Inclusion body myopathy, Paget's disease of the bone and frontotemporal dementia: recurrence of the VCP R155H mutation in an Italian family and implications for genetic counselling

The acronym IBMPFD denotes a syndrome including inclusion body myopathy, Paget's disease of the bone (PDB) and frontotemporal dementia (FTD) as cardinal features, which is caused by missense mutations in the VCP gene. We studied the clinical characteristics and the histopathological features in two siblings and their mother who presented with adult-onset myopathy and presenile, rapidly progressive FTD. One sibling also showed PDB. Light and electron microscopy performed on muscle biopsies demonstrated degenerative changes with inclusion bodies and abnormal aggregates. Mutation analysis of the VCP gene on affected siblings revealed a heterozygous missense mutation (R155H) in a hot spot. This is the first Italian family with multiple individuals diagnosed as having IBMPFD and carrying the recurrent R155H mutation. The implications for genetic counselling were also discussed, with regard to the procedures that may be offered to families suffering from a multisystem disorder with high risk of cognitive decline.     

Manifestations in a family with autosomal dominant bone fragility and limb-girdle myopathy

We report on an unusual family with an autosomal dominant limb-girdle type of myopathy and bone fragility. This family was previously reported by Henry et al. [1958] as autosomal dominant progressive limb girdle "muscular dystrophy" with propensity to fractures and defective healing of long bones. Clinical, biochemical, and radiological aspects were evaluated in eight living relatives in this family (three males and five females) and in eight deceased individuals. The average age-of-onset of the limb-girdle myopathy was 31 years occurring in 87% of affected individuals. The average age of onset of fractures was 24 years occurring in 88% of affected individuals. Biochemical analysis showed a mean alkaline phosphatase (ALP) of 64 U/L (normal 30-120) and borderline high creatine kinase (CK) of 213 U/L (normal 4-220). Radiographs revealed coarse trabeculation, patchy sclerosis, cortical thickening, and narrowing of the medullary cavity with an appearance not considered typical of Paget disease of bone (PDB) or of fibrous dysplasia. Results of nerve conduction studies were normal, and electromyograms and muscle biopsies documented non-specific myopathic changes. There is premature graying with thin hair, thin skin, hernias and the affected individuals appear older than their chronological age, and three members had a clotting disorder. Linkage analysis for markers for the chromosome 9p22.3-q12 locus indicated that the disorder in this family does not segregate with markers in the critical region of limb-girdle/inclusion body myopathy, PDB, and frontotemporal dementia (FTD) [IBMPFD, OMIM #605382]. Sequencing of Valosin-containing protein (VCP), the gene associated with IBMPFD, did not identify mutations. We have excluded linkage to the known loci for limb-girdle type of myopathy and bone disease and excluded several candidate genes. Elucidation of the novel molecular basis of this disorder may provide valuable links between bone, collagen and muscle, and targeted therapeutic options.     

Heterogeneity in familial dominant Paget disease of bone and muscular dystrophy

The combination of autosomal dominant, early onset Paget disease of bone (PDB) and muscular dystrophy is an unusual disorder. We recently mapped the disorder in a large family from central Illinois with PDB and proximal limb-girdle type of muscular dystrophy (LGMD), and in 3 additional families with hereditary inclusion body myopathy (HIBM), Paget disease of bone and frontotemporal dementia, to a unique locus on chromosome 9p21.1-q12. The present study describes an unrelated 10-member family with autosomal dominant PDB and a scapuloperoneal type of muscular dystrophy. Clinical, biochemical, and radiological evaluations were performed to delineate clinical features in this family. Progression of the muscular dystrophy begins with weakness in the distal muscles of the legs accompanied by foot drop. EMG and muscle biopsy are compatible with a primary dystrophy. Onset of Paget disease is early, at a mean age of 41 years, with initial distribution in the long bones and eventual infiltration of the spine and pelvis. Creatine phosphokinase (CPK) and alkaline phosphatase levels are elevated in affected individuals. Molecular analyses excluded all known loci for Paget disease of bone, scapuloperoneal muscular dystrophy (SPMD), fascioscapulohumeral muscular dystrophy (FSH), amyotrophic lateral sclerosis (ALS), Bethlem myopathy, two forms of autosomal dominant limb-girdle muscular dystrophy (LGMD), and the critical region for LGMD or HIBM/PDB on chromosome 9p21.1-q12, thus providing evidence for genetic heterogeneity among families with the unique combination of muscular dystrophy and Paget disease of bone.     

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.     

