The most common type of FTLD-FUS (aFTLD-U) is associated with a distinct clinical form of frontotemporal dementia but is not related to mutations in the FUS gene.
FUS (fused in sarcoma) mislocalization and cytoplasmic aggregation are hallmark pathologies in FUS-related amyotrophic lateral sclerosis and frontotemporal dementia.
In addition to familial ALS, abnormal aggregates of FUS are present in a portion of FTD and other neurodegenerative diseases independent of their mutations.
To the most important recentdiscoveries belong TAR DNA binding protein [TARDBP or TDP-43] and the fused in sarcoma gene [FUS] and their implication in these disorders.FTD and ALS are the focus of this review which aims to 1. summarize clinical features by describing the diagnostic criteria and specific symptomatology, 2. describe the morphological aspects and related pathology, 3. describe the genetic factors associated with the diseases and 4. summarize the current status of clinical trials and treatment options.
In fact, it has been demonstrated that lncRNAs are dysregulated upon either depletion or unavailability of functional TDP-43 or FUS/TLS in a range of different models and diseases, including post-mortem samples from subjects with FTLD-TDP.
The seminal discoveries of accumulation of TDP-43 in most cases of ALS and the most frequent form of FTD, frontotemporal lobar degeneration with ubiquitinated inclusions, followed by identification of FUS as the novel pathological protein in a small subset of patients with ALS and various FTD subtypes provide clear evidence that these disorders are related.
We investigated the contribution of rare variants in seven genes of known relevance to dementias (β-amyloid precursor protein (APP), PSEN1/2, MAPT (microtubule-associated protein tau), fused in sarcoma (FUS), granulin (GRN) and TAR DNA-binding protein 43 (TDP-43)) to PD and PD plus dementia (PD+D) in a discovery sample of 376 individuals with PD and followed by the genotyping of 25 out of the 27 identified variants with a minor allele frequency <5% in 975 individuals with PD, 93 cases with Lewy body disease on neuropathological examination, 613 individuals with Alzheimer's disease (AD), 182 cases with frontotemporal dementia and 1014 general population controls.
Knowing the type of protein abnormality (proteinopathy) from among the three most common in FTD (tau, TDP-43, or fused in sarcoma) can help treating clinicians to advise families on the future course of illness and future clinical drug trials that would be most applicable to each patient.
FTD usually belongs to the frontotemporal lobar degeneration (FTLD) disease group, and its familial forms are dominantly inherited and linked to a group of genes relevant to frontal and temporal brain pathology, such as MAPT, GRN, C9ORF72, TARDBP, CHMP2B, VCP, and FUS.
In the case of ALS and FTD, these protein aggregates are found in the cytoplasm of affected neurons and contain certain RNA-binding proteins (RBPs), namely the TAR DNA-binding protein of 43 kDa (TDP-43) and the fused in sarcoma (FUS) gene product.
On the basis of the nature of the characteristic protein inclusions, frontotemporal lobar degeneration (FTLD) can be subdivided into the common FTLD-tau and FTLD-TDP as well as the less common FTLD-FUS and FTLD-UPS.
We propose that mutations in FUS and hexanucleotide expansions in C9orf72 and aging all converge on the impairment of nucleocytoplasmic transport, which results in the hallmark pathological feature of ALS/FTD - cytoplasmic aggregation of TDP-43 or FUS.
The neuropathological correlate of FTD is frontotemporal lobar degeneration (FTLD), characterized by tau-, TDP-43-, and FUS-immunoreactive neuronal inclusions.
We found that FUS, an oscillating expressed nuclear protein implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), exerted a novel feedback route to regulate circadian gene expression.
Subcellular mislocalization and aggregation of the human FUS protein occurs in neurons of patients with subtypes of amyotrophic lateral sclerosis and frontotemporal dementia.
Inclusions containing Fused in Sarcoma (FUS) are found in familial and sporadic cases of the incurable progressive motor neuron disease amyotrophic lateral sclerosis and in a common form of dementia, frontotemporal dementia.
We discuss how TDP-43 and FUS may exit the nucleus and how defects in both nuclear and cytosolic mRNA processing events, and possibly nuclear export defects, may contribute to neurodegeneration and ALS/FTD pathogenesis.
Aggregation of fused in sarcoma (FUS) protein, and mutations in FUS gene, are causative to a range of neurodegenerative disorders including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia.
Pathological FUS inclusions are found in 10% of patients with frontotemporal dementia (FTD) and those with amyotrophic lateral sclerosis (ALS) carrying FUS mutations.
The link between RNA processing and ALS was further strengthened by the discovery that another genetic locus linking familial ALS (fALS) and FTD was due to mutation of the fused in sarcoma (FUS) gene.
Phase-separated compartments can concentrate specific RNA-binding proteins (RBPs), such as TDP-43 and fused in sarcoma (FUS), that through low-complexity, prion-like domains have an intrinsic tendency to form self-templating fibrils that are closely tied to fatal neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia.