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author:("holden, Henry")
1.  Mutations in gamma adducin are associated with inherited cerebral palsy 
Annals of neurology  2013;74(6):805-814.
Cerebral palsy is estimated to affect nearly 1 in 500 children, and although prenatal and perinatal contributors have been well-characterized, at least 20% of cases are believed to be inherited. Previous studies have identified mutations in the actin-capping protein KANK1 and the adaptor protein -4 complex in forms of inherited cerebral palsy, suggesting a role for components of the dynamic cytoskeleton in the genesis of the disease.
We studied a multiplex consanguineous Jordanian family by homozygosity mapping and exome sequencing, then used patient-derived fibroblasts to examine functional consequences of the mutation we identified in vitro. We subsequently studied the effects of adducin loss of function in drosophila.
We identified a homozygous c.1100G>A [p.G367D] mutation in ADD3, encoding gamma adducin in all affected members of the index family. Follow-up experiments in patient fibroblasts found that the p.G367D mutation, which occurs within the putative oligomerization critical region, impairs the ability of gamma adducin to associate with the alpha subunit. This mutation impairs the normal actin capping function of adducin, leading to both abnormal proliferation and migration in cultured patient fibroblasts. Loss of function studies of the Drosophila adducin ortholog hts confirmed a critical role for adducin in locomotion.
Although likely a rare cause of cerebral palsy, our findings indicate a critical role for adducins in regulating the activity of the actin cytoskeleton, suggesting that impaired adducin function may lead to neuromotor impairment and further implicating abnormalities of the dynamic cytoskeleton as a pathogenic mechanism contributing to cerebral palsy.
PMCID: PMC3952628  PMID: 23836506
2.  Defective N-linked protein glycosylation pathway in congenital myasthenic syndromes 
Brain  2013;136(3):692-695.
PMCID: PMC3580274  PMID: 23436500
3.  The Parkinson’s disease genes Fbxo7 and Parkin interact to mediate mitophagy 
Nature neuroscience  2013;16(9):10.1038/nn.3489.
Compelling evidence indicates that two autosomal recessive Parkinson’s disease genes, PINK1 (PARK6) and Parkin (PARK2), co-operate to mediate the autophagic clearance of damaged mitochondria (mitophagy). Mutations in the F-box domain containing protein Fbxo7 (PARK15) also cause early onset autosomal recessive Parkinson’s disease by an unknown mechanism. Here we show that Fbxo7 participates in mitochondrial maintenance through direct interaction with PINK1 and Parkin and plays a role in Parkin-mediated mitophagy. Cells with reduced Fbxo7 expression show deficiencies in Parkin mitochondrial translocation, ubiquitination of mitofusin 1 and mitophagy. In Drosophila, ectopic overexpression of Fbxo7 rescued loss of Parkin supporting a functional relationship between the two proteins. Parkinson’s disease-causing mutations in Fbxo7 interfere with this process, emphasising the importance of mitochondrial dysfunction in Parkinson’s disease pathogenesis.
PMCID: PMC3827746  PMID: 23933751
Fbxo7; Parkin; PINK1; mitofusin 1; mitophagy; Drosophila; Parkinson’s disease
4.  Mutational analysis of parkin and PINK1 in multiple system atrophy 
Neurobiology of aging  2010;32(3):548.e5-548.e7.
Multiple system atrophy (MSA) and Parkinson’s disease (PD) are progressive neurodegenerative disorders with overlapping clinical, biochemical and genetic features. To test the hypothesis that the Parkinson’s disease genes parkin and PINK1 also play a role in the pathogenesis of MSA, we performed a mutational screening study involving 87 pathology-proven MSA cases. In parkin we identified eight sequence variants and four heterozygous deletions, and in PINK1 we identified nine variants of which two silent mutations have not been previously reported (p.Gly189Gly and p.Arg337Arg). The frequencies of the observed variants were not significantly different from previously published control data and none of the possibly pathogenic variants were found in a homozygous state. Our results indicate that genetic variants at the parkin and PINK1 loci do not play a critical role in the pathogenesis of MSA.
PMCID: PMC3934211  PMID: 20034704
multiple system atrophy; Parkinson’s disease; PINK1; parkin
5.  Kohlschütter–Tönz Syndrome: Mutations in ROGDI and Evidence of Genetic Heterogeneity 
Human mutation  2012;34(2):296-300.