VCP mutations in familial and sporadic amyotrophic lateral sclerosis

Mutations in the valosin-containing protein (VCP) gene were recently reported to be the cause of 1%-2% of familial amyotrophic lateral sclerosis (ALS) cases. VCP mutations are known to cause inclusion body myopathy (IBM) with Paget's disease (PDB) and frontotemporal dementia (FTD). The presence of VCP mutations in patients with sporadic ALS, sporadic ALS-FTD, and progressive muscular atrophy (PMA), a known clinical mimic of inclusion body myopathy, is not known. To determine the identity and frequency of VCP mutations we screened a cohort of 93 familial ALS, 754 sporadic ALS, 58 sporadic ALS-FTD, and 264 progressive muscular atrophy patients for mutations in the VCP gene. Two nonsynonymous mutations were detected; 1 known mutation (p.R159H) in a patient with familial ALS with several family members suffering from FTD, and 1 mutation (p.I114V) in a patient with sporadic ALS. Conservation analysis and protein prediction software indicate the p.I114V mutation to be a rare benign polymorphism. VCP mutations are a rare cause of familial ALS. The role of VCP mutations in sporadic ALS, if present, appears limited.     

Genotype–phenotype studies of VCP‐associated inclusion body myopathy with Paget disease of bone and/or frontotemporal dementia

Valosin containing protein (VCP) disease associated with inclusion body myopathy, Paget disease of the bone and frontotemporal dementia is a progressive autosomal dominant disorder caused by mutations in Valosin containing protein gene. To establish genotype–phenotype correlations we analyzed clinical and biochemical markers from a database of 190 members in 27 families harboring 10 missense mutations. Individuals were grouped into three categories: symptomatic, presymptomatic carriers and noncarriers. The symptomatic families were further divided into ten groups based on their VCP mutations. There was marked intra and inter‐familial variation; and significant genotype–phenotype correlations were difficult to establish because of small numbers. Nevertheless when comparing the two most common mutations, R155C mutation was found to be more severe, with an earlier onset of myopathy and Paget (p = 0.03). Survival analysis of all subjects revealed an average life span after diagnosis of myopathy and Paget of 18 and 19 years respectively, and after dementia only 6 years. R155C had a reduced survival compared to the R155H mutation (p = 0.03).We identified amyotrophic lateral sclerosis (ALS) was diagnosed in 13 individuals (8.9%) and Parkinson's disease in five individuals (3%); however, there was no genotypic correlation. This study represents the largest dataset of patients with VCP disease and expands our understanding of the natural history and provides genotype–phenotype correlations in this unique disease.     

Mutational analysis of VCP gene in familial amyotrophic lateral sclerosis

Mutations in valosin-containing protein (VCP) gene, already known to be associated with the multisystemic disorder, inclusion body myopathy with Paget's disease and frontotemporal dementia (IBMPFD), have been recently found also in familial cases of amyotrophic lateral sclerosis (ALS). To further define the frequency of VCP mutations in ALS Italian population, we screened a cohort of 166 familial ALS and 14 ALS-frontotemporal dementia (FTD) individuals. We identified a previously reported synonymous mutation (c.2093A>C; p.Q568Q), 2 intronic variants (c.1749-14C>T; c.2085-3C>T), and 1 nucleotide change (c.2814G>T) in the 3' untranslated region (UTR). Bioinformatical analyses predicted no changes in splicing process or microRNA binding sites. Our results do not confirm a main contribution of VCP gene to familial ALS in the Italian population.     

Mutation analysis of VCP in familial and sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive loss of motor neurons in the motor cortex, brain stem and spinal cord. Mutations in the valosin-containing protein gene (VCP) were recently described in ALS families. Some of these families included diagnoses of other clinical features including frontotemporal dementia, Paget's disease, inclusion body myopathy, Parkinsonism and limb weakness. We sought to determine the prevalence of VCP mutations in Australian familial (n = 131) and sporadic (n = 48) ALS cohorts diagnosed with classic ALS. No mutations were identified indicating that VCP mutations are not a common cause of classic ALS among Australian cases with predominantly European ancestry.     

