Whisker kinematics in the cerebellum.

The whisker system is widely used as a model system for understanding sensorimotor integration. Purkinje cells in the crus regions of the cerebellum have been reported to linearly encode whisker midpoint, but it is unknown whether the paramedian and simplex lobules as well as their target neurons in the cerebellar nuclei also encode whisker kinematics and if so which ones. Elucidating how these kinematics are represented throughout the cerebellar hemisphere is essential for understanding how the cerebellum coordinates multiple sensorimotor modalities. Exploring the cerebellar hemisphere of mice using optogenetic stimulation, we found that whisker movements can be elicited by stimulation of Purkinje cells in not only crus1 and crus2, but also in the paramedian lobule and lobule simplex; activation of cells in the medial paramedian lobule had on average the shortest latency, whereas that of cells in lobule simplex elicited similar kinematics as those in crus1 and crus2. During spontaneous whisking behaviour, simple spike activity correlated in general better with velocity than position of the whiskers, but it varied between protraction and retraction as well as per lobule. The cerebellar nuclei neurons targeted by the Purkinje cells showed similar activity patterns characterized by a wide variety of kinematic signals, yet with a dominance for velocity. Taken together, our data indicate that whisker movements are much more prominently and diversely represented in the cerebellar cortex and nuclei than assumed, highlighting the rich repertoire of cerebellar control in the kinematics of movements that can be engaged during coordination. KEY POINTS: Excitation of Purkinje cells throughout the cerebellar hemispheres induces whisker movement, with the shortest latency and longest duration within the paramedian lobe. Purkinje cells have differential encoding for the fast and slow components of whisking. Purkinje cells encode not only the position but also the velocity of whiskers. Purkinje cells with high sensitivity for whisker velocity are preferentially located in the medial part of lobule simplex, crus1 and lateral paramedian. In the downstream cerebellar nuclei, neurons with high sensitivity for whisker velocity are located at the intersection between the medial and interposed nucleus.

Purkinje Cell Activity Resonation Generates Rhythmic Behaviors at the Preferred Frequency of 8 Hz.

Neural activity exhibits oscillations, bursts, and resonance, enhancing responsiveness at preferential frequencies. For example, theta-frequency bursting and resonance in granule cells facilitate synaptic transmission and plasticity mechanisms at the input stage of the cerebellar cortex. However, whether theta-frequency bursting of Purkinje cells is involved in generating rhythmic behavior has remained neglected. We recorded and optogenetically modulated the simple and complex spike activity of Purkinje cells while monitoring whisker movements with a high-speed camera of awake, head-fixed mice. During spontaneous whisking, both simple spike activity and whisker movement exhibit peaks within the theta band. Eliciting either simple or complex spikes at frequencies ranging from 0.5 to 28 Hz, we found that 8 Hz is the preferred frequency around which the largest movement is induced. Interestingly, oscillatory whisker movements at 8 Hz were also generated when simple spike bursting was induced at 2 and 4 Hz, but never via climbing fiber stimulation. These results indicate that 8 Hz is the resonant frequency at which the cerebellar-whisker circuitry produces rhythmic whisking.

Olivocerebellar control of movement symmetry.

Coordination of bilateral movements is essential for a large variety of animal behaviors. The olivocerebellar system is critical for the control of movement, but its role in bilateral coordination has yet to be elucidated. Here, we examined whether Purkinje cells encode and influence synchronicity of left-right whisker movements. We found that complex spike activity is correlated with a prominent left-right symmetry of spontaneous whisker movements within parts, but not all, of Crus1 and Crus2. Optogenetic stimulation of climbing fibers in the areas with high and low correlations resulted in symmetric and asymmetric whisker movements, respectively. Moreover, when simple spike frequency prior to the complex spike was higher, the complex spike-related symmetric whisker protractions were larger. This finding alludes to a role for rebound activity in the cerebellar nuclei, which indeed turned out to be enhanced during symmetric protractions. Tracer injections suggest that regions associated with symmetric whisker movements are anatomically connected to the contralateral cerebellar hemisphere. Together, these data point toward the existence of modules on both sides of the cerebellar cortex that can differentially promote or reduce the symmetry of left and right movements in a context-dependent fashion.

Assessing the requirements of prenatal UBE3A expression for rescue of behavioral phenotypes in a mouse model for Angelman syndrome.

BACKGROUND: Angelman syndrome (AS) is a rare neurodevelopmental disorder caused by the loss of functional ubiquitin protein ligase E3A (UBE3A). In neurons, UBE3A expression is tightly regulated by a mechanism of imprinting which suppresses the expression of the paternal UBE3A allele. Promising treatment strategies for AS are directed at activating paternal UBE3A gene expression. However, for such strategies to be successful, it is important to know when such a treatment should start, and how much UBE3A expression is needed for normal embryonic brain development. METHODS: Using a conditional mouse model of AS, we further delineated the critical period for UBE3A expression during early brain development. Ube3a gene expression was induced around the second week of gestation and mouse phenotypes were assessed using a behavioral test battery. To investigate the requirements of embryonic UBE3A expression, we made use of mice in which the paternal Ube3a allele was deleted. RESULTS: We observed a full behavioral rescue of the AS mouse model phenotypes when Ube3a gene reactivation was induced around the start of the last week of mouse embryonic development. We found that full silencing of the paternal Ube3a allele was not completed till the first week after birth but that deletion of the paternal Ube3a allele had no significant effect on the assessed phenotypes. LIMITATIONS: Direct translation to human is limited, as we do not precisely know how human and mouse brain development aligns over gestational time. Moreover, many of the assessed phenotypes have limited translational value, as the underlying brain regions involved in these tasks are largely unknown. CONCLUSIONS: Our findings provide further important insights in the requirement of UBE3A expression during brain development. We found that loss of up to 50% of UBE3A protein during prenatal mouse brain development does not significantly impact the assessed mouse behavioral phenotypes. Together with previous findings, our results indicate that the most critical function for mouse UBE3A lies in the early postnatal period between birth and P21.

