Novel VCP mutations in inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia

Sex influences clinical phenotype in valosin-containing protein mutations: A case family report and systematic literature review

OBJECTIVE

Mutations in the valosin-containing protein (VCP) gene cause autosomal dominant multisystem proteinopathy 1 (MSP1), characterized by a variable combination of inclusion body myopathy (IBM), Paget's disease of bone (PDB), and frontotemporal dementia (FTD). Here we report a novel VCP missense mutations in an Italian family with FTD as the prevalent manifestation and compare our results with those described in the literature.

METHODS

We described the clinical, molecular, and imaging data of the studied family. We also conducted a systematic literature search with the aim of comparing our findings with previously reported VCP-related phenotypes.

RESULTS

A novel heterozygous VCP missense mutation (c 0.473 T > C/p.Met158Thr) was found in all the affected family members. The proband is a 69-year-old man affected by progressive muscle weakness since the age of 49. Muscle MRI showed patchy fatty infiltration in most muscles, and STIR sequences revealed an unusual signal increase in distal leg muscles. At age 65, he presented a cognitive disorder suggestive of behavioral variant FTD. A bone scintigraphy also revealed PDB. The patient's mother, his maternal aunt and her daughter had died following a history of cognitive deterioration consistent with FTD; the mother also had PDB. No relatives had any muscular impairments. Reviewing the literature data, we observed a different sex distribution of VCP-related phenotypes, being FTD prevalence higher among women as compared to men (51.2 % vs 31.2 %) and IBM prevalence higher among men as compared to women (92.1 % vs 72.8 %).

DISCUSSION

This study broadened our clinical, genetic, and imaging knowledge of VCP-related disorders.

Valosin containing protein (VCP): initiator, modifier, and potential drug target for neurodegenerative diseases

The AAA+ ATPase valosin containing protein (VCP) is essential for cell and organ homeostasis, especially in cells of the nervous system. As part of a large network, VCP collaborates with many cofactors to ensure proteostasis under normal, stress, and disease conditions. A large number of mutations have revealed the importance of VCP for human health. In particular, VCP facilitates the dismantling of protein aggregates and the removal of dysfunctional organelles. These are critical events to prevent malfunction of the brain and other parts of the nervous system. In line with this idea, VCP mutants are linked to the onset and progression of neurodegeneration and other diseases. The intricate molecular mechanisms that connect VCP mutations to distinct brain pathologies continue to be uncovered. Emerging evidence supports the model that VCP controls cellular functions on multiple levels and in a cell type specific fashion. Accordingly, VCP mutants derail cellular homeostasis through several mechanisms that can instigate disease. Our review focuses on the association between VCP malfunction and neurodegeneration. We discuss the latest insights in the field, emphasize open questions, and speculate on the potential of VCP as a drug target for some of the most devastating forms of neurodegeneration.

Frontotemporal Dementia, Where Do We Stand? A Narrative Review

Frontotemporal dementia (FTD) is a neurodegenerative disease of growing interest, since it accounts for up to 10% of middle-age-onset dementias and entails a social, economic, and emotional burden for the patients and caregivers. It is characterised by a (at least initially) selective degeneration of the frontal and/or temporal lobe, generally leading to behavioural alterations, speech disorders, and psychiatric symptoms. Despite the recent advances, given its extreme heterogeneity, an overview that can bring together all the data currently available is still lacking. Here, we aim to provide a state of the art on the pathogenesis of this disease, starting with established findings and integrating them with more recent ones. In particular, advances in the genetics field will be examined, assessing them in relation to both the clinical manifestations and histopathological findings, as well as considering the link with other diseases, such as amyotrophic lateral sclerosis (ALS). Furthermore, the current diagnostic criteria will be explored, including neuroimaging methods, nuclear medicine investigations, and biomarkers on biological fluids. Of note, the promising information provided by neurophysiological investigations, i.e., electroencephalography and non-invasive brain stimulation techniques, concerning the alterations in brain networks and neurotransmitter systems will be reviewed. Finally, current and experimental therapies will be considered.

Novel Variants in the VCP Gene Causing Multisystem Proteinopathy 1

Valosin-containing protein (VCP) gene mutations have been associated with a rare autosomal dominant, adult-onset progressive disease known as multisystem proteinopathy 1 (MSP1), or inclusion body myopathy (IBM), Paget's disease of bone (PDB), frontotemporal dementia (FTD), (IBMPFD), and amyotrophic lateral sclerosis (ALS). We report the clinical and genetic analysis findings in five patients, three from the same family, with novel VCP gene variants: NM_007126.5 c.1106T>C (p.I369T), c.478G>A (p.A160T), and c.760A>T (p.I254F), associated with cardinal MSP1 manifestations including myopathy, PDB, and FTD. Our report adds to the spectrum of heterozygous pathogenic variants found in the VCP gene and the high degree of clinical heterogeneity. This case series prompts increased awareness and early consideration of MSP1 in the differential diagnosis of myopathies and/or PDB, dementia, or ALS to improve the diagnosis and early management of clinical symptoms.

The p97-UBXD8 complex regulates ER-Mitochondria contact sites by altering membrane lipid saturation and composition

The intimate association between the endoplasmic reticulum (ER) and mitochondrial membranes at ER-Mitochondria contact sites (ERMCS) is a platform for critical cellular processes, particularly lipid synthesis. How contacts are remodeled and the impact of altered contacts on lipid metabolism remains poorly understood. We show that the p97 AAA-ATPase and its adaptor ubiquitin-X domain adaptor 8 (UBXD8) regulate ERMCS. The p97-UBXD8 complex localizes to contacts and its loss increases contacts in a manner that is dependent on p97 catalytic activity. Quantitative proteomics and lipidomics of ERMCS demonstrates alterations in proteins regulating lipid metabolism and a significant change in membrane lipid saturation upon UBXD8 deletion. Loss of p97-UBXD8 increased membrane lipid saturation via SREBP1 and the lipid desaturase SCD1. Aberrant contacts can be rescued by unsaturated fatty acids or overexpression of SCD1. We find that the SREBP1-SCD1 pathway is negatively impacted in the brains of mice with p97 mutations that cause neurodegeneration. We propose that contacts are exquisitely sensitive to alterations to membrane lipid composition and saturation.

