilia of all cell and tissue types. Despite its ubiquitous expression throughout the body, studies of PC2 have focused primarily on its role in the kidney, as mutations in PC2 lead to the development of autosomal dominant polycystic kidney disease (ADPKD), a debilitating condition for which there is no cure. However, the endogenous role that PC2 plays in the regulation of general cellular homeostasis remains unclear. In this study, we measure how PC2 expression changes in different pathological states, determine that its abundance is increased under conditions of cellular stress in multiple tissues including human disease, and conclude that PC2-deficient cells have increased susceptibility to cell death induced by stress. Our results offer new insight into the normal function of PC2 as a ubiquitous stress-sensitive protein whose expression is up-regulated in response to cell stress to protect against pathological cell death in multiple diseases.

Reactive oxygen species-responsive drug delivery systems for the treatment of neurodegenerative diseases

Neurodegenerative diseases and disorders seriously impact memory and cognition and can become life-threatening. Current medical techniques attempt to combat these detrimental effects mainly through the administration of neuromedicine. However, drug efficacy is limited by rapid dispersal of the drugs to off-target sites while the site of administration is prone to overdose. Many neuropathological conditions are accompanied by excessive reactive oxygen species (ROS) due to the inflammatory response. Accordingly, ROS-responsive drug delivery systems have emerged as a promising solution. To guide intelligent and comprehensive design of ROS-responsive drug delivery systems, this review article discusses the two following topics: (1) the biology of ROS in both healthy and diseased nervous systems and (2) recent developments in ROS-responsive, drug delivery system design. Overall, this review article would assist efforts to make better decisions about designing ROS-responsive, neural drug delivery systems, including the selection of ROS-responsive functional groups.

Heterozygous loss of epilepsy gene KCNQ2 alters social, repetitive and exploratory behaviors

KCNQ/K_v7 channels conduct voltage‐dependent outward potassium currents that potently decrease neuronal excitability. Heterozygous inherited mutations in their principle subunits K_v7.2/KCNQ2 and K_v7.3/KCNQ3 cause benign familial neonatal epilepsy whereas patients with de novo heterozygous K_v7.2 mutations are associated with early‐onset epileptic encephalopathy and neurodevelopmental disorders characterized by intellectual disability, developmental delay and autism. However, the role of K_v7.2‐containing K_v7 channels in behaviors especially autism‐associated behaviors has not been described. Because pathogenic K_v7.2 mutations in patients are typically heterozygous loss‐of‐function mutations, we investigated the contributions of K_v7.2 to exploratory, social, repetitive and compulsive‐like behaviors by behavioral phenotyping of both male and female KCNQ2^+/− mice that were heterozygous null for the KCNQ2 gene. Compared with their wild‐type littermates, male and female KCNQ2^+/− mice displayed increased locomotor activity in their home cage during the light phase but not the dark phase and showed no difference in motor coordination, suggesting hyperactivity during the inactive light phase. In the dark phase, KCNQ2^+/− group showed enhanced exploratory behaviors, and repetitive grooming but decreased sociability with sex differences in the degree of these behaviors. While male KCNQ2^+/− mice displayed enhanced compulsive‐like behavior and social dominance, female KCNQ2^+/− mice did not. In addition to elevated seizure susceptibility, our findings together indicate that heterozygous loss of K_v7.2 induces behavioral abnormalities including autism‐associated behaviors such as reduced sociability and enhanced repetitive behaviors. Therefore, our study is the first to provide a tangible link between loss‐of‐function K_v7.2 mutations and the behavioral comorbidities of K_v7.2‐associated epilepsy.

Loss of fragile X protein FMRP impairs homeostatic synaptic downscaling through tumor suppressor p53 and ubiquitin E3 ligase Nedd4-2

