A current view of mitochondria damage and the diversity of lipopigment inclusions in neuronal ceroid lipofuscinose type 2 from rectal biopsy.

Neuronal ceroid lipofuscinoses (NCLs) are a growing group of neurodegenerative storage diseases, in which specific features are sought to facilitate the creation of a universal diagnostic algorithm in the future. In our ultrastructural studies, the group of NCLs was represented by the CLN2 disease caused by a defect in the TPP1 gene encoding the enzyme tripeptidyl-peptidase 1. A 3.5-year-old girl was affected by this disease. Due to diagnostic difficulties, the spectrum of clinical, enzymatic, and genetic tests was extended to include analysis of the ultrastructure of cells from a rectal biopsy. The aim of our research was to search for pathognomonic features of CLN2 and to analyse the mitochondrial damage accompanying the disease. In the examined cells of the rectal mucosa, as expected, filamentous deposits of the curvilinear profile (CVP) type were found, which dominated quantitatively. Mixed deposits of the CVP/fingerprint profile (FPP) type were observed less frequently in the examined cells. A form of inclusions of unknown origin, not described so far in CLN2 disease, were wads of osmophilic material (WOMs). They occurred alone or co-formed mixed deposits. In addition, atypically damaged mitochondria were observed in muscularis mucosae. Their deformed cristae had contact with inclusions that looked like CVPs. Considering the confirmed role of the c subunit of the mitochondrial ATP synthase in the formation of filamentous lipopigment deposits in the group of NCLs, we suggest the possible significance of other mitochondrial proteins, such as mitochondrial contact site and cristae organizing system (MICOS), in the formation of these deposits. The presence of WOMs in the context of searching for ultrastructural pathognomonic features in CLN2 disease also requires further research.

Alpha-synuclein inclusion responsive microglia are resistant to CSF1R inhibition.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder that is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies), markers of neuroinflammation and the progressive loss of nigrostriatal dopamine (DA) neurons. These pathological features can be recapitulated in vivo using the α-syn preformed fibril (PFF) model of synucleinopathy. We have previously determined that microglia proximal to PFF-induced nigral α-syn inclusions increase in soma size, upregulate major-histocompatibility complex-II (MHC-II) expression, and increase expression of a suite of inflammation-associated transcripts. This microglial response is observed months prior to degeneration, suggesting that microglia reacting to α-syn inclusion may contribute to neurodegeneration and could represent a potential target for novel therapeutics. The goal of this study was to determine whether colony stimulating factor-1 receptor (CSF1R)-mediated microglial depletion impacts the magnitude of α-syn aggregation, nigrostriatal degeneration, or the response of microglial in the context of the α-syn PFF model. METHODS: Male Fischer 344 rats were injected intrastriatally with either α-syn PFFs or saline. Rats were continuously administered Pexidartinib (PLX3397B, 600 mg/kg), a CSF1R inhibitor, to deplete microglia for a period of either 2 or 6 months. RESULTS: CSF1R inhibition resulted in significant depletion (~ 43%) of ionized calcium-binding adapter molecule 1 immunoreactive (Iba-1ir) microglia within the SNpc. However, CSF1R inhibition did not impact the increase in microglial number, soma size, number of MHC-II immunoreactive microglia or microglial expression of Cd74, Cxcl10, Rt-1a2, Grn, Csf1r, Tyrobp, and Fcer1g associated with phosphorylated α-syn (pSyn) nigral inclusions. Further, accumulation of pSyn and degeneration of nigral neurons was not impacted by CSF1R inhibition. Paradoxically, long term CSF1R inhibition resulted in increased soma size of remaining Iba-1ir microglia in both control and PFF rats, as well as expression of MHC-II in extranigral regions. CONCLUSIONS: Collectively, our results suggest that CSF1R inhibition does not impact the microglial response to nigral pSyn inclusions and that CSF1R inhibition is not a viable disease-modifying strategy for PD.

Stochastic Optical Reconstruction Microscopy Imaging of Multiple System Atrophy Inclusions Suggests Stepwise α-Synuclein Aggregation.