Inclusion body myopathy-associated mutations in p97/VCP impair endoplasmic reticulum-associated degradation

Mutations in the AAA+ protein (ATPase associated with a variety of cellular activities) p97/VCP (valosin-containing protein) cause a dominantly inherited syndrome of inclusion body myopathy with Paget's disease of the bone and fronto-temporal dementia (IBMPFD). p97/VCP is a ubiquitously expressed protein that participates in a number of cellular processes including endoplasmic reticulum-associated degradation (ERAD). p97/VCP aids in the extraction of ubiquitinated proteins from the endoplasmic reticulum (ER) and facilitates their delivery to the proteasome. This study focuses on the effects of disease-associated p97/VCP mutations on this pathway. We show that p97/VCP containing the most prevalent IBMPFD-associated mutation, R155H, has normal ATPase activity and hexameric structure. However, when expressed in cultured cells, both this and a second IBMPFD-associated p97/VCP mutant increase the overall level of ubiquitin-conjugated proteins and specifically impair degradation of mutant DeltaF508-CFTR handled by the ERAD pathway. These effects are similar to those previously described for an ATPase deficient p97/VCP mutant and suggest that IBMPFD mutations impair p97/VCP cellular function. In a subset of cells, IBMPFD mutations also promote formation of aggregates that contain p97/VCP, ubiquitin conjugates and ER-resident proteins. Undegraded mutant DeltaF508-CFTR also accumulates in these aggregates. We conclude that IBMPFD mutations in p97/VCP disrupt ERAD and that this may contribute to the pathogenesis of IBMPFD.     

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

Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD, OMIM 167320) has recently been attributed to eight missense mutations in valosin-containing protein (VCP). We report novel VCP mutations N387H and L198W in six individuals from two families who presented with proximal muscle weakness at a mean age of diagnosis of 40 years, most losing the ability to walk within a few years of onset. Electromyographic studies in four individuals were suggestive of 'myopathic' changes, and neuropathic pattern was identified in one individual in family 1. Muscle biopsy in four individuals showed myopathic changes characterized by variable fiber size, two individuals showing rimmed vacuoles and IBM-type cytoplasmic inclusions in muscle fibers, and electron microscopy in one individual revealing abundant intranuclear inclusions. Frontotemporal dementia associated with characteristic behavioral changes including short-term memory loss, language difficulty, and antisocial behavior was observed in three individuals at a mean age of 47 years. Detailed brain pathology in one individual showed cortical degenerative changes, most severe in the temporal lobe and hippocampus. Abundant ubiquitin-positive tau-, alpha-synuclein-, polyglutamine repeat-negative neuronal intranuclear inclusions and only rare intracytoplasmic VCP positive inclusions were seen. These new mutations may cause structural changes in VCP and provide some insight into the functional effects of pathogenic mutations.     

No association of common VCP variants with sporadic frontotemporal dementia

Mutations in the gene for valosin containing protein (VCP) cause autosomal dominant inclusion body myopathy associated with Paget disease and frontotemporal dementia (IBMPFD). To investigate the role of this novel gene in sporadic forms of frontotemporal dementia (FTD), we genotyped 27 single nucleotide polymorphisms covering the entire VCP genomic region in 198 patients with sporadic FTD and 184 matched controls from Germany. No significant association could be demonstrated. There is no evidence, that common variants in VCP confer a strong risk to the development of sporadic FTD.     

Clinical Delineation and Localization to Chromosome 9p13.3–p12 of a Unique Dominant Disorder in Four Families: Hereditary Inclusion Body Myopathy, Paget Disease of Bone, and Frontotemporal Dementia

Autosomal dominant myopathy, Paget disease of bone, and dementia constitute a unique disorder (MIM 605382). Here we describe the clinical, biochemical, radiological, and pathological characteristics of 49 affected (23 male, 26 female) individuals from four unrelated United States families. Among these affected individuals 90% have myopathy, 43% have Paget disease of bone, and 37% have premature frontotemporal dementia. EMG shows myopathic changes and muscle biopsy reveals nonspecific myopathic changes or blue-rimmed vacuoles. After candidate loci were excluded, a genome-wide screen in the large Illinois family showed linkage to chromosome 9 (maximum LOD score 3.64 with marker D9S301). Linkage analysis with a high density of chromosome 9 markers generated a maximum two-point LOD score of 9.29 for D9S1791, with a maximum multipoint LOD score of 12.24 between D9S304 and D9S1788. Subsequent evaluation of three additional families demonstrating similar clinical characteristics confirmed this locus, refined the critical region, and further delineated clinical features of this unique disorder. Hence, autosomal dominant inclusion body myopathy (HIBM), Paget disease of bone (PDB), and frontotemporal dementia (FTD) localizes to a 1.08-6.46 cM critical interval on 9p13.3-12 in the region of autosomal recessive IBM2.     

APOE is a potential modifier gene in an autosomal dominant form of frontotemporal dementia (IBMPFD).