Kohlschütter–Tönz syndrome (KTS) is a rare autosomal recessive disorder characterized by amelogenesis imperfecta, psychomotor delay or regression and seizures starting early in childhood. KTS was established as a distinct clinical entity after the first report by Kohlschütter in 1974, and to date, only a total of 20 pedigrees have been reported. The genetic etiology of KTS remained elusive until recently when mutations in ROGDI were independently identified in three unrelated families and in five likely related Druze families. Herein, we report a clinical and genetic study of 10 KTS families. By using a combination of whole exome sequencing, linkage analysis, and Sanger sequencing, we identify novel homozygous or compound heterozygous ROGDI mutations in five families, all presenting with a typical KTS phenotype. The other families, mostly presenting with additional atypical features, were negative for ROGDI mutations, suggesting genetic heterogeneity of atypical forms of the disease.
PMCID: PMC3902979  PMID: 23086778
Kohlschütter–Tönz; ROGDI; amelogenesis imperfecta; epilepsy
6.  Hereditary sensory and autonomic neuropathy type 1 (HSANI) caused by a novel mutation in SPTLC2 
Neurology  2013;80(23):2106-2111.
To describe the clinical and neurophysiologic phenotype of a family with hereditary sensory and autonomic neuropathy type 1 (HSANI) due to a novel mutation in SPTLC2 and to characterize the biochemical properties of this mutation.
We screened 107 patients with HSAN who were negative for other genetic causes for mutations in SPTLC2. The biochemical properties of a new mutation were characterized in cell-free and cell-based activity assays.
A novel mutation (A182P) was found in 2 subjects of a single family. The phenotype of the 2 subjects was an ulcero-mutilating sensory-predominant neuropathy as described previously for patients with HSANI, but with prominent motor involvement and earlier disease onset in the first decade of life. Affected patients had elevated levels of plasma 1-deoxysphingolipids (1-deoxySLs). Biochemically, the A182P mutation was associated with a reduced canonical activity but an increased alternative activity with alanine, which results in largely increased 1-deoxySL levels, supporting their pathogenicity.
This study confirms that mutations in SPTLC2 are associated with increased deoxySL formation causing HSANI.
PMCID: PMC3716354  PMID: 23658386
7.  Genetic risk factors for intracranial aneurysms 
Neurology  2013;80(23):2154-2165.
There is an urgent need to identify risk factors for sporadic intracranial aneurysm (IA) development and rupture. A genetic component has long been recognized, but firm conclusions have been elusive given the generally small sample sizes and lack of replication. Genome-wide association studies have overcome some limitations, but the number of robust genetic risk factors for IA remains uncertain.
We conducted a comprehensive systematic review and meta-analysis of all genetic association studies (including genome-wide association studies) of sporadic IA, conducted according to Strengthening the Reporting of Genetic Association Studies and Human Genome Epidemiology Network guidelines. We tested the robustness of associations using random-effects and sensitivity analyses.
Sixty-one studies including 32,887 IA cases and 83,683 controls were included. We identified 19 single nucleotide polymorphisms associated with IA. The strongest associations, robust to sensitivity analyses for statistical heterogeneity and ethnicity, were found for the following single nucleotide polymorphisms: on chromosome 9 within the cyclin-dependent kinase inhibitor 2B antisense inhibitor gene (rs10757278: odds ratio [OR] 1.29; 95% confidence interval [CI] 1.21–1.38; and rs1333040: OR 1.24; 95% CI 1.20–1.29), on chromosome 8 near the SOX17 transcription regulator gene (rs9298506: OR 1.21; 95% CI 1.15–1.27; and rs10958409: OR 1.19; 95% CI 1.13–1.26), and on chromosome 4 near the endothelin receptor A gene (rs6841581: OR 1.22; 95% CI 1.14–1.31).
Our comprehensive meta-analysis confirms a substantial genetic contribution to sporadic IA, implicating multiple pathophysiologic pathways, mainly relating to vascular endothelial maintenance. However, the limited data for IA compared with other complex diseases necessitates large-scale replication studies in a full spectrum of populations, with investigation of how genetic variants relate to phenotype (e.g., IA size, location, and rupture status).
PMCID: PMC3716358  PMID: 23733552
8.  TDP-43 pathology in a patient carrying G2019S LRRK2 mutation and a novel p.Q124E MAPT☆ 
Neurobiology of Aging  2013;34(12):2889.e5-2889.e9.