Synaptic scaling allows neurons to homeostatically readjust synaptic strength upon chronic neural activity perturbations. Although altered synaptic scaling has been implicated to underlie imbalanced brain excitability in neurological disorders such as autism spectrum disorders and epilepsy, the molecular dysregulation and restoration of synaptic scaling in those diseases have not been demonstrated. Here, we showed that the homeostatic synaptic downscaling is absent in the hippocampal neurons of Fmr1 KO mice, the mouse model of the most common inherited autism, fragile X syndrome (FXS). We found that the impaired homeostatic synaptic downscaling in Fmr1 KO neurons is caused by loss-of-function dephosphorylation of an epilepsy-associated ubiquitin E3 ligase, neural precursor cell expressed developmentally down-regulated gene 4-2, Nedd4-2. Such dephosphorylation of Nedd4-2 is surprisingly caused by abnormally stable tumor suppressor p53 and subsequently destabilized kinase Akt. Dephosphorylated Nedd4-2 fails to elicit 14-3-3-dependent ubiquitination and down-regulation of the GluA1 subunit of AMPA receptor, and therefore impairs synaptic downscaling. Most importantly, using a pharmacological inhibitor of p53, Nedd4-2 phosphorylation, GluA1 ubiquitination and synaptic downscaling are all restored in Fmr1 KO neurons. Together, our results discover a novel cellular mechanism underlying synaptic downscaling, and demonstrate the dysregulation and successful restoration of this mechanism in the FXS mouse model.

Helicobacter pylori Infection Modulates Host Cell Metabolism through VacA-Dependent Inhibition of mTORC1

Helicobacter pylori (Hp) vacuolating cytotoxin (VacA) is a bacterial exotoxin that enters host cells and induces mitochondrial dysfunction. However, the extent to which VacA-dependent mitochondrial perturbations affect overall cellular metabolism is poorly understood. We report that VacA perturbations in mitochondria are linked to alterations in cellular amino acid homeostasis, which results in the inhibition of mammalian target of rapamycin complex 1 (mTORC1) and subsequent autophagy. mTORC1, which regulates cellular metabolism during nutrient stress, is inhibited during Hp infection by a VacA-dependent mechanism. This VacA-dependent inhibition of mTORC1 signaling is linked to the dissociation of mTORC1 from the lysosomal surface and results in activation of cellular autophagy through the Unc 51-like kinase 1 (Ulk1) complex. VacA intoxication results in reduced cellular amino acids, and bolstering amino acid pools prevents VacA-mediated mTORC1 inhibition. Overall, these studies support a model that Hp modulate host cell metabolism through the action of VacA at mitochondria.

Reduced axonal surface expression and phosphoinositide sensitivity in Kv7 channels disrupts their function to inhibit neuronal excitability in Kcnq2 epileptic encephalopathy

Neuronal K_v7/KCNQ channels are voltage-gated potassium channels composed of K_v7.2/KCNQ2 and K_v7.3/KCNQ3 subunits. Enriched at the axonal membrane, they potently suppress neuronal excitability. De novo and inherited dominant mutations in K_v7.2 cause early onset epileptic encephalopathy characterized by drug resistant seizures and profound psychomotor delay. However, their precise pathogenic mechanisms remain elusive. Here, we investigated selected epileptic encephalopathy causing mutations in calmodulin (CaM)-binding helices A and B of K_v7.2. We discovered that R333W, K526N, and R532W mutations located peripheral to CaM contact sites decreased axonal surface expression of heteromeric channels although only R333W mutation reduced CaM binding to K_v7.2. These mutations also altered gating modulation by phosphatidylinositol 4,5-bisphosphate (PIP₂), revealing novel PIP₂ binding residues. While these mutations disrupted K_v7 function to suppress excitability, hyperexcitability was observed in neurons expressing K_v7.2-R532W that displayed severe impairment in voltage-dependent activation. The M518 V mutation at the CaM contact site in helix B caused most defects in K_v7 channels by severely reducing their CaM binding, K⁺ currents, and axonal surface expression. Interestingly, the M518 V mutation induced ubiquitination and accelerated proteasome-dependent degradation of K_v7.2, whereas the presence of K_v7.3 blocked this degradation. Furthermore, expression of K_v7.2-M518V increased neuronal death. Together, our results demonstrate that epileptic encephalopathy mutations in helices A and B of K_v7.2 cause abnormal K_v7 expression and function by disrupting K_v7.2 binding to CaM and/or modulation by PIP₂. We propose that such multiple K_v7 channel defects could exert more severe impacts on neuronal excitability and health, and thus serve as pathogenic mechanisms underlying Kcnq2 epileptic encephalopathy.

