Prenatal treatment with rapamycin restores enhanced hippocampal mGluR-LTD and mushroom spine size in a Down's syndrome mouse model

Intellectual disability: A potentially treatable condition

The application of genomics has greatly increased the diagnosis of specific monogenic causes of intellectual disability and improved our understanding of the neuronal processes that result in cognitive impairment. Meanwhile, families are building rare disease communities and seeking disease-specific treatments to change the trajectory of health and developmental outcomes for their children. To date, treatments for intellectual disability have focussed on metabolic disorders, where early treatment has improved cognition and neurodevelopmental outcomes. In this article, we discuss the treatment strategies that may be possible to change the neurodevelopmental outcome in a broader range of genetic forms of intellectual disability. These strategies include substrate modification, enzyme replacement therapy, gene therapy and molecular therapies. We argue that intellectual disability should now be considered a potentially treatable condition and a strong candidate for precision medicine.

Brain Mitochondrial Bioenergetics in Genetic Neurodevelopmental Disorders: Focus on Down, Rett and Fragile X Syndromes

Mitochondria, far beyond their prominent role as cellular powerhouses, are complex cellular organelles active as central metabolic hubs that are capable of integrating and controlling several signaling pathways essential for neurological processes, including neurogenesis and neuroplasticity. On the other hand, mitochondria are themselves regulated from a series of signaling proteins to achieve the best efficiency in producing energy, in establishing a network and in performing their own de novo synthesis or clearance. Dysfunctions in signaling processes that control mitochondrial biogenesis, dynamics and bioenergetics are increasingly associated with impairment in brain development and involved in a wide variety of neurodevelopmental disorders. Here, we review recent evidence proving the emerging role of mitochondria as master regulators of brain bioenergetics, highlighting their control skills in brain neurodevelopment and cognition. We analyze, from a mechanistic point of view, mitochondrial bioenergetic dysfunction as causally interrelated to the origins of typical genetic intellectual disability-related neurodevelopmental disorders, such as Down, Rett and Fragile X syndromes. Finally, we discuss whether mitochondria can become therapeutic targets to improve brain development and function from a holistic perspective.

Updates on the Physiopathology of Group I Metabotropic Glutamate Receptors (mGluRI)-Dependent Long-Term Depression

Group I metabotropic glutamate receptors (mGluRI), including mGluR1 and mGluR5 subtypes, modulate essential brain functions by affecting neuronal excitability, intracellular calcium dynamics, protein synthesis, dendritic spine formation, and synaptic transmission and plasticity. Nowadays, it is well appreciated that the mGluRI-dependent long-term depression (LTD) of glutamatergic synaptic transmission (mGluRI-LTD) is a key mechanism by which mGluRI shapes connectivity in various cerebral circuitries, directing complex brain functions and behaviors, and that it is deranged in several neurological and psychiatric illnesses, including neurodevelopmental disorders, neurodegenerative diseases, and psychopathologies. Here, we will provide an updated overview of the physiopathology of mGluRI-LTD, by describing mechanisms of induction and regulation by endogenous mGluRI interactors, as well as functional physiological implications and pathological deviations.

Aggression Results in the Phosphorylation of ERK1/2 in the Nucleus Accumbens and the Dephosphorylation of mTOR in the Medial Prefrontal Cortex in Female Syrian Hamsters

Like many social behaviors, aggression can be rewarding, leading to behavioral plasticity. One outcome of reward-induced aggression is the long-term increase in the speed in which future aggression-based encounters is initiated. This form of aggression impacts dendritic structure and excitatory synaptic neurotransmission in the nucleus accumbens, a brain region well known to regulate motivated behaviors. Yet, little is known about the intracellular signaling mechanisms that drive these structural/functional changes and long-term changes in aggressive behavior. This study set out to further elucidate the intracellular signaling mechanisms regulating the plasticity in neurophysiology and behavior that underlie the rewarding consequences of aggressive interactions. Female Syrian hamsters experienced zero, two or five aggressive interactions and the phosphorylation of proteins in reward-associated regions was analyzed. We report that aggressive interactions result in a transient increase in the phosphorylation of extracellular-signal related kinase 1/2 (ERK1/2) in the nucleus accumbens. We also report that aggressive interactions result in a transient decrease in the phosphorylation of mammalian target of rapamycin (mTOR) in the medial prefrontal cortex, a major input structure to the nucleus accumbens. Thus, this study identifies ERK1/2 and mTOR as potential signaling pathways for regulating the long-term rewarding consequences of aggressive interactions. Furthermore, the recruitment profile of the ERK1/2 and the mTOR pathways are distinct in different brain regions.

