Combined fused in sarcoma-positive (FUS+) basophilic inclusion body disease and atypical tauopathy presenting with an amyotrophic lateral sclerosis/motor neurone disease (ALS/MND)-plus phenotype

Brait-Fahn-Schwartz Disease: A Unique Co-Occurrence of Parkinson's Disease and Amyotrophic Lateral Sclerosis

The Parkinson's disease-amyotrophic lateral sclerosis (ALS) complex typically manifests as levodopa-responsive parkinsonism, followed by ALS. It is extremely rare for Parkinson's disease and ALS to coexist without other neurological disorders. Named after the scientists who first described this overlap of two neurodegenerative conditions, it is referred to as Brait-Fahn-Schwartz disease. Given its variable presentation, increasing rarity, and lack of any diagnostic test, it poses a diagnostic challenge for physicians. We present a case of a 55-year-old Pakistani male experiencing progressive quadriparesis with spastic lower limbs and flaccid upper limbs, in addition to the cardinal features of idiopathic Parkinson's disease. Since there is currently no cure available for either Parkinson's disease or ALS, all available treatment focuses on improving quality of life, which we achieved in our patient. This case is unique in being the first incidence of Parkinson's disease-ALS complex in a novel geographic region such as Pakistan, where genetic testing and cost constraints limit the diagnosis of rare disorders. The coexistence of extrapyramidal symptoms and pyramidal symptoms is uncommon. In such situations, physicians may overlook one group of symptoms, potentially leading to a misdiagnosis. This case highlights the value of a thorough physical examination and electrodiagnostic studies and suggests the association between Parkinson's disease and ALS. This case demonstrates the significance of understanding when Parkinson's disease symptoms start to appear in patients with ALS and the need to start dopaminergic therapy in those who had Parkinson's disease features before ALS to alleviate the suffering of an individual and enhance quality of life.

Bradykinesia in motoneuron diseases

OBJECTIVE

Only few studies investigated voluntary movement abnormalities in patients with motoneuron diseases (MNDs) or their neurophysiological correlates. We aimed to kinematically assess finger tapping abnormalities in patients with amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS), as compared to healthy controls (HCs), and their relationship with motoneuron involvement.

METHODS

Fourteen ALS and 5 PLS patients were enrolled. Finger tapping was assessed by a motion analysis system. Patients underwent a central motor conduction time assessment, a motor nerve conduction study, and needle electromyography. Data were compared to those of 79 HCs using non-parametric tests. Possible relationships between clinical, kinematic, and neurophysiological data were assessed in patients.

RESULTS

As a major finding, ALS and PLS patients performed finger tapping slower than HCs. In both conditions, movement slowness correlated with muscle strength. In ALS, movement slowness also correlated with the amplitude of the compound muscle action potential recorded from the muscles involved in the task and with denervation activity. No correlations were found between slowness, measures of upper motoneuron involvement, and other clinical and neurophysiological data.

CONCLUSIONS

This study provides novel information on voluntary movement abnormalities in MNDs.

SIGNIFICANCE

The results highlight the pathophysiological role of motoneurons in generating movement slowness.

Aberrant interaction between FUS and SFPQ in neurons in a wide range of FTLD spectrum diseases

Fused in sarcoma (FUS) is genetically and clinicopathologically linked to frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). We have previously reported that intranuclear interactions of FUS and splicing factor, proline- and glutamine-rich (SFPQ) contribute to neuronal homeostasis. Disruption of the FUS-SFPQ interaction leads to an increase in the ratio of 4-repeat tau (4R-tau)/3-repeat tau (3R-tau), which manifests in FTLD-like phenotypes in mice. Here, we examined FUS-SFPQ interactions in 142 autopsied individuals with FUS-related ALS/FTLD (ALS/FTLD-FUS), TDP-43-related ALS/FTLD (ALS/FTLD-TDP), progressive supranuclear palsy, corticobasal degeneration, Alzheimer's disease, or Pick's disease as well as controls. Immunofluorescent imaging showed impaired intranuclear co-localization of FUS and SFPQ in neurons of ALS/FTLD-FUS, ALS/FTLD-TDP, progressive supranuclear palsy and corticobasal degeneration cases, but not in Alzheimer's disease or Pick's disease cases. Immunoprecipitation analyses of FUS and SFPQ revealed reduced interactions between the two proteins in ALS/FTLD-TDP and progressive supranuclear palsy cases, but not in those with Alzheimer disease. Furthermore, the ratio of 4R/3R-tau was elevated in cases with ALS/FTLD-TDP and progressive supranuclear palsy, but was largely unaffected in cases with Alzheimer disease. We concluded that impaired interactions between intranuclear FUS and SFPQ and the subsequent increase in the ratio of 4R/3R-tau constitute a common pathogenesis pathway in FTLD spectrum diseases.