BACKGROUND: The architecture and composition of glial (GCI) and neuronal (NCI) α-synuclein inclusions observed in multiple system atrophy (MSA) remain to be precisely defined to better understand the disease. METHODS: Here, we used stochastic optical reconstruction microscopy (STORM) to characterize the nanoscale organization of glial (GCI) and neuronal (NCI) α-synuclein inclusions in cryopreserved brain sections from MSA patients. RESULTS: STORM revealed a dense cross-linked internal structure of α-synuclein in all GCI and NCI. The internal architecture of hyperphosphorylated α-synuclein (p-αSyn) inclusions was similar in glial and neuronal cells, suggesting a common aggregation mechanism. A similar sequence of p-αSyn stepwise intracellular aggregation was defined in oligodendrocytes and neurons, starting from the perinuclear area and growing inside the cells. Consistent with this hypothesis, we found a higher mitochondrial density in GCI and NCI compared to oligodendrocytes and neurons from unaffected donors (P < 0.01), suggesting an active recruitment of the organelles during the aggregation process. CONCLUSIONS: These first STORM images of GCI and NCI suggest stepwise α-synuclein aggregation in MSA. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Frontal deficits and atrophy in a patient with familial encephalopathy with neuroserpin inclusion bodies detected by single-case voxel-based morphometry: a case report.

BACKGROUND: Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is a rare genetic disorder characterized by progressive cognitive decline and myoclonic epilepsy, caused by pathogenic variants of SERPINI1. We reported a case of genetically confirmed FENIB with de novo H338R mutation in the SERPINI1, in which frontal deficits including inattention and disinhibition, and relevant atrophy in the vmPFC on brain MRI were observed in the early stage of the disease. CASE PRESENTATION: A 23-year-old Japanese man presented with progressive inattention and disinhibition over 4 years followed by myoclonic epilepsy. The whole-genome sequencing and filtering analysis showed de novo heterozygous H338R mutation in the SERPINI1, confirming the diagnosis of FENIB. Single-case voxel-based morphometry using brain magnetic resonance imaging obtained at the initial visit revealed focal gray matter volume loss in the ventromedial prefrontal cortices, which is presumed to be associated with inattention and disinhibition. CONCLUSION: Frontal deficits including inattention and disinhibition can be the presenting symptoms of patients with FENIB. Single-case voxel-based morphometry may be useful for detecting regional atrophy of the frontal lobe in FENIB. Detecting these abnormalities in the early stage of disease may be key findings for differentiating FENIB from other causes of progressive myoclonic epilepsy.

Nuclear pore pathology underlying multisystem proteinopathy type 3-related inclusion body myopathy.

OBJECTIVE: Multisystem proteinopathy type 3 (MSP3) is an inherited, pleiotropic degenerative disorder caused by a mutation in heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), which can affect the muscle, bone, and/or nervous system. This study aimed to determine detailed histopathological features and transcriptomic profile of HNRNPA1-mutated skeletal muscles to reveal the core pathomechanism of hereditary inclusion body myopathy (hIBM), a predominant phenotype of MSP3. METHODS: Histopathological analyses and RNA sequencing of HNRNPA1-mutated skeletal muscles harboring a c.940G > A (p.D314N) mutation (NM_031157) were performed, and the results were compared with those of HNRNPA1-unlinked hIBM and control muscle tissues. RESULTS: RNA sequencing revealed aberrant alternative splicing events that predominantly occurred in myofibril components and mitochondrial respiratory complex. Enrichment analyses identified the nuclear pore complex (NPC) and nucleocytoplasmic transport as suppressed pathways. These two pathways were linked by the hub genes NUP50, NUP98, NUP153, NUP205, and RanBP2. In immunohistochemistry, these nucleoporin proteins (NUPs) were mislocalized to the cytoplasm and aggregated mostly with TAR DNA-binding protein 43 kDa and, to a lesser extent, with hnRNPA1. Based on ultrastructural observation, irregularly shaped myonuclei with deep invaginations were frequently observed in atrophic fibers, consistent with the disorganization of NPCs. Additionally, regarding the expression profiles of overall NUPs, reduced expression of NUP98, NUP153, and RanBP2 was shared with HNRNPA1-unlinked hIBMs. INTERPRETATION: The shared subset of altered NUPs in amyotrophic lateral sclerosis (ALS), as demonstrated in prior research, HNRNPA1-mutated, and HNRNPA1-unlinked hIBM muscle tissues may provide evidence regarding the underlying common nuclear pore pathology of hIBM, ALS, and MSP.

Survival in sporadic ALS is associated with lower p62 burden in the spinal cord.

