PATHOLOGIES OF AXONAL TRANSPORT IN NEURODEGENERATIVE DISEASES

Transcriptomic analysis and 3D bioengineering of astrocytes indicate ROCK inhibition produces cytotrophic astrogliosis

Astrocytes provide trophic, structural and metabolic support to neurons, and are considered genuine targets in regenerative neurobiology, as their phenotype arbitrates brain integrity during injury. Inhibitors of Rho kinase (ROCK) cause stellation of cultured 2D astrocytes, increased L-glutamate transport, augmented G-actin, and elevated expression of BDNF and anti-oxidant genes. Here we further explored the signposts of a cytotrophic, “healthy” phenotype by data-mining of our astrocytic transcriptome in the presence of Fasudil. Gene expression profiles of motor and autophagic cellular cascades and inflammatory/angiogenic responses were all inhibited, favoring adoption of an anti-migratory phenotype. Like ROCK inhibition, tissue engineered bioscaffolds can influence the extracellular matrix. We built upon our evidence that astrocytes maintained on 3D poly-ε-caprolactone (PCL) electrospun scaffolds adopt a cytotrophic phenotype similar to that produced by Fasudil. Using these procedures, employing mature 3D cultured astrocytes, Fasudil (100 μM) or Y27632 (30 μM) added for the last 72 h of culture altered arborization, which featured numerous additional minor processes as shown by GFAP and AHNAK immunolabelling. Both ROCK inhibitors decreased F-actin, but increased G-actin labeling, indicative of disassembly of actin stress fibers. ROCK inhibitors provide additional beneficial effects for bioengineered 3D astrocytes, including enlargement of the overall arbor. Potentially, the combined strategy of bio-compatible scaffolds with ROCK inhibition offers unique advantages for the management of glial scarring. Overall these data emphasize that manipulation of the astrocyte phenotype to achieve a “healthy biology” offers new hope for the management of inflammation in neuropathologies.

New approach to capture and characterize synaptic proteome

Little is known regarding the identity of the population of proteins that are transported and localized to synapses. Here we describe a new approach that involves the isolation and systematic proteomic characterization of molecular motor kinesins to identify the populations of proteins transported to synapses. We used this approach to identify and compare proteins transported to synapses by kinesin (Kif) complexes Kif5C and Kif3A in the mouse hippocampus and prefrontal cortex. Approximately 40-50% of the protein cargos identified in our proteomics analysis of kinesin complexes are known synaptic proteins. We also found that the identity of kinesins and where they are expressed determine what proteins they transport. Our results reveal a previously unappreciated role of kinesins in regulating the composition of synaptic proteome.

Cytoplasmic dynein heavy chain: the servant of many masters

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The cytoplasmic dynein complex is the main retrograde motor in all eukaryotic cells.

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This complex is built around a dimer of cytoplasmic dynein heavy chains (DYNC1H1).

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Mouse DYNC1H1 mutants have sensory defects, but motor defects have been controversial.

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Now human DYNC1H1 mutations with sensory, motor, and cognitive deficits are being found.

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The study of these mutations will give us new insight into DYNC1H1 function in the nervous system.

Cytoplasmic dynein is the main retrograde motor in all eukaryotic cells. This complex comprises different subunits assembled on a cytoplasmic dynein heavy chain 1 (DYNC1H1) dimer. Cytoplasmic dynein is particularly important for neurons because it carries essential signals and organelles from distal sites to the cell body. In the past decade, several mouse models have helped to dissect the numerous functions of DYNC1H1. Additionally, several DYNC1H1 mutations have recently been found in human patients that give rise to a broad spectrum of developmental and midlife-onset disorders. Here, we discuss the effects of mutations of mouse and human DYNC1H1 and how these studies are giving us new insight into the many critical roles DYNC1H1 plays in the nervous system.