PURPOSE: Inclusion-body myopathy, Paget's disease of bone and frontotemporal dementia is an adult-onset autosomal dominant illness (IBMPFD) caused by mutations in the valosin-containing protein (VCP) on chromosome 9p21.1-p12. The penetrance of the gene is 82% for myopathy, 49% for Paget's disease, but may be as low as 30% for frontotemporal dementia. Modifier genes could account for decreased frontotemporal dementia penetrance. In this study apolipoprotein-E (APOE) was evaluated for this role in IBMPFD families based on its known modifier effect in Alzheimer's disease. METHODS: From a database of 231 members of 15 families, 174 had APOE genotype available for analysis. Logistic regressions on APOE genotype and frontotemporal dementia were performed, using appropriate covariates. RESULTS AND CONCLUSION: FTD was associated with APOE 4 genotype (P=0.0002), myopathy (P=0.0006), and age (P=0.01), but not microtubule associated protein tau (MAPT) H2 haplotype (P=0.5) or gender (0.09) after adjustment for membership in pedigrees with at least one APOE 4 genotype. These data suggest a potential link between APOE 4 genotype and the specific form of frontotemporal dementia found in IBMPFD. The molecular basis of this link bears further investigation. We did not observe an association of frontotemporal dementia and H2 MAPT haplotype.     

Transgenic expression of inclusion body myopathy associated mutant p97/VCP causes weakness and ubiquitinated protein inclusions in mice

Mutations in p97/VCP cause the autosomal-dominant, inherited syndrome inclusion body myopathy (IBM) associated with Paget's disease of the bone and frontotemporal dementia (IBMPFD) (Watts, G.D., Wymer, J., Kovach, M.J., Mehta, S.G., Mumm, S., Darvish, D., Pestronk, A., Whyte, M.P. and Kimonis, V.E. (2004) Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia is caused by mutant valosin-containing protein. p97/VCP is a multi-functional protein with a role in the ubiquitin-proteasome system (UPS) (Wang, Q., Song, C. and Li, C.C. (2004) Molecular perspectives on p97-VCP: progress in understanding its structure and diverse biological functions. To understand how mutations in this protein lead to a myopathy, we generated several lines of transgenic mice expressing p97/VCP-WT (TgVCP-WT) or the most common IBMPFD mutant, p97/VCP R155H (TgVCP-RH), under a muscle-specific promoter. TgVCP-RH animals, but not controls, became progressively weaker in a dose-dependent manner starting at 6 months of age. Abnormal muscle pathology, which included coarse internal architecture, vacuolation and disorganized membrane morphology with reduced caveolin-3 expression at the sarcolemma developed coincident with the onset of weakness. These changes were not associated with alterations in sarcolemmal integrity as measured by muscle fiber uptake of Evan's blue dye. Even before animals displayed measurable weakness, there was an increase in ubiquitin-containing protein inclusions and high-molecular-weight ubiquitinated proteins, markers of UPS dysfunction. We suggest that this early and persistent increase in ubiquitinated proteins induced by IBMPFD mutations in p97/VCP may ultimately lead to animal weakness and the observed muscle pathology. TgVCP-RH animals will be a valuable tool for understanding the pathogenesis of IBM and the role of the UPS in skeletal muscle.     

Enhanced ATPase activities as a primary defect of mutant valosin‐containing proteins that cause inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia

Valosin‐containing protein (VCP) has been shown to colocalize with abnormal protein aggregates, such as nuclear inclusions of Huntington disease and Machado‐Joseph disease, Lewy bodies in Parkinson disease. Several mis‐sense mutations in the human VCP gene have been identified in patients suffering inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD). Recently, we have shown that VCP possesses both aggregate‐forming and aggregate‐clearing activities. Here, we showed that in cells treated with proteasome inhibitors VCP first appeared as several small aggregates throughout the cells; and then, these small aggregates gathered together into a single big aggregate. Subcellular localization and ATPase activity of VCP clearly influenced the localization of the aggregates. Furthermore, all tested IBMPFD‐causing mutant VCPs, possessed elevated ATPase activities and enhanced aggregate‐forming activities in cultured cells. In Drosophila, these mutants and VCP(T761E), a super active VCP, did not appear to spontaneously induce eye degeneration, but worsened the phenotype when co‐expressed with polyglutamines. Unexpectedly, these VCPs did not apparently change sizes and the amounts of polyglutamine aggregates in Drosophila eyes. Elevated ATPase activities, thus, may be a hidden primary defect causing IBMPFD pathological phenotypes, which would be revealed when abnormal proteins are accumulated, as typically observed in aging.     