The autophagy marker p62 appears as a consistent component of pathological aggregates in amyotrophic lateral sclerosis (ALS) and its modulation to facilitate protein degradation has been proposed as a potential therapeutic target. Importantly, recent studies have implicated diffuse phosphorylated TDP-43 inclusions that are immuno-negative for p62 in more rapid disease, highlighting the need for better understanding of p62 involvement in ALS pathogenesis. The present study set out to assess p62 pathology in the motor neurons of 31 patients with sporadic ALS that had either a short (<2 years) or longer (4-7 years) disease duration to determine its association with pTDP-43 pathology, motor neuron loss, and survival in sporadic disease. Our results identified significantly more cytoplasmic p62 aggregates in the spinal cord of patients with a shorter survival. Disease duration demonstrated a negative association with p62 burden and density of remaining motor neurons in the spinal cord, suggesting that survival in sporadic ALS is associated with the successful clearance of lower motor neurons with p62 aggregates. These findings implicate the autophagy pathway in ALS survival and provide support for further study of p62 as a potential prognostic biomarker in ALS.

Rare Pseudo-Chediak-Higashi Inclusions in Therapy-Related Acute Myeloid Leukemia with Myelodysplasia-Related Changes.

BACKGROUND: Defined as rare large azurophilic cytoplasmic inclusions, Pseudo-Chediak-Higashi granules mimic those in granulocytes cytoplasm of Chediak-Higashi syndrome. Rare cases of hematopoietic and lymphoid tissues tumors showed Pseudo-Chediak-Higashi inclusions in cytoplasm, some of which presented with unusual morphological characteristics. METHODS: Herein, we report the first case, in which rare pseudo-Chediak-Higashi inclusions were observed in therapy-related acute myeloid leukemia with myelodysplasia-related changes (t-AML-MRC). RESULTS: The rare pseudo-Chediak-Higashi inclusions may be positive for Sudan black, and some scholars think that these rare inclusions are a kind of dysgranulopoiesis. CONCLUSIONS: The case highlights the significance of an integrated diagnostic work-up, with an interesting effect for morphology.

Differential immunophenotypes of neuronal cytoplasmic inclusions in the dentate gyrus of multiple system atrophy and their association with clinicopathological features.

Although hippocampal pathologies of multiple system atrophy (MSA) and their association with dementia have been reported, no studies have reported clinicopathological differences among MSA patients with and without neuronal cytoplasmic inclusions (NCIs) in the dentate gyrus (dntNCIs). We investigated hippocampal NCI pathology in 18 MSA patient autopsies, focusing on phosphorylated α-synuclein (pAS)- and phosphorylated tau (pT)-positive dntNCIs. There were 8 MSA patients without and 10 with dntNCIs. The latter group was subclassified by immunophenotype: those with pAS-positive dntNCIs (pAS-dntNCI subtype), those with pT-positive dntNCIs (pT-dntNCI subtype), and those with both types of dntNCIs. MSA patients with dntNCIs survived longer with prolonged tracheostomy and had dementia more frequently than those without dntNCIs. The brain weights of patients with dntNCIs were lower than those without dntNCIs. The presence of dementia was similar among the dntNCI subtypes. The pAS-dntNCI subtype was associated with longer survival and smaller brain weights; the pT-dntNCI subtype exhibited more frequent tau pathologies than the pAS-dntNCI subtype. Thus, MSA with dntNCIs is a possible pathological subtype of longer survivors that correlates with longer disease duration, prolonged tracheostomy, and high frequency of dementia. Understanding clinicopathological differences in MSA patients with and without dntNCIs may lead to improved personalized management strategies.

Mutated FUS in familial amyotrophic lateral sclerosis involves multiple hnRNPs in the formation of neuronal cytoplasmic inclusions.

Fused in sarcoma (FUS), coded by FUS, is a heterogeneous nuclear ribonucleoprotein (hnRNP). FUS mutations are among the major mutations in familial amyotrophic lateral sclerosis (ALS-FUS: ALS6). The pathological hallmarks of ALS-FUS are FUS-positive neuronal cytoplasmic inclusions (NCI). We examined various hnRNPs in FUS NCIs in the hippocampus in ALS-FUS cases with different FUS mutations (Case 1, H517P; Case 2, R521C). We also examined TDP43-positive NCIs in sporadic ALS hippocampi. Immunohistochemistry was performed using primary antibodies against FUS, p-TDP43, TDP43, hnRNPA1, hnRNPD, PCBP1, PCBP2, and p62. Numerous FUS inclusions were found in the hippocampal granule and pyramidal cell layers. Double immunofluorescence revealed colocalization of FUS and p-TDP43, and FUS and PCBP2 (p-TDP43/FUS: 64.3%, PCBP2/FUS: 23.9%). Colocalization of FUS and PCBP1, however, was rare (PCBP1/FUS: 7.6%). In the hippocampi of patients with sporadic ALS, no colocalization was observed between TDP43-positive inclusions and other hnRNPs. This is the first study to show that FUS inclusions colocalize with other hnRNPs, such as TDP43, PCBP2, and PCBP1. These findings suggest that in ALS-FUS, FUS inclusions are the initiators, followed by alterations of multiple other hnRNPs, resulting in impaired RNA metabolism.

