Gabrb3 is required for the functional integration of pyramidal neuron subtypes in the somatosensory cortex.

Dysfunction of gamma-aminobutyric acid (GABA)ergic circuits is strongly associated with neurodevelopmental disorders. However, it is unclear how genetic predispositions impact circuit assembly. Using in vivo two-photon and widefield calcium imaging in developing mice, we show that Gabrb3, a gene strongly associated with autism spectrum disorder (ASD) and Angelman syndrome (AS), is enriched in contralaterally projecting pyramidal neurons and is required for inhibitory function. We report that Gabrb3 ablation leads to a developmental decrease in GABAergic synapses, increased local network synchrony, and long-lasting enhancement in functional connectivity of contralateral-but not ipsilateral-pyramidal neuron subtypes. In addition, Gabrb3 deletion leads to increased cortical response to tactile stimulation at neonatal stages. Using human transcriptomics and neuroimaging datasets from ASD subjects, we show that the spatial distribution of GABRB3 expression correlates with atypical connectivity in these subjects. Our studies reveal a requirement for Gabrb3 during the emergence of interhemispheric circuits for sensory processing.

Effective Low-Cost Ophthalmological Screening With a Novel iPhone Fundus Camera at Community Centers.

Ophthalmologic care is inaccessible to many people due to a variety of factors, including the availability of providers, cost of equipment for ophthalmologic care, and transportation to clinics and appointments. Because many causes of blindness are both highly prevalent and preventable once identified, it is essential to address gaps in care for underserved populations. We developed a novel 3D-printed mobile retinal camera. In this study, we organized recurring student-run screening events around New York City that took place in community centers and churches, at which we utilized our device to take retinal images. Our screening events reached a diverse population of New Yorkers, disproportionately those with lower household income, many of whom had not had recent eye exams. To validate the device for use in telehealth ophthalmologic visits, we transmitted the images to a remote ophthalmologist for evaluation and compared the result with an on-site attending physician's dilated eye exam. The subjective assessment indicated that 97% of images captured with the mobile retinal camera were acceptable for telehealth analysis. Remote image assessment by achieved 92% sensitivity and 83% specificity in detecting optic disc cupping, compared to the gold-standard on-site dilated eye exam. In addition, the device was portable, affordable, and able to be used by those with relatively little ophthalmologic training. We have demonstrated the utility of this affordable mobile retinal camera for telehealth ophthalmologic evaluation during community screening events that reached an underserved population to detect disease and connect with long-term care.

Cocaine- and stress-primed reinstatement of drug-associated memories elicit differential behavioral and frontostriatal circuit activity patterns via recruitment of L-type Ca2+ channels.

Cocaine-associated memories are critical drivers of relapse in cocaine-dependent individuals that can be evoked by exposure to cocaine or stress. Whether these environmental stimuli recruit similar molecular and circuit-level mechanisms to promote relapse remains largely unknown. Here, using cocaine- and stress-primed reinstatement of cocaine conditioned place preference to model drug-associated memories, we find that cocaine drives reinstatement by increasing the duration that mice spend in the previously cocaine-paired context whereas stress increases the number of entries into this context. Importantly, both forms of reinstatement require Cav1.2 L-type Ca2+ channels (LTCCs) in cells of the prelimbic cortex that project to the nucleus accumbens core (PrL→NAcC). Utilizing fiber photometry to measure circuit activity in vivo in conjunction with the LTCC blocker, isradipine, we find that LTCCs drive differential recruitment of the PrL→ NAcC pathway during cocaine- and stress-primed reinstatement. While cocaine selectively activates PrL→NAcC cells prior to entry into the cocaine-paired chamber, a measure that is predictive of duration in that chamber, stress increases persistent activity of this projection, which correlates with entries into the cocaine-paired chamber. Using projection-specific chemogenetic manipulations, we show that PrL→NAcC activity is required for both cocaine- and stress-primed reinstatement, and that activation of this projection in Cav1.2-deficient mice restores reinstatement. These data indicate that LTCCs are a common mediator of cocaine- and stress-primed reinstatement. However, they engage different patterns of behavior and PrL→NAcC projection activity depending on the environmental stimuli. These findings establish a framework to further study how different environmental experiences can drive relapse, and supports further exploration of isradipine, an FDA-approved LTCC blocker, as a potential therapeutic for the prevention of relapse in cocaine-dependent individuals.

Correction: Cocaine- and stress-primed reinstatement of drug-associated memories elicit differential behavioral and frontostriatal circuit activity patterns via recruitment of L-type Ca2+ channels.

