Comparison of the in vivo induction and transmission of α-synuclein pathology by mutant α-synuclein fibril seeds in transgenic mice

Abstract

Parkinson's disease (PD) is one of many neurodegenerative diseases termed synucleinopathies, neuropathologically defined by inclusions containing aggregated α-synuclein (αS). αS gene (SNCA) mutations can directly cause autosomal dominant PD. In vitro studies demonstrated that SNCA missense mutations may either enhance or diminish αS aggregation but cross-seeding of mutant and wild-type αS proteins appear to reduce aggregation efficiency. Here, we extended these studies by assessing the effects of seeded αS aggregation in αS transgenic mice through intracerebral or peripheral injection of various mutant αS fibrils. We observed modestly decreased time to paralysis in mice transgenic for human A53T αS (line M83) intramuscularly injected with H50Q, G51D or A53E αS fibrils relative to wild-type αS fibrils. Conversely, E46K αS fibril seeding was significantly delayed and less efficient in the same experimental paradigm. However, the amount and distribution of αS inclusions in the central nervous system were similar for all αS fibril muscle injected mice that developed paralysis. Mice transgenic for human αS (line M20) injected in the hippocampus with wild-type, H50Q, G51D or A53E αS fibrils displayed induction of αS inclusion pathology that increased and spread over time. By comparison, induction of αS aggregation following the intrahippocampal injection of E46K αS fibrils in M20 mice was much less efficient. These findings show that H50Q, G51D or A53E can efficiently cross-seed and induce αS pathology in vivo. In contrast, E46K αS fibrils are intrinsically inefficient at seeding αS inclusion pathology. Consistent with previous in vitro studies, E46K αS polymers are likely distinct aggregated conformers that may represent a unique prion-like strain of αS.

Carboxy‐terminal truncations of mouse α‐synuclein alter aggregation and prion‐like seeding

“…When combinations of 1‐135 with C‐truncated forms of αsyn were co‐fibrillized, a 1 : 1 molar ratio was used at a 5 mg·mL −1 total concentration. PFFs were diluted in sterile PBS and fragmented into an array of shortened fibrils by mild water bath sonication for 1 h prior to seeding in cell culture or intrahippocampal injection .…”

“…For comparison of prion‐like seeding properties between FL and C‐truncated forms of αsyn, three cohorts of eight mice were stereotactically injected unilaterally into the hippocampus (coordinates from Bregma: anterior/posterior −2.2 mm, lateral ± 1.6 mm, dorsal/ventral −1.2 mm) at ~ 2 months of age as previously described . For injection, 2 µL of solution (sterile PBS) containing 4 µg of FL mPFFs or the molar equivalent of mPFFs comprised of either 1‐125 or 1‐129 C‐truncated mouse αsyn was utilized.…”

Nuclear Factor-κB Dysregulation and α-Synuclein Pathology: Critical Interplay in the Pathogenesis of Parkinson’s Disease

“…Another peculiarity of α-syn relates to its transmission from cell-to-cell and to the spreading of its pathological aggregates from the peripheral nervous system (PNS) to the central nervous system (CNS), or vice versa, in experimental models (Luk et al, 2012;Ulusoy et al, 2013Ulusoy et al, , 2017Recasens and Dehay, 2014;Dehay et al, 2016;Emmanouilidou and Vekrellis, 2016;Helwig et al, 2016;Cavaliere et al, 2017;Rutherford et al, 2017;Grozdanov and Danzer, 2018). The capability of pathological forms of α-syn to spread seems to be corroborated by neuropathological examination of post-mortem brains from patients who received fetal neuron grafts over one decade prior to death and showing the development of LB within grafted neuronal cells (Kordower et al, 2008a,b;Chu and Kordower, 2010;Li et al, 2010;Kurowska et al, 2011).…”

Localized Induction of Wild-Type and Mutant Alpha-Synuclein Aggregation Reveals Propagation along Neuroanatomical Tracts

“…To better understand the spread of ␣S pathology, several in vivo studies have utilized intracerebral injection in nontransgenic and ␣S transgenic mouse models and describe a propagation of ␣S inclusions away from the injection site (23)(24)(25)(26)(27). Additionally, investigators have peripherally administered human or mouse ␣S inclusions into mice and demonstrated the ability for these to induce central nervous system (CNS) ␣S pathology, suggesting a neuroinvasive nature of ␣S and supporting the theory that ␣S pathology begins in the peripheral nervous system (PNS) and spreads to the CNS (18,19,(28)(29)(30)(31)(32)(33). Although these data are analogous to the propagation of prions along neuroanatomically connected neuronal populations, there are caveats in each of these studies in which the injection routes had the potential to result in a widespread dissemination of the ␣S-containing inocula.…”

“…For instance, for both the intracerebral and intramuscular (i.m.) routes of injections, there is a strong potential for the inoculum to get into the bloodstream or the needle to alter the cellular homeostasis, thereby allowing the ␣S seeds to access the CNS via multiple points of entry (32,33). Due to these scenarios, there still exists a lack of understanding as to the mechanism(s) of spread and/or induction of ␣S pathology.…”