FDA-Approved Kinase Inhibitors in Preclinical and Clinical Trials for Neurological Disorders

Cancers and neurological disorders are two major types of diseases. We previously developed a new concept termed "Aberrant Cell Cycle Diseases" (ACCD), revealing that these two diseases share a common mechanism of aberrant cell cycle re-entry. The aberrant cell cycle re-entry is manifested as kinase/oncogene activation and tumor suppressor inactivation, which are hallmarks of both tumor growth in cancers and neuronal death in neurological disorders. Therefore, some cancer therapies (e.g., kinase inhibition, tumor suppressor elevation) can be leveraged for neurological treatments. The United States Food and Drug Administration (US FDA) has so far approved 74 kinase inhibitors, with numerous other kinase inhibitors in clinical trials, mostly for the treatment of cancers. In contrast, there are dire unmet needs of FDA-approved drugs for neurological treatments, such as Alzheimer's disease (AD), intracerebral hemorrhage (ICH), ischemic stroke (IS), traumatic brain injury (TBI), and others. In this review, we list these 74 FDA-approved kinase-targeted drugs and identify those that have been reported in preclinical and/or clinical trials for neurological disorders, with a purpose of discussing the feasibility and applicability of leveraging these cancer drugs (FDA-approved kinase inhibitors) for neurological treatments.

Proteomic characterization of spinal cord synaptoneurosomes from Tg-SOD1/G93A mice supports a role for MNK1 and local translation in the early stages of amyotrophic lateral sclerosis

The isolation of synaptoneurosomes (SNs) represents a useful means to study synaptic events. However, the size and density of synapses varies in different regions of the central nervous system (CNS), and this also depends on the experimental species studied, making it difficult to define a generic protocol for SNs preparation. To characterize synaptic failure in the spinal cord (SC) in the Tg-SOD1/G93A mouse model of amyotrophic lateral sclerosis (ALS), we applied a method we originally designed to isolate cortical and hippocampal SNs to SC tissue. Interestingly, we found that the SC SNs were isolated in a different gradient fraction to the cortical/hippocampal SNs. We compared the relative levels of synaptoneurosomal proteins in wild type (WT) animals, with control (Tg-SOD1) or Tg-SOD1/G93A mice at onset and those that were symptomatic using iTRAQ proteomics. The results obtained suggest that an important regulator of local synaptic translation, MNK1 (MAP kinase interacting serine/threonine kinase 1), might well influence the early stages of ALS.

Brain circuit pathology in Down syndrome: from neurons to neural networks

Down syndrome (DS), a genetic pathology caused by triplication of chromosome 21, is characterized by brain hypotrophy and impairment of cognition starting from infancy. While studies in mouse models of DS have elucidated the major neuroanatomical and neurochemical defects of DS, comparatively fewer investigations have focused on the electrophysiology of the DS brain. Electrical activity is at the basis of brain functioning. Therefore, knowledge of the way in which brain circuits operate in DS is fundamental to understand the causes of behavioral impairment and devise targeted interventions. This review summarizes the state of the art regarding the electrical properties of the DS brain, starting from individual neurons and culminating in signal processing in whole neuronal networks. The reported evidence derives from mouse models of DS and from brain tissues and neurons derived from individuals with DS. EEG data recorded in individuals with DS are also provided as a key tool to understand the impact of brain circuit alterations on global brain activity.

The Challenging Pathway of Treatment for Neurogenesis Impairment in Down Syndrome: Achievements and Perspectives

Down syndrome (DS), also known as trisomy 21, is a genetic disorder caused by triplication of Chromosome 21. Gene triplication may compromise different body functions but invariably impairs intellectual abilities starting from infancy. Moreover, after the fourth decade of life people with DS are likely to develop Alzheimer’s disease. Neurogenesis impairment during fetal life stages and dendritic pathology emerging in early infancy are thought to be key determinants of alterations in brain functioning in DS. Although the progressive improvement in medical care has led to a notable increase in life expectancy for people with DS, there are currently no treatments for intellectual disability. Increasing evidence in mouse models of DS reveals that pharmacological interventions in the embryonic and neonatal periods may greatly benefit brain development and cognitive performance. The most striking results have been obtained with pharmacotherapies during embryonic life stages, indicating that it is possible to pharmacologically rescue the severe neurodevelopmental defects linked to the trisomic condition. These findings provide hope that similar benefits may be possible for people with DS. This review summarizes current knowledge regarding (i) the scope and timeline of neurogenesis (and dendritic) alterations in DS, in order to delineate suitable windows for treatment; (ii) the role of triplicated genes that are most likely to be the key determinants of these alterations, in order to highlight possible therapeutic targets; and (iii) prenatal and neonatal treatments that have proved to be effective in mouse models, in order to rationalize the choice of treatment for human application. Based on this body of evidence we will discuss prospects and challenges for fetal therapy in individuals with DS as a potential means of drastically counteracting the deleterious effects of gene triplication.

Biocompatibility Study of a Commercial Printed Circuit Board for Biomedical Applications: Lab-on-PCB for Organotypic Retina Cultures

Printed circuit board (PCB) technology is well known, reliable, and low-cost, and its application to biomedicine, which implies the integration of microfluidics and electronics, has led to Lab-on-PCB. However, the biocompatibility of the involved materials has to be examined if they are in contact with biological elements. In this paper, the solder mask (PSR-2000 CD02G/CA-25 CD01, Taiyo Ink (Suzhou) Co., Ltd., Suzhou, China) of a commercial PCB has been studied for retinal cultures. For this purpose, retinal explants have been cultured over this substrate, both on open and closed systems, with successful results. Cell viability data shows that the solder mask has no cytotoxic effect on the culture allowing the application of PCB as the substrate of customized microelectrode arrays (MEAs). Finally, a comparative study of the biocompatibility of the 3D printer Uniz zSG amber resin has also been carried out.