Multisystem Proteinopathy Due to VCP Mutations: A Review of Clinical Heterogeneity and Genetic Diagnosis

In this work, we review clinical features and genetic diagnosis of diseases caused by mutations in the gene encoding valosin-containing protein (VCP/p97), the functionally diverse AAA-ATPase. VCP is crucial to a multitude of cellular functions including protein quality control, stress granule formation and clearance, and genomic integrity functions, among others. Pathogenic mutations in VCP cause multisystem proteinopathy (VCP-MSP), an autosomal dominant, adult-onset disorder causing dysfunction in several tissue types. It can result in complex neurodegenerative conditions including inclusion body myopathy, frontotemporal dementia, amyotrophic lateral sclerosis, or combinations of these. There is also an association with other neurodegenerative phenotypes such as Alzheimer-type dementia and Parkinsonism. Non-neurological presentations include Paget disease of bone and may also include cardiac dysfunction. We provide a detailed discussion of genotype-phenotype correlations, recommendations for genetic diagnosis, and genetic counselling implications of VCP-MSP.

Valosin-containing protein (VCP) regulates the stability of fused in sarcoma (FUS) granules in cells by changing ATP concentrations

Fused in sarcoma (FUS), a DNA/RNA-binding protein, undergoes liquid-liquid phase separation to form granules in cells. Aberrant FUS granulation is associated with neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal lobar degeneration. We found that FUS granules contain a multifunctional AAA ATPase, valosin-containing protein (VCP), which is known as a key regulator of protein degradation. FUS granule stability depends on ATP concentrations in cells. VCP ATPase changes the FUS granule stability time-dependently by consuming ATP to reduce its concentrations in the granules: VCPs in de novo FUS granules stabilize the granules, while long-lasting VCP colocalization destabilizes the granules. The proteolysis-promoting function of VCP may subsequently dissolve the unstabilized granules. We propose that VCP colocalized to the FUS granules acts as a timer to limit the residence time of the granules in cells.

Clinical, Biochemical, Radiological, and Genetic Analyses of a Patient with VCP Gene Variant-Induced Paget's Disease of Bone

Paget's disease of bone (PDB) is a rare metabolic bone disorder, which is extremely rare in Asian population. This study aimed to investigate the phenotypes and the pathogenic mutations of woman with early-onset PDB. The clinical features, bone mineral density, x-ray, radionuclide bone scan, and serum levels of alkaline phosphatase (ALP), procollagen type 1 N-terminal propeptide (P1NP), and β-carboxy-terminal cross-linked telopeptide of type 1 collagen (β-CTX) were measured in detail. The pathogenic mutations were identified by whole-exon sequencing and confirmed by Sanger sequencing. We also evaluated the effects of intravenous infusion of zoledronic acid on the bones of the patient and summarized the phenotypic characteristics of reported patients with mutation at position 155 of the valosin-containing protein (VCP). The patient only exhibited bone pain as the initial manifestation with vertebral compression fracture and extremely elevated ALP, P1NP, and β-CTX levels; she had no inclusion body myopathy and frontotemporal dementia. The missense mutation in exon 5 of the VCP gene (p.Arg155His) was identified by whole-exome sequencing and further confirmed by Sanger sequencing. No mutation in candidate genes of PDB, such as SQSTM1, CSF1, TM7SF4, OPTN, PFN1, and TNFRSF11A, were identified in the patient by Sanger sequencing. Rapid relief of bone pain and a marked decline in ALP, P1NP, and β-CTX levels were observed after zoledronic acid treatment. Previously reported patients with VCP missense mutation at position 155 (R155H) always had myopathy, frontotemporal dementia, and PDB, but the patient in this study exhibited only PDB. This was the first report of R155H mutation-induced early-onset in the VCP gene in Asian population. PDB was the only manifestation having a favorable response to zoledronic acid treatment. We broadened the genetic and clinical phenotype spectra of the VCP mutation.

Frontotemporal Dementia and Glucose Metabolism

Frontotemporal dementia (FTD), hallmarked by antero-temporal degeneration in the human brain, is the second most common early onset dementia. FTD is a diverse disease with three main clinical presentations, four different identified proteinopathies and many disease-associated genes. The exact pathophysiology of FTD remains to be elucidated. One common characteristic all forms of FTD share is the dysregulation of glucose metabolism in patients’ brains. The brain consumes around 20% of the body’s energy supply and predominantly utilizes glucose as a fuel. Glucose metabolism dysregulation could therefore be extremely detrimental for neuronal health. Research into the association between glucose metabolism and dementias has recently gained interest in Alzheimer’s disease. FTD also presents with glucose metabolism dysregulation, however, this remains largely an unexplored area. A better understanding of the link between FTD and glucose metabolism may yield further insight into FTD pathophysiology and aid the development of novel therapeutics. Here we review our current understanding of FTD and glucose metabolism in the brain and discuss the evidence of impaired glucose metabolism in FTD. Lastly, we review research potentially suggesting a causal relationship between FTD proteinopathies and impaired glucose metabolism in FTD.

Valosin Containing Protein (VCP): A Multistep Regulator of Autophagy

Valosin containing protein (VCP) has emerged as a central protein in the regulation of the protein quality control (PQC) system. VCP mutations are causative of multisystem proteinopathies, which include neurodegenerative diseases (NDs), and share various signs of altered proteostasis, mainly associated with autophagy malfunctioning. Autophagy is a complex multistep degradative system essential for the maintenance of cell viability, especially in post-mitotic cells as neurons and differentiated skeletal muscle cells. Interestingly, many studies concerning NDs have focused on autophagy impairment as a pathological mechanism or autophagy activity boosting to rescue the pathological phenotype. The role of VCP in autophagy has been widely debated, but recent findings have defined new mechanisms associated with VCP activity in the regulation of autophagy, showing that VCP is involved in different steps of this pathway. Here we will discuss the multiple activity of VCP in the autophagic pathway underlying its leading role either in physiological or pathological conditions. A better understanding of VCP complexes and mechanisms in regulating autophagy could define the altered mechanisms by which VCP directly or indirectly causes or modulates different human diseases and revealing possible new therapeutic approaches for NDs.

A Novel Mutation (D395A) in Valosin-Containing Protein Gene Is Associated With Early Onset Frontotemporal Dementia in an Italian Family

Inclusion body myopathy (IBM) with Paget's disease of bone (PDB) and/or frontotemporal dementia (FTD) (IBMPFD) was recently identified as rare autosomal dominant disorder due to mutations in VCP gene. However, VCP mutations have also been documented in patients with amyotrophic lateral sclerosis (ALS), Charcot-Marie-Tooth type 2 (CMT2) disease, and hereditary spastic paraplegia (HSP), underlining the heterogeneity of the phenotypes due to VCP mutations. In this study, we reported a novel missense heterozygous variant c.1184A > C (p.D395A) in exon 10 of VCP gene identified in three patients (two sisters and one brother) belonging to an Italian family. The patients underwent a detailed clinical evaluation including medical history, neurological examination, and neuropsychological assessment. Brain's morphologic and functional analysis was also performed. The whole picture was consistent with the criteria of behavioral variant frontotemporal dementia (bvFTD) without IBM and PBD. Our report confirms the high degree of heterogeneity of VCP disease. A VCP analysis should be considered for the genetic screening of familial bvFTD with an early onset also in absence of IBM or PDB signs.

