During brain development, the small GTPases Rac1/Rac3 play key roles in neuronal migration, neuritogenesis, synaptic formation and plasticity, via control of actin cytoskeleton dynamic. Their activity is positively and negatively regulated by GEFs and GAPs molecules, respectively. However their in vivo roles are poorly known. The ArhGAP15 gene, coding for a Rac-specific GAP protein, is expressed in both excitatory and inhibitory neurons of the adult hippocampus, and its loss results in the hyperactivation of Rac1/Rac3. In the CA3 and dentate gyrus (DG) regions of the ArhGAP15 mutant hippocampus the CR+, PV+ and SST+ inhibitory neurons are reduced in number, due to reduced efficiency and directionality of their migration, while pyramidal neurons are unaffected. Loss of ArhGAP15 alters neuritogenesis and the balance between excitatory and inhibitory synapses, with a net functional result consisting in increased spike frequency and bursts, accompanied by poor synchronization. Thus, the loss of ArhGAP15 mainly impacts on interneuron-dependent inhibition. Adult ArhGAP15−/− mice showed defective hippocampus-dependent functions such as working and associative memories. These findings indicate that a normal architecture and function of hippocampal inhibitory neurons is essential for higher hippocampal functions, and is exquisitely sensitive to ArhGAP15-dependent modulation of Rac1/Rac3.

Pain sensation and aversive behaviors entail the activation of nociceptor neurons, whose function is largely conserved across animals. The functional heterogeneity of nociceptors and ethical concerns are challenges for their study in mammalian models. Here, we investigate the function of a single type of genetically identified C. elegans thermonociceptor named FLP. Using calcium imaging in vivo, we demonstrate that FLP encodes thermal information in a tonic and graded manner over a wide thermal range spanning from noxious cold to noxious heat (8 C-36 C). This tonic-signaling mode allows FLP to trigger sustained behavioral changes necessary for escape behavior. Furthermore, we identify specific transient receptor potential, voltage-gated calcium, and sodium ''leak'' channels controlling sensory gain, thermal sensitivity, and signal kinetics, respectively, and show that the ryanodine receptor is required for long-lasting activation. Our work elucidates the task distribution among specific ion channels to achieve remarkable sensory properties in a tonic thermonociceptor in vivo.

The ability to adapt behavior to environmental fluctuations is critical for survival of organisms ranging from invertebrates to mammals. can learn to avoid sodium chloride when it is paired with starvation. This behavior may help animals avoid areas without food. Although some genes have been implicated in this salt-aversive learning behavior, critical genetic components, and the neural circuit in which they act, remain elusive. Here, we show that the sole worm ortholog of mammalian CaMKI/IV, CMK-1, is essential for salt-aversive learning behavior in hermaphrodites. We find that CMK-1 acts in the primary salt-sensing ASE neurons to regulate this behavior. By characterizing the intracellular calcium dynamics in ASE neurons using microfluidics, we find that loss of has subtle effects on sensory-evoked calcium responses in ASE axons and their modulation by salt conditioning. Our study implicates the expression of the conserved CaMKI/CMK-1 in chemosensory neurons as a regulator of behavioral plasticity to environmental salt in Like other animals, the nematode depends on salt for survival and navigates toward high concentrations of this essential mineral. In addition to its role as an essential nutrient, salt also causes osmotic stress at high concentrations. A growing body of evidence indicates that balances the requirement for salt with the danger it presents through a process called salt-aversive learning. We show that this behavior depends on expression of a calcium/calmodulin-dependent kinase, CMK-1, in the ASE salt-sensing neurons. Our study identifies CMK-1 and salt-sensitive chemosensory neurons as key factors in this form of behavioral plasticity.

Understanding how the nervous system bridges sensation and behavior requires the elucidation of complex neural and molecular networks. Forward genetic approaches, such as screens conducted in C. elegans, have successfully identified genes required to process natural sensory stimuli. However, functional redundancy within the underlying neural circuits, which are often organized with multiple parallel neural pathways, limits our ability to identify ‘neural pathway-specific genes’, i.e. genes that are essential for the function of some, but not all of these redundant neural pathways. To overcome this limitation, we developed a ‘forward optogenetics’ screening strategy in which natural stimuli are initially replaced by the selective optogenetic activation of a specific neural pathway. We used this strategy to address the function of the polymodal FLP nociceptors mediating avoidance of noxious thermal and mechanical stimuli. According to our expectations, we identified both mutations in ‘general’ avoidance genes that broadly impact avoidance responses to a variety of natural noxious stimuli (unc-4, unc-83, and eat-4) and mutations that produce a narrower impact, more restricted to the FLP pathway (syd-2, unc-14 and unc-68). Through a detailed follow-up analysis, we further showed that the Ryanodine receptor UNC-68 acts cell-autonomously in FLP to adjust heat-evoked calcium signals and aversive behaviors. As a whole, our work (i) reveals the importance of properly regulated ER calcium release for FLP function, (ii) provides new entry points for new nociception research and (iii) demonstrates the utility of our forward optogenetic strategy, which can easily be transposed to analyze other neural pathways.