The Reemergence of Measles.

OBJECTIVES: Present-day pathologists may be unfamiliar with the histopathologic features of measles, which is a reemerging disease. Awareness of these features may enable early diagnosis of measles in unsuspected cases, including those with an atypical presentation. Using archived tissue samples from historic patients, a unique source of histopathologic information about measles and other reemerging infectious diseases, we performed a comprehensive analysis of the histopathologic features of measles seen in commonly infected tissues during prodrome, active, and late phases of the disease. METHODS: Subspecialty pathologists analyzed H&E-stained slides of specimens from 89 patients accessioned from 1919 to 1998 and correlated the histopathologic findings with clinical data. RESULTS: Measles caused acute and chronic histopathologic changes, especially in the respiratory, lymphoid (including appendix and tonsils), and central nervous systems. Bacterial infections in lung and other organs contributed significantly to adverse outcomes, especially in immunocompromised patients. CONCLUSIONS: Certain histopathologic features, especially Warthin-Finkeldey cells and multinucleated giant cells without inclusions, allow pathologists to diagnose or suggest the diagnosis of measles in unsuspected cases.

An in situ and in vitro investigation of cytoplasmic TDP-43 inclusions reveals the absence of a clear amyloid signature.

Introduction: Several neurodegenerative conditions are associated with a common histopathology within neurons of the central nervous system, consisting of the deposition of cytoplasmic inclusions of TAR DNA-binding protein 43 (TDP-43). Such inclusions have variably been described as morphologically and molecularly ordered aggregates having amyloid properties, as filaments without the cross-ß-structure and dye binding specific for amyloid, or as amorphous aggregates with no defined structure and fibrillar morphology.Aims and Methods: Here we have expressed human full-length TDP-43 in neuroblastoma x spinal cord 34 (NSC-34) cells to investigate the morphological, structural, and tinctorial properties of TDP-43 inclusions in situ. We have used last-generation amyloid diagnostic probes able to cross the cell membrane and detect amyloid in the cytoplasm and have adopted Raman and Fourier transform infrared microspectroscopies to study in situ the secondary structure of the TDP-43 protein in the inclusions. We have then used transmission electron microscopy to study the morphology of the TDP-43 inclusions.Results: The results show the absence of amyloid dye binding, the lack of an enrichment of cross-ß structure in the inclusions, and of a fibrillar texture in the round inclusions. The aggregates formed in vitro from the purified protein under conditions in which it is initially native also lack all these characteristics, ruling out a clear amyloid-like signature.Conclusions: These findings indicate a low propensity of TDP-43 to form amyloid fibrils and even non-amyloid filaments, under conditions in which the protein is initially native and undergoes its typical nucleus-to-cell mislocalization. It cannot be excluded that filaments emerge on the long time scale from such inclusions, but the high propensity of the protein to form initially other types of inclusions appear to be an essential characteristic of TDP-43 proteinopathies.KEY MESSAGESCytoplasmic inclusions of TDP-43 formed in NSC-34 cells do not stain with amyloid-diagnostic dyes, are not enriched with cross-ß structure, and do not show a fibrillar morphology.TDP-43 assemblies formed in vitro from pure TDP-43 do not have any hallmarks of amyloid.

Auer rods and faggot cells: A review of the history, significance and mimics of two morphological curiosities of enduring relevance.