Abstract LB-330: Investigating how extracellular signals contribute to single cancer cell heterogeneity using near-infrared quantum dots

Cancer cells heterogeneity presents a major roadblock in clinical diagnostics and therapy. Investigations of tumor cell heterogeneity using single-cell analytical techniques have revealed not only the presence of multiple clonal subpopulations but also phenotypic variability among genetically identical cells. This heterogeneity plays a critical role in therapeutics, as population extrema, rather than cells near the ensemble mean, can dominate pathogenesis as well as drug resistance. To characterize single cell heterogeneity, multiple techniques quantifying single-cell gene expression have been developed. However, there's a lack of experimental techniques to measure how cellular decision-making processes underlying population variability derive from extracellular biochemical input signals, such as peptide growth factors, which cannot be measured at the single-cell level. Here, to digitally count growth factors in single cells, we develop a novel method combining fluorescent quantum dots and calibrated three-dimensional deconvolution microscopy (QDC-3DM). Using quantum dots with near-infrared emission to overcome intrinsic cellular autofluorescence, we were able to detect and accurately count individual quantum dots conjugated to epidermal growth factor (EGF) using their fluorescent intensities. Analyzing triple-negative breast cancer cells (MDA-MB-231) with QDC-3DM, we observed that single-cell heterogeneity in growth factor stimulation led to heterogeneity in receptor activation. When treating cells with increasing concentration of phamarcological inhibitor blocking receptor activation, we observed a proportional increase in receptor activation heterogeneity. Together, our results indicate that external stimulation contributes to signaling variation and drug response variation at the single-cell level. We anticipate that QDC-3DM can be applied to any peptidic ligands to study how extracellular signaling stimulation contributes to phenotypic variability to provide new insight into cancer cell heterogeneity that plays a critical role in therapeutic resistance.

Citation Format: Phuong Le, Brian C. Baculis, Hee Jung Chung, Kristpher Kilian, Andrew M. Smith. Investigating how extracellular signals contribute to single cancer cell heterogeneity using near-infrared quantum dots [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-330.

Mdm2 mediates FMRP- and Gp1 mGluR-dependent protein translation and neural network activity

Activating Group 1 (Gp1) metabotropic glutamate receptors (mGluRs), including mGluR1 and mGluR5, elicits translation-dependent neural plasticity mechanisms that are crucial to animal behavior and circuit development. Dysregulated Gp1 mGluR signaling has been observed in numerous neurological and psychiatric disorders. However, the molecular pathways underlying Gp1 mGluR-dependent plasticity mechanisms are complex and have been elusive. In this study, we identified a novel mechanism through which Gp1 mGluR mediates protein translation and neural plasticity. Using a multi-electrode array (MEA) recording system, we showed that activating Gp1 mGluR elevates neural network activity, as demonstrated by increased spontaneous spike frequency and burst activity. Importantly, we validated that elevating neural network activity requires protein translation and is dependent on fragile X mental retardation protein (FMRP), the protein that is deficient in the most common inherited form of mental retardation and autism, fragile X syndrome (FXS). In an effort to determine the mechanism by which FMRP mediates protein translation and neural network activity, we demonstrated that a ubiquitin E3 ligase, murine double minute-2 (Mdm2), is required for Gp1 mGluR-induced translation and neural network activity. Our data showed that Mdm2 acts as a translation suppressor, and FMRP is required for its ubiquitination and down-regulation upon Gp1 mGluR activation. These data revealed a novel mechanism by which Gp1 mGluR and FMRP mediate protein translation and neural network activity, potentially through de-repressing Mdm2. Our results also introduce an alternative way for understanding altered protein translation and brain circuit excitability associated with Gp1 mGluR in neurological diseases such as FXS.

Efficacy of Stiripentol in Dravet Syndrome with or without SCN1A Mutations

Background and Purpose

The aim of this study was to determine the effectiveness of stiripentol (STP) add-on therapy to valproate and clobazam in patients with Dravet syndrome (DS) according to the presence of mutations in the sodium channel alpha-1 subunit gene (SCN1A).

Methods

We performed direct sequencing to analyze SCN1A mutations in 32 patients with clinically confirmed with DS, and classified them into mutation (pathogenic or likely pathogenic) and nonmutation groups based on American College of Medical Genetics and Genomics guidelines. We compared the efficacy of STP in reducing the seizure frequency between the two groups.