Light affects many physiological processes in mammals such as entrainment of the circadian clock, regulation of mood, and relaxation of blood vessels. At the molecular level, a stimulus such as light initiates a cascade of kinases that phosphorylate CREB at various sites, including serine 133 (S133). This modification leads CREB to recruit the co-factor CRCT1 and the histone acetyltransferase CBP to stimulate the transcription of genes containing a CRE element in their promoters, such as Period 1 (Per1). However, the details of this pathway are poorly understood. Here we provide evidence that PER2 acts as a co-factor of CREB to facilitate the formation of a transactivation complex on the CRE element of the Per1 gene regulatory region in response to light or forskolin. Using in vitro and in vivo approaches, we show that PER2 modulates the interaction between CREB and its co-regulator CRTC1 to support complex formation only after a light or forskolin stimulus. Furthermore, the absence of PER2 abolished the interaction between the histone acetyltransferase CBP and CREB. This process was accompanied by a reduction of histone H3 acetylation and decreased recruitment of RNA Pol II to the Per1 gene. Collectively, our data show that PER2 supports the stimulus-dependent induction of the Per1 gene via modulation of the CREB/CRTC1/CBP complex.

Loss of synapses or alteration of synaptic activity is associated with cognitive impairment observed in a number of psychiatric and neurological disorders, such as schizophrenia and Alzheimer’s disease. Therefore successful development of in vitro methods that can investigate synaptic function in a high-throughput format could be highly impactful for neuroscience drug discovery. We present here the development, characterisation and validation of a novel high-throughput in vitro model for assessing neuronal function and synaptic transmission in primary rodent neurons. The novelty of our approach resides in the combination of the electrical field stimulation (EFS) with data acquisition in spatially separated areas of an interconnected neuronal network. We integrated our methodology with state of the art drug discovery instrumentation (FLIPR Tetra) and used selective tool compounds to perform a systematic pharmacological validation of the model. We investigated pharmacological modulators targeting pre- and post-synaptic receptors (AMPA, NMDA, GABA-A, mGluR2/3 receptors and Nav, Cav voltage-gated ion channels) and demonstrated the ability of our model to discriminate and measure synaptic transmission in cultured neuronal networks. Application of the model described here as an unbiased phenotypic screening approach will help with our long term goals of discovering novel therapeutic strategies for treating neurological disorders.

Bicaudal-D (BicD) is a dynein adaptor that transports different cargoes along microtubules. Reducing the activity of BicD specifically in freshly laid Drosophila eggs by acute protein degradation revealed that BicD is needed to produce normal female meiosis II products, to prevent female meiotic products from re-entering the cell cycle, and for pronuclear fusion. As BicD is required to localize the spindle assembly checkpoint (SAC) components Mad2 and BubR1 to the female meiotic products, it appears that BicD functions to localize them to control metaphase arrest of polar bodies. BicD interacts with Clathrin heavy chain (Chc), and both proteins localize to centrosomes, mitotic spindles, and the tandem spindles during female meiosis II. Furthermore, BicD is required to correctly localize clathrin and the microtubule-stabilizing factors, D-TACC and Msps, to the meiosis II spindles, suggesting that failure to localize these proteins may perturb SAC function. Furthermore, right after the establishment of the female pronucleus, D-TACC and C. elegansBicD, tacc, and Chc are also needed for pronuclear fusion, pointing to the possibility that the underlying mechanism might be more widely used.

Ontogeny requires the coordinated regulation of multi-gene programs by a plethora of extracellular and intracellular signals. As a result, stem cells transition between states of self-renewal, proliferative expansion and differentiation. Disruption of this regulation may cause oncogenic transformation in which stem cells are "arrested" in the proliferative state. Systems biology postulates computational modules which integrate environmental (extraand intra-cellular) information to control entry into the cell cycle and promote perpetual self-renewal by the stem cells. We have identified an analogous Feed-Forward-And Gate network module that effects postmitotic development and neuronal differentiation by the stem cells. In the center of this module resides a novel gene-activating mechanism "Integrative Nuclear Fibroblast Growth Factor Receptor-1 (FGFR1) Signaling" (INFS). We will discuss how stochastic molecular collisions among nuclear proteins lead to an activation of coordinate gene programs. The aim-of-present experimental investigation is to attempt to differentiate between those with concordant (C) and discordant (D) mirror-movements (MMs)/Mirror-Dystonia in Parkinson disease and other movement disorders writer's cramp (WC), in order to establish that there is a quantifiable difference between these two groups and to design/fabricate a multi-channel ENMG system. 12 consecutive-subjects (M:F = 11:1) with their mean-age (68.5 ± 3 yrs), mean-disease-duration (104 ± 126.3 months) diagnosed to have Parkinson-and-WC were included in this study. All subjects (right handed) were informed about study and written informed consent was obtained. Five muscles were selected for microelectrode placement, namely ECR, ECU, FCR, FCU were analyzed in all subjects and one more muscle (which showed maximum discordance on mirror-dystonia) of right hand (RH) was included. Mean-amplitudes for right-hand-writing-signal (RHWS) and left-hand-writing-signal (LHWS) for the same muscles though differ significantly in statistical-terms, showed a consistent pattern only in fifth-muscle with larger-mean-amplitudes on left side in all subjects and were not of value in differentiating between concordant (C)/discordant (D) groups-of-subjects. ENMG signals were asynchronously recorded in all 5 muscles while subjects wrote with their RH first (RHWS) and then LH (LHWS). Based on wrist position during writing with RH-and-LH, subjects A1, A7, A11, and A12 fell in the category of 'Discordant' (D) group. The rest 8 were 'Concordant' (C) (for MMs-at-the-wrist).The principal-component (PC) scores of 12 subject's showed 80% variance in our computation in the scatter plot. The cluster-analysis based on dissimilarity among the subjects' signals show a possibility that, in addition to the grouping of subjects as C or D, some-other-groupings may also be meaningful. ENMG-ENMG coherence was assessed in the Parkinsonism-WC-hand muscles, namely: ECR, ECU, FCR, and FCU, followed by fifth-muscle. The coherence-computed-evaluated and compared between flexor-aspect...