Leucine-rich repeat kinase 2 (LRRK2) mutation is the most common cause of genetic-related parkinsonism and is usually associated with Lewy body pathology; however, tau, α-synuclein, and ubiquitin pathologies have also been reported. We report the case of a patient carrying the LRRK2 G2019S mutation and a novel heterozygous variant c.370C>G, p.Q124E in exon 4 of the microtubule-associated protein tau (MAPT). The patient developed parkinsonism with good levodopa response in her 70s. Neuropathological analysis revealed nigral degeneration and Alzheimer-type tau pathology without Lewy bodies. Immunohistochemical staining using phospho-TDP-43 antibodies identified occasional TDP-43 pathology in the hippocampus, temporal neocortex, striatum, and substantia nigra. However, TDP-43 pathology was not identified in another 4 archival LRRK2 G2019S cases with Lewy body pathology available in the Queen Square Brain Bank. Among other published cases of patients carrying LRRK2 G2019S mutation, only 3 were reportedly evaluated for TDP-43 pathology, and the results were negative. The role of the MAPT variant in the clinical and pathological manifestation in LRRK2 cases remains to be determined.
PMCID: PMC3906605  PMID: 23664753
LRRK2; MAPT; Parkinson's disease; TDP-43; tau
9.  A novel α-synuclein missense mutation in Parkinson disease 
Neurology  2013;80(11):1062-1064.
Alpha-synuclein (SNCA) is central to the pathogenesis of Parkinson disease (PD), with 3 missense mutations reported to date. We report a novel mutation (p.H50Q) in a pathologically proven case.
PMCID: PMC3653201  PMID: 23427326
10.  Exome sequencing reveals riboflavin transporter mutations as a cause of motor neuron disease 
Brain  2012;135(9):2875-2882.
Brown–Vialetto–Van Laere syndrome was first described in 1894 as a rare neurodegenerative disorder characterized by progressive sensorineural deafness in combination with childhood amyotrophic lateral sclerosis. Mutations in the gene, SLC52A3 (formerly C20orf54), one of three known riboflavin transporter genes, have recently been shown to underlie a number of severe cases of Brown–Vialetto–Van Laere syndrome; however, cases and families with this disease exist that do not appear to be caused by SLC52A3 mutations. We used a combination of linkage and exome sequencing to identify the disease causing mutation in an extended Lebanese Brown–Vialetto–Van Laere kindred, whose affected members were negative for SLC52A3 mutations. We identified a novel mutation in a second member of the riboflavin transporter gene family (gene symbol: SLC52A2) as the cause of disease in this family. The same mutation was identified in one additional subject, from 44 screened. Within this group of 44 patients, we also identified two additional cases with SLC52A3 mutations, but none with mutations in the remaining member of this gene family, SLC52A1. We believe this strongly supports the notion that defective riboflavin transport plays an important role in Brown–Vialetto–Van Laere syndrome. Initial work has indicated that patients with SLC52A3 defects respond to riboflavin treatment clinically and biochemically. Clearly, this makes an excellent candidate therapy for the SLC52A2 mutation-positive patients identified here. Initial riboflavin treatment of one of these patients shows promising results.
PMCID: PMC3437022  PMID: 22740598
motor neuron disease; ALS; riboflavin; BVVL; SLC52A2
11.  The genetics and neuropathology of Parkinson’s disease 
Acta neuropathologica  2012;124(3):325-338.
There has been tremendous progress toward understanding the genetic basis of Parkinson’s disease and related movement disorders. We summarize the genetic, clinical and pathological findings of autosomal dominant disease linked to mutations in SNCA, LRRK2, ATXN2, ATXN3, MAPT, GCH1, DCTN1 and VPS35. We then discuss the identification of mutations in PARK2, PARK7, PINK1, ATP13A2, FBXO7, PANK2 and PLA2G6 genes. In particular we discuss the clinical and pathological characterization of these forms of disease, where neuropathology has been important in the likely coalescence of pathways highly relevant to typical PD. In addition to the identification of the causes of monogenic forms of PD, significant progress has been made in defining genetic risk loci for PD; we discuss these here, including both risk variants at LRRK2 and GBA, in addition to discussing the results of recent genome-wide association studies and their implications for PD. Finally, we discuss the likely path of genetic discovery in PD over the coming period and the implications of these findings from a clinical and etiological perspective.
