Neuronal Intermediate Filament Research Articles

Patterns of glucose hypometabolism can help differentiate FTLD-FET from other types of FTLD.

FTLD-FET is a newly described subtype of frontotemporal lobar degeneration (FTLD characterized by pathologic inclusions of FET proteins: fused in sarcoma (FUS), Ewing sarcoma, and TATA-binding protein-associated factor 2N (TAF15)). Severe caudate volume loss on MRI has been linked to FTLD-FUS, yet glucose hypometabolism in FTLD-FET has not been studied. We assessed [18F] fluorodeoxyglucose PET (FDG-PET) hypometabolism in FTLD-FET subtypes and compared metabolism to FTLD-tau and FTLD-TDP. We retrospectively reviewed medical records of 26 autopsied FTLD patients (six FTLD-FET, ten FTLD-Tau, and ten FTLD-TDP) who had completed antemortem FDG-PET. We evaluated five regions, caudate nucleus, medial frontal cortex, lateral frontal cortex, and medial temporal using a 0-3 visual rating scale and validated our findings quantitatively using CORTEX-ID suite Z scores. Of the six FTLD-FET cases (three females) with median age at onset = 36, three were atypical FTLD-U (aFTLD-U) and three were neuronal intermediate filament inclusion disease (NIFID). bvFTD was the most common presentation. Four of the six FTLD cases (3 aFTLD-U + 1 NIFID) showed prominent caudate hypometabolism relatively early in the disease course. FTLD-tau and FTLD-TDP did not show early prominent caudate hypometabolism. Hypometabolism in medial and lateral temporal cortex was associated with FTLD-TDP, while FTLD-tau had normal-minimal regional metabolism. Prominent caudate hypometabolism, especially early in the disease course, appears to be a hallmark feature of the aFTLD-U subtype of FTLD-FET. Assessing caudate and temporal hypometabolism on FDG-PET will help to differentiate FTLD-FET from FTLD-tau and FTLD-TDP.

Neurological autoimmunity in patients with non-pulmonary neuroendocrine neoplasms: clinical manifestations and neural autoantibody profiles.

Paraneoplastic neurological autoimmunity is well described with small-cell lung cancer, but information is limited for other neuroendocrine neoplasms (NENs). Adult patients with histopathologically confirmed non-pulmonary NENs, neurological autoimmunity within 5 years of NEN diagnosis, and neural antibody testing performed at the Mayo Clinic Neuroimmunology Laboratory (January 2008 to March 2023) were retrospectively identified. Control sera were available from patients with NENs without neurological autoimmunity (116). Thirty-four patients were identified (median age 68 years, range 31-87). The most common primary tumor sites were pancreas (nine), skin (Merkel cell, eight), small bowel/duodenum (seven), and unknown (seven). Five patients received immune checkpoint inhibitor (ICI) therapy before symptom onset; symptoms preceded cancer diagnosis in 62.1% of non-ICI-treated patients. The most frequent neurological phenotypes (non-ICI-treated) were movement disorders (12; cerebellar ataxia in 10), dysautonomia (six), peripheral neuropathy (eight), encephalitis (four), and neuromuscular junction disorders (four). Neural antibodies were detected in 55.9% of patients studied (most common specificities: P/Q-type voltage-gated calcium channel [seven], muscle-type acetylcholine receptor [three], anti-neuronal nuclear antibody type 1 [three], and neuronal intermediate filaments [two]), but in only 6.9% of controls. Amongst patients receiving cancer or immunosuppressive therapy, 51.6% had partial or complete recovery. Outcomes were unfavorable in 48.3% (non-ICI-treated) and neural autoantibody positivity was associated with poor neurological outcome. Neurological autoimmunity associated with non-pulmonary NENs is often multifocal and can be treatment responsive, underscoring the importance of rapid recognition and early treatment.

Paraneoplastic Neuronal Intermediate Filament Autoimmunity with Hepatocellular Carcinoma.

