Axon outgrowth and neuronal differentiation defects after a-SMN and FL-SMN silencing in primary hippocampal cultures

A CRISPR/Cas9-Based Assay for High-Throughput Studies of Cancer-Induced Innervation

The aggressive nature of certain cancers and their adverse effects on patient outcomes have been linked to cancer innervation, where neurons infiltrate and differentiate within the cancer stroma. Recently we demonstrated how cancer plasticity and TGFβ signaling could promote breast cancer innervation that is associated with increased cancer aggressivity. Despite the promising potential of cancer innervation as a target for anti-cancer therapies, there is currently a significant lack of effective methods to study cancer-induced neuronal differentiation, hindering the development of high-throughput approaches for identifying new targets or pharmacological inhibitors against cancer innervation. To overcome this challenge, we used CRISPR-based endogenous labeling of the neuronal marker β3-tubulin in neuronal precursors to investigate cancer-induced neuronal differentiation in nerve-cancer cocultures and provide a tool that allows for better standardization and reproducibility of studies about cancer-induced innervation. Our approach demonstrated that β3-tubulin gene editing did not affect neuronal behavior and enabled accurate reporting of cancer-induced neuronal differentiation dynamics in high-throughput settings, which makes this approach suitable for screening large cohorts of cells or testing various biological contexts. In a more context-based approach, by combining this method with a cell model of breast cancer epithelial-mesenchymal transition, we revealed the role of cancer cell plasticity in promoting neuronal differentiation, suggesting that cancer innervation represents an underexplored path for epithelial-mesenchymal transition-mediated cancer aggressivity.

NSC Physiological Features in Spinal Muscular Atrophy: SMN Deficiency Effects on Neurogenesis

While the U.S. Food and Drug Administration and the European Medicines Evaluation Agency have recently approved new drugs to treat spinal muscular atrophy 1 (SMA1) in young patients, they are mostly ineffective in older patients since many motor neurons have already been lost. Therefore, understanding nervous system (NS) physiology in SMA patients is essential. Consequently, studying neural stem cells (NSCs) from SMA patients is of significant interest in searching for new treatment targets that will enable researchers to identify new pharmacological approaches. However, studying NSCs in these patients is challenging since their isolation damages the NS, making it impossible with living patients. Nevertheless, it is possible to study NSCs from animal models or create them by differentiating induced pluripotent stem cells obtained from SMA patient peripheral tissues. On the other hand, therapeutic interventions such as NSCs transplantation could ameliorate SMA condition. This review summarizes current knowledge on the physiological properties of NSCs from animals and human cellular models with an SMA background converging on the molecular and neuronal circuit formation alterations of SMA fetuses and is not focused on the treatment of SMA. By understanding how SMA alters NSC physiology, we can identify new and promising interventions that could help support affected patients.

Organotypic spinal cord cultures: An <em>in vitro</em> 3D model to preliminary screen treatments for spinal muscular atrophy

Spinal muscular atrophy (SMA) is a severe neuromuscular disease affecting children, due to mutation/deletion of survival motor neuron 1 (SMN1) gene. The lack of functional protein SMN determines motor neuron (MN) degeneration and skeletal muscle atrophy, leading to premature death due to respiratory failure. Nowadays, the Food and Drug Administration approved the administration of three drugs, aiming at increasing the SMN production: although assuring noteworthy results, all these therapies show some non-negligible limitations, making essential the identification of alternative/synergistic therapeutic strategies. To offer a valuable in vitro experimental model for easily performing preliminary screenings of alternative promising treatments, we optimized an organotypic spinal cord culture (derived from murine spinal cord slices), which well recapitulates the pathogenetic features of SMA. Then, to validate the model, we tested the effects of human mesenchymal stem cells (hMSCs) or murine C2C12 cells (a mouse skeletal myoblast cell line) conditioned media: 1/3 of conditioned medium (obtained from either hMSCs or C2C12 cells) was added to the conventional medium of the organotypic culture and maintained for 7 days. Then the slices were fixed and immunoreacted to evaluate the MN survival. In particular we observed that the C2C12 and hMSCs conditioned media positively influenced the MN soma size and the axonal length respectively, without modulating the glial activation. These data suggest that trophic factors released by MSCs or muscular cells can exert beneficial effects, by acting on different targets, and confirm the reliability of the model. Overall, we propose the organotypic spinal cord culture as an excellent tool to preliminarily screen molecules and drugs before moving to in vivo models, in this way partly reducing the use of animals and the costs.

Axonal Transport and Local Translation of mRNA in Neurodegenerative Diseases

Since neurons have long neurites including axons, it is crucial for the axons to transport many intracellular substances such as proteins and mitochondria in order to maintain their morphology and function. In addition, mRNAs have also been shown to be transported within axons. RNA-binding proteins form complexes with mRNAs, and regulate transport of the mRNAs to axons, as well as locally translate them into proteins. Local translation of mRNAs actively occurs during the development and damage of neurons, and plays an important role in axon elongation, regeneration, and synapse formation. In recent years, it has been reported that impaired axonal transport and local translation of mRNAs may be involved in the pathogenesis of some neurodegenerative diseases. In this review, we discuss the significance of mRNA axonal transport and their local translation in amyotrophic lateral sclerosis/frontotemporal dementia, spinal muscular atrophy, Alzheimer’s disease, and fragile X syndrome.

Mechanisms of axon polarization in pyramidal neurons

Neurons are highly polarized cells that have specialized regions for synaptic input, the dendrites, and synaptic output, the axons. This polarity is critical for appropriate neural circuit formation and function. One of the central gaps in our knowledge is understanding how developing neurons initiate axon polarity. Given the critical nature of this polarity on neural circuit formation and function, neurons have evolved multiple mechanisms comprised of extracellular and intracellular cues that allow them to initiate and form axons. These mechanisms engage a variety of signaling cascades that provide positive and negative cues to ensure axon polarization. This review highlights our current knowledge of the molecular underpinnings of axon polarization in pyramidal neurons and their relevance to the development of the brain.