The molecular and cellular basis of copper dysregulation and its relationship with human pathologies

Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu⁺ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.

Characteristics of VCP mutation-associated cardiomyopathy

VCP associated inclusion body myopathy, Paget's disease of bone, and Frontotemporal Dementia (IBMPFD, VCP disease, or multisystem proteinopathy type 1 (MSP1)) is an autosomal dominant disease caused by missense mutations in the VCP gene, which plays a crucial role in ubiquitin-proteasome dependent degradation of cytosolic proteins. Those diagnosed with the disorder often suffer from cardiovascular complications in the advanced stages. We conducted an observational cross-section study to investigate echocardiographic features of asymptomatic carriers and those affected by the disease to determine the differences and potential early features of the VCP-associated cardiomyopathy. The study cohort constituted of 32 patients with VCP mutations including 23 affected individuals diagnosed with myopathy +/- Paget disease of bone, and 9 asymptomatic carriers. Among the affected individuals, 95.7% had myopathy, 43.5% had Paget's disease of bone, and none had frontotemporal dementia, and the carriers were asymptomatic. Not surprisingly the carriers were younger (mean age 38.4 ± 3.8 years), than the affected cohort (mean age 50.6 ± 9.1 years; p < 0.001). There was a 43.5% prevalence of diastolic dysfunction on echocardiogram among patients who were symptomatic from VCP disease, whereas none of the two asymptomatic carriers manifested diastolic dysfunction (p = 0.017). Among the 5 affected individuals who had consequential echocardiograms 2-3 years apart, three affected individuals developed diastolic dysfunction, and two already had diastolic dysfunction on the initial study. The two carriers did not develop diastolic function changes. This present study represents the largest series of echocardiograms performed in patients and asymptomatic carriers with VCP myopathy, and will pave the way for future, large-scale studies that may include other imaging modalities such as cardiac MRI and strain evaluation in patients at all stages of the disease.

An autopsy report of a familial amyotrophic lateral sclerosis case carrying VCP Arg487His mutation with a unique TDP-43 proteinopathy

We here report an autopsy case of familial amyotrophic lateral sclerosis (ALS) with p.Arg487His mutation in the valosin-containing protein (VCP) gene (VCP), in which upper motor neurons (UMNs) were predominantly involved. Moreover, our patient developed symptoms of frontotemporal dementia later in life and pathologically exhibited numerous phosphorylated transactivation response DNA-binding protein of 43 kDa (p-TDP-43)-positive neuronal cytoplasmic inclusions and short dystrophic neurites with a few lentiform neuronal intranuclear inclusions, sharing the features of frontotemporal lobar degeneration with TDP-43 pathology type A pattern. A review of previous reports of ALS with VCP mutations suggests that our case is unique in terms of its UMN-predominant lesion pattern and distribution of p-TDP-43 pathology. Thus, this case report effectively expands the clinical and pathological phenotype of ALS in patients with a VCP mutation.

The M1311V variant of ATP7A is associated with impaired trafficking and copper homeostasis in models of motor neuron disease

Disruption in copper homeostasis causes a number of cognitive and motor deficits. Wilson's disease and Menkes disease are neurodevelopmental disorders resulting from mutations in the copper transporters ATP7A and ATP7B, with ATP7A mutations also causing occipital horn syndrome, and distal motor neuropathy. A 65 year old male presenting with brachial amyotrophic diplegia and diagnosed with amyotrophic lateral sclerosis (ALS) was found to harbor a p.Met1311Val (M1311V) substitution variant in ATP7A. ALS is a fatal neurodegenerative disease associated with progressive muscle weakness, synaptic deficits and degeneration of upper and lower motor neurons. To investigate the potential contribution of the ATP7A^M1311V variant to neurodegeneration, we obtained and characterized both patient-derived fibroblasts and patient-derived induced pluripotent stem cells differentiated into motor neurons (iPSC-MNs), and compared them to control cell lines. We found reduced localization of ATP7A^M1311V to the trans-Golgi network (TGN) at basal copper levels in patient-derived fibroblasts and iPSC-MNs. In addition, redistribution of ATP7A^M1311V out of the TGN in response to increased extracellular copper was defective in patient fibroblasts. This manifested in enhanced intracellular copper accumulation and reduced survival of ATP7A^M1311V fibroblasts. iPSC-MNs harboring the ATP7A^M1311V variant showed decreased dendritic complexity, aberrant spontaneous firing, and decreased survival. Finally, expression of the ATP7A^M1311V variant in Drosophila motor neurons resulted in motor deficits. Apilimod, a drug that targets vesicular transport and recently shown to enhance survival of C9orf72-ALS/FTD iPSC-MNs, also increased survival of ATP7A^M1311V iPSC-MNs and reduced motor deficits in Drosophila expressing ATP7A^M1311V. Taken together, these observations suggest that ATP7A^M1311V negatively impacts its role as a copper transporter and impairs several aspects of motor neuron function and morphology.

Modelling frontotemporal dementia using patient-derived induced pluripotent stem cells

Frontotemporal dementia (FTD) describes a group of clinically heterogeneous conditions that frequently affect people under the age of 65 (Le Ber et al., 2013). There are multiple genetic causes of FTD, including coding or splice-site mutations in MAPT, GRN mutations that lead to haploinsufficiency of progranulin protein, and a hexanucleotide GGGGCC repeat expansion in C9ORF72. Pathologically, FTD is characterised by abnormal protein accumulations in neurons and glia. These aggregates can be composed of the microtubule-associated protein tau (observed in FTD with MAPT mutations), the DNA/RNA-binding protein TDP-43 (seen in FTD with mutations in GRN or C9ORF72 repeat expansions) or dipeptide proteins generated by repeat associated non-ATG translation of the C9ORF72 repeat expansion. There are currently no disease-modifying therapies for FTD and the availability of in vitro models that recapitulate pathologies in a disease-relevant cell type would accelerate the development of novel therapeutics. It is now possible to generate patient-specific stem cells through the reprogramming of somatic cells from a patient with a genotype/phenotype of interest into induced pluripotent stem cells (iPSCs). iPSCs can subsequently be differentiated into a plethora of cell types including neurons, astrocytes and microglia. Using this approach has allowed researchers to generate in vitro models of genetic FTD in human cell types that are largely inaccessible during life. In this review we explore the recent progress in the use of iPSCs to model FTD, and consider the merits, limitations and future prospects of this approach.

