Wnt effectors were tightly clustered with presenilin1 (PSEN1) and granulin (GRN), which cause dominantly inherited forms of Alzheimer's disease and frontotemporal dementia (FTD), respectively.
With new genetic causes, most notably a hexanucleotide expansion in C9orf72 associated with both MND and FTD, the development of biomarkers against which to test therapeutic candidates is a priority.
Whilst it remains unclear how mutations in C9orf72 lead to neurodegeneration in ALS/FTD, dysfunction to the nucleolus and R loop formation are implicated as pathogenic mechanisms.
While the neuropathology underlying these disorders is most consistent with a widespread alteration in the metabolism of transactive response DNA-binding protein 43 (TDP-43), in both ALS with cognitive impairment (ALSci) and ALS with FTD (ALS-FTD; also known as MND-FTD) there is evidence for alterations in the metabolism of the microtubule associated protein tau.
While the neuropathology underlying these disorders is most consistent with a widespread alteration in the metabolism of transactive response DNA-binding protein 43 (TDP-43), in both ALS with cognitive impairment (ALSci) and ALS with FTD (ALS-FTD; also known as MND-FTD) there is evidence for alterations in the metabolism of the microtubule associated protein tau.
While the identification of multiple mutations in more than two dozen genes elucidated the involvement of several mechanisms in the pathogenesis of both diseases, identifying the hexanucleotide repeat expansion in C9orf72, the most common genetic abnormality in ALS and FTD, opened the door to the discovery of several novel pathogenic biological routes, including chromatin remodeling and transcriptome alteration.
While cytoplasmic aggregation of TDP-43 is a pathological hallmark of amyotrophic lateral sclerosis and frontotemporal dementia, how aggregates form and what drives its nuclear clearance have not been determined.
While astrocytic differentiation was not impaired in FTD NPCs derived from one patient carrying the N279KMAPT mutation, FTD astrocytes appeared larger, expressed increased levels of 4R-TAU isoforms, demonstrated increased vulnerability to oxidative stress and elevated protein ubiquitination and exhibited disease-associated changes in transcriptome profiles when compared to astrocytes derived from one control individual and to the isogenic control.
Whereas wild-type UBQLN2 accumulates in intraneuronal deposits in several common age-related neurodegenerative diseases, mutations in the gene encoding this protein result in X-linked amyotrophic lateral sclerosis/frontotemporal dementia associated with TDP43 accumulation.
When the primary pathology is cytoplasmic and/or nuclear aggregates of phosphorylated TAR-DNA-binding protein (TDP-43), the pathological diagnosis is FTLD-TDP.
Western blots of cortical lysates, in contrast to those of sporadic MND/ALS and FTLD-TDP, showed high p62 levels and low TDP-43 levels with no high molecular weight smearing.
Western blots of cortical lysates, in contrast to those of sporadic MND/ALS and FTLD-TDP, showed high p62 levels and low TDP-43 levels with no high molecular weight smearing.
Western blot of lysates from FTLD-TDP frontal cortex and TDP-43-positive SALS spinal cord revealed decreased levels of OPTN protein compared to controls (p < 0.05), however, this correlated with decreased neuronal numbers in the brain.
Western blot of lysates from FTLD-TDP frontal cortex and TDP-43-positive SALS spinal cord revealed decreased levels of OPTN protein compared to controls (p < 0.05), however, this correlated with decreased neuronal numbers in the brain.
WES also unraveled pathogenic mutations in genes not commonly linked to FTD, including mutations in Alzheimer (PSEN1, PSEN2), lysosomal (CTSF, 7-exon macro-deletion) and cholesterol homeostasis pathways (CYP27A1).ConclusionOur unbiased approach reveals a wide genetic spectrum underlying clinical FTD, including 11% of seemingly sporadic FTD.
We used stem cell-derived microglia to study the consequences of missense mutations in the microglial-expressed protein triggering receptor expressed on myeloid cells 2 (TREM2), which are causal for frontotemporal dementia-like syndrome and Nasu-Hakola disease.
We used next generation sequencing of the whole gene (n = 700), exon 2 Sanger sequencing (n = 2634), p.R47H genotyping (n = 3518), and genome wide association study imputation (n = 13,048) to determine whether TREM2 variants are risk factors or phenotypic modifiers in patients with AD (n = 1002), frontotemporal dementia (n = 358), sporadic (n = 2500), and variant (n = 115) Creutzfeldt-Jakob disease (CJD).
We used microtubule-associated protein tau (MAPT) exon 10, whose missplicing causes frontotemporal dementia, to test the reporter in screening libraries of known bioactive compounds.
We therefore investigated 33 patients with FTLD-tau (including 9 with MAPT mutation) for TDP-43 pathological changes, and 45 patients with FTLD-TDP (including 12 with hexanucleotide expansion in C9ORF72 and 12 with GRN mutation), and 23 patients with motor neurone disease (3 with hexanucleotide expansion in C9ORF72), for tauopathy.
We therefore investigated 33 patients with FTLD-tau (including 9 with MAPT mutation) for TDP-43 pathological changes, and 45 patients with FTLD-TDP (including 12 with hexanucleotide expansion in C9ORF72 and 12 with GRN mutation), and 23 patients with motor neurone disease (3 with hexanucleotide expansion in C9ORF72), for tauopathy.
We therefore investigated 33 patients with FTLD-tau (including 9 with MAPT mutation) for TDP-43 pathological changes, and 45 patients with FTLD-TDP (including 12 with hexanucleotide expansion in C9ORF72 and 12 with GRN mutation), and 23 patients with motor neurone disease (3 with hexanucleotide expansion in C9ORF72), for tauopathy.
We therefore conducted a systematic review and meta-analysis to evaluate the diagnostic utility of TDP-43 detected in the cerebrospinal fluid (CSF) of patients with FTD-ALS spectrum disorder.