Myeloid differentiation in blasts is distinguished by the presence of one or more needle-shaped crystalline structures called Auer rods. Auer rods manifest either alone or as faggot cells (containing bundles of Auer rods) in various types of acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN). Their presence largely portends a better prognosis in AML (as markers of maturation/differentiation) and upstages cases of MDS and MDS/MPN. Observation of these rods in residual blasts in treated cases of AML indicates an absence of remission. This article traces their historical discovery and examines their pathogenetic intricacies, as well as our current understanding of their relevance in myeloid neoplasms. Studies evaluating their prognostic impact in AML and MDS are catalogued. We also discuss a variety of other hematological and non-hematological neoplasms where structures potentially mistakable for Auer rods have been described. Even as the diagnostic approach to hematological malignancies has evolved from a morphology + cytochemistry + immunophenotyping-dependent one in the last century to a predominantly molecular genetics-based classification currently, and even as high-throughput sequencing and structural variation detection techniques surpass morphology in detecting clinically-relevant sub-categories of similar-appearing tumours, we review these curious microscopic structures that have withstood the test of time with respect to their diagnostic relevance.

[Lafora disease with a fatal outcome]. / Bolezn' Lafory s letal'nym iskhodom.

Lafora disease is a rare hereditary genetic pathology of the nervous system (a group of progressive myoclonic epilepsies). The distinctive morphological feature of this disease is the presence of specific abnormal structures - polyglucosane bodies («Lafora bodies¼) in the brain tissue, myocardium, liver, and epithelium of the sweat gland ducts. The article discusses the clinical data of the course of Lafora's disease in an 18-year-old patient with a fatal outcome and the results of a post-mortem examination. The diagnosis of Lafora disease was confirmed by genetic analysis data - the presence of a homozygous mutation in the 2nd exon of the EPM2A gene - laforin (chr6:146007412G>A, rs137852915). When analyzing literature, we did not find a description of Lafora's disease cases with a fatal outcome with the presentation of macroscopic examination data at autopsy, as well as the results of a pathohistological examination of altered organ tissues with the morphological manifestations specific for this pathology (Lafora bodies in the the brain, heart, sweat gland epithelium).

Role of SERPINI1 pathogenic variants in familial encephalopathy with neuroserpin inclusion bodies: A case report and literature review.

BACKGROUND: Familial encephalopathy with neuroserpin inclusion bodies (FENIB), a rare neurogenetic disease, is characterized by progressive cognitive decline and myoclonus and caused by pathogenic variants of the SERPINI1 gene that lead to the formation of neuroserpin inclusion bodies. METHODS: We described the case of an Asian patient with FENIB associated with a pathogenic variant of SERPINI1 and summarized and analyzed the clinical characteristics of the case. In addition, we conducted a literature review of previously reported patients with this disease. RESULTS: The patient, a 16-year-old Chinese girl, presented with progressive cognitive decline and myoclonus that had started at the age of 11 years. The girl was found to carry a de novo heterozygous c.1175G>A (p.G392E) variant of the SERPINI1 gene, which is a pathogenic variant according to the guidelines of the American College of Medical Genetics and Genomics. She had responded poorly to antiseizure medications (ASMs). At the last follow-up, her myoclonus was still out of control, and her self-care ability was poor. Our literature review revealed that 13 similar cases (including 9 cases in male patients) have been reported so far, in which six pathogenetic variations in SERPINI1, including G392E, were responsible for FENIB. All the patients presented with myoclonus, and 12 patients had experienced at least one other type of seizure. Further, as observed in our case, 9 out of 12 patients did not respond to ASMs. Progressive cognitive decline was observed in all the patients, and 10 out of 13 patients had dyskinesia. The median age of disease onset was 21 years, and the median age at the time of death was 33 years. Further, 9 out of 13 patients showed signs of cerebral and/or cerebellar atrophy. Finally, neuroserpin inclusion bodies were identified in six patients who underwent brain biopsy or autopsy. CONCLUSIONS: Pathogenic variants of SERPINI1 should be suspected in children with progressive cognitive decline and myoclonus, especially in those with progressive myoclonus epilepsy. Further, gene detection and brain biopsy are important means for the diagnosis of FENIB.

Lafora Body Epilepsy: A Challenging Diagnosis.

Lafora body disease (LBD) is a progressive myoclonic genetic epilepsy syndrome characterized by the presence of Lafora inclusion bodies within neurons and other cells. It is a complex neurodegenerative disease presenting in adolescence with seizures, myoclonus, and rapid cognitive decline. Diagnosis is often challenging requiring a thorough history including family history, identification of Lafora bodies in apocrine sweat glands of axillary skin, and specific DNA sequencing. There is no cure and management is mainly supportive. We present one of the only few cases from Pakistan of LBD based on characteristic biopsy findings, history of similar ailment in siblings, and EPM2B mutation. This case emphasizes the need for physicians and neurologists to be aware of diagnostic challenges associated with LBD and its characteristic findings. Key Words: Lafora body, Progressive epilepsy, Myoclonus, Axillary skin biopsy, EPM2B.

