CLASS 3 SECRETED SEMAPHORIN REGULATION OF NEURONAL MORPHOLOGY DURING CENTRAL NERVOUS SYSTEM DEVELOPMENT

Cortical pyramidal neurons have exquisite morphology and electrophysiological properties, and elucidating how these features develop and are maintained is essential to understanding the physiological development of the central nervous system (CNS). The secreted semaphorins Sema3A and Sema3F have remarkably distinct effects on the development of deep layer cortical pyramidal neurons. Specifically, Sema3A promotes the elaboration of basal dendrites whereas Sema3F constrains spine density. This remarkable functional divergence implicates Sema3A and Sema3F, and their distinct holoreceptor complexes, in the establishment of neuronal architecture. However, the molecular mechanisms by which neuropilins, the secreted semaphorin ligand binding subunits of the Sema3A and Sema3F holoreceptors, exert their effects are largely unknown. Here, I demonstrate that the two Npns, Npn-1 and Npn-2, are S-palmitoylated in cortical neurons and in the mouse brain. Interestingly, Npn-1, which binds Sema3A, and Npn-2, which binds Sema3F, exhibit distinct cell surface distribution patterns; Npn-2 is clustered whereas Npn-1 is diffusely distributed. Importantly, inhibition of Npn-2 palmitoylation abolishes Npn-2 clustering whereas it does not affect Npn-1 localization. These data suggest that palmitoylation conveys to Npn-2, but not Npn-1, a distinct localization pattern and, possibly, function. I therefore investigated the role of palmitoylation in Npn-2 localization and function. I demonstrate that mutation of the membrane-proximal Npn-2 cysteines abolishes the ability of Npn-2 to mediate spine constraint in response to Sema3F and causes profound defects in Npn-2 distribution and trafficking in cortical neurons. On the contrary, C-terminal Npn-2 cysteine residues are dispensable for these effects. Thus, there is a strong functional segregation within the Npn-2 structure regarding cysteine residue functions. Interestingly, Npn-1 and Npn-2 serve as substrates for distinct palmitoyl acyltransferases. The palmitoyltransferase DHHC15 is involved in Sema3F/Npn-2–induced spine constraint, whereas it is not required for Sema3A/Npn-1–mediated dendritic elaboration of deep layer cortical neurons. On the other hand, the palmitoyltransferase DHHC8 is apparently indispensable for Sema3A/Npn-1–mediated dendritic elaboration but not for Sema3F/Npn-2–induced spine constraint. These observations are in accordance with biochemical and genetic experiments showing that DHHC15 and DHHC8 have distinct substrates. Palmitoyltransferase substrate specificity, therefore, plays critical roles in establishing neuronal cue signaling specificity in the CNS

Retrograde semaphorin-plexin signalling drives homeostatic synaptic plasticity.

Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin-plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b-PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin-plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour

ESC-MRAC of MIMO systems for constrained robotic motion tasks in deformable environments

Performance of constrained movements in multiple directions of a workspace simultaneously and in presence of uncertainty is a great challenge for robots. Achieving such tasks by employing control policies which are fully determined a priori and do not take into account the system uncertainty can cause undesired stress on the robot end-effector or the environment and result in poor performance. Instead, a sophisticated control policy is required, which can adjust to the varying conditions of a task while taking into account the coupling of motion dynamics between different directions of movement. To this aim, in this paper, we propose a MIMO Extremum Seeking Control (ESC)-Model Reference Adaptive Control (MRAC) approach with the view of executing fine motion tasks in presence of uncertain task dynamics. ESC enhances robustness of the system to non-parametric uncertainties compared to single MRAC. The proposed approach ensures state tracking as well as optimization of a global state-dependent cost criterion in all directions of movement. We evaluate our approach in simulations and in a real-world robotic engraving task

Esc-Mrac Of Mimo Systems For Constrained Robotic Motion Tasks In Deformable Environments