Paraneoplastic Neuronal Intermediate Filament Autoimmunity with Hepatocellular Carcinoma.

Proteostatic modulation in brain aging without associated Alzheimer's disease-and age-related neuropathological changes.

(Phospho)proteomics of old-aged subjects without cognitive or behavioral symptoms, and without AD-neuropathological changes and lacking any other neurodegenerative alteration will increase understanding about the physiological state of human brain aging without associate neurological deficits and neuropathological lesions. (Phospho)proteomics using conventional label-free- and SWATH-MS (Sequential window acquisition of all theoretical fragment ion spectra mass spectrometry) has been assessed in the frontal cortex (FC) of individuals without NFTs, senile plaques (SPs) and age-related co-morbidities classified by age (years) in four groups; group 1 (young, 30-44); group 2 (middle-aged: MA, 45-52); group 3 (early-elderly, 64-70); and group 4 (late-elderly, 75-85). Protein levels and deregulated protein phosphorylation linked to similar biological terms/functions, but involving different individual proteins, are found in FC with age. The modified expression occurs in cytoskeleton proteins, membranes, synapses, vesicles, myelin, membrane transport and ion channels, DNA and RNA metabolism, ubiquitin-proteasome-system (UPS), kinases and phosphatases, fatty acid metabolism, and mitochondria. Dysregulated phosphoproteins are associated with the cytoskeleton, including microfilaments, actin-binding proteins, intermediate filaments of neurons and glial cells, and microtubules; membrane proteins, synapses, and dense core vesicles; kinases and phosphatases; proteins linked to DNA and RNA; members of the UPS; GTPase regulation; inflammation; and lipid metabolism. Noteworthy, protein levels of large clusters of hierarchically-related protein expression levels are stable until 70. However, protein levels of components of cell membranes, vesicles and synapses, RNA modulation, and cellular structures (including tau and tubulin filaments) are markedly altered from the age of 75. Similarly, marked modifications occur in the larger phosphoprotein clusters involving cytoskeleton and neuronal structures, membrane stabilization, and kinase regulation in the late elderly. Present findings may increase understanding of human brain proteostasis modifications in the elderly in the subpopulation of individuals not having AD neuropathological change and any other neurodegenerative change in any telencephalon region.

Clinical and Paraclinical Features of Non-Paraneoplastic NIF-Mediated Disease Associated With Concurrent SARS-CoV-2 Infection

Objective To describe clinical and paraclinical features of non-paraneoplastic NIF-mediated disease associated with concurrent SARS-CoV-2 infection. Background Neurologic syndromes associated with neuronal intermediate filament (NIF) immunoglobulin G (IgG) most often are characterized by encephalopathy, cerebellar ataxia, or myelopathy. NIF-IgG has been strongly correlated with the presence of an underlying malignancy, with neuroendocrine tumors being most prevalent. Despite the intracellular target of this antibody, patients with NIF-IgG mediated disease tend to improve clinically with immunotherapy. While some cases have been described in a parainfectious context, this is the first such case in the context of a SARS-CoV-2 infection. Design/Methods NA. Results We reported a case of non-paraneoplastic NIF-mediated disease in the setting of SARS-CoV-2 infection. The patient presented with first time seizure. He was found to have frequent left temporal lobe spikes then two left temporal lobe seizures on neurotelemetry. Brain MRI displayed abnormal signal throughout the left hippocampus and mesial temporal lobe, without contrast enhancement. LP was subsequently performed. CSF showed elevated protein, 14-3-3, T-tau, interleukin 13, interleukin 2 receptor, and interleukin 6. The meningitis/encephalitis panel, and HSV-1/2 IgG were negative. Serum autoimmune encephalitis panel revealed a high-positive titer for anti-NIF 1:960, with concurrent NIF heavy chain cell-based assay positive. He improved with three days of IV steroids and treatment with levetiracetam and lacosamide. He has since been seizure free. Conclusions NIF-mediated diseases usually present with encephalopathy, cerebellar ataxia, or myelopathy and are generally seen in the setting of malignancy. Our case illustrated an example of NIF-mediated disease presenting as seizure in the setting of infection. This highlights the importance of consideration of parainfectious autoimmunity.