Results

The 32 patients comprised 15 patients in the mutation group (with definite SCN1A mutations) and 17 patients in the nonmutation group with variants of unknown significance or benign variants. The clinical profile did not differ significantly between the mutation and nonmutation groups. The seizure frequency relative to baseline reduced by 72.53±23.00% (mean±SD) in the mutation group versus 50.58±40.14% in the nonmutation group (p=0.004). The efficacy of STP was better in DS patients with missense mutations that in those with truncation mutations, and was not favorable in patients with mutations at linkers between domains (DII–DIII), linkers between segments of domain I (DI S1–S2), or splice sites, although the small number of patients prevented statistical analyses.

Conclusions

The efficacy of STP was significantly better in DS patients with definite SCN1A mutations than in those without mutations.

Electroconvulsive Seizures in Rats and Fractionation of Their Hippocampi to Examine Seizure-induced Changes in Postsynaptic Density Proteins

Electroconvulsive seizure (ECS) is an experimental animal model of electroconvulsive therapy, the most effective treatment for severe depression. ECS induces generalized tonic-clonic seizures with low mortality and neuronal death and is a widely-used model to screen anti-epileptic drugs. Here, we describe an ECS induction method in which a brief 55-mA current is delivered for 0.5 s to male rats 200 - 250 g in weight via ear-clip electrodes. Such bilateral stimulation produced stage 4 - 5 clonic seizures that lasted about 10 s. After the cessation of acute or chronic ECS, most rats recovered to be behaviorally indistinguishable from sham "no seizure" rats. Because ECS globally elevates brain activity, it has also been used to examine activity-dependent alterations of synaptic proteins and their effects on synaptic strength using multiple methods. In particular, subcellular fractionation of the postsynaptic density (PSD) in combination with Western blotting allows for the quantitative determination of the abundance of synaptic proteins at this specialized synaptic structure. In contrast to a previous fractionation method that requires large amount of rodent brains, we describe here a small-scale fractionation method to isolate the PSD from the hippocampi of a single rat, without sucrose gradient centrifugation. Using this method, we show that the isolated PSD fraction contains postsynaptic membrane proteins, including PSD95, GluN2B, and GluA2. Presynaptic marker synaptophysin and soluble cytoplasmic protein α-tubulin were excluded from the PSD fraction, demonstrating successful PSD isolation. Furthermore, chronic ECS decreased GluN2B expression in the PSD, indicating that our small-scale PSD fractionation method can be applied to detect the changes in hippocampal PSD proteins from a single rat after genetic, pharmacological, or mechanical treatments.

Reduction of magnetic damping and isotropic coercivity and increase of saturation magnetization in Rh-incorporated CoIr system

Replacing Ir with Rh in a CoIr system possessing negative uniaxial magnetocrystalline anisotropy (K _u ) substantially reduces its magnetic damping and coercivity by more than half while retaining its high negative K _u . Moreover, a higher saturation magnetization (M _s ) and more isotropic coercivity are achieved. Such material development makes it particularly suitable for use as the soft underlayer (SUL) of magnetic recording media for reducing noise, and as the oscillation layer of a spin-torque oscillator (STO) for achieving higher oscillation frequency, larger AC magnetic field and lower driving current, which can be readily integrated with the current recording head for microwave-assisted magnetic recording. Finally, we recommend a composite free layer by coupling CoIr with a spin polarizer (Co or Co/Cu/Co) for the enhancement of the spin-polarization rate and, therefore, the improvement of STO efficiency. These could pave the way for CoIr-based materials to be implemented in devices requiring a negative K_u with low damping and high 'softness', such as oscillators.

Three Dimensional Conjugation of Recombinant N-Cadherin to a Hydrogel for In Vitro Anisotropic Neural Growth

Living cells are extensively being studied to build functional tissues that are useful for both fundamental and applied bioscience studies. Increasing evidence suggests that cell-cell adhesion controlled by intercellular cadherin junction plays important roles in the quality of the resulting engineered tissue. These findings prompted efforts to interrogate biological effects of cadherin at a molecular scale; however, few efforts were made to harness the effects of cadherin on cells cultured in an in vivo-like three dimensional matrix. To this end, this study reports a hydrogel matrix three dimensionally functionalized with a controlled number of Fc-tagged recombinant N-cadherins (N-Cad-Fc). To retain the desired conformation of N-Cad, these cadherins were immobilized and oriented to the gel by anti-Fc-antibodies chemically coupled to gels. The gels were processed to present N-Cad-Fc in uniaxially aligned microchannels or randomly oriented micropores. Culturing cortical cells in the functionalized gels generated a large fraction of neurons that are functional as indicated by increased intracellular calcium ion concentrations with the microchanneled gel. In contrast, direct N-Cad-Fc immobilization to microchannel or micropore walls of the gel limited the growth of neurons and increased the glial to neuron ratio. The results of this study will be highly useful to organize a wide array of cadherin molecules in a series of biomaterials used for three-dimensional cell culture and to regulate phenotypic activities of tissue-forming cells in an elaborate manner.