Pathomechanism Heterogeneity in the Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Disease Spectrum: Providing Focus Through the Lens of Autophagy

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) constitute aggressive neurodegenerative pathologies that lead to the progressive degeneration of upper and lower motor neurons and of neocortical areas, respectively. In the past decade, the identification of several genes that cause these disorders indicated that the two diseases overlap in a multifaceted spectrum of conditions. The autophagy-lysosome system has been identified as a main intersection for the onset and progression of neurodegeneration in ALS/FTD. Genetic evidence has revealed that several genes with a mechanistic role at different stages of the autophagy process are mutated in patients with ALS/FTD. Moreover, the three main proteins aggregating in ALS/FTD, including in sporadic cases, are also targeted by autophagy and affect this process. Here, we examine the varied dysfunctions and degrees of involvement of the autophagy-lysosome system that have been discovered in ALS/FTD. We argue that these findings shed light on the pathological mechanisms in the ALS/FTD spectrum and conclude that they have important consequences both for treatment options and for the basic biomolecular understanding of how this process intersects with RNA metabolism, the other major cellular process reported to be dysfunctional in part of the ALS/FTD spectrum.

[Molecular mechanism of amyotrophic lateral sclerosis (ALS) from the viewpoint of the formation and degeneration of transactive response DNA-binding protein 43 kDa (TDP-43) inclusions]

Sporadic amyotrophic lateral sclerosis (SALS) and many cases of familial ALS (FALS) demonstrate cytoplasmic transactive response DNA-binding protein 43 kDa (TDP-43)-positive inclusion bodies. Thus, TDP-43 plays a vital role in ALS pathogenesis. Functional analysis of the ALS causative genes advanced the elucidation of the mechanism associated with the formation and degradation of TDP-43 aggregates. Stress granules, which are non-membranous organelles, are attracting attention as sites of aggregate formation, with involvement of FUS and C9orf72. Concurrently, ALS causative genes related to the ubiquitin-proteasome and autophagy systems, which are aggregate degradation mechanisms, have also been reported. Therefore, therapeutic research based on the molecular pathology common to SALS and FALS has been advanced.

SQSTM1/p62 variants in 486 patients with familial ALS from Germany and Sweden

Several studies reported amyotrophic lateral sclerosis (ALS)-linked mutations in TBK1, OPTN, VCP, UBQLN2, and SQSTM1 genes encoding proteins involved in autophagy. SQSTM1 was originally identified by a candidate gene approach because it encodes p62, a multifunctional protein involved in protein degradation both through proteasomal regulation and autophagy. Both p62 and optineurin (encoded by OPTN) are direct interaction partners and substrates of TBK1, and these 3 proteins form the core of a genetic and functional network that may connect autophagy with ALS. Considering the molecular and conceptual relevance of the TBK1/OPTN/SQSTM1 "triangle," we here performed a targeted screen for SQSTM1 variants in 486 patients with familial ALS from Germany and Sweden by analyzing whole-exome sequencing data. We report 9 novel and 5 previously reported rare variants in SQSTM1 and discuss the current evidence for SQSTM1 as a primary disease gene for ALS. We conclude that the evidence for causality remains vague for SQSTM1 and is weaker than for the other autophagy genes, for example, TBK1 and OPTN.

VCP/p97 controls signals of the ERK1/2 pathway transmitted via the Shoc2 scaffolding complex: novel insights into IBMPFD pathology

Valosin-containing protein (VCP), also named p97, is an essential hexameric AAA+ ATPase with diverse functions in the ubiquitin system. Here we demonstrate that VCP is critical in controlling signals transmitted via the essential Shoc2-ERK1/2 signaling axis. The ATPase activity of VCP modulates the stoichiometry of HUWE1 in the Shoc2 complex as well as HUWE1-mediated allosteric ubiquitination of the Shoc2 scaffold and the RAF-1 kinase. Abrogated ATPase activity leads to augmented ubiquitination of Shoc2/RAF-1 and altered phosphorylation of RAF-1. We found that in fibroblasts from patients with inclusion body myopathy with Paget’s disease of bone and frontotemporal dementia (IBMPFD) that harbor germline mutations in VCP, the levels of Shoc2 ubiquitination and ERK1/2 phosphorylation are imbalanced. This study provides a mechanistic basis for the critical role of VCP in the regulation of the ERK1/2 pathway and reveals a previously unrecognized function of the ERK1/2 pathway in the pathogenesis of IBMPFD.

Autophagy as a common pathway in amyotrophic lateral sclerosis

Age-dependent neurodegenerative diseases are associated with a decline in protein quality control systems including autophagy. Amyotrophic lateral sclerosis (ALS) is a motor neuron degenerative disease of complex etiology with increasing connections to other neurodegenerative conditions such as frontotemporal dementia. Among the diverse genetic causes for ALS, a striking feature is the common connection to autophagy and its associated pathways. There is a recurring theme of protein misfolding as in other neurodegenerative diseases, but importantly there is a distinct common thread among ALS genes that connects them to the cascade of autophagy. However, the roles of autophagy in ALS remain enigmatic and it is still unclear whether activation or inhibition of autophagy would be a reliable avenue to ameliorate the disease. The main evidence that links autophagy to different genetic forms of ALS is discussed.

Genotype-phenotype study in patients with valosin-containing protein mutations associated with multisystem proteinopathy

Mutations in valosin-containing protein (VCP), an ATPase involved in protein degradation and autophagy, cause VCP disease, a progressive autosomal dominant adult onset multisystem proteinopathy. The goal of this study is to examine if phenotypic differences in this disorder could be explained by the specific gene mutations. We therefore studied 231 individuals (118 males and 113 females) from 36 families carrying 15 different VCP mutations. We analyzed the correlation between the different mutations and prevalence, age of onset and severity of myopathy, Paget's disease of bone (PDB), and frontotemporal dementia (FTD), and other comorbidities. Myopathy, PDB and FTD was present in 90%, 42% and 30% of the patients, respectively, beginning at an average age of 43, 41, and 56 years, respectively. Approximately 9% of patients with VCP mutations had an amyotrophic lateral sclerosis (ALS) phenotype, 4% had been diagnosed with Parkinson's disease (PD), and 2% had been diagnosed with Alzheimer's disease (AD). Large interfamilial and intrafamilial variation made establishing correlations difficult. We did not find a correlation between the mutation type and the incidence of any of the clinical features associated with VCP disease, except for the absence of PDB with the R159C mutation in our cohort and R159C having a later age of onset of myopathy compared with other molecular subtypes.