Two Cases of Isolated Neurofilament Heavy Chain Antibody Syndrome

Objective Novel clinical and laboratory findings in anti-neurofilament heavy chain encephalitis Background Antibodies to mature components of neuronal intermediate filament (NIF) have been implicated in several neurological disorders, including multiple sclerosis, amyotrophic lateral sclerosis, and more recently, various autoimmune encephalitides. The components include a-internexin, light chain and heavy chain. In the largest case series of anti-NIF syndromes (McKeon et al, 2021), patients' cell-based assays revealed antibodies to one, two or all three components. Heavy chain antibodies (anti-NfH) were present in most, including three out of four patients with encephalopathy and cerebellar involvement. One was due to a paraneoplastic phenomenon. Anti-NfH was also elevated in two cases of encephalopathy with spasticity. It was the lone autoantibody in one of the six aforementioned cases. Design/Methods N/A. Results Case 1: 37-year old female with a history of ovarian carcinoma, treated in 2016. Cognitive impairment started in fall 2019, with significant worsening to the point of catatonia and coma in October 2020. Though encephalopathy improved, severe ataxia and nystagmus persisted. Two MRI brain studies and an EEG were unremarkable, and no radiological evidence of cancer recurrence. Oligoclonal bands (in both CSF and serum) and serum anti-NfH were elevated. Case 2: 59 year-old female with gradual cognitive decline since March 2018, followed by rapid cognitive deterioration in Oct 2020. There was limb weakness, severe rigidity, clonus and a witnessed seizure. EEG showed intermittent rhythmic delta activity. MRI brain indicated severe bilateral hippocampal atrophy. CSF Protein and CSF anti-NfH were elevated. Conclusions This case series contains the first reported paraneoplastic encephalopathy with cerebellar involvement from isolated anti-NfH. Also presented is the first reported case of PERMS from any NIF antibody. Further research is needed on quantitative and qualitative factors of anti-NIF syndromes. Specifically, the clinical relevance of the number of antibodies, and associations between phenotype and specific antibody combination.

Anti-Neuronal Nuclear Antibody 3 Autoimmunity Targets Dachshund Homolog 1

Objective To identify the autoantigen defined by Anti-Neuronal Nuclear Antibody-type 3 (ANNA3)-IgG and describe the clinical phenotype of seropositive patients. Background ANNA3 was described in 11 patients with multifocal neurological presentations and cancer; its detection is based on the characteristic immunofluorescence staining on mouse tissue sections; ignorance of the antigen's molecular identity has precluded its ready detection in clinical practice. Design/Methods This study was performed at the Mayo Clinic Neuroimmunology Laboratory. The ANNA3-IgG antigen, identified by immunoprecipitation and mass spectrometry as Dachshund-homolog 1 (DACH1), was confirmed by using a commercial DACH1-specific IgG for immunohistochemical colocalization, antigen-specific Western blot, transfected cell-based immunofluorescence, and immune absorption experiments. Clinical data were abstracted from patients' medical records or provided by referring physicians. Results IgG in 32 ANNA3 seropositive patient sera, but in none of 145 controls, bound to DACH1. Clinical information was available for 30 patients (median age, 63.5 years [range, 49-88]; 67% female). Neurological manifestations included neuropathy, 12; cognitive difficulties or encephalitis, 11; ataxia, 8; dysautonomia, 7 (two additionally had diarrhea and esophageal spasm); chorioretinopathy, 1. Clinical improvement was noted in 8 of 11, all treated with immunosuppressants or oncologic treatment. In two patients, the neurological syndrome appeared or worsened during immune checkpoint inhibitor cancer immunotherapy. A neoplasm was found in 27 patients (90%); fourteen were of neuroendocrine lineage. Coexisting neural autoantibodies were detected in 14 patients (47%), and most predicted a neuroendocrine tumor (specific for neuronal intermediate filaments, collapsin response-mediator protein-5, voltage-gated calcium channel [P/Q-type], ANNA1, SOX1, Purkinje-cell cytoplasmic autoantibody type 2/microtubule-associated-protein-1B). Conclusions IgG specific for DACH1 is a serological biomarker of neurological autoimmunity and cancer in patients of middle-age or older. DACH1-IgG is a valuable addition to comprehensive autoimmune and paraneoplastic neural antibody evaluations in clinical practice.