PMCID: PMC3589971  PMID: 22806825
Parkinson’s disease; Genetics; Pathology; Synuclein; LRRK2; PARK2; PARK6; PARK7
12.  Analysis of ATP13A2 in large neurodegeneration with brain iron accumulation (NBIA) and dystonia-parkinsonism cohorts 
Neuroscience letters  2012;523(1):35-38.
Several causative genes have been identified for both dystonia-parkinsonism and neurodegeneration with brain iron accumulation (NBIA), yet many patients do not have mutations in any of the known genes. Mutations in the ATP13A2 lead to Kufor Rakeb disease, a form of autosomal recessive juvenile parkinsonism that also features oromandibular dystonia. More recently, evidence of iron deposition in the caudate and putamen have been reported in patients with ATP13A2 mutations. We set out to determine the frequency of ATP13A2 mutations in cohorts of idiopathic NBIA and dystonia-parkinsonism. We screened for large deletions using whole genome arrays, and sequenced the entire coding region in 92 cases of NBIA and 76 cases of dystonia-parkinsonism. A number of coding and non-coding sequence variants were identified in a heterozygous state, but none were predicted to be pathogenic based on in silico analyses. Our results indicate that ATP13A2 mutations are a rare cause of both NBIA and dystonia-parkinsonism.
PMCID: PMC3619445  PMID: 22743658
Neurodegeneration; Iron; NBIA; Kufor Rakeb; ATP13A2; Dystonia; Parkinsonism
13.  Charcot-Marie-Tooth disease: frequency of genetic subtypes and guidelines for genetic testing 
Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of diseases with approximately 45 different causative genes described. The aims of this study were to determine the frequency of different genes in a large cohort of patients with CMT and devise guidelines for genetic testing in practice.
The genes known to cause CMT were sequenced in 1607 patients with CMT (425 patients attending an inherited neuropathy clinic and 1182 patients whose DNA was sent to the authors for genetic testing) to determine the proportion of different subtypes in a UK population.
A molecular diagnosis was achieved in 62.6% of patients with CMT attending the inherited neuropathy clinic; in 80.4% of patients with CMT1 (demyelinating CMT) and in 25.2% of those with CMT2 (axonal CMT). Mutations or rearrangements in PMP22, GJB1, MPZ and MFN2 accounted for over 90% of the molecular diagnoses while mutations in all other genes tested were rare.
Four commonly available genes account for over 90% of all CMT molecular diagnoses; a diagnostic algorithm is proposed based on these results for use in clinical practice. Any patient with CMT without a mutation in these four genes or with an unusual phenotype should be considered for referral for an expert opinion to maximize the chance of reaching a molecular diagnosis.
PMCID: PMC3736805  PMID: 22577229
16.  Mutation in FAM134B causing severe hereditary sensory neuropathy 
The hereditary sensory and autonomic neuropathies (HSAN) are rare inherited neuropathies presenting with sensory loss and complications, including ulcers, infections, osteomyelitis and amputations. Usually, sensory symptoms predominate although motor involvement can occur. Autonomic features may be minimal (then hereditary sensory neuropathy, HSN, is preferred). HSAN has been classified into five subtypes depending on clinical presentation.1
Hereditary sensory and autonomic neuropathy II (HSANII or HSNII) is an early onset, autosomal recessive sensory neuropathy with ulcero-mutilating complications due to mutations in the HSN2 isoform of the WNK1 gene.2 Recently, a similar phenotype was described in a Saudi-Arabian family, and a homozygous nonsense mutation found in a new gene, FAM134B (family with sequence similarity 134, member B), encoding a newly identified Golgi protein. The index case in this family was initially thought to have leprosy. Three additional families (out of 75 patients) with similar phenotypes were found to have homozygous loss of function mutations in FAM134B.3
Here, we report the clinical and pathological findings in a further patient with HSNII due to a homozygous mutation in FAM134B.
PMCID: PMC3721196  PMID: 21115472
18.  Dopaminergic Neuronal Imaging in Genetic Parkinson's Disease: Insights into Pathogenesis 
PLoS ONE  2013;8(7):e69190.
To compare the dopaminergic neuronal imaging features of different subtypes of genetic Parkinson's Disease.
A retrospective study of genetic Parkinson's diseases cases in which DaTSCAN (123I-FP-CIT) had been performed. Specific non-displaceable binding was calculated for bilateral caudate and putamen for each case. The right:left asymmetry index and striatal asymmetry index was calculated.