Pathological Appearance of a Case of Preclinical Multiple System Atrophy: A Comparison With Advanced Cases.

We aimed to investigate the frequency of multiple system atrophy (MSA) in a large number of forensic autopsies and characterize the pathological appearance of preclinical MSA. We investigated a series of 1930 brains from forensic autopsies. In addition to performing immunohistochemistry for phosphorylated α-synuclein, the levels of 3 autonomic nervous system markers (catecholaminergic, serotonergic, and cholinergic) were used to assess the peripheral nerve (heart and superior cervical ganglion) and medulla oblongata. The results were compared to those of healthy control and Parkinson disease (PD) cases. Four cases (0.21%) were identified as having MSA. Cases 1-3 were symptomatic, and Case 4 was incipient; that is, although no neuronal loss was evident, the cerebellar dentate nucleus exhibited marked grumose degeneration. Immunohistochemistry revealed a marked reduction in autonomic nervous system marker levels expressed in the medulla; this reduction was more prominent in the 3 symptomatic MSA cases than in the PD case. The opposite occurred for the peripheral nerve. Case 4 exhibited mild cholinergic nerve reduction. Two cases showed possible significant pathological changes in the heart. Grumose degeneration, few oligodendroglial cytoplasmic inclusions without neuronal loss, and less reduction of autonomic nervous tissue were more prominent in the preclinical case than in symptomatic cases.

Neuropathology and neuroanatomy of TDP-43 amyotrophic lateral sclerosis.

PURPOSE OF REVIEW: Intracellular inclusions consisting of the abnormal TDP-43 protein and its nucleocytoplasmic mislocalization in selected cell types are hallmark pathological features of sALS. Descriptive (histological, morphological), anatomical, and molecular studies all have improved our understanding of the neuropathology of sporadic amyotrophic lateral sclerosis (sALS). This review highlights some of the latest developments in the field. RECENT FINDINGS: Increasing evidence exists from experimental models for the prion-like nature of abnormal TDP-43, including a strain-effect, and with the help of neuroimaging-based studies, for spreading of disease along corticofugal connectivities in sALS. Progress has also been made with respect to finding and establishing reliable biomarkers (neurofilament levels, diffusor tensor imaging). SUMMARY: The latest findings may help to elucidate the preclinical phase of sALS and to define possible mechanisms for delaying or halting disease development and progression.

Multiple system atrophy prions transmit neurological disease to mice expressing wild-type human α-synuclein.

In multiple system atrophy (MSA), the protein α-synuclein misfolds into a prion conformation that self-templates and causes progressive neurodegeneration. While many point mutations in the α-synuclein gene, SNCA, have been identified as the cause of heritable Parkinson's disease (PD), none have been identified as causing MSA. To examine whether MSA prions can transmit disease to mice expressing wild-type (WT) human α-synuclein, we inoculated transgenic (Tg) mice denoted TgM20+/- with brain homogenates prepared from six different deceased MSA patients. All six samples transmitted CNS disease to the mice, with an average incubation period of ~ 280 days. Interestingly, TgM20+/- female mice developed disease > 60 days earlier than their male counterparts. Brains from terminal mice contained phosphorylated α-synuclein throughout the hindbrain, consistent with the distribution of α-synuclein inclusions in MSA patients. In addition, using our α-syn-YFP cell lines, we detected α-synuclein prions in brain homogenates prepared from terminal mice that retained MSA strain properties. To our knowledge, the studies described here are the first to show that MSA prions transmit neurological disease to mice expressing WT SNCA and that the rate of transmission is sex dependent. By comparison, TgM20+/- mice inoculated with WT preformed fibrils (PFFs) developed severe neurological disease in ~ 210 days and exhibited robust α-synuclein neuropathology in both limbic regions and the hindbrain. Brain homogenates from these animals exhibited biological activities that are distinct from those found in MSA-inoculated mice when tested in the α-syn-YFP cell lines. Differences between brains from MSA-inoculated and WT PFF-inoculated mice potentially argue that α-synuclein prions from MSA patients are distinct from the PFF inocula and that PFFs do not replicate MSA strain biology.