It has been hypothesized that α-synuclein (αS) misfolding may begin in peripheral nerves and spread to the central nervous system (CNS), leading to Parkinson disease and related disorders. Although recent data suggest that αS pathology can spread within the mouse brain, there is no direct evidence for spread of disease from a peripheral site. In the present study, we show that hind limb intramuscular (IM) injection of αS can induce pathology in the CNS in the human Ala53Thr (M83) and wild-type (M20) αS transgenic (Tg) mouse models. Within 2-3 mo after IM injection in αS homozygous M83 Tg mice and 3-4 mo for hemizygous M83 Tg mice, these animals developed a rapid, synchronized, and predictable induction of widespread CNS αS inclusion pathology, accompanied by astrogliosis, microgliosis, and debilitating motor impairments. In M20 Tg mice, starting at 4 mo after IM injection, we observed αS inclusion pathology in the spinal cord, but motor function remained intact. Transection of the sciatic nerve in the M83 Tg mice significantly delayed the appearance of CNS pathology and motor symptoms, demonstrating the involvement of retrograde transport in inducing αS CNS inclusion pathology. Outside of scrapie-mediated prion disease, to our knowledge, this findiing is the first evidence that an entire neurodegenerative proteinopathy associated with a robust, lethal motor phenotype can be initiated by peripheral inoculation with a pathogenic protein. Furthermore, this facile, synchronized rapid-onset model of α-synucleinopathy will be highly valuable in testing disease-modifying therapies and dissecting the mechanism(s) that drive αS-induced neurodegeneration.amyloid | Parkinson disease S ynucleinopathies are a group of diseases defined by the presence of amyloidogenic α-synuclein (αS) inclusions that can occur in neurons and glia of the central nervous system (CNS) (1-4). In Parkinson disease (PD), a causative role for αS has been established via the discovery of mutations in the αS gene SNCA resulting in autosomal-dominant PD (4-11). Although αS inclusions (e.g., Lewy bodies) are the hallmark pathology of PD, how they contribute to disease pathogenesis remains controversial (1,3,4,12).Postmortem studies have suggested that αS pathology may spread following neuroanatomical tracts (13-15) and between cells (16-18). αS pathology has also been found in the peripheral nervous system (PNS): for example, in the enteric and pelvic plexus (19,20). And it has been suggested that αS pathology might originate in the nerves of the PNS and spread to the CNS (14). Experimentally, it has been reported that intracerebral injections of preformed amyloidogenic αS fibrils in nontransgenic (nTg) and αS transgenic (Tg) mice induce the formation of intracellular αS inclusions that appear to progress from the site of injection (21-26). Collectively, these studies support the notion that αS inclusion pathology may propagate via a prion-like conformational self-templating mechanism (27, 28). A caveat of the direct intracerebral injection of αS is tha...

To further evaluate the parameters whereby intracerebral administration of recombinant α-synuclein (αS) induces pathological phenotypes in mice, we conducted a series of studies where αS fibrils were injected into the brains of M83 (A53T) and M47 (E46K) αS transgenic (Tg) mice, and non-transgenic (nTg) mice. Using multiple markers to assess αS inclusion formation, we find that injected fibrillar human αS induced widespread cerebral αS inclusion formation in the M83 Tg mice, but in both nTg and M47 Tg mice, induced αS inclusion pathology is largely restricted to the site of injection. Furthermore, mouse αS fibrils injected into nTg mice brains also resulted in inclusion pathology restricted to the site of injection with no evidence for spread. We find no compelling evidence for extensive spread of αS pathology within white matter tracts, and we attribute previous reports of white matter tract spreading to cross-reactivity of the αS pSer129/81A antibody with phosphorylated neurofilament subunit L (NFL). These studies suggest that with the exception of the M83 mice which appear to be uniquely susceptible to induction of inclusion pathology by exogenous forms of αS there are significant barriers in mice to widespread induction of αS pathology following intracerebral administration of amyloidogenic αS.