Scans were available from 37 cases of monogenetic Parkinson's disease (7 glucocerebrosidase (GBA) mutations, 8 alpha-synuclein, 3 LRRK2, 7 PINK1, 12 Parkin). The asymmetry of radioligand uptake for Parkinson's disease with GBA or LRRK2 mutations was greater than that for Parkinson's disease with alpha synuclein, PINK1 or Parkin mutations.
The asymmetry of radioligand uptake in Parkinsons disease associated with GBA or LRRK2 mutations suggests that interactions with additional genetic or environmental factors may be associated with dopaminergic neuronal loss.
PMCID: PMC3720622  PMID: 23935950
19.  NDUFA4 Mutations Underlie Dysfunction of a Cytochrome c Oxidase Subunit Linked to Human Neurological Disease 
Cell Reports  2013;3(6):1795-1805.
The molecular basis of cytochrome c oxidase (COX, complex IV) deficiency remains genetically undetermined in many cases. Homozygosity mapping and whole-exome sequencing were performed in a consanguineous pedigree with isolated COX deficiency linked to a Leigh syndrome neurological phenotype. Unexpectedly, affected individuals harbored homozygous splice donor site mutations in NDUFA4, a gene previously assigned to encode a mitochondrial respiratory chain complex I (NADH:ubiquinone oxidoreductase) subunit. Western blot analysis of denaturing gels and immunocytochemistry revealed undetectable steady-state NDUFA4 protein levels, indicating that the mutation causes a loss-of-function effect in the homozygous state. Analysis of one- and two-dimensional blue-native polyacrylamide gels confirmed an interaction between NDUFA4 and the COX enzyme complex in control muscle, whereas the COX enzyme complex without NDUFA4 was detectable with no abnormal subassemblies in patient muscle. These observations support recent work in cell lines suggesting that NDUFA4 is an additional COX subunit and demonstrate that NDUFA4 mutations cause human disease. Our findings support reassignment of the NDUFA4 protein to complex IV and suggest that patients with unexplained COX deficiency should be screened for NDUFA4 mutations.
Graphical Abstract
•Mutations in NDUFA4, assigned to encode a complex I subunit, cause human COX deficiency•Confirmed interaction between NDUFA4 and the COX holoenzyme in control muscle•The COX holoenzyme without NDUFA4 is detectable with no abnormal subassemblies in patient muscle•NDUFA4 is essential for complex IV activity, but is not required for assembly of the COX holoenzyme
Isolated cytochrome c oxidase (COX) deficiency is a frequent finding in human mitochondrial disease. Mutations in nuclear-encoded structural subunits are extremely rare, and, in many cases, the molecular basis remains undetermined. Recent evidence in cell lines has suggested that NDUFA4, previously assigned to encode a complex I subunit, actually encodes a structural component of COX. Hanna and colleagues now demonstrate that NDUFA4 mutations cause human COX deficiency, thus confirming NDUFA4 as a COX subunit that is essential for the enzyme’s activity.
PMCID: PMC3701321  PMID: 23746447
20.  α-Synuclein mutations cluster around a putative protein loop☆ 
Neuroscience Letters  2013;546(100):67-70.
•We map all five missense SNCA mutations on the proposed α-synuclein protein models.•4 mutations cluster around the protein loop linking the two legs of the hairpin.•4 mutations cluster around the point of hairpin convergence for tetramer formation.
With the recent identification of two new pathogenic mutations in α-synuclein, we map the five known pathogenic mutations onto the best available models of the protein structure. We show that four of the five mutations map to a potential fold in the protein with the exception being the A30P mutation in which the substitution would be expected to have a profound effect on protein structure. We discuss this localisation in terms of the proposed mechanisms for mutation pathogenicity.
PMCID: PMC3694303  PMID: 23669636
α-Synuclein; SNCA; Genetics; Parkinson's disease
21.  PRRT2 gene mutations 
Neurology  2012;79(21):2115-2121.
The proline-rich transmembrane protein (PRRT2) gene was recently identified using exome sequencing as the cause of autosomal dominant paroxysmal kinesigenic dyskinesia (PKD) with or without infantile convulsions (IC) (PKD/IC syndrome). Episodic neurologic disorders, such as epilepsy, migraine, and paroxysmal movement disorders, often coexist and are thought to have a shared channel-related etiology. To investigate further the frequency, spectrum, and phenotype of PRRT2 mutations, we analyzed this gene in 3 large series of episodic neurologic disorders with PKD/IC, episodic ataxia (EA), and hemiplegic migraine (HM).
