A comparative clinical, pathological, biochemical and genetic study of fused in sarcoma proteinopathies

Abstract

Neuronal intermediate filament inclusion disease and atypical frontotemporal lobar degeneration are rare diseases characterized by ubiquitin-positive inclusions lacking transactive response DNA-binding protein-43 and tau. Recently, mutations in the fused in sarcoma gene have been shown to cause familial amyotrophic lateral sclerosis and fused in sarcoma-positive neuronal inclusions have subsequently been demonstrated in neuronal intermediate filament inclusion disease and atypical frontotemporal lobar degeneration with ubiquitinated inclusions. Here we provide clinical, imaging, morphological findings, as well as genetic and biochemical data in 14 fused in sarcoma proteinopathy cases. In this cohort, the age of onset was variable but included cases of young-onset disease. Patients with atypical frontotemporal lobar degeneration with ubiquitinated inclusions all presented with behavioural variant frontotemporal dementia, while the clinical presentation in neuronal intermediate filament inclusion disease was more heterogeneous, including cases with motor neuron disease and extrapyramidal syndromes. Neuroimaging revealed atrophy of the frontal and anterior temporal lobes as well as the caudate in the cases with atypical frontotemporal lobar degeneration with ubiquitinated inclusions, but was more heterogeneous in the cases with neuronal intermediate filament inclusion disease, often being normal to visual inspection early on in the disease. The distribution and severity of fused in sarcoma-positive neuronal cytoplasmic inclusions, neuronal intranuclear inclusions and neurites were recorded and fused in sarcoma was biochemically analysed in both subgroups. Fused in sarcoma-positive neuronal cytoplasmic and intranuclear inclusions were found in the hippocampal granule cell layer in variable numbers. Cortical fused in sarcoma-positive neuronal cytoplasmic inclusions were often 'Pick body-like' in neuronal intermediate filament inclusion disease, and annular and crescent-shaped inclusions were seen in both conditions. Motor neurons contained variable numbers of compact, granular or skein-like cytoplasmic inclusions in all fused in sarcoma-positive cases in which brainstem and spinal cord motor neurons were available for study (five and four cases, respectively). No fused in sarcoma mutations were found in any cases. Biochemically, two major fused in sarcoma species were found and shown to be more insoluble in the atypical frontotemporal lobar degeneration with ubiquitinated inclusions subgroup compared with neuronal intermediate filament inclusion disease. There is considerable overlap and also significant differences in fused in sarcoma-positive pathology between the two subgroups, suggesting they may represent a spectrum of the same disease. The co-existence of fused in sarcoma-positive inclusions in both motor neurons and extramotor cerebral structures is a characteristic finding in sporadic fused in sarcoma proteinopathies, indicating a multisystem disorder.

Phosphorylation of C-terminal tyrosine 526 in FUS impairs its nuclear import

“…Although all ALS-FUS individuals have mutations in FUS, it is curious that no mutations of FUS are reported in FTLD-FUS cases (Neumann et al, 2009a,b;Urwin et al, 2010;Lashley et al, 2011;Snowden et al, 2011). There seems to be a more general dysfunction of TNPO1-mediated import of the three FET proteins because FUS, EWSR1 and TAF15 colocalise with TNPO1 in the cytoplasmic inclusions.…”

“…In contrast to ALS-FUS, FTLD-FUS individuals do not have mutations in the gene encoding FUS (Neumann et al, 2009a,b;Urwin et al, 2010;Lashley et al, 2011;Snowden et al, 2011). Another difference is that cytoplasmic inclusions in FTLD-FUS cases also include the FUS homologues EWS RNA-binding protein 1 (EWSR1) and TATA box binding protein associated factor (TAF15), and nuclear import factor TNPO1, which are absent in ALS-FUS inclusions, implying that there are key differences in the mechanisms underlying inclusion formation in the two disease groups Neumann et al, 2011Neumann et al, , 2012Troakes et al, 2013).…”

Sequential Extraction of Soluble and Insoluble Alpha-Synuclein from Parkinsonian Brains

“…Here, a biochemical extraction protocol (see scheme presented in Figure 1) for increasingly insoluble α-syn deposits from human post-mortem PD brain tissue that harbour α-syn aggregates to varying degrees has been described. This technique can also be adapted with modifications in buffer compositions to study aggregate proteins from other neurodegenerative diseases 23,24 and also from transgenic animal brain tissue Note: Blots can also be developed manually using developer and fixer from a commercial source in case an automated developer machine is not available.…”

Aggregation of FET Proteins as a Pathological Change in Amyotrophic Lateral Sclerosis

“…In contrast, several papers have supported decreased solubility of FUS in FTLD-FUS cases, including atypical FTLD-U, BIBD, and NIFID. Compared to non-neurological controls, higher levels of FUS in FTLD-FUS cases were insoluble in RIPA buffer (50 mM Tris, 150 mM NaCl, 5 mM EDTA, 1 % NP-40, 0.5 % sodium deoxycholate, and 0.1 % SDS) but soluble in either 2 % SDS or 7 M urea (Neumann et al 2009Lashley et al 2011;Page et al 2011). While insolubilization of FUS proteins in FTLD-FUS cases was statistically significant, the level of insoluble FUS appeared to correlate with the severity of FUS pathologies and were even comparable to those of controls in some cases (Neumann et al 2009).…”