Alterations in Tau Metabolism in ALS and ALS-FTSD

There is increasing acceptance that amyotrophic lateral sclerosis (ALS), classically considered a neurodegenerative disease affecting almost exclusively motor neurons, is syndromic with both clinical and biological heterogeneity. This is most evident in its association with a broad range of neuropsychological, behavioral, speech and language deficits [collectively termed ALS frontotemporal spectrum disorder (ALS-FTSD)]. Although the most consistent pathology of ALS and ALS-FTSD is a disturbance in TAR DNA binding protein 43 kDa (TDP-43) metabolism, alterations in microtubule-associated tau protein (tau) metabolism can also be observed in ALS-FTSD, most prominently as pathological phosphorylation at Thr¹⁷⁵ (pThr¹⁷⁵tau). pThr¹⁷⁵ has been shown to promote exposure of the phosphatase activating domain (PAD) in the tau N-terminus with the consequent activation of GSK3β mediated phosphorylation at Thr²³¹ (pThr²³¹tau) leading to pathological oligomer formation. This pathological cascade of tau phosphorylation has been observed in chronic traumatic encephalopathy with ALS (CTE-ALS) and in both in vivo and in vitro experimental paradigms, suggesting that it is of critical relevance to the pathobiology of ALS-FTSD. It is also evident that the co-existence of alterations in the metabolism of TDP-43 and tau acts synergistically in a rodent model to exacerbate the pathology of either.

Untangling the origin and function of granulovacuolar degeneration bodies in neurodegenerative proteinopathies

In the brains of tauopathy patients, tau pathology coincides with the presence of granulovacuolar degeneration bodies (GVBs) both at the regional and cellular level. Recently, it was shown that intracellular tau pathology causes GVB formation in experimental models thus explaining the strong correlation between these neuropathological hallmarks in the human brain. These novel models of GVB formation provide opportunities for future research into GVB biology, but also urge reevaluation of previous post-mortem observations. Here, we review neuropathological data on GVBs in tauopathies and other neurodegenerative proteinopathies. We discuss the possibility that intracellular aggregates composed of proteins other than tau are also able to induce GVB formation. Furthermore, the potential mechanisms of GVB formation and the downstream functional implications hereof are outlined in view of the current available data. In addition, we provide guidelines for the identification of GVBs in tissue and cell models that will help to facilitate and streamline research towards the elucidation of the role of these enigmatic and understudied structures in neurodegeneration.

Synergistic toxicity in an in vivo model of neurodegeneration through the co-expression of human TDP-43M337V and tauT175D protein

Although it has been suggested that the co-expression of multiple pathological proteins associated with neurodegeneration may act synergistically to induce more widespread neuropathology, experimental evidence of this is sparse. We have previously shown that the expression of Thr¹⁷⁵Asp-tau (tau^T175D) using somatic gene transfer with a stereotaxically-injected recombinant adeno-associated virus (rAAV9) vector induces tau pathology in rat hippocampus. In this study, we have examined whether the co-expression of human tau^T175D with mutant human TDP-43 (TDP-43^M337V) will act synergistically. Transgenic female Sprague-Dawley rats that inducibly express mutant human TDP-43^M337V using the choline acetyltransferase (ChAT) tetracycline response element (TRE) driver with activity modulating tetracycline-controlled transactivator (tTA) were utilized in these studies. Adult rats were injected with GFP-tagged tau protein constructs in a rAAV9 vector through bilateral stereotaxic injection into the hippocampus. Injected tau constructs were: wild-type GFP-tagged 2N4R human tau (tau^WT; n = 8), GFP-tagged tau^T175D 2N4R human tau (tau^T175D, pseudophosphorylated, toxic variant, n = 8), and GFP (control, n = 8). Six months post-injection, mutant TDP-43^M337V expression was induced for 30 days. Behaviour testing identified motor deficits within 3 weeks after TDP-43 expression irrespective of tau expression, though social behaviour and sensorimotor gating remained unchanged. Increased tau pathology was observed in the hippocampus of both tau^WT and tau^T175D expressing rats and tau^T175D pathology was increased in the presence of cholinergic neuronal expression of human TDP-43^M337V. These data indicate that co-expression of pathological TDP-43 and tau protein exacerbate the pathology associated with either individual protein.