Genetics of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating, uniformly lethal degenerative disorder of motor neurons that overlaps clinically with frontotemporal dementia (FTD). Investigations of the 10% of ALS cases that are transmitted as dominant traits have revealed numerous gene mutations and variants that either cause these disorders or influence their clinical phenotype. The evolving understanding of the genetic architecture of ALS has illuminated broad themes in the molecular pathophysiology of both familial and sporadic ALS and FTD. These central themes encompass disturbances of protein homeostasis, alterations in the biology of RNA binding proteins, and defects in cytoskeletal dynamics, as well as numerous downstream pathophysiological events. Together, these findings from ALS genetics provide new insight into therapies that target genetically distinct subsets of ALS and FTD.

Novel valosin-containing protein mutations associated with multisystem proteinopathy

Over fifty missense mutations in the gene coding for valosin-containing protein (VCP) are associated with a unique autosomal dominant adult-onset progressive disease associated with combinations of proximo-distal inclusion body myopathy (IBM), Paget's disease of bone (PDB), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS). We report the clinical, histological, and molecular findings in four new patients/families carrying novel VCP mutations: c.474 G > A (p.M158I); c.478 G > C (p.A160P); c.383G > C (p.G128A); and c.382G > T (p.G128C). Clinical features included myopathy, PDB, ALS and Parkinson's disease though frontotemporal dementia was not an associated feature in these families. One of the patients was noted to have severe manifestations of PDB and was suspected of having neoplasia. There were wide inter- and intra-familial variations making genotype-phenotype correlations difficult between the novel mutations and frequency or age of onset of IBM, PDB, FTD, ALS and Parkinson's disease. Increasing awareness of the full spectrum of clinical presentations will improve diagnosis of VCP-related diseases and thus proactively manage or prevent associated clinical features such as PDB.

Interaction between the AAA ATPase p97/VCP and a concealed UBX domain in the copper transporter ATP7A is associated with motor neuron degeneration

The copper-transporting ATPase ATP7A contains eight transmembrane domains and is required for normal human copper homeostasis. Mutations in the ATP7A gene may lead to infantile-onset cerebral degeneration (Menkes disease); occipital horn syndrome (OHS), a related but much milder illness; or an adult-onset isolated distal motor neuropathy. The ATP7A missense mutation T994I is located in the sixth transmembrane domain of ATP7A, represents one of the variants associated with the latter phenotype, and is associated with an abnormal interaction with p97/valosin-containing protein (VCP), a hexameric AAA ATPase (ATPase associated with diverse cellular activities) with multiple biological functions. In this study, we further characterized this interaction and discovered a concealed UBX domain in the third lumenal loop of ATP7A, between its fifth and sixth transmembrane domains. We show that the T994I substitution results in conformational exposure of the UBX domain, which then binds the N-terminal domain of p97/VCP. We also show that this abnormal interaction occurs at or near the cell plasma membrane. The UBX domain has a conserved hydrophobic FP (Phe-Pro) motif, and substitution with di-alanine abrogated the interaction and restored the proper intracellular localization of ATP7A in the trans-Golgi network. Using protein MS, we identified potential coordinating components of the ATP7A^T994I-p97 complex, including NSFL1 cofactor (NSF1C or p47) that may be relevant to the pathophysiology and clinical effects associated with ATP7A^T994I Our study represents the first report of p97/VCP binding to a UBX domain that is not normally exposed, resulting in an aberrant protein-protein interaction leading to motor neuron degeneration.

Interaction between the AAA+ ATPase p97 and its cofactor ataxin3 in health and disease: Nucleotide-induced conformational changes regulate cofactor binding

p97 is an essential ATPase associated with various cellular activities (AAA⁺) that functions as a segregase in diverse cellular processes, including the maintenance of proteostasis. p97 interacts with different cofactors that target it to distinct pathways; an important example is the deubiquitinase ataxin3, which collaborates with p97 in endoplasmic reticulum-associated degradation. However, the molecular details of this interaction have been unclear. Here, we characterized the binding of ataxin3 to p97, showing that ataxin3 binds with low-micromolar affinity to both wild-type p97 and mutants linked to degenerative disorders known as multisystem proteinopathy 1 (MSP1); we further showed that the stoichiometry of binding is one ataxin3 molecule per p97 hexamer. We mapped the binding determinants on each protein, demonstrating that ataxin3's p97/VCP-binding motif interacts with the inter-lobe cleft in the N-domain of p97. We also probed the nucleotide dependence of this interaction, confirming that ataxin3 and p97 associate in the presence of ATP and in the absence of nucleotide, but not in the presence of ADP. Our experiments suggest that an ADP-driven downward movement of the p97 N-terminal domain dislodges ataxin3 by inducing a steric clash between the D1-domain and ataxin3's C terminus. In contrast, MSP1 mutants of p97 bind ataxin3 irrespective of their nucleotide state, indicating a failure by these mutants to translate ADP binding into a movement of the N-terminal domain. Our model provides a mechanistic explanation for how nucleotides regulate the p97-ataxin3 interaction and why atypical cofactor binding is observed with MSP1 mutants.

A clinicopathological approach to the diagnosis of dementia

The most definitive classification systems for dementia are based on the underlying pathology which, in turn, is categorized largely according to the observed accumulation of abnormal protein aggregates in neurons and glia. These aggregates perturb molecular processes, cellular functions and, ultimately, cell survival, with ensuing disruption of large-scale neural networks subserving cognitive, behavioural and sensorimotor functions. The functional domains affected and the evolution of deficits in these domains over time serve as footprints that the clinician can trace back with various levels of certainty to the underlying neuropathology. The process of phenotyping and syndromic classification has substantially improved over decades of careful clinicopathological correlation, and through the discovery of in vivo biomarkers of disease. Here, we present an overview of the salient features of the most common dementia subtypes - Alzheimer disease, vascular dementia, frontotemporal dementia and related syndromes, Lewy body dementias, and prion diseases - with an emphasis on neuropathology, relevant epidemiology, risk factors, and signature signs and symptoms.