A correction to this paper has been published and can be accessed via a link at the top of the paper.

Assemblies of Perisomatic GABAergic Neurons in the Developing Barrel Cortex.

The developmental journey of cortical interneurons encounters several activity-dependent milestones. During the early postnatal period in developing mice, GABAergic neurons are transient preferential recipients of thalamic inputs and undergo activity-dependent migration arrest, wiring, and programmed cell-death. Despite their importance for the emergence of sensory experience and the role of activity in their integration into cortical networks, the collective dynamics of GABAergic neurons during that neonatal period remain unknown. Here, we study coordinated activity in GABAergic cells of the mouse barrel cortex using in vivo calcium imaging. We uncover a transient structure in GABAergic population dynamics that disappears in a sensory-dependent process. Its building blocks are anatomically clustered GABAergic assemblies mostly composed by prospective parvalbumin-expressing cells. These progressively widen their territories until forming a uniform perisomatic GABAergic network. Such transient patterning of GABAergic activity is a functional scaffold that links the cortex to the external world prior to active exploration. VIDEO ABSTRACT.

GABAergic Restriction of Network Dynamics Regulates Interneuron Survival in the Developing Cortex.

During neonatal development, sensory cortices generate spontaneous activity patterns shaped by both sensory experience and intrinsic influences. How these patterns contribute to the assembly of neuronal circuits is not clearly understood. Using longitudinal in vivo calcium imaging in un-anesthetized mouse pups, we show that spatially segregated functional assemblies composed of interneurons and pyramidal cells are prominent in the somatosensory cortex by postnatal day (P) 7. Both reduction of GABA release and synaptic inputs onto pyramidal cells erode the emergence of functional topography, leading to increased network synchrony. This aberrant pattern effectively blocks interneuron apoptosis, causing increased survival of parvalbumin and somatostatin interneurons. Furthermore, the effect of GABA on apoptosis is mediated by inputs from medial ganglionic eminence (MGE)-derived but not caudal ganglionic eminence (CGE)-derived interneurons. These findings indicate that immature MGE interneurons are fundamental for shaping GABA-driven activity patterns that balance the number of interneurons integrating into maturing cortical networks.

Layer I Interneurons Sharpen Sensory Maps during Neonatal Development.

The neonatal mammal faces an array of sensory stimuli when diverse neuronal types have yet to form sensory maps. How these inputs interact with intrinsic neuronal activity to facilitate circuit assembly is not well understood. By using longitudinal calcium imaging in unanesthetized mouse pups, we show that layer I (LI) interneurons, delineated by co-expression of the 5HT3a serotonin receptor (5HT3aR) and reelin (Re), display spontaneous calcium transients with the highest degree of synchrony among cell types present in the superficial barrel cortex at postnatal day 6 (P6). 5HT3aR Re interneurons are activated by whisker stimulation during this period, and sensory deprivation induces decorrelation of their activity. Moreover, attenuation of thalamic inputs through knockdown of NMDA receptors (NMDARs) in these interneurons results in expansion of whisker responses, aberrant barrel map formation, and deficits in whisker-dependent behavior. These results indicate that recruitment of specific interneuron types during development is critical for adult somatosensory function. VIDEO ABSTRACT.

Neuronal activity controls the development of interneurons in the somatosensory cortex.

BACKGROUND: Neuronal activity in cortical areas regulates neurodevelopment by interacting with defined genetic programs to shape the mature central nervous system. Electrical activity is conveyed to sensory cortical areas via intracortical and thalamocortical neurons, and includes oscillatory patterns that have been measured across cortical regions. OBJECTIVE: In this work, we review the most recent findings about how electrical activity shapes the developmental assembly of functional circuitry in the somatosensory cortex, with an emphasis on interneuron maturation and integration. We include studies on the effect of various neurotransmitters and on the influence of thalamocortical afferent activity on circuit development. We additionally reviewed studies describing network activity patterns. METHODS: We conducted an extensive literature search using both the PubMed and Google Scholar search engines. The following keywords were used in various iterations: "interneuron", "somatosensory", "development", "activity", "network patterns", "thalamocortical", "NMDA receptor", "plasticity". We additionally selected papers known to us from past reading, and those recommended to us by reviewers and members of our lab. RESULTS: We reviewed a total of 132 articles that focused on the role of activity in interneuronal migration, maturation, and circuit development, as well as the source of electrical inputs and patterns of cortical activity in the somatosensory cortex. 79 of these papers included in this timely review were written between 2007 and 2016. CONCLUSIONS: Neuronal activity shapes the developmental assembly of functional circuitry in the somatosensory cortical interneurons. This activity impacts nearly every aspect of development and acquisition of mature neuronal characteristics, and may contribute to changing phenotypes, altered transmitter expression, and plasticity in the adult. Progressively changing oscillatory network patterns contribute to this activity in the early postnatal period, although a direct requirement for specific patterns and origins of activity remains to be demonstrated.

