Neurosphere formation is commonly used as a surrogate for neural stem cell (NSC) function but the relationship between neurosphere-initiating cells (NICs) and NSCs remains unclear. We prospectively identified, and isolated by flow cytometry, adult mouse lateral ventricle subventricular zone (SVZ) NICs as GlastmidEGFRhighPlexinB2highCD24−/lowO4/PSA-NCAM−/lowTer119/CD45− (GEPCOT) cells. They were highly mitotic and short-lived in vivo based on fate-mapping with Ascl1CreERT2 and Dlx1CreERT2. In contrast, pre-GEPCOT cells were quiescent, expressed higher Glast, and lower EGFR and PlexinB2. Pre-GEPCOT cells could not form neurospheres but expressed the stem cell markers Slc1a3-CreERT, GFAP-CreERT2, Sox2CreERT2, and Gli1CreERT2 and were long-lived in vivo. While GEPCOT NICs were ablated by temozolomide, pre-GEPCOT cells survived and repopulated the SVZ. Conditional deletion of the Bmi-1 polycomb protein depleted pre-GEPCOT and GEPCOT cells, though pre-GEPCOT cells were more dependent upon Bmi-1 for Cdkn2a (p16Ink4a) repression. Our data distinguish quiescent NSCs from NICs and make it possible to study their properties in vivo.DOI: http://dx.doi.org/10.7554/eLife.02669.001

Heterozygous de novo mutations in the neuronal protein Munc18-1 are linked to epilepsies, intellectual disability, movement disorders, and neurodegeneration. These devastating diseases have a poor prognosis and no known cure, due to lack of understanding of the underlying disease mechanism. To determine how mutations in Munc18-1 cause disease, we use newly generated S. cerevisiae strains, C. elegans models, and conditional Munc18-1 knockout mouse neurons expressing wild-type or mutant Munc18-1, as well as in vitro studies. We find that at least five disease-linked missense mutations of Munc18-1 result in destabilization and aggregation of the mutant protein. Aggregates of mutant Munc18-1 incorporate wild-type Munc18-1, depleting functional Munc18-1 levels beyond hemizygous levels. We demonstrate that the three chemical chaperones 4-phenylbutyrate, sorbitol, and trehalose reverse the deficits caused by mutations in Munc18-1 in vitro and in vivo in multiple models, offering a novel strategy for the treatment of varied encephalopathies.

α-Synuclein aggregation is a pathological hallmark of Parkinson's disease (PD), Lewy body dementia, multiple system atrophy, and a variety of other synucleinopathies (1). The occurrence of familial PD due to α-synuclein mutations, gene duplication and triplication, as well as polymorphisms in regulatory elements of the α-synuclein gene, supports a causative role of α-synuclein in these neurodegenerative diseases (reviewed in ref.2). In addition, a prion-like spread of α-synuclein pathology has been proposed, by propagation of neurotoxic α-synuclein aggregates from one neuron to the other (3). Attenuating or stopping aggregation of α-synuclein is thus a highly pursued strategy to combat pathology in these diseases (Fig. 1). A number of factors have been reported to influence the aggregation propensity of α-synuclein, including oxidative stress, posttranslational modifications in α-synuclein, and increased local concentration. Proposed strategies to stop or reduce α-synuclein aggregation include enhancing the levels of heat shock proteins to stabilize protein folding, using compounds with antioxidant or antiaggregant activity, promoting intracellular degradation of α-synuclein, or immunotherapies to clear α-synuclein (reviewed in ref. 4).However, none of these approaches has had success in translation to the clinic, and treatments for PD remain symptomatic, focusing on treating the movement disorder symptoms associated with loss of dopaminergic neurons in the substantia nigra pars compacta. Treatment of the nonmotor symptoms is much more challenging and less established, and no therapy is available that slows down or stops the progression of PD. In PNAS, Perni et al. (5) report an inhibitory effect of squalamine-an antimicrobial agent derived from the dogfish shark-on α-synuclein aggregation in vitro and toxicity in vivo, via displacing α-synuclein from phospholipid membranes.Physiologically, α-synuclein exists in a dynamic equilibrium between a natively unfolded cytosolic state and a multimeric membrane-bound state on synaptic vesicles (6, 7). The N-terminal sequence of α-synuclein forms an amphipathic α-helix that mediates association of α-synuclein with lipid membranes (8). This region also contains the non-amyloid-β component (NAC), an area believed to be responsible for α-synuclein aggregation (9). The interaction between α-synuclein and synaptic membranes is believed to be a key feature for mediating its proposed cellular functions: the presynaptic localization of α-synuclein, its interaction with synaptic vesicles and synaptobrevin-2, its SNARE complex-chaperoning activity, its effects on vesicle clustering, and its changes during periods of song acquisition-related synaptic rearrangements in birds (reviewed in ref. 10) strongly suggest that α-synuclein plays a role in neurotransmitter Fig. 1. Physiological and pathological conformations of α-synuclein and strategies to combat α-synuclein aggregation and toxicity. Physiologically, α-synuclein exists in an equilibrium between α-helical multimers bound to syn...