Myogenic differentiation of VCP disease-induced pluripotent stem cells: A novel platform for drug discovery

Valosin Containing Protein (VCP) disease is an autosomal dominant multisystem proteinopathy caused by mutations in the VCP gene, and is primarily associated with progressive muscle weakness, including atrophy of the pelvic and shoulder girdle muscles. Currently, no treatments are available and cardiac and respiratory failures can lead to mortality at an early age. VCP is an AAA ATPase multifunction complex protein and mutations in the VCP gene resulting in disrupted autophagic clearance. Due to the rarity of the disease, the myopathic nature of the disorder, ethical and practical considerations, VCP disease muscle biopsies are difficult to obtain. Thus, disease-specific human induced pluripotent stem cells (hiPSCs) now provide a valuable resource for the research owing to their renewable and pluripotent nature. In the present study, we report the differentiation and characterization of a VCP disease-specific hiPSCs into precursors expressing myogenic markers including desmin, myogenic factor 5 (MYF5), myosin and heavy chain 2 (MYH2). VCP disease phenotype is characterized by high expression of TAR DNA Binding Protein-43 (TDP-43), ubiquitin (Ub), Light Chain 3-I/II protein (LC3-I/II), and p62/SQSTM1 (p62) protein indicating disruption of the autophagy cascade. Treatment of hiPSC precursors with autophagy stimulators Rapamycin, Perifosine, or AT101 showed reduction in VCP pathology markers TDP-43, LC3-I/II and p62/SQSTM1. Conversely, autophagy inhibitors chloroquine had no beneficial effect, and Spautin-1 or MHY1485 had modest effects. Our results illustrate that hiPSC technology provide a useful platform for a rapid drug discovery and hence constitutes a bridge between clinical and bench research in VCP and related diseases.

Protein Quality Control and the Amyotrophic Lateral Sclerosis/Frontotemporal Dementia Continuum

Protein homeostasis, or proteostasis, has an important regulatory role in cellular function. Protein quality control mechanisms, including protein folding and protein degradation processes, have a crucial function in post-mitotic neurons. Cellular protein quality control relies on multiple strategies, including molecular chaperones, autophagy, the ubiquitin proteasome system, endoplasmic reticulum (ER)-associated degradation (ERAD) and the formation of stress granules (SGs), to regulate proteostasis. Neurodegenerative diseases are characterized by the presence of misfolded protein aggregates, implying that protein quality control mechanisms are dysfunctional in these conditions. Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative diseases that are now recognized to overlap clinically and pathologically, forming a continuous disease spectrum. In this review article, we detail the evidence for dysregulation of protein quality control mechanisms across the whole ALS-FTD continuum, by discussing the major proteins implicated in ALS and/or FTD. We also discuss possible ways in which protein quality mechanisms could be targeted therapeutically in these disorders and highlight promising protein quality control-based therapeutics for clinical trials.

Frontotemporal Dementia

Frontotemporal dementia (FTD) is a heterogeneous disorder with distinct clinical phenotypes associated with multiple neuropathologic entities. Presently, the term FTD encompasses clinical disorders that include changes in behavior, language, executive control, and often motor symptoms. The core FTD spectrum disorders include behavioral variant FTD, nonfluent/agrammatic variant primary progressive aphasia, and semantic variant PPA. Related FTD disorders include frontotemporal dementia with motor neuron disease, progressive supranuclear palsy syndrome, and corticobasal syndrome. In this article, the authors discuss the clinical presentation, diagnostic criteria, neuropathology, genetics, and treatments of these disorders.

Activation of the NLRP3 Inflammasome Is Associated with Valosin-Containing Protein Myopathy

Aberrant activation of the NOD-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome, triggers a pathogenic inflammatory response in many inherited neurodegenerative disorders. Inflammation has recently been associated with valosin-containing protein (VCP)-associated diseases, caused by missense mutations in the VCP gene. This prompted us to investigate whether NLRP3 inflammasome plays a role in VCP-associated diseases, which classically affects the muscles, bones, and brain. In this report, we demonstrate (i) an elevated activation of the NLRP3 inflammasome in VCP myoblasts, derived from induced pluripotent stem cells (iPSCs) of VCP patients, which was significantly decreased following in vitro treatment with the MCC950, a potent and specific inhibitor of NLRP3 inflammasome; (ii) a significant increase in the expression of NLRP3, caspase 1, IL-1β, and IL-18 in the quadriceps muscles of VCP^R155H/+ heterozygote mice, an experimental mouse model that has many clinical features of human VCP-associated myopathy; (iii) a significant increase of number of IL-1β⁽⁺⁾F4/80⁽⁺⁾Ly6C⁽⁺⁾ inflammatory macrophages that infiltrate the muscles of VCP^R155H/+ mice; (iv) NLRP3 inflammasome activation and accumulation IL-1β⁽⁺⁾F4/80⁽⁺⁾Ly6C⁽⁺⁾ macrophages positively correlated with high expression of TDP-43 and p62/SQSTM1 markers of VCP pathology in damaged muscle; and (v) treatment of VCP^R155H/+ mice with MCC950 inhibitor suppressed activation of NLRP3 inflammasome, reduced the F4/80⁽⁺⁾Ly6C⁽⁺⁾IL-1β⁽⁺⁾ macrophage infiltrates in the muscle, and significantly ameliorated muscle strength. Together, these results suggest that (i) NLRP3 inflammasome and local IL-1β⁽⁺⁾F4/80⁽⁺⁾Ly6C⁽⁺⁾ inflammatory macrophages contribute to pathogenesis of VCP-associated myopathy and (ii) identified MCC950 specific inhibitor of the NLRP3 inflammasome with promising therapeutic potential for the treatment of VCP-associated myopathy.

Mutations in the Human AAA+ Chaperone p97 and Related Diseases

A number of neurodegenerative diseases have been linked to mutations in the human protein p97, an abundant cytosolic AAA⁺ (ATPase associated with various cellular activities) ATPase, that functions in a large number of cellular pathways. With the assistance of a variety of cofactors and adaptor proteins, p97 couples the energy of ATP hydrolysis to conformational changes that are necessary for its function. Disease-linked mutations, which are found at the interface between two main domains of p97, have been shown to alter the function of the protein, although the pathogenic mutations do not appear to alter the structure of individual subunit of p97 or the formation of the hexameric biological unit. While exactly how pathogenic mutations alter the cellular function of p97 remains unknown, functional, biochemical and structural differences between wild-type and pathogenic mutants of p97 are being identified. Here, we summarize recent progress in the study of p97 pathogenic mutants.

One family, one gene and three phenotypes: A novel VCP (valosin-containing protein) mutation associated with myopathy with rimmed vacuoles, amyotrophic lateral sclerosis and frontotemporal dementia

BACKGROUND

VCP (valosin-containing protein gene) variants have been associated with peripheral and central neurodegenerative processes, including inclusion body myopathy (IBM), Paget disease of bone (PDB), frontotemporal dementia (FTD), and familial amyotrophic lateral sclerosis (ALS) type 14. The combination of IBM, PDB (IBMPFD1) can presented in one individual. However, the association of IBMPFD1 and ALS in the same family is rare.