Alzheimer's disease cerebrospinal fluid biomarkers differentiate patients with Creutzfeldt-Jakob disease and autoimmune encephalitis.

Autoimmune encephalitis (AE) is a potentially treatable cause of rapidly progressive dementia that may mimic Creutzfeldt-Jakob disease (CJD). Alzheimer disease (AD) cerebrospinal fluid (CSF) biomarkers may discriminate CJD from AD, but utility in discriminating CJD and AE is unclear. This study compared AD CSF biomarkers in CJD and AE. Patients with probable or definite CJD and probable or definite AE who underwent Roche Elecsys AD CSF biomarker testing at Mayo Clinic from March 2020 through April 2021 were included. Total-tau, phosphorylated181 tau and amyloid-β42 levels were compared. Of 11 CJD cases, four were autopsy proven; the rest had positive real-time quaking-induced conversion testing. Disease-associated autoantibodies were detected in 8/15 cases of AE: leucine-rich glioma-inactivated 1 and neuronal intermediate filaments (two cases each), and N-methyl-d-aspartate receptor, contactin-associated protein-like 2, dipeptidyl-peptidase-like protein 6 and immunoglobulin-like cell adhesion molecule IgLON family member 5. Total-tau provided excellent discrimination between CJD and AE in a univariate model (odds ratio 1.46 per 100 pg/ml, 95% confidence interval 1.17-2.11, p < 0.05, c=0.93). Total-tau was elevated in 91% of CJD cases (median > 1300, range 236->1300 pg/ml), of which 55% were above the limit of assay measurement (>1300 pg/ml). Total-tau was elevated in 20% of AE cases (median 158, range 80->1300 pg/ml). Total-tau was greater in CJD than AE. Given that amyloid-β42 and phosphorylated181 tau were comparable, the ratio differences were probably driven by elevated total-tau in CJD. This study supports the role for AD biomarker testing in patients with rapidly progressive dementia.

Neuronal intermediate filament paraneoplastic autoimmunity complicating avelumab therapy of Merkel cell carcinoma

A 67-years-old woman developed subacute oculomotor nerve palsy and cerebellar gait instability while receiving avelumab as immunotherapy for Merkel cell carcinoma. Brain MRI revealed oculomotor nerve T2/FLAIR hyperintensity and contrast enhancement, CSF cell number and protein concentration were slightly increased. Antibodies against intracellular and surface antigens were excluded through commercial assays, but home-made immunohistochemistry on rat brain sections showed a “neurofilament-like” pattern. Antibodies against neuronal intermediate filament (NIF-IgG) were thus tested and resulted positive in both serum and CSF, confirming the diagnosis of NIF-IgG autoimmunity. Avelumab was discontinued and treatment with steroids and intravenous immunoglobulins led to partial improvement.

Probing neurofilament sidearm IDR morphology with engineered recombinant subunits

Neurofilaments (NFs) are neuronal intermediate filaments that play important roles in axonal structure. NFs are composed of several subunit proteins including neurofilament light (NF-L), medium (NF-M), and heavy (NF-H), each with a “sidearm” intrinsically disordered region (IDR) that protrudes from the filament core to create a bottlebrush-like architecture. The length and charge of these sidearm IDRs vary widely between the different NF subunit proteins, and the relative abundance of different sidearm IDRs may govern inter-filament interactions and spacing via changes in the bottlebrush morphology.