The PRRT2 gene was sequenced in 58 family probands/sporadic individuals with PKD/IC, 182 with EA, 128 with HM, and 475 UK and 96 Asian controls.
PRRT2 genetic mutations were identified in 28 out of 58 individuals with PKD/IC (48%), 1/182 individuals with EA, and 1/128 individuals with HM. A number of loss-of-function and coding missense mutations were identified; the most common mutation found was the p.R217Pfs*8 insertion. Males were more frequently affected than females (ratio 52:32). There was a high proportion of PRRT2 mutations found in families and sporadic cases with PKD associated with migraine or HM (10 out of 28). One family had EA with HM and another large family had typical HM alone.
This work expands the phenotype of mutations in the PRRT2 gene to include the frequent occurrence of migraine and HM with PKD/IC, and the association of mutations with EA and HM and with familial HM alone. We have also extended the PRRT2 mutation type and frequency in PKD and other episodic neurologic disorders.
PMCID: PMC3511930  PMID: 23077024
22.  Pathogenic VCP Mutations Induce Mitochondrial Uncoupling and Reduced ATP Levels 
Neuron  2013;78(1):57-64.
Valosin-containing protein (VCP) is a highly expressed member of the type II AAA+ ATPase family. VCP mutations are the cause of inclusion body myopathy, Paget’s disease of the bone, and frontotemporal dementia (IBMPFD) and they account for 1%–2% of familial amyotrophic lateral sclerosis (ALS). Using fibroblasts from patients carrying three independent pathogenic mutations in the VCP gene, we show that VCP deficiency causes profound mitochondrial uncoupling leading to decreased mitochondrial membrane potential and increased mitochondrial oxygen consumption. This mitochondrial uncoupling results in a significant reduction of cellular ATP production. Decreased ATP levels in VCP-deficient cells lower their energy capacity, making them more vulnerable to high energy-demanding processes such as ischemia. Our findings propose a mechanism by which pathogenic VCP mutations lead to cell death.
► VCP deficiency is associated with mitochondrial depolarization ► VCP deficiency leads to increased mitochondrial respiration and uncoupling ► ATP levels are decreased in VCP-deficient cells due to lower ATP production
In this study, Bartolome et al. show that three independent pathogenic VCP mutations induce mitochondrial uncoupling, resulting in low cellular ATP production, rendering the cells more susceptible to cell death under stress-induced ischemic conditions.
PMCID: PMC3843114  PMID: 23498975
23.  Frequency of the C9ORF72 hexanucleotide repeat expansion in ALS and FTD in diverse populations: a cross-sectional study 
Lancet Neurology  2012;11(4):323-330.
A hexanucleotide repeat expansion in the C9ORF72 gene has recently been shown to cause a large proportion of amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD).
We screened 4,448 patients diagnosed with ALS and 1,425 patients diagnosed with FTD drawn from diverse populations for the hexanucleotide expansion using a repeat-primed PCR assay. ALS and FTD were diagnosed according to the El Escorial and Lund-Manchester criteria respectively. Familial status was based on self-reported family history of similar neurodegenerative diseases at the time of sample collection. Haplotype data of 262 patients carrying the expansion were compared with the known Finnish founder risk haplotype across the chromosomal locus. Age-related penetrance was calculated by the Kaplan-Meier method using data from 603 individuals carrying the expansion.
The mutation was observed among 7·0% (n = 236 of 3,377) of Caucasians, 4·1% (n = 2 of 49) of African-Americans, and 8·3% (n = 6 of 72) of Hispanic individuals diagnosed with sporadic ALS, whereas the rate was 6·0% (n = 59 of 981) among Caucasians diagnosed with sporadic FTD. Among Asians, 5·0% (n = 1 of 20) of familial ALS and 66·6% (n = 2 of 3) of familial FTD cases carried the repeat expansion. In contrast, mutations were not observed among patients of Native American (n = 3 sporadic ALS), Indian (n = 31 sporadic ALS, n = 31 sporadic FTD), and Pacific Islander (n = 90 sporadic ALS) ethnicity. All patients with the repeat expansion carried, either partially or fully, the founder haplotype suggesting that the expansion occurred on a single occasion in the past (~1,500 years ago). The pathogenic expansion was non-penetrant below 35 years of age, increasing to 50·0% penetrance by 58 years of age, and was almost fully penetrant by 80 years of age.