METHODS

We reported three individuals from a Brazilian kindred with intrafamilial phenotype variability. Whole exome sequencing (WES) of the proband was performed and revealed a novel VCP variant. VCP Sanger sequencing was performed in the proband and his family members to confirm WES finding and segregation. We performed a systematic review of the literature regarding the genotypic-phenotypic VCP correlations.

RESULTS

Each individual presented with either myopathy with rimmed vacuoles, ALS, or FTD. There was no PDB. WES of the proband identified the heterozygous variant c.271A>T (p.Asn91Tyr) in the exon 3 of VCP. Sanger sequencing confirmed the segregation of this variant in an autosomal-dominant pattern.

CONCLUSION

This study expands the genotypic spectrum of the missense mutations of the VCP gene with a novel p.Asn91Tyr variant found in a Brazilian family presenting with the unusual intrafamiliar association of myopathy with rimmed vacuoles, ALS and FTD.

Delineating the relationship between amyotrophic lateral sclerosis and frontotemporal dementia: Sequence and structure-based predictions

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are related neurodegenerative disorders which are characterized by a rapid decline in cognitive and motor functions, and short survival. Both syndromes may be present within the same family or even in the same person. The genetic findings for both diseases also support the existence of a continuum, with mutations in the same genes being found in patients with ALS, FTD or FTD/ALS. Little is known about the molecular mechanisms underlying the differences in mutations of the same protein causing either ALS or FTD. Here, we shed light on 348 ALS and FTD missense mutations in 14 genes focusing on genic intolerance and protein stability based on available 3D structures. Using EvoTol, we prioritized the disease-causing genes and their domain. The most intolerant genes predicted by EvoTol are SQSTM1 and OPTN which are involved in protein homeostasis. Further, using ENCoM (Elastic Network Contact Model) that predicts stability based on vibrational entropy, we predicted that most of the missense mutations with destabilizing energies are in the structural regions that control the protein-protein interaction, and only a few mutations affect protein folding. We found a trend that energy changes are higher for ALS compared to FTD mutations. The stability of the ALS mutants correlated well with the duration of disease progression as compared to FTD-ALS mutants. This study provides a comprehensive understanding of the mechanism of ALS and illustrates the significance of structure-energy based studies in differentiating ALS and FTD mutations.

Clinical and Electrophysiological Findings in Hereditary Inclusion Body Myopathy Compared With Sporadic Inclusion Body Myositis

OBJECTIVE

To compare the clinical and electrophysiological findings in hereditary inclusion body myopathy (hIBM) and sporadic inclusion body myositis (sIBM) patients.

METHODS

We retrospectively identified 8 genetically proven hIBM patients and 1 DNAJB6 myopathy with pathological features of hIBM, and compared their clinical, electromyographic, and serological data with a group of 51 pathologically proven sIBM patients.

RESULTS

hIBM patients had a younger mean age of onset (36 vs. 60 years, P = 0.0001). Diagnostic delay was shorter in sIBM (6 vs. 15 years, P = 0.0003). Wrist flexors (P = 0.02), digit flexors (P = 0.01), digit extensors (P = 0.02), and quadriceps (P = 0.008) muscles were more frequently affected in sIBM. Fibrillation potentials were more common in sIBM patients (P = 0.03). Electrical myotonia was found in 4 hIBM patients, not significantly different from sIBM patients (P = 0.45). Creatinine kinase was higher in sIBM patients (799 vs 232, P = 0.03).

CONCLUSIONS

sIBM and hIBM seem to have similar electromyographic changes. The combination of clinical, serological, and histopathological findings can guide genetic testing to the final diagnosis.

Clinical spectrum of valosin containing protein (VCP)-opathy

INTRODUCTION

Valosin containing protein (VCP) mutations cause a rare disorder characterized by hereditary inclusion body myopathy, Paget disease of bone (PDB), and frontotemporal dementia (FTD) with variable penetrance. VCP mutations have also been linked to amyotrophic lateral sclerosis and Charcot-Marie-Tooth disease type 2.

METHODS

Review of clinical, serological, electrophysiological, and myopathological findings of 6 VCP-opathy patients from 4 unrelated families.

RESULTS

Patients manifested muscle weakness between ages 40 and 53 years and developed predominant asymmetric limb girdle weakness. One patient had distal weakness at onset and co-existing peripheral neuropathy. Another patient had PDB, 1 had mild cognitive deficits, and 1 had FTD. All patients had myopathic and neurogenic electromyographic findings with predominant neurogenic changes in 2. Rimmed vacuoles were infrequent, while neurogenic changes were prominent in muscle biopsies.

CONCLUSIONS

VCP-opathy is a multifaceted disorder in which myopathy and peripheral neuropathy can coexist. The electrophysiological and pathological neurogenic changes raise the possibility of coexisting motor neuron involvement. Muscle Nerve, 2015 Muscle Nerve 54: 94-99, 2016 Muscle Nerve 54: 94-99, 2016.

[A patient with familial amyotrophic lateral sclerosis associated with a new valosin-containing protein (VCP) gene mutation]

In this communication, we report a patient with familial amyotrophic lateral sclerosis (ALS) associated with a familial dyslipidemia. Genetic analysis revealed a novel heterozygous valosin-containing protein (VCP) mutation (c.466G>T (p.G156C)). The other gene analysis also disclosed a known homozygous LCAT mutation (c.101C>T (p.P10L)). VCP gene mutation shown should be responsible for familial ALS because of following reasons. The patient's father also was also affected by ALS. The VCP gene mutation (p.G156C) in the patient was located in the vicinity of a site frequently associated with pathogenic VCP variants. The same amino acid transformation as that of this patient has been reported to be involved in the pathogenesis of inclusion body myopathy with Paget's disease of the bone and frontotemporal dementia. This is the first case report of rare association of ALS with VCP mutation and dyslipidemia with LCAT mutation.