Effects of Earthworms and Agricultural Plant Species on the Soil Nematode Community in a Microcosm Experiment.

Both earthworms and plants may affect the soil nematode community. However, the effects of earthworms and plant species interactions on soil nematode community are poorly understood. We explored how an epigeic earthworm Eisenia fetida affects the soil nematode community in systems with three representative plants (wheat, cotton and cabbage) which were grown in pots with or without added earthworms under greenhouse conditions. Earthworm presence decreased the abundance of total nematode and all four nematode trophic groups, except for the fungivore and predator/omnivore nematodes in wheat systems, but increased the genus richness of nematode in all treatments. Due to plant identity and different root exudates, plants had significant effects on soil nematode abundance. Compared with the no plant and without earthworm treatment, wheat and cabbage had the higher stimulation of the abundance of total nematode, bacterivores and fungivores, and cotton had the higher stimulation of the abundance of fungivores and predators-omnivores; whereas earthworm presence mostly weakened the stimulation effects of plant species on soil nematode abundance which indicated earthworms had the enhanced effects in the presence of plants. The interaction affected soil nematode abundance (total nematodes, bacterivore, fungivore and omnivore-predators) and community diversity indices (diversity index H', evenness index J', community maturity index ∑MI, Simpson dominance index λ and nematode channel ratio NCR). Principal component analysis showed that plant species affected soil nematode community composition. Redundancy analysis indicated plant species and biomass accounted for 41.60% and 34.13% of the variation in soil nematode community structure, respectively; while earthworms explained only 6.13%. Overall, current study suggest that earthworm could inhibit nematode abundance; whereas, plants have exerted greater influences on nematode community structure than earthworm presence due to their species-specific effects on different trophic groups of nematodes.

Reduction of inflammatory responses by L-serine treatment leads to neuroprotection in mice after traumatic brain injury.

This study was designed to evaluate the neuroprotective effect of l-serine and the underlying mechanisms in mice after traumatic brain injury (TBI) induced using a weight drop model. The mice were intraperitoneally injected with l-serine 3 h after TBI and then injected twice each day for 7 days or until the end of the experiment. The neurological severity score, brain water content, lesion volume, and neurone loss were determined. The levels of TNF-α, IL-1ß, IL-6, and IL-10 and the number of GFAP- and Iba-1-positive cells and activated caspase-3-positive neurones in the brain tissue ipsilateral to TBI were also measured. Simultaneously, the influences of l-serine on these variables were observed. In addition, the expression of glycine receptors and l-serine-induced currents were measured. We found l-serine treatment: 1) decreased the neurological deficit score, brain water content, lesion volume, and neurone loss; 2) inhibited activated caspase-3; and 3) reduced the levels of TNF-α, IL-1ß and IL-6 and the number of GFAP- and Iba-1-positive cells. The effects of l-serine were antagonised by the administration of strychnine, an antagonist of glycine receptors. In addition, we found that glycine receptors were expressed mainly in the cortical neurones but less in the astrocytes or microglial cells, and l-serine activated these receptors and induced strychnine-sensitive currents in these neurones. In conclusion, l-serine induces the activation of glycine receptors, which alleviates neuronal excitotoxicity, a secondary brain injury process, thereby reduces the activation of astrocytes and microglial cells and secretion of proinflammatory cytokines and inhibits neuronal apoptosis. Thus, l-serine treatment leads to neuroprotection of brain tissue through reducing inflammatory responses and improves recovery of the neurological functions in mice after traumatic brain injury.

Up-regulation of NFATc4 involves in neuronal apoptosis following intracerebral hemorrhage.

Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4), a transcriptional factor, is involved in the control about the flow of genetic information and the modulation of diverse cellular activities. Accumulating evidence has demonstrated that NFATc4 exerted a pro-apoptotic effect in multiple diseases. Here, we explored the NFATc4's roles during the pathophysiological processes of intracerebral hemorrhage (ICH). An ICH rat model was built and evaluated according to behavioral testing. Using Western blot, immunohistochemistry, and immunofluorescence, significant up-regulation of NFATc4 was found in neurons in brain areas surrounding the hematoma following ICH. Increasing NFATc4 expression was found to be accompanied by the up-regulation of Fas ligand (FasL), active caspase-8, and active caspase-3, respectively. Besides, NFATc4 co-localized with active caspase-3 in neurons, indicating its role in neuronal apoptosis. Our in vitro study, using NFATc4 RNA interference in PC12 cells, further confirmed that NFATc4 might exert its pro-apoptotic function in neuronal apoptosis through extrinsic pathway. Thus, NFATc4 may play a role in promoting the brain secondary damage following ICH.