Sacsin Deletion Induces Aggregation of Glial Intermediate Filaments.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disorder commonly diagnosed in infants and characterized by progressive cerebellar ataxia, spasticity, motor sensory neuropathy and axonal demyelination. ARSACS is caused by mutations in the SACS gene that lead to truncated or defective forms of the 520 kDa multidomain protein, sacsin. Sacsin function is exclusively studied on neuronal cells, where it regulates mitochondrial network organization and facilitates the normal polymerization of neuronal intermediate filaments (i.e., neurofilaments and vimentin). Here, we show that sacsin is also highly expressed in astrocytes, C6 rat glioma cells and N9 mouse microglia. Sacsin knockout in C6 cells (C6Sacs−/−) induced the accumulation of the glial intermediate filaments glial fibrillary acidic protein (GFAP), nestin and vimentin in the juxtanuclear area, and a concomitant depletion of mitochondria. C6Sacs−/− cells showed impaired responses to oxidative challenges (Rotenone) and inflammatory stimuli (Interleukin-6). GFAP aggregation is also associated with other neurodegenerative conditions diagnosed in infants, such as Alexander disease or Giant Axonal Neuropathy. Our results, and the similarities between these disorders, reinforce the possible connection between ARSACS and intermediate filament-associated diseases and point to a potential role of glia in ARSACS pathology.

Update in Autoimmune Movement Disorders: Newly Described Antigen Targets in Autoimmune and Paraneoplastic Cerebellar Ataxia.

Movement disorders are a common feature of many antibody-associated neurological disorders. In fact, cerebellar ataxia is one of the most common manifestations of autoimmune neurological diseases. Some of the first autoantibodies identified against antigen targets include anti-neuronal nuclear antibody type 1 (ANNA-1 or anti-Hu) and Purkinje cell cytoplasmic antibody (PCA-1) also known as anti-Yo have been identified in paraneoplastic cerebellar degeneration. Historically these antibodies have been associated with an underlying malignancy; however, recently discovered antibodies can occur in the absence of cancer as well, resulting in the clinical syndrome of autoimmune cerebellar ataxia. The pace of discovery of new antibodies associated with autoimmune or paraneoplastic cerebellar ataxia has increased rapidly over the last few years, and pathogenesis and potential treatment options remains to be explored. Here we will review the literature on recently discovered antibodies associated with autoimmune and paraneoplastic cerebellar ataxia including adaptor protein-3B2 (AP3B2); inositol 1,4,5-trisphophate receptor type 1 (ITPR1); tripartite motif-containing (TRIM) proteins 9, 67, and 46; neurochondrin; neuronal intermediate filament light chain (NIF); septin 5; metabotropic glutamate receptor 2 (mGluR2); seizure-related 6 homolog like 2 (SEZ6L2) and homer-3 antibodies. We will review their clinical characteristics, imaging and CSF findings and treatment response. In addition, we will discuss two clinical case examples of autoimmune cerebellar ataxia.

Optimal Valve Selection in Contemporary Transcatheter Aortic Valve Replacement for Women with Small Aortic Annuli