Performance of constrained movements in multiple directions of a workspace simultaneously and in presence of uncertainty is a great challenge for robots. Achieving such tasks by employing control policies which are fully determined a priori and do not take into account the system uncertainty can cause undesired stress on the robot end-effector or the environment and result in poor performance. Instead, a sophisticated control policy is required, which can adjust to the varying conditions of a task while taking into account the coupling of motion dynamics between different directions of movement. To this aim, in this paper, we propose a MIMO Extremum Seeking Control (ESC)-Model Reference Adaptive Control (MRAC) approach with the view of executing fine motion tasks in presence of uncertain task dynamics. ESC enhances robustness of the system to non-parametric uncertainties compared to single MRAC. The proposed approach ensures state tracking as well as optimization of a global state-dependent cost criterion in all directions of movement. We evaluate our approach in simulations and in a real-world robotic engraving task

An Adaptive Dynamic Inversion-Extremum Seeking Control Approach For Constrained Robotic Motion Tasks

In this paper, an adaptive control approach is proposed for performance of constrained robot end-effector movements in presence of uncertainty. In real-world scenarios, complex physical phenomena occuring at the place of interaction may introduce nonlinearities in the system dynamics, which have to be taken into account for proper system control. We currently propose an Extremum Seeking (ES) Model Reference Adaptive Control (MRAC) approach for state tracking of multiple-input multiple-output systems which enclose nonlinearities in their dynamics and involve parametric uncertainty by employing Adaptive Dynamic Inversion (ADI). According to ADI, system nonlinearities are assumed known and are taken into account in the design of the system control law. The proposed scheme is based on MRAC and ADI while the unknown controller parameters are adapted by ES control. The system is shown to achieve global and asymptotic reference state tracking under the proposed control law by performing Lyapunov and averaging analysis. The approach is evaluated in simulation and in an experimental robot task

Genetic Evaluation of In Vitro Micropropagated and Regenerated Plants of Cannabis sativa L. Using SSR Molecular Markers

Simple sequence repeat (SSR) markers were used to evaluate the genetic stability of the acclimatized micropropagated and regenerated plants of a high cannabidiol (H-CBD) and a high cannabigerol (H-CBG) variety of Cannabis sativa L. Shoot regeneration and proliferation were achieved by culturing calli in Murashige and Skoog basal medium (MS) supplemented with several concentrations of 6-benzyladenine (BA) or thidiazuron (TDZ). Calli derived mostly from stem explants, rather than leaves, cultured on MS supplemented with 2,4-Dichlorophenoxyacetic acid (2,4-D) or combination of kinetin (KIN) with 1-Naphthaleneacetic acid (NAA) or 2,4-D. Rooting of the regenerated plantlets accomplished on half-strength MS medium supplemented with indole-3-butyric acid (IBA). Previous studies performed have developed an efficient in vitro micropropagation protocol for mass production. Both in vitro methodologies can be employed in genetic breeding via molecular techniques. The genetic stability of micropropagated and regenerated plants was accomplished using twelve SSR primer pairs that produced reproducible and clear bands, ranging from 90 to 330 bp in size, and resulted in amplification of one or two alleles, corresponding to homozygous or heterozygous individuals. The SSR amplification products were monomorphic across all the micropropagated and regenerated plants and comparable to mother plants. The monomorphic banding pattern confirmed the genetic homogeneity of the in vitro cultured acclimatized and mother plants as no somaclonal variation was detected in clones for these specific SSRs. Our results evidently suggest that the developed culture protocols for in vitro multiplication is appropriate and applicable for clonal mass propagation of the C. sativa varieties and demonstrate the reliability of this in vitro propagation system

An Extremum-Seeking Control Approach For Constrained Robotic Motion Tasks

In this paper, we propose two adaptive control schemes for multiple-input systems for execution of robot end-effector movements in the presence of parametric system uncertainties. The design of these schemes is based on Model Reference Adaptive Control (MRAC) while the adaptation of the controller parameters is achieved by Extremum Seeking Control (ESC). The two control schemes, which are called Multiple-Input ESC-MRAC and Multiple-Input Adaptive-Dynamic-Inversion ESC-MRAC, are suitable for linear and nonlinear systems respectively. Lyapunov and averaging analysis shows that the proposed schemes achieve practical asymptotic reference state tracking. The proposed methods are evaluated in simulations and in a real-world robotic experiment