Lentiviral vector-mediated overexpression of mutant ataxin-7 recapitulates SCA7 pathology and promotes accumulation of the FUS/TLS and MBNL1 RNA-binding proteins.

BACKGROUND: We used lentiviral vectors (LVs) to generate a new SCA7 animal model overexpressing a truncated mutant ataxin-7 (MUT ATXN7) fragment in the mouse cerebellum, in order to characterize the specific neuropathological and behavioral consequences of the genetic defect in this brain structure. RESULTS: LV-mediated overexpression of MUT ATXN7 into the cerebellum of C57/BL6 adult mice induced neuropathological features similar to that observed in patients, such as intranuclear aggregates in Purkinje cells (PC), loss of synaptic markers, neuroinflammation, and neuronal death. No neuropathological changes were observed when truncated wild-type ataxin-7 (WT ATXN7) was injected. Interestingly, the local delivery of LV-expressing mutant ataxin-7 (LV-MUT-ATXN7) into the cerebellum of wild-type mice also mediated the development of an ataxic phenotype at 8 to 12 weeks post-injection. Importantly, our data revealed abnormal levels of the FUS/TLS, MBNL1, and TDP-43 RNA-binding proteins in the cerebellum of the LV-MUT-ATXN7 injected mice. MUT ATXN7 overexpression induced an increase in the levels of the pathological phosphorylated TDP-43, and a decrease in the levels of soluble FUS/TLS, with both proteins accumulating within ATXN7-positive intranuclear inclusions. MBNL1 also co-aggregated with MUT ATXN7 in most PC nuclear inclusions. Interestingly, no MBNL2 aggregation was observed in cerebellar MUT ATXN7 aggregates. Immunohistochemical studies in postmortem tissue from SCA7 patients and SCA7 knock-in mice confirmed SCA7-induced nuclear accumulation of FUS/TLS and MBNL1, strongly suggesting that these proteins play a physiopathological role in SCA7. CONCLUSIONS: This study validates a novel SCA7 mouse model based on lentiviral vectors, in which strong and sustained expression of MUT ATXN7 in the cerebellum was found sufficient to generate motor defects.

Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders.

Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

The autophagy/lysosome pathway is impaired in SCA7 patients and SCA7 knock-in mice.

There is still no treatment for polyglutamine disorders, but clearance of mutant proteins might represent a potential therapeutic strategy. Autophagy, the major pathway for organelle and protein turnover, has been implicated in these diseases. To determine whether the autophagy/lysosome system contributes to the pathogenesis of spinocerebellar ataxia type 7 (SCA7), caused by expansion of a polyglutamine tract in the ataxin-7 protein, we looked for biochemical, histological and transcriptomic abnormalities in components of the autophagy/lysosome pathway in a knock-in mouse model of the disease, postmortem brain and peripheral blood mononuclear cells (PBMC) from patients. In the mouse model, mutant ataxin-7 accumulated in inclusions immunoreactive for the autophagy-associated proteins mTOR, beclin-1, p62 and ubiquitin. Atypical accumulations of the autophagosome/lysosome markers LC3, LAMP-1, LAMP2 and cathepsin-D were also found in the cerebellum of the SCA7 knock-in mice. In patients, abnormal accumulations of autophagy markers were detected in the cerebellum and cerebral cortex of patients, but not in the striatum that is spared in SCA7, suggesting that autophagy might be impaired by the selective accumulation of mutant ataxin-7. In vitro studies demonstrated that the autophagic flux was impaired in cells overexpressing full-length mutant ataxin-7. Interestingly, the expression of the early autophagy-associated gene ATG12 was increased in PBMC from SCA7 patients in correlation with disease severity. These results provide evidence that the autophagy/lysosome pathway is impaired in neurons undergoing degeneration in SCA7. Autophagy/lysosome-associated molecules might, therefore, be useful markers for monitoring the effects of potential therapeutic approaches using modulators of autophagy in SCA7 and other autophagy/lysosome-associated neurodegenerative disorders.

Interferon ß induces clearance of mutant ataxin 7 and improves locomotion in SCA7 knock-in mice.

We showed previously, in a cell model of spinocerebellar ataxia 7, that interferon beta induces the expression of PML protein and the formation of PML protein nuclear bodies that degrade mutant ataxin 7, suggesting that the cytokine, used to treat multiple sclerosis, might have therapeutic value in spinocerebellar ataxia 7. We now show that interferon beta also induces PML-dependent clearance of ataxin 7 in a preclinical model, SCA7(266Q/5Q) knock-in mice, and improves motor function. Interestingly, the presence of mutant ataxin 7 in the mice induces itself the expression of endogenous interferon beta and its receptor. Immunohistological studies in brains from two patients with spinocerebellar ataxia 7 confirmed that these modifications are also caused by the disease in humans. Interferon beta, administered intraperitoneally three times a week in the knock-in mice, was internalized with its receptor in Purkinje and other cells and translocated to the nucleus. The treatment induced PML protein expression and the formation of PML protein nuclear bodies and decreased mutant ataxin 7 in neuronal intranuclear