Quinolinic acid (QUIN) is a neuroactive metabolite of the kinurenine pathway, considered to be involved in aging and some neurodegenerative disorders, including Huntington׳s disease. In the present work we have studied the long-lasting effect of acute intrastriatal injection of QUIN (150 nmol/0.5 µL) in 30 day-old rats on the phosphorylating system associated with the astrocytic and neuronal intermediate filament (IF) proteins: glial fibrillary acidic protein (GFAP), and neurofilament (NF) subunits (NFL, NFM and NFH) respectively, until 21 days after injection. The acute administration of QUIN altered the homeostasis of IF phosphorylation in a selective manner, progressing from striatum to cerebral cortex and hippocampus. Twenty four hours after QUIN injection, the IFs were hyperphosphorylated in the striatum. This effect progressed to cerebral cortex causing hypophosphorylation at day 14 and appeared in the hippocampus as hyperphosphorylation at day 21 after QUIN infusion. PKA and PKCaMII have been activated in striatum and hippocampus, since Ser55 and Ser57 in NFL head domain were hyperphosphorylated. However, MAPKs (Erk1/2, JNK and p38MAPK) were hyperphosphorylated/activated only in the hippocampus, suggesting different signaling mechanisms in these two brain structures during the first weeks after QUIN infusion. Also, protein phosphatase 1 (PP1) and 2B (PP2B)-mediated hypophosphorylation of the IF proteins in the cerebral cortex 14 after QUIN injection reinforce the selective signaling mechanisms in different brain structures. Increased GFAP immunocontent in the striatum and cerebral cortex 24 h and 14 days after QUIN injection respectively, suggests reactive astrocytes in these brain regions. We propose that disruption of cytoskeletal homeostasis in neural cells takes part of the long-lasting molecular mechanisms of QUIN toxicity in adolescent rats, showing selective and progressive misregulation of the signaling mechanisms targeting the IF proteins in the striatum, cerebral cortex and hippocampus with important implications for brain function.

Neuronal intermediate filament IgGs in CSF: Autoimmune Axonopathy Biomarkers.

ObjectivesTo describe CSF‐defined neuronal intermediate filament (NIF) autoimmunity.MethodsNIF‐IgG CSF‐positive patients (41, 0.03% of 118599 tested, 1996–2019) were included (serum was neither sensitive nor specific). Criteria‐based patient NIF‐IgG staining of brain and myenteric NIFs was detected by indirect immunofluorescence assay (IFA); NIF‐specificity was confirmed by cell‐based assays (CBAs, alpha internexin, neurofilament light [NF‐L]), heavy‐[NF‐H] chain).ResultsSixty‐one percent of 41 patients were men, median age, 61 years (range, 21–88). Syndromes were encephalopathy predominant (23), cerebellar ataxia predominant (11), or myeloradiculoneuropathies (7). MRI abnormalities (T2 hyperintensities of brain, spinal cord white matter tracts. and peripheral nerve axons) and neurophysiologic testing (EEG, EMG, evoked potentials) co‐localized with clinical neurological phenotypes (multifocal in 29%). Thirty patients (73%) had ≥ 1 immunological perturbation: cancer (paraneoplastic), 22; systemic infection (parainfectious [including ehrlichosis, 3] or HIV), 7; checkpoint‐inhibitor cancer immunotherapy, 4; other, 5. Cancers were as follows: neuroendocrine‐lineage carcinomas, 12 (small cell, 6; Merkel cell, 5; pancreatic, 1 [11/12 had NF‐L‐IgG detected, versus 8/29 others, P = 0.0005]) and other, 11. Onset was predominantly subacute (92%) and accompanied by inflammatory CSF (75%), and immunotherapy response (77%). In contrast, CSF controls (15684 total) demonstrated NIF‐IgG negativity (100% of test validation controls), and low frequencies of autoimmune diagnoses (20% of consecutively referred clinical specimens) and neuroendocrine‐lineage carcinoma diagnosis (3.1% vs. 30% of NIF cases), P < 0.0001. Median NF‐L protein concentration was higher in 8 NF‐L‐IgG‐positive patients (median, 6718 ng/L) than 16 controls.InterpretationNeurological autoimmunity, defined by CSF‐detected NIF‐IgGs, represents a continuum of treatable axonopathies, sometimes paraneoplastic or parainfectious.