Comparative efficacy of alemtuzumab and established treatment in the management of multiple sclerosis.

Alemtuzumab is the newest disease-modifying therapy approved for the treatment of relapsing multiple sclerosis. Alemtuzumab is an anti-CD52 targeted antibody that causes lysis of T and B lymphocytes, monocytes, natural killer cells, macrophages, and dendritic cells. Following its administration, a prolonged T-cell lymphopenia results with emergence of a reconstituted immune system that differs in its composition from that pretreatment. In clinical trials, alemtuzumab has shown impressive efficacy with regard to clinical and radiological outcomes in relapsing multiple sclerosis, along with sustained long-term beneficial effects, and it is attractive for its once-yearly administration. Despite this, the occurrence of serious secondary autoimmune disorders, infections, and a potential risk of malignancy necessitates a careful evaluation of risks versus benefits for an individual patient prior to its use. The requirement of patient commitment to the intense mandatory monitoring program is also a factor to be considered when incorporating alemtuzumab into the treatment regimen.

Reduced Purkinje cell dendritic arborization and loss of dendritic spines in essential tremor.

Based on accumulating post-mortem evidence of abnormalities in Purkinje cell biology in essential tremor, we hypothesized that regressive changes in dendritic morphology would be apparent in the Purkinje cell population in essential tremor cases versus age-matched controls. Cerebellar cortical tissue from 27 cases with essential tremor and 27 age-matched control subjects was processed by the Golgi-Kopsch method. Purkinje cell dendritic anatomy was quantified using a Neurolucida microscopic system interfaced with a motorized stage. In all measures, essential tremor cases demonstrated significant reductions in dendritic complexity compared with controls. Median values in essential tremor cases versus controls were: 5712.1 versus 10 403.2 µm (total dendrite length, P=0.01), 465.9 versus 592.5 µm (branch length, P=0.01), 22.5 versus 29.0 (maximum branch order, P=0.001), and 165.3 versus 311.7 (number of terminations, P=0.008). Furthermore, the dendritic spine density was reduced in essential tremor cases (medians=0.82 versus 1.02 µm(-1), P=0.03). Our demonstration of regressive changes in Purkinje cell dendritic architecture and spines in essential tremor relative to control brains provides additional evidence of a pervasive abnormality of Purkinje cell biology in this disease, which affects multiple neuronal cellular compartments including their axon, cell body, dendrites and spines.

Purkinje cell axonal anatomy: quantifying morphometric changes in essential tremor versus control brains.

Growing clinical, neuro-imaging and post-mortem data have implicated the cerebellum as playing an important role in the pathogenesis of essential tremor. Aside from a modest reduction of Purkinje cells in some post-mortem studies, Purkinje cell axonal swellings (torpedoes) are present to a greater degree in essential tremor cases than controls. Yet a detailed study of more subtle morphometric changes in the Purkinje cell axonal compartment has not been undertaken. We performed a detailed morphological analysis of the Purkinje cell axonal compartment in 49 essential tremor and 39 control brains, using calbindin D28k immunohistochemistry on 100-µm cerebellar cortical vibratome tissue sections. Changes in axonal shape [thickened axonal profiles (P = 0.006), torpedoes (P = 0.038)] and changes in axonal connectivity [axonal recurrent collaterals (P < 0.001), axonal branching (P < 0.001), terminal axonal sprouting (P < 0.001)] were all present to an increased degree in essential tremor cases versus controls. The changes in shape and connectivity were significantly correlated [e.g. correlation between thickened axonal profiles and recurrent collaterals (r = 0.405, P < 0.001)] and were correlated with tremor duration among essential tremor cases with age of onset >40 years. In essential tremor cases, thickened axonal profiles, axonal recurrent collaterals and branched axons were 3- to 5-fold more frequently seen on the axons of Purkinje cells with torpedoes versus Purkinje cells without torpedoes. We document a range of changes in the Purkinje cell axonal compartment in essential tremor. Several of these are likely to be compensatory changes in response to Purkinje cell injury, thus illustrating an important feature of Purkinje cells, which is that they are relatively resistant to damage and capable of mobilizing a broad range of axonal responses to injury. The extent to which this plasticity of the Purkinje cell axon is partially neuroprotective or ultimately ineffective at slowing further cellular changes and cell death deserves further study in essential tremor.