We confirm that a common single Mendelian genetic lesion is implicated in a large proportion of sporadic and familial ALS and FTD. Testing for this pathogenic expansion will be important in the management and genetic counseling of patients with these fatal neurodegenerative diseases.
See Acknowledgements.
PMCID: PMC3322422  PMID: 22406228
24.  Genetic dysfunction of MT-ATP6 causes axonal Charcot-Marie-Tooth disease 
Neurology  2012;79(11):1145-1154.
Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, affecting 1 in 2,500 individuals. Mitochondrial DNA (mtDNA) mutations are not generally considered within the differential diagnosis of patients with uncomplicated inherited neuropathy, despite the essential requirement of ATP for axonal function. We identified the mtDNA mutation m.9185T>C in MT-ATP6, encoding the ATP6 subunit of the mitochondrial ATP synthase (OXPHOS complex V), at homoplasmic levels in a family with mitochondrial disease in whom a severe motor axonal neuropathy was a striking feature. This led us to hypothesize that mutations in the 2 mtDNA complex V subunit encoding genes, MT-ATP6 and MT-ATP8, might be an unrecognized cause of isolated axonal CMT and distal hereditary motor neuropathy (dHMN).
A total of 442 probands with CMT type 2 (CMT2) (270) and dHMN (172) were screened for MT-ATP6/8 mutations after exclusion of mutations in known CMT2/dHMN genes. Mutation load was quantified using restriction endonuclease analysis. Blue-native gel electrophoresis (BN-PAGE) was performed to analyze the effects of m.9185T>C on complex V structure and function.
Three further probands with CMT2 harbored the m.9185T>C mutation. Some relatives had been classified as having dHMN. Patients could be separated into 4 groups according to their mutant m.9185T>C levels. BN-PAGE demonstrated both impaired assembly and reduced activity of the complex V holoenzyme.
We have shown that m.9185T>C in MT-ATP6 causes CMT2 in 1.1% of genetically undefined cases. This has important implications for diagnosis and genetic counseling. Recognition that mutations in MT-ATP6 cause CMT2 enhances current understanding of the pathogenic basis of axonal neuropathy.
PMCID: PMC3525307  PMID: 22933740
25.  α-Synucleinopathy associated with G51D SNCA mutation: a link between Parkinson’s disease and multiple system atrophy? 
Acta Neuropathologica  2013;125(5):753-769.
We report a British family with young-onset Parkinson’s disease (PD) and a G51D SNCA mutation that segregates with the disease. Family history was consistent with autosomal dominant inheritance as both the father and sister of the proband developed levodopa-responsive parkinsonism with onset in their late thirties. Clinical features show similarity to those seen in families with SNCA triplication and to cases of A53T SNCA mutation. Post-mortem brain examination of the proband revealed atrophy affecting frontal and temporal lobes in addition to the caudate, putamen, globus pallidus and amygdala. There was severe loss of pigmentation in the substantia nigra and pallor of the locus coeruleus. Neuronal loss was most marked in frontal and temporal cortices, hippocampal CA2/3 subregions, substantia nigra, locus coeruleus and dorsal motor nucleus of the vagus. The cellular pathology included widespread and frequent neuronal α-synuclein immunoreactive inclusions of variable morphology and oligodendroglial inclusions similar to the glial cytoplasmic inclusions of multiple system atrophy (MSA). Both inclusion types were ubiquitin and p62 positive and were labelled with phosphorylation-dependent anti-α-synuclein antibodies In addition, TDP-43 immunoreactive inclusions were observed in limbic regions and in the striatum. Together the data show clinical and neuropathological similarities to both the A53T SNCA mutation and multiplication cases. The cellular neuropathological features of this case share some characteristics of both PD and MSA with additional unique striatal and neocortical pathology. Greater understanding of the disease mechanism underlying the G51D mutation could aid in understanding of α-synuclein biology and its impact on disease phenotype.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-013-1096-7) contains supplementary material, which is available to authorized users.
PMCID: PMC3681325  PMID: 23404372
Parkinson’s disease; Multiple system atrophy; α-Synuclein; SNCA

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