Regulation of STEP61 and tyrosine-phosphorylation of NMDA and AMPA receptors during homeostatic synaptic plasticity

Background

Sustained changes in network activity cause homeostatic synaptic plasticity in part by altering the postsynaptic accumulation of N-methyl-D-aspartate receptors (NMDAR) and α-amino-3-hydroxyle-5-methyl-4-isoxazolepropionic acid receptors (AMPAR), which are primary mediators of excitatory synaptic transmission. A key trafficking modulator of NMDAR and AMPAR is STriatal-Enriched protein tyrosine Phosphatase (STEP₆₁) that opposes synaptic strengthening through dephosphorylation of NMDAR subunit GluN2B and AMPAR subunit GluA2. However, the role of STEP₆₁ in homeostatic synaptic plasticity is unknown.

Findings

We demonstrate here that prolonged activity blockade leads to synaptic scaling, and a concurrent decrease in STEP₆₁ level and activity in rat dissociated hippocampal cultured neurons. Consistent with STEP₆₁ reduction, prolonged activity blockade enhances the tyrosine phosphorylation of GluN2B and GluA2 whereas increasing STEP₆₁ activity blocks this regulation and synaptic scaling. Conversely, prolonged activity enhancement increases STEP₆₁ level and activity, and reduces the tyrosine phosphorylation and level of GluN2B as well as GluA2 expression in a STEP₆₁–dependent manner.

Conclusions

Given that STEP₆₁-mediated dephosphorylation of GluN2B and GluA2 leads to their internalization, our results collectively suggest that activity-dependent regulation of STEP₆₁ and its substrates GluN2B and GluA2 may contribute to homeostatic stabilization of excitatory synapses.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-015-0148-4) contains supplementary material, which is available to authorized users.

Manipulation of a quasi-natural cell block for high-efficiency transplantation of adherent somatic cells

Recent advances have raised hope that transplantation of adherent somatic cells could provide dramatic new therapies for various diseases. However, current methods for transplanting adherent somatic cells are not efficient enough for therapeutic applications. Here, we report the development of a novel method to generate quasi-natural cell blocks for high-efficiency transplantation of adherent somatic cells. The blocks were created by providing a unique environment in which cultured cells generated their own extracellular matrix. Initially, stromal cells isolated from mice were expanded in vitro in liquid cell culture medium followed by transferring the cells into a hydrogel shell. After incubation for 1 day with mechanical agitation, the encapsulated cell mass was perforated with a thin needle and then incubated for an additional 6 days to form a quasi-natural cell block. Allograft transplantation of the cell block into C57BL/6 mice resulted in perfect adaptation of the allograft and complete integration into the tissue of the recipient. This method could be widely applied for repairing damaged cells or tissues, stem cell transplantation, ex vivo gene therapy, or plastic surgery.

N-methyl-D-aspartate receptors mediate activity-dependent down-regulation of potassium channel genes during the expression of homeostatic intrinsic plasticity

BACKGROUND

Homeostatic intrinsic plasticity encompasses the mechanisms by which neurons stabilize their excitability in response to prolonged and destabilizing changes in global activity. However, the milieu of molecular players responsible for these regulatory mechanisms is largely unknown.

RESULTS

Using whole-cell patch clamp recording and unbiased gene expression profiling in rat dissociated hippocampal neurons cultured at high density, we demonstrate here that chronic activity blockade induced by the sodium channel blocker tetrodotoxin leads to a homeostatic increase in action potential firing and down-regulation of potassium channel genes. In addition, chronic activity blockade reduces total potassium current, as well as protein expression and current of voltage-gated Kv1 and Kv7 potassium channels, which are critical regulators of action potential firing. Importantly, inhibition of N-Methyl-D-Aspartate receptors alone mimics the effects of tetrodotoxin, including the elevation in firing frequency and reduction of potassium channel gene expression and current driven by activity blockade, whereas inhibition of L-type voltage-gated calcium channels has no effect.

