miR126-5p Downregulation Facilitates Axon Degeneration and NMJ Disruption via a Non-Cell-Autonomous Mechanism in ALS.

Axon degeneration and disruption of neuromuscular junctions (NMJs) are key events in amyotrophic lateral sclerosis (ALS) pathology. Although the disease\u27s etiology is not fully understood, it is thought to involve a non-cell-autonomous mechanism and alterations in RNA metabolism. Here, we identified reduced levels of miR126-5p in presymptomatic ALS male mice models, and an increase in its targets: axon destabilizing Type 3 Semaphorins and their coreceptor Neuropilins. Using compartmentalize

CRMP2 mediates Sema3F-dependent axon pruning and dendritic spine remodeling

Regulation of axon guidance and pruning of inappropriate synapses by class 3 semaphorins are key to the development of neural circuits. Collapsin response mediator protein 2 (CRMP2) has been shown to regulate axon guidance by mediating semaphorin 3A (Sema3A) signaling;however, nothing is known about its role in synapse pruning. Here, using newly generated crmp2(-/-) mice we demonstrate that CRMP2 has a moderate effect on Sema3A-dependent axon guidance in vivo, and its deficiency leads to a mild defect in axon guidance in peripheral nerves and the corpus callosum. Surprisingly, crmp2(-/-) mice display prominent defects in stereotyped axon pruning in hippocampus and visual cortex and altered dendritic spine remodeling, which is consistent with impaired Sema3F signaling and with models of autism spectrum disorder (ASD). We demonstrate that CRMP2 mediates Sema3F signaling in primary neurons and that crmp2(-/-) mice display ASD-related social behavior changes in the early postnatal period as well as in adults. Together, we demonstrate that CRMP2 mediates Sema3F-dependent synapse pruning and its dysfunction shares histological and behavioral features of ASD

Altered localization of staufen1 in amyotrophic lateral sclerosis: DOI: 10.14800/rd.1210

Localized protein expression is crucial for the health and survival of axons and dendrites in a rapidly changing environment. This process, however, cannot take place without the precise spatiotemporal localization of the cellular translational machinery and of mRNA. mRNA transport and localization requires a variety of RNA-binding proteins. Here, we highlight a recent publication which presents evidence for the altered localization of the dsRNA-binding protein Staufen1 as a result of Amyotrophic Lateral Sclerosis (ALS) linked mutations, supporting the perception of ALS as a RNA spatiotemporal mislocalization disease

Phosphatidylserine improves axonal transport by inhibition of HDAC and has potential in treatment of neurodegenerative diseases

Familial dysautonomia (FD) is a rare children neurodegenerative disease caused due to a point mutation in the IKBKAP gene that results in decreased IKK complex-associated protein (IKAP) protein production. The disease affects mostly the dorsal root ganglion (DRG) and the sympathetic ganglion. Recently, we found that the molecular mechanisms underlying neurodegeneration in FD patients are defects in axonal transport of nerve growth factors and microtubule stability in the DRG. Neurons are highly polarized cells with very long axons. In order to survive and maintain proper function, neurons depend on transport of proteins and other cellular components from the neuronal body along the axons. We further demonstrated that IKAP is necessary for axon maintenance and showed that phosphatidylserine acts as an HDAC6 inhibitor to rescue neuronal function in FD cells. In this review, we will highlight our latest research findings

Looking for answers far away from the soma—the (un)known axonal functions of TDP-43, and their contribution to early NMJ disruption in ALS

Abstract Axon degeneration and Neuromuscular Junction (NMJ) disruption are key pathologies in the fatal neurodegenerative disease Amyotrophic Lateral Sclerosis (ALS). Despite accumulating evidence that axons and NMJs are impacted at a very early stage of the disease, current knowledge about the mechanisms leading to their degeneration remains elusive. Cytoplasmic mislocalization and accumulation of the protein TDP-43 are considered key pathological hallmarks of ALS, as they occur in ~ 97% of ALS patients, both sporadic and familial. Recent studies have identified pathological accumulation of TDP-43 in intramuscular nerves of muscle biopsies collected from pre-diagnosed, early symptomatic ALS patients. These findings suggest a gain of function for TDP-43 in axons, which might facilitate early NMJ disruption. In this review, we dissect the process leading to axonal TDP-43 accumulation and phosphorylation, discuss the known and hypothesized roles TDP-43 plays in healthy axons, and review possible mechanisms that connect TDP-43 pathology to the axon and NMJ degeneration in ALS

Multiple Copies of microRNA Binding Sites in Long 3′UTR Variants Regulate Axonal Translation

Rapid responses to changes within subcellular compartments of highly polarized cells, such as neuron axons, depend on local translation and post-transcriptional regulation. The mechanism by which microRNAs (miRNAs) regulate this process is not fully understood. Here, using live cell imaging and RNA sequencing analysis, we demonstrated how miRNAs can differentially control hundreds of transcripts at the subcellular level. We demonstrated that the seed match length of the miRNA target-sequence regulates both mRNA stability and protein translation rates. While longer seed matches have an increased inhibitory effect, transcriptome analysis did not reveal differences in seed match length between axonal and somata mRNAs of motor neurons. However, mRNA variants with longer 3′UTR are enriched in axons and contain multiple repeats of specific miRNA target sequences. Finally, we demonstrated that the long 3′UTR mRNA variant of the motor protein Kif5b is enriched explicitly in motor neuron axons and contains multiple sequence repeats for binding miR-129-5p. This subsequently results in the differential post-transcriptional regulation of kif5b and its synthesis in axons. Thus, we suggest that the number of miRNA binding sites at the 3′UTR of the mRNA, rather than the miRNA seed match length, regulates the axonal transcriptome