Jiang, Peizhou

Abstract Extracellular vesicles (EVs) have emerged as critical mediators of intercellular communication and promising biomarkers and therapeutics in the central nervous system (CNS). Human brain‐derived EVs (BDEVs) provide a comprehensive snapshot of physiological changes in the brain's environment, however, the isolation of BDEVs and the comparison of different methods for this purpose have not been fully investigated. In this study, we compared the yield, morphology, subtypes and protein cargo composition of EVs isolated from the temporal cortex of aged human brains using three established separation methods: size‐exclusion chromatography (SEC), phosphatidylserine affinity capture (MagE) and sucrose gradient ultracentrifugation (SG‐UC). Our results showed that SG‐UC method provided the highest yield and collected larger EVs compared to SEC and MagE methods as assessed by transmission electron microscopy and nanoparticle tracking analysis (NTA). Quantitative tandem mass‐tag (TMT) mass spectrometry analysis of EV samples from three different isolation methods identified a total of 1158 proteins, with SG‐UC showing the best enrichment of common EV proteins with less contamination of non‐EV proteins. In addition, SG‐UC samples were enriched in proteins associated with ATP activity and CNS maintenance, and were abundant in neuronal and oligodendrocytic molecules. In contrast, MagE samples were more enriched in molecules related to lipoproteins, cell‐substrate junction and microglia, whereas SEC samples were highly enriched in molecules related to extracellular matrix, Alzheimer's disease and astrocytes. Finally, we validated the proteomic results by performing single‐particle analysis using the super‐resolution microscopy and flow cytometry. Overall, our findings demonstrate the differences in yield, size, enrichment of EV cargo molecules and single EV assay by different isolation methods, suggesting that the choice of isolation method will have significant impact on the downstream analysis and protein discovery.

G 4 C 2 repeat–derived poly(GR) plays a key role in mediating TDP-43 mislocalization and aggregation in vitro and in vivo.

Abstract Genetic variants that define two distinct haplotypes at the TMEM106B locus have been implicated in multiple neurodegenerative diseases and in healthy brain ageing. In frontotemporal dementia (FTD), the high expressing TMEM106B risk haplotype was shown to increase susceptibility for FTD with TDP-43 inclusions (FTD-TDP) and to modify disease penetrance in progranulin mutation carriers (FTD-GRN). To elucidate the biological function of TMEM106B and determine whether lowering TMEM106B may be a viable therapeutic strategy, we performed brain transcriptomic analyses in 8-month-old animals from our recently developed Tmem106b−/− mouse model. We included 10 Tmem106b+/+ (wild-type), 10 Tmem106b+/− and 10 Tmem106−/− mice. The most differentially expressed genes (153 downregulated and 60 upregulated) were identified between Tmem106b−/− and wild-type animals, with an enrichment for genes implicated in myelination-related cellular processes including axon ensheathment and oligodendrocyte differentiation. Co-expression analysis also revealed that the most downregulated group of correlated genes was enriched for myelination-related processes. We further detected a significant loss of OLIG2-positive cells in the corpus callosum of Tmem106b−/− mice, which was present already in young animals (21 days) and persisted until old age (23 months), without worsening. Quantitative polymerase chain reaction revealed a reduction of differentiated but not undifferentiated oligodendrocytes cellular markers. While no obvious changes in myelin were observed at the ultrastructure levels in unchallenged animals, treatment with cuprizone revealed that Tmem106b−/− mice are more susceptible to cuprizone-induced demyelination and have a reduced capacity to remyelinate, a finding which we were able to replicate in a newly generated Tmem106b CRISPR/cas9 knock-out mouse model. Finally, using a TMEM106B HeLa knock-out cell line and primary cultured oligodendrocytes, we determined that loss of TMEM106B leads to abnormalities in the distribution of lysosomes and PLP1. Together these findings reveal an important function for TMEM106B in myelination with possible consequences for therapeutic strategies aimed at lowering TMEM106B levels.

ABSTRACT The accumulation of filamentous a‐synuclein (α‐S) is associated with Parkinson's disease. It remains controversial as to the mode (antiparallel or parallel) of α‐S self‐assembly and whether an exact alignment of the central hydrophobic region is essential. In the present study, we performed in vitro assembly using α‐S with or without the attachment of artificial leucine zippers (Zips) capable of forming either parallel or antiparallel coiled coils and included a spacer in one derivative. Results showed that Zips accelerate filament assembly in both the parallel and antiparallel fashions, that a precise alignment of the central hydrophobic region is not essential, and that the antiparallel pairs displayed the highest thioflavin T signals. More importantly, cells expressing Zip‐fused α‐S, but not α‐S alone, formed α‐S immunopositive and thioflavin S‐positive inclusions in 7 days. The results suggest that α‐S can assemble in both parallel and antiparallel modes but have a higher tendency to assemble in the latter mode and that cells overexpressing Zip‐fused α‐S may be used to screen α‐S assembly inhibitors due to enhanced ability to form inclusions.—Jiang, P., Ko, L., Jansen, K. R., Golde, T. E., Yen, S.‐H. Using leucine zipper to facilitate α‐synuclein assembly. FASEB J. 22, 3165–3174 (2008)