Quantification of cerebellar hemispheric purkinje cell linear density: 32 ET cases versus 16 controls.

Although essential tremor (ET) is among the most prevalent neurological diseases, its precise pathogenesis is not understood. Purkinje cell loss has been observed in some studies and is the focus of interest and debate. Expressing these data as Purkinje cells/layer length allows one to adjust for the inherent curved nature of the cerebellar folia. Capitalizing on the Essential Tremor Centralized Brain Repository, we quantified Purkinje cell linear density in cases versus controls. Free-floating 100-µm parasagittal cerebellar hemispheric sections were subjected to rabbit polyclonal anti-Calbindin D28k antibody, and 10 random fields/brain were selected for quantification of Purkinje cells/mm(-1) Purkinje cell layer. Purkinje cell linear density was lower in 32 ET cases than in16 controls (1.14 ± 0.32 vs. 1.35 ± 0.31/mm(-1) , P = 0.03). Purkinje cell linear density was inversely associated with torpedo count (r = -0.38, P = 0.028). The current sample of ET cases demonstrates a reduction in Purkinje cell number relative to that of controls. Greater Purkinje cell axonal remodeling (torpedoes) was found in individuals who had the most Purkinje cell drop out. The role of Purkinje cell loss in the pathogenesis of this disorder merits additional study.

The inferior olivary nucleus: a postmortem study of essential tremor cases versus controls.

The pathogenesis of essential tremor is poorly understood. Historically, it has been hypothesized that the inferior olivary nucleus plays an important role in the generation of tremor in essential tremor, yet a detailed, controlled, anatomic-pathological study of that brain region has yet to be conducted. A detailed postmortem study was undertaken of the microscopic changes in the inferior olivary nucleus of 14 essential tremor cases versus 15 age-matched controls at the Essential Tremor Centralized Brain Repository. A series of metrics was used to quantify microscopic neuronal and glial changes in the inferior olivary nucleus and its input and output tracts. Olivary linear neuronal density also was assessed. Cases and controls did not differ from one another with respect to any of the assessed metrics (P values ranged from 0.23 to 1.0). Olivary linear neuronal density also was similar in cases and controls (P = 0.62). Paddle-shaped neurons, a morphologic shape change in olivary neurons, which, to our knowledge, have not been previously recognized, occurred to an equal degree in essential tremor cases and controls (P = 0.89) and were correlated with several markers of neuronal loss and gliosis. A systematic postmortem study of the microscopic changes in the inferior olivary nucleus did not detect any differences between cases and controls. These data, along with positron emission tomography data, which have failed to identify any metabolic abnormality of the olive, indicate that, if the olive is involved in essential tremor, then there is no clearly identifiable structural or metabolic correlate.

Essential tremor followed by progressive supranuclear palsy: postmortem reports of 11 patients.

For many years, clinicians have commented on the development of signs of parkinsonism among their essential tremor (ET) patients, but the links between ET and parkinsonism are not well understood. We report 11 (12.4%) of 89 ET patients who were prospectively collected at the Essential Tremor Centralized Brain Repository during the course of its first 9 years. All patients had long-standing ET (median duration, 38 years); there was a 5- to 49-year latency from the onset of ET to the development of either parkinsonism or dementia.Despite the presence of parkinsonism or dementia during life, none had been diagnosed clinically with progressive supranuclear palsy(PSP). All 11 received the postmortem diagnosis of PSP. The prevalence of PSP in this ET sample (12.4%) is clearly larger than the population prevalence of PSP (0.001%-0.0065%). It is also 2 to 5 times the proportion of normal cases with incidental PSP in 2 previous autopsy series. This case series raises the questions of an association between ET and PSP, whether ET patients are at an increased risk of developing PSP, and what the proportion of ET patients who develop presumed Parkinson disease or Alzheimer disease in life actually have PSP (i.e. ET + PSP).

Neurofilament protein levels: quantitative analysis in essential tremor cerebellar cortex.