Neurologic autoimmunity and immune checkpoint inhibitors

To describe neural autoantibody profiles and outcomes in patients with neurologic autoimmunity associated with immune checkpoint inhibitor (ICI) cancer immunotherapy. In this retrospective descriptive study, 63 patients with ICI-related neurologic autoimmunity were included: 39 seen at the Mayo Clinic Neurology Department (clinical cohort) and 24 whose serum/CSF was referred to the Mayo Clinic Neuroimmunology Laboratory for autoantibody testing. Serum/CSF samples were tested for neural-specific autoantibodies. Predictors of unfavorable outcome (residual adverse event severity grade ≥3) were explored (logistic regression). Median age at neurologic symptom onset was 65 years (range 31-86); 40% were female. Neurologic manifestations were CNS-restricted (n = 26), neuromuscular (n = 30), combined (n = 5), or isolated retinopathy (n = 2). Neural-specific autoantibodies were common in patients with CNS involvement (7/13 [54%] in the unbiased clinical cohort) and included known or unidentified neural-restricted specificities. Only 11/31 patients with CNS manifestations had neuroendocrine malignancies typically associated with paraneoplastic autoimmunity. Small-cell lung cancer (SCLC)-predictive antibodies were seen in 3 patients with non-neuroendocrine tumors (neuronal intermediate filament immunoglobulin G [IgG] and antineuronal nuclear antibody 1 with melanoma; amphiphysin IgG with non-SCLC). A median of 10 months from onset (range, 0.5-46), 14/39 in the clinical cohort (36%) had unfavorable outcomes; their characteristics were age ≥70 years, female, CNS involvement, lung cancer, higher initial severity grade, and lack of systemic autoimmunity. By multivariate analysis, only age remained independently associated with poor outcome (p = 0.01). Four of 5 patients with preexistent neurologic autoimmunity experienced irreversible worsening after ICI. Neural-specific autoantibodies are not uncommon in patients with ICI-related CNS neurologic autoimmunity. Outcomes mostly depend on the pre-ICI treatment characteristics and clinical phenotype.

Functional Characterization of Neurofilament Light Splicing and Misbalance in Zebrafish.

Neurofilaments (NFs), a major cytoskeletal component of motor neurons, play a key role in the differentiation, establishment and maintenance of their morphology and mechanical strength. The de novo assembly of these neuronal intermediate filaments requires the presence of the neurofilament light subunit (NEFL), whose expression is reduced in motor neurons in amyotrophic lateral sclerosis (ALS). This study used zebrafish as a model to characterize the NEFL homologue neflb, which encodes two different isoforms via a splicing of the primary transcript (neflbE4 and neflbE3). In vivo imaging showed that neflb is crucial for proper neuronal development, and that disrupting the balance between its two isoforms specifically affects the NF assembly and motor axon growth, with resultant motor deficits. This equilibrium is also disrupted upon the partial depletion of TDP-43 (TAR DNA-binding protein 43), an RNA-binding protein encoded by the gene TARDBP that is mislocalized into cytoplasmic inclusions in ALS. The study supports the interaction of the NEFL expression and splicing with TDP-43 in a common pathway, both biologically and pathogenetically.

Neuronal Intermediate Filament (NIF) Antibody Positivity in a Patient with Glial Fibrillary Acidic Protein (GFAP) Astrocytopathy (551)

Neuronal Intermediate Filament (NIF) Antibody Positivity in a Patient with Glial Fibrillary Acidic Protein (GFAP) Astrocytopathy (551)

A Prospective Clinical Validation of Neuronal Intermediate Filament IgGs (2195)

A Prospective Clinical Validation of Neuronal Intermediate Filament IgGs (2195)

The Photoreceptor Cells in Retina and Pineal Gland of Amphibian Hoplobatrachus rugulosus