The RNA-binding protein fused-in-sarcoma (FUS) has been associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), two neurodegenerative disorders that share similar clinical and pathological features. Both missense mutations and overexpression of wild-type FUS protein can be pathogenic in human patients. To study the molecular and cellular basis by which FUS mutations and overexpression cause disease, we generated novel transgenic mice globally expressing low levels of human wild-type protein (FUS WT ) and a pathological mutation (FUS R521G A myotrophic lateral sclerosis (ALS) is characterized by the degeneration of upper and lower motor neurons, leading to muscle weakness, paralysis, and death within 3-5 y of onset. Interestingly, ∼10-15% of ALS patients have clinical features of frontotemporal lobar degeneration (FTLD), marked by a decline in decision-making, behavioral control, emotion, and language, and as many as half have mild-to-moderate cognitive or behavioral abnormalities (1). FTLD comprises a group of heterogeneous diseases characterized by progressive neurodegeneration of the frontal and temporal lobes and clinically by frontotemporal dementia (FTD) with or without motor neuron disease. There is no cure or effective therapy for those who suffer from ALS or FTLD, and the mechanisms by which these diseases occur are not well understood.The clinical, pathological, and genetic overlap between ALS and FTLD suggests that there are mechanisms shared by these diseases. The RNA-binding proteins fused in sarcoma (FUS) and transactive response DNA-binding protein-43 (TDP-43) are the major protein components of inclusions that are characteristic of ALS and FTLD-U (FTLD with ubiquitinated inclusions) (2). More than 50 genetic FUS mutations have been identified in these related neurodegenerative disorders (3). Similarly, more than 40 dominant mutations in the TDP-43 gene have been linked to ALS cases and, to a lesser extent, to FTLD (4). The identification of mutations in the FUS and TDP-43 genes has provided insights for uncovering the disease mechanisms for ALS and FTLD.FUS is a ubiquitously expressed RNA-binding protein that exists in dynamic ribonucleoprotein complexes involved in pre-mRNA splicing, mRNA stability, and mRNA transport. FUS is a member of the FET family of proteins that bind RNAs (5) and contains an RNA recognition motif, three arginine-glycine-glycine (RGG) boxes, and a zinc finger (ZnF) (6). RGG2-ZnF-RGG3 is the major RNA-binding domain, which has a preference for GUrich sequences (7,8). The N terminus of FUS contains a lowcomplexity sequence domain involved in RNA granule formation (9). Nucleocytoplasmic shuttling of FUS occurs by a nonclassical proline-tyrosine nuclear localization signal (PY-NLS) and a nuclear export signal (NES) (10). Methylation of the C-terminal RGG3 domain of FUS is necessary for transportin 1 interaction and nuclear localization (11).The majority of clinical ALS/FTLD-associated FUS mutations occur in its C-terminal PY-NLS seque...

Intracerebral injection of amyloidogenic ␣-synuclein (␣S) has been shown to induce ␣S pathology in the CNS of nontransgenic mice and ␣S transgenic mice, albeit with varying efficiencies. In this study, using wild-type human ␣S transgenic mice (line M20), we demonstrate that intracerebral injection of recombinant amyloidogenic or soluble ␣S induces extensive ␣S intracellular inclusion pathology that is associated with robust gliosis. Near the injection site, a significant portion of ␣S inclusions are detected in neurons but also in astrocytes and microglia. Aberrant induction of expression of the intermediate filament protein peripherin, which is associated with CNS neuronal injury, was also observed predominantly near the site of injection. In addition, many pSer129 ␣S-induced inclusions colocalize with the low-molecular-mass neurofilament subunit (NFL) or peripherin staining. ␣S inclusion pathology was also induced in brain regions distal from the injection site, predominantly in neurons. Unexpectedly, we also find prominent p62-immunoreactive, ␣S-, NFL-, and peripherin-negative inclusions. These findings provide evidence that exogenous ␣S challenge induces ␣S pathology but also results in the following: (1) a broader disruption of proteostasis; (2) glial activation; and (3) a marker of a neuronal injury response. Such data suggest that induction of ␣S pathology after exogenous seeding may involve multiple interdependent mechanisms.

Two types of gas‐phase flow patterns have been discussed and observed in the in situ air sparging (ISAS) literature: bubble flow and air channels. A critical factor affecting the flow pattern at a given location is the grain size of the porous medium. Visualization experiments reported in the literature indicate that a change in the flow pattern occurs around 1 to 2 mm grain diameters, with air channels occurring below the transition size and bubbles above. Analysis of capillary and buoyancy forces suggests that for a given gas‐liquid‐solid system, there is a critical size that dictates the dominant force, and the dominant force will in turn dictate the flow pattern. The dominant forces, and consequently the two‐phase flow patterns, were characterized using a Bond number modified with the porous media aspect ratio (pore throat to pore body ratio). Laboratory experiments were conducted to observe flow patterns as a function of porous media size and air flow rate. The experimental results and the modified Bond number analysis support the relationship of flow patterns to grain size reported in the literature.