CONCLUSIONS

Collectively, our data suggest that homeostatic intrinsic plasticity induced by chronic activity blockade is accomplished in part by decreased calcium influx through N-Methyl-D-Aspartate receptors and subsequent transcriptional down-regulation of potassium channel genes.

The differences in clinical aspect between specific language impairment and global developmental delay

OBJECTIVE

To compare and analyze the clinical characteristics of children with delayed language acquisition due to two different diagnoses, which were specific language impairment (SLI, a primarily delayed language development) and global developmental delay (GDD, a language delay related to cognitive impairment).

METHODS

Among 1,598 children who had visited the developmental delay clinic from March 2005 to February 2011, 467 children who were diagnosed with GDD and 183 children who were diagnosed with SLI were included in this study. All children were questioned about past, family, and developmental history, and their language competences and cognitive function were assessed. Some children got electroencephalography (EEG), in case of need.

RESULTS

The presence of the perinatal risk factors showed no difference in two groups. In the children with GDD, they had more delayed acquisition of independent walking and more frequent EEG abnormalities compared with the children with SLI (p<0.01). The positive family history of delayed language development was more prevalent in children with SLI (p<0.01). In areas of language ability, the quotient of receptive language and expressive language did not show any meaningful statistical differences between the two groups. Analyzing in each group, the receptive language quotient was higher than expressive language quotient in both group (p<0.01). In the GDD group, the Bayley Scales of Infant Development II (BSID-II) showed a marked low mental and motor quotient while the Wechsler Intelligence Scale showed low verbal and nonverbal IQ. In the SLI group, the BSID-II and Wechsler Intelligence Scale showed low scores in mental area and verbal IQ but sparing motor area and nonverbal IQ.

CONCLUSION

The linguistic profiles of children with language delay could not differentiate between SLI and GDD. The clinicians needed to be aware of these developmental issues, and history taking and clinical evaluation, including cognitive assessment, could be helpful to diagnose adequately and set the treatment plan for each child.

Small quantum dots conjugated to nanobodies as immunofluorescence probes for nanometric microscopy

Immunofluorescence, a powerful technique to detect specific targets using fluorescently labeled antibodies, has been widely used in both scientific research and clinical diagnostics. The probes should be made with small antibodies and high brightness. We conjugated GFP binding protein (GBP) nanobodies, small single-chain antibodies from llamas, with new ∼7 nm quantum dots. These provide simple and versatile immunofluorescence nanoprobes with nanometer accuracy and resolution. Using the new probes we tracked the walking of individual kinesin motors and measured their 8 nm step sizes; we tracked Piezo1 channels, which are eukaryotic mechanosensitive channels; we also tracked AMPA receptors on living neurons. Finally, we used a new super-resolution algorithm based on blinking of (small) quantum dots that allowed ∼2 nm precision.

Adjunctive levetiracetam treatment in pediatric Lennox-Gastaut syndrome

BACKGROUND

Our aim was to investigate the efficacy and tolerability of levetiracetam as an add-on treatment in pediatric patients with Lennox-Gastaut syndrome.

METHODS

The study was an open-label, multicenter, observational clinical trial of levetiracetam as an add-on treatment in Lennox-Gastaut syndrome. Fifty-five patients aged 1.1-18.6 years (mean, 10.0 years) were enrolled. The study included a 4-8-week titration period and an 8-week maintenance period. The maintenance dose of levetiracetam was 20-80 mg/kg/day, according to its effectiveness and tolerability. The primary end point was reduction in seizure frequency, and related variables were also evaluated.

RESULTS

Among 55 patents, 51 patients (92.7%) completed the study. Thirty-two patients (58.2%) experienced a more than 50% reduction in seizure frequency, and 15 patients (27.3%) became seizure free. A reduction in seizure frequency of more than 50% was observed in 21 of 36 patients (58.3%) with convulsive seizures, 7 of 12 patients (58.3%) with drop attacks, 2 of 4 patients (50.0%) with myoclonic seizures, and 2 of 3 patients (66.7%) with epileptic spasms. Overall, 34.5% of patients reported adverse events. None of the adverse events were life threatening, and the most common adverse event was hyperactivity (12.7%).

CONCLUSIONS

This study suggests that levetiracetam is a safe and effective treatment in pediatric patients with Lennox-Gastaut syndrome.