Hoplobatrachus rugulosus, commonly referred to as tiger‐skinned frog, is to be chosen the animal model in this study. It has been found that both chicken α‐internexin and zebrafish inaa (an ortholog of mammalian α‐internexin) were developmentally distributed not only in photoreceptors of retina but also in the photoreceptor‐like cells of the pineal gland from our previous studies. However, from an evolutionary point of view, there is still lack of evidence to illustrate the temporal and spatial distribution of frog α‐internexin protein in the developing pineal gland. According to other studies about Xenopus laevis, the animal model that is usually used for amphibian developmental research, the mRNA sequence which encodes Xenopus α‐internexin had been identified as “xefiltin”. Although H. rugulosus is not the same species with X. laevis, both of them are classified in the same order. The aims of this study is to characterize the expression pattern of α‐internexin‐like proteins, internexin neuronal intermediate filament protein alpha S homeolog (ina.S) and low molecular weight neuronal intermediate filament S homeolog (nif.S) which might be expressed in the developing retina and the pineal gland of the tiger‐skinned frog. Thus, the specific antibodies were generated to detect the frog α‐internexin‐like proteins and to confirm the distribution of these proteins in the developing frog retina as well as the pineal gland by western blot and immunohistochemistry. Furthermore, the markers applied to detect the photoreceptor cell in the retina and the pineal gland are recoverin and XAP1, both of them are reported to be specific to photoreceptors. Based on the distribution patterns in frog retina, immunopositive staining of anti‐nif.S could be observed in the outer segment of photoreceptors, but anti‐ina.S could only be found in retinal neurons. In the pineal gland, both photoreceptor markers, recoverin and XAP1, could be detected. The α‐internexin‐like protein, ina.S and nif.S, could be detected only in a few photoreceptor‐like cells at the early stage of the frog pineal gland. In summary, the distribution patterns of photoreceptor cells in retina and in pineal gland of developing tiger‐skinned frogs has been characterized in this study. It can be concluded that XAP1 could be a good marker to identify the photoreceptor cells in the developing pineal gland of frogs.Support or Funding InformationGrant SponsorMinistry of Science and Technology, Taiwan; Grant Number: MOST 108‐2312‐B‐002‐030‐MY2.

Neuronal intermediate filament inclusion disease may be incorrectly classified as a subtype of FTLD-FUS.

The majority of cases of frontotemporal lobar degeneration (FTLD) are characterized by focal cortical atrophy with an underlying tau or TDP-43 proteinopathy. A subset of FTLD cases, however, lack tau and TDP-43 immuno-reactivity, but have neuronal inclusions positive for ubiquitin, referred to as atypical FTLD (aFTLD-U). Studies have demonstrated that ubiquitin-positive inclusions in aFTLD-U are immuno-reactive for fused in sarcoma (FUS). As such, the current nosology for this entity is FTLD-FUS, which is thought to include not only aFTLD-U, but also neuronal intermediate filament inclusion disease (NIFID) and basophilic inclusion body disease. To compare pathological features of cases of aFTLD-U and NIFID. We reviewed the neuropathology of 15 patients (10 males and 5 females; average age at death 54 years (range 41-69 years)) with an antemortem clinical diagnosis of a frontotemporal dementia and pathological diagnosis of aFTLD-U (n=8) or NIFID (n=7). Sections were processed for immunohistochemistry and immunoelectron microscopy with FUS, TDP-43, and α-internexin (αINX) antibodies. Eight cases had pathologic features consistent with FTLD-FUS, with severe striatal atrophy (7/8 cases), as well as FUS-positive neuronal cytoplasmic and vermiform intranuclear inclusions, but no αINX immuno-reactivity. Five cases had features consistent with NIFID, with neuronal inclusions positive for both FUS and αINX. Striatal atrophy was present in only 2 of the NIFID cases. Two cases had αINX-positive neuronal inclusions consistent with NIFID, but both lacked striatal atrophy and FUS immunoreactivity. Surprisingly, one of these two NIFID cases had lesions immunoreactive for TDP-43. While FUS pathology remains a prominent feature of aFTLD-U, there is pathologic heterogeneity, including rare cases of NIFID with TDP-43- rather than FUS-positive inclusions.