Targeted excision of VCP R155H mutation by Cre-LoxP technology as a promising therapeutic strategy for valosin-containing protein disease

Inclusion body myopathy associated with Paget's disease of the bone and frontotemporal dementia is attributed to mutations in the valosin-containing protein (VCP) gene, mapped to chromosomal region 9p13.3-12. Affected individuals exhibit scapular winging and die from progressive muscle weakness and cardiac and respiratory failure in their 40s to 50s. Mutations in the VCP gene have also been associated with amyotrophic lateral sclerosis in 10-15% of individuals with hereditary inclusion body myopathy and 2-3% of isolated familial amyotrophic lateral sclerosis. Currently, there are no effective treatments for VCP-related myopathy or dementia. To determine the effects of targeted excision of the most common R155H mutation in VCP disease, we generated the Cre-ER™-VCPR155H/+ tamoxifen-inducible model. We administered tamoxifen (0.12 mg/g body weight) or corn oil (vehicle) to the pregnant dams by oral gavage and monitored survival and muscle strength measurements of the pups until 18 months of age. We confirmed efficient removal of exons 4 and 5 and recombination of the mutant/floxed VCP copies by Q-PCR analyses. The activity and specificity of Cre recombinase was confirmed by immunostaining. Herein, we report that Cre-ER™-VCPR155H/+ mice demonstrated improved muscle strength and quadriceps fibers architecture, autophagy signaling pathway, reduced brain neuropathology, decreased apoptosis, and less severe Paget-like bone changes. The Cre-ER™-VCPR155H/+ mouse model provides proof of principle by demonstrating that removal of the mutated exons could be beneficial to patients with VCP-related neurodegenerative diseases, and serves as an excellent platform in understanding the underlying pathophysiological mechanism(s) in the hopes of a promising therapeutic approach.

Emerging mechanisms of molecular pathology in ALS

Amyotrophic lateral sclerosis (ALS) is a devastating degenerative disease characterized by progressive loss of motor neurons in the motor cortex, brainstem, and spinal cord. Although defined as a motor disorder, ALS can arise concurrently with frontotemporal lobal dementia (FTLD). ALS begins focally but disseminates to cause paralysis and death. About 10% of ALS cases are caused by gene mutations, and more than 40 ALS-associated genes have been identified. While important questions about the biology of this disease remain unanswered, investigations of ALS genes have delineated pathogenic roles for (a) perturbations in protein stability and degradation, (b) altered homeostasis of critical RNA- and DNA-binding proteins, (c) impaired cytoskeleton function, and (d) non-neuronal cells as modifiers of the ALS phenotype. The rapidity of progress in ALS genetics and the subsequent acquisition of insights into the molecular biology of these genes provide grounds for optimism that meaningful therapies for ALS are attainable.

Rapamycin and chloroquine: the in vitro and in vivo effects of autophagy-modifying drugs show promising results in valosin containing protein multisystem proteinopathy

Mutations in the valosin containing protein (VCP) gene cause hereditary Inclusion body myopathy (hIBM) associated with Paget disease of bone (PDB), frontotemporal dementia (FTD), more recently termed multisystem proteinopathy (MSP). Affected individuals exhibit scapular winging and die from progressive muscle weakness, and cardiac and respiratory failure, typically in their 40s to 50s. Histologically, patients show the presence of rimmed vacuoles and TAR DNA-binding protein 43 (TDP-43)-positive large ubiquitinated inclusion bodies in the muscles. We have generated a VCP^R155H/+ mouse model which recapitulates the disease phenotype and impaired autophagy typically observed in patients with VCP disease. Autophagy-modifying agents, such as rapamycin and chloroquine, at pharmacological doses have previously shown to alter the autophagic flux. Herein, we report results of administration of rapamycin, a specific inhibitor of the mechanistic target of rapamycin (mTOR) signaling pathway, and chloroquine, a lysosomal inhibitor which reverses autophagy by accumulating in lysosomes, responsible for blocking autophagy in 20-month old VCP^R155H/+ mice. Rapamycin-treated mice demonstrated significant improvement in muscle performance, quadriceps histological analysis, and rescue of ubiquitin, and TDP-43 pathology and defective autophagy as indicated by decreased protein expression levels of LC3-I/II, p62/SQSTM1, optineurin and inhibiting the mTORC1 substrates. Conversely, chloroquine-treated VCP^R155H/+ mice revealed progressive muscle weakness, cytoplasmic accumulation of TDP-43, ubiquitin-positive inclusion bodies and increased LC3-I/II, p62/SQSTM1, and optineurin expression levels. Our in vitro patient myoblasts studies treated with rapamycin demonstrated an overall improvement in the autophagy markers. Targeting the mTOR pathway ameliorates an increasing list of disorders, and these findings suggest that VCP disease and related neurodegenerative multisystem proteinopathies can now be included as disorders that can potentially be ameliorated by rapalogs.

Frontotemporal lobar degeneration: defining phenotypic diversity through personalized medicine

Frontotemporal lobar degeneration (FTLD) comprises two main classes of neurodegenerative diseases characterized by neuronal/glial proteinaceous inclusions (i.e., proteinopathies) including tauopathies (i.e., FTLD-Tau) and TDP-43 proteinopathies (i.e., FTLD-TDP) while other very rare forms of FTLD are known such as FTLD with FUS pathology (FTLD-FUS). This review focuses mainly on FTLD-Tau and FLTD-TDP, which may present as several clinical syndromes: a behavioral/dysexecutive syndrome (behavioral variant frontotemporal dementia); language disorders (primary progressive aphasia variants); and motor disorders (amyotrophic lateral sclerosis, corticobasal syndrome, progressive supranuclear palsy syndrome). There is considerable heterogeneity in clinical presentations of underlying neuropathology and current clinical criteria do not reliably predict underlying proteinopathies ante-mortem. In contrast, molecular etiologies of hereditary FTLD are consistently associated with specific proteinopathies. These include MAPT mutations with FTLD-Tau and GRN, C9orf72, VCP and TARDBP with FTLD-TDP. The last decade has seen a rapid expansion in our knowledge of the molecular pathologies associated with this clinically and neuropathologically heterogeneous group of FTLD diseases. Moreover, in view of current limitations to reliably diagnose specific FTLD neuropathologies prior to autopsy, we summarize the current state of the science in FTLD biomarker research including neuroimaging, biofluid and genetic analyses. We propose that combining several of these biomarker modalities will improve diagnostic specificity in FTLD through a personalized medicine approach. The goals of these efforts are to enhance power for clinical trials focused on slowing or preventing progression of spread of tau, TDP-43 and other FTLD-associated pathologies and work toward the goal of defining clinical endophenotypes of FTD.

A network of RNA and protein interactions in Fronto Temporal Dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by degeneration of the fronto temporal lobes and abnormal protein inclusions. It exhibits a broad clinicopathological spectrum and has been linked to mutations in seven different genes. We will provide a picture, which connects the products of these genes, albeit diverse in nature and function, in a network. Despite the paucity of information available for some of these genes, we believe that RNA processing and post-transcriptional regulation of gene expression might constitute a common theme in the network. Recent studies have unraveled the role of mutations affecting the functions of RNA binding proteins and regulation of microRNAs. This review will combine all the recent findings on genes involved in the pathogenesis of FTD, highlighting the importance of a common network of interactions in order to study and decipher the heterogeneous clinical manifestations associated with FTD. This approach could be helpful for the research of potential therapeutic strategies.