Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease and is characterized by the degeneration of upper and lower motor neurons. It has become increasingly clear that RNA dysregulation is a key contributor to ALS pathogenesis. The major ALS genes SOD1, TARDBP, FUS, and C9orf72 are involved in aspects of RNA metabolism processes such as mRNA transcription, alternative splicing, RNA transport, mRNA stabilization, and miRNA biogenesis. In this review, we highlight the current understanding of RNA dysregulation in ALS pathogenesis involving these major ALS genes and discuss the potential of therapeutic strategies targeting disease RNAs for treating ALS.

The most common genetic cause of amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD) is a hexanucleotide repeat expansion within theC9orf72gene. Reduced levels ofC9orf72mRNA and protein have been found in ALS/FTD patients, but the role of this protein in disease pathogenesis is still poorly understood. Here, we report the generation and characterization of a stable C9orf72 loss-of-function (LOF) model in the zebrafish. We show that reducedC9orf72function leads to motor defects, muscle atrophy, motor neuron loss and mortality in early larval and adult stages. Analysis of the structure and function of the neuromuscular junctions (NMJs) of the larvae, reveal a marked reduction in the number of presynaptic and postsynaptic structures and an impaired release of quantal synaptic vesicles at the NMJ. Strikingly, we demonstrate a downregulation of SV2a upon C9orf72-LOF and a reduced rate of synaptic vesicle cycling. Furthermore, we show a reduced number and size of Rab3a-postive synaptic puncta at NMJs. Altogether, these results reveal a key function for C9orf72 in the control of presynaptic vesicle trafficking and release at the zebrafish larval NMJ. Our study demonstrates an important role for C9orf72 in ALS/FTD pathogenesis, where it regulates synaptic vesicle release and neuromuscular functions.

One important challenge in treating avascular-degraded cartilage is the development of new drugs for both pain management and joint preservation. Considerable efforts have been invested in developing nanosystems using biomaterials, such as chitosan, a widely used natural polymer exhibiting numerous advantages, i.e., non-toxic, biocompatible and biodegradable. However, even if chitosan is generally recognized as safe, the safety and biocompatibility of such nanomaterials must be addressed because of potential for greater interactions between nanomaterials and biological systems. Here, we developed chitosan-based nanogels as drug-delivery platforms and established an initial biological risk assessment for osteocartilaginous applications. We investigated the influence of synthesis parameters on the physicochemical characteristics of the resulting nanogels and their potential impact on the biocompatibility on all types of human osteocartilaginous cells. Monodisperse nanogels were synthesized with sizes ranging from 268 to 382 nm according to the acidic solution used (i.e., either citric or acetic acid) with overall positive charge surface. Our results demonstrated that purified chitosan-based nanogels neither affected cell proliferation nor induced nitric oxide production in vitro. However, nanogels were moderately genotoxic in a dose-dependent manner but did not significantly induce acute embryotoxicity in zebrafish embryos, up to 100 µg∙mL⁻¹. These encouraging results hold great promise for the intra-articular delivery of drugs or diagnostic agents for joint pathologies.

A new theoretical framework that enables the use of differential dynamic microscopy (DDM) in fluorescence imaging mode to quantify in situ protein adsorption onto nanoparticles (NP) while simultaneously monitoring for NP aggregation is proposed. This methodology is used to elucidate the thermodynamic and kinetic properties of the protein corona (PC) in vitro and in vivo. The results show that protein adsorption triggers particle aggregation over a wide concentration range and that the formed aggregate structures can be quantified using the proposed methodology. Protein affinity for polystyrene (PS) NPs is observed to be dependent on particle concentration. For complex protein mixtures, this methodology identifies that the PC composition changes with the dilution of serum proteins, demonstrating a Vroman effect never quantitatively assessed in situ on NPs. Finally, DDM allows monitoring of the evolution of the PC in vivo. This results show that the PC composition evolves significantly over time in zebrafish larvae, confirming the inherently dynamic nature of the PC. The performance of the developed methodology allows to obtain quantitative insights into nano‐bio interactions in a vast array of physiologically relevant conditions that will serve to further improve the design of nanomedicine.

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BLOC-one-related complex (BORC) is a multiprotein complex composed of eight subunits named BORCS1–8. BORC associates with the cytosolic face of lysosomes, where it sequentially recruits the small GTPase ARL8 and kinesin-1 and -3 microtubule motors to promote anterograde transport of lysosomes toward the peripheral cytoplasm in non-neuronal cells and the distal axon in neurons. The physiological and pathological importance of BORC in humans, however, remains to be determined. Here, we report the identification of compound heterozygous variants [missense c.85T>C (p.Ser29Pro) and frameshift c.71-75dupTGGCC (p.Asn26Trpfs*51)] and homozygous variants [missense c.196A>C (p.Thr66Pro) and c.124T>C (p.Ser42Pro)] in BORCS8 in five children with a severe early-infantile neurodegenerative disorder from three unrelated families. The children exhibit global developmental delay, severe-to-profound intellectual disability, hypotonia, limb spasticity, muscle wasting, dysmorphic facies, optic atrophy, leuko-axonopathy with hypomyelination, and neurodegenerative features with prevalent supratentorial involvement. Cellular studies using a heterologous transfection system show that the BORCS8 missense variants p.Ser29Pro, p.Ser42Pro and p.Thr66Pro are expressed at normal levels but exhibit reduced assembly with other BORC subunits and reduced ability to drive lysosome distribution toward the cell periphery. The BORCS8 frameshift variant p.Asn26Trpfs*51, on the other hand, is expressed at lower levels and is completely incapable of assembling with other BORC subunits and promoting lysosome distribution toward the cell periphery. Therefore, all the BORCS8 variants are partial or total loss-of-function alleles and are thus likely pathogenic. Knockout of the orthologous borcs8 in zebrafish causes decreased brain and eye size, neuromuscular anomalies and impaired locomotion, recapitulating some of the key traits of the human disease. These findings thus identify BORCS8 as a novel genetic locus for an early-infantile neurodegenerative disorder and highlight the critical importance of BORC and lysosome dynamics for the development and function of the central nervous system.