Essential tremor (ET) is among the most prevalent neurological diseases. A substantial increase in the number of Purkinje cell axonal swellings (torpedoes) has been identified in ET brains. We recently demonstrated that torpedoes in ET contain an over-accumulation of disorganized neurofilament (NF) proteins. This now raises the question whether NF protein composition and/or phosphorylation state in cerebellar tissue might differ between ET cases and controls. We used a Western blot analysis to compare the levels and phosphorylation state of NF proteins and α-internexin in cerebellar tissue from 47 ET cases versus 26 controls (2:1 ratio). Cases and controls did not differ with respect to the cerebellar levels of NF-light (NF-L), NF-medium (NF-M), NF-heavy (NF-H), or α-internexin. However, SMI-31 levels (i.e., phosphorylated NF-H) and SMI-32 levels (i.e., non-phosphorylated NF-H) were significantly higher in ET cases than controls (1.28±0.47 vs. 1.06±0.32, p=0.02; and 1.38±0.75 vs. 1.00±0.42, p=0.006). Whether the abnormal phosphorylation state that we observed is a cause of defective axonal transport and/or function of NFs in ET is not known. NF abnormalities have been demonstrated in several neurodegenerative diseases. Regardless of whether these protein aggregates are the cause or consequence of these diseases, NF abnormalities have been shown to be an important factor in the cellular disruption observed in several neurodegenerative diseases. Therefore, further analyses of these NF abnormalities and their mechanisms are important to enhance our understanding of disease pathogenesis in ET.

Macroautophagy abnormality in essential tremor.

Macroautophagy is a cellular mechanism for the clearance of protein aggregates and damaged organelles. Impaired macroautophagy has been observed in neurodegenerative disorders. We investigated the macroautophagy pathway in essential tremor (ET) cases compared to age-matched controls. We analyzed microtubule-associated protein light chain 3-II (LC3-II), S6K, phosphorylated S6K, beclin-1, and mitochondrial membrane proteins levels by Western blot in the post-mortem cerebellum of 10 ET cases and 11 controls. We also performed immunohistochemistry in 12 ET cases and 13 controls to quantify LC3 clustering in Purkinje cells (PCs). LC3-II protein levels were significantly lower in ET cases vs. controls on Western blot (0.84 ± 0.14 vs. 1.00 ± 0.14, p = 0.02), and LC3-II clustering in PCs by immunohistochemistry was significantly lower in ET cases vs. controls (2.03 ± 3.45 vs. 8.80 ± 9.81, p = 0.03). In ET cases, disease duration was inversely correlated with LC3-II protein level (r = -0.64, p = 0.046). We found that mitochondrial membrane proteins were accumulated in ET (TIM23: 1.36 ± 0.11 in ET cases vs. 1.00 ± 0.08 in controls, p = 0.02; TOMM20: 1.63 ± 0.87 in ET cases vs. 1.00 ± 0.14 in controls, p = 0.03). Beclin-1, which is involved in macroautophagy, was strikingly deficient in ET (0.42 ± 0.13 vs. 1.00 ± 0.35, p<0.001). Decreased macroautophagy was observed in the ET cerebellum, and this could be due to a decrease in beclin-1 levels, which subsequently lead to mitochondrial accumulation as a result of autophagic failure. This provides a possible means by which perturbed macroautophagy could contribute to PC pathology in ET.

Cerebellar pathology of a dual clinical diagnosis: patients with essential tremor and dystonia.

BACKGROUND: Clinical studies have implicated the cerebellum in the pathogenesis of essential tremor (ET), and recent postmortem studies have identified structural changes in the ET cerebellum. While the basal ganglia have traditionally been implicated in dystonia, cerebellar involvement has been suggested as well, and a recent study showed Purkinje cell (PC) loss. We conducted a detailed postmortem examination of the brain in four individuals with clinical diagnoses of ET and dystonia, and hypothesized that pathological changes in the cerebellum would be greater in these four ET cases than in published ET cases without dystonia. METHODS: After a complete neuropathological assessment, a standard parasagittal neocerebellar tissue block was harvested in each brain. One 7-µm thick section was stained with luxol fast blue/hematoxylin and eosin, and one section with the Bielschowsky method. We quantified PCs, torpedoes, heterotopic PCs, PC dendritic swellings, and basket cell changes. RESULTS: Two ET+dystonia cases had more microscopic changes in the cerebellum than published ET cases; the other two cases had similar changes to published ET cases. DISCUSSION: This is the first report that uses human autopsy tissue to study patients with both ET and dystonia. The findings were heterogeneous. Additional studies, with larger samples, are needed.