Inclusion body myopathy and frontotemporal dementia caused by a novel VCP mutation

Hereditary inclusion body myopathy (IBM) with Paget's disease of the bone (PDB) and frontotemporal dementia (FTD) is a rare autosomal dominant disease caused by mutations in the valosin-containing protein (VCP) gene. We report a novel heterozygous VCP gene mutation (R159C) in a 69-year-old Italian patient presenting with slowly progressive muscle weakness of the distal upper and proximal lower limbs since the age of 50 years, 18 years later FTD supervened. No dementia or myopathies were revealed in the family history covering two generations. Degenerative changes and rimmed vacuoles together with VCP- and ubiquitin-positive cytoplasmic and nuclear aggregates were observed at the muscle biopsy. Several elements support the pathogenic role of the R159C VCP gene mutation: the occurrence at the same codon of a different, previously identified pathogenic mutation within a VCP gene mutational hot-spot, the histopathological and biochemical evidence of muscle VCP accumulation and the combined clinical presentation of IBM and FTD. These findings suggest VCP gene investigation even in apparently sporadic cases.     

Different dynamic movements of wild‐type and pathogenic VCPs and their cofactors to damaged mitochondria in a Parkin‐mediated mitochondrial quality control system

VCP/p97 is a hexameric ring‐shaped AAA⁺ ATPase that participates in various ubiquitin‐associated cellular functions. Mis‐sense mutations in VCP gene are associated with the pathogenesis of two inherited diseases: inclusion body myopathy associated with Paget's disease of the bone and front‐temporal dementia (IBMPFD) and familial amyotrophic lateral sclerosis (ALS). These pathogenic VCPs have higher affinities for several cofactors, including Npl4, Ufd1 and p47. In Parkin‐dependent mitochondrial quality control systems, VCP migrates to damaged mitochondria (e.g., those treated with uncouplers) to aid in the degradation of mitochondrial outer membrane proteins and to eliminate mitochondria. We showed that endogenous Npl4 and p47 also migrate to mitochondria after uncoupler treatment, and Npl4, Ufd1 or p47 silencing causes defective mitochondria clearance after uncoupler treatment. Moreover, pathogenic VCPs show impaired migration to mitochondria, and the exogenous pathogenic VCP expression partially inhibits Npl4 and p47 localization to mitochondria. These results suggest that the increased affinities of pathogenic VCPs for these cofactors cause the impaired movement of pathogenic VCPs. In adult flies, exogenous expression of wild‐type VCP, but not pathogenic VCPs, reduces the number of abnormal mitochondria in muscles. Failure of pathogenic VCPs to function on damaged mitochondria may be related to the pathogenesis of IBMPFD and ALS.     

Mutation analysis of VCP in British familial and sporadic amyotrophic lateral sclerosis patients

Mutations in the valosin-containing-protein (VCP) gene are associated with the multidisorder disease, inclusion body myopathy with Pagets and associated frontotemporal dementia. This disease is characterized pathologically by large ubiquitinated, TAR DNA Binding Protein 43 (TDP-43) positive inclusions. These inclusions are also a common feature in neurological diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTLD). Mutations in the VCP gene have been identified in ALS patients, therefore we aimed to characterize VCP variations in our own cohort of familial and sporadic ALS patients by sequencing all 17 coding exons of VCP. This study failed to detect any exonic variations in a subset of British familial and sporadic ALS patients.     

Clinical studies in benign (Becker type) X-linked muscular dystrophy

Ten extensive families with benign (Becker type) X-linked muscular dystrophy have been studied, in which there was a total of 67 affected males. Reliable information was available on 41 of these males, 29 of whom were alive at the time of the study.
The disorder was characterised by a predominantly proximal myopathy, associated with pseudohypertrophy of the calf muscles, particularly in the early stages of the disease. The early development of contractures was not a feature of the disease in these families and cardiac involvement, when present, was a late manifestation. The clinical findings in these patients are discussed in detail and compared with those in a large unselected group of patients with Duchenne muscular dystrophy. The results indicate that the best criterion for distinguishing between these two disorders is the age of becoming chair-bound.
Electrocardiographic studies revealed no consistent abnormality and no evidence of an abnormal algebraic sum of the R and S waves in lead Vi, as is found in patients with Duchenne muscular dystrophy.
Serum creatine kinase levels are significantly elevated, particularly in the early stages of the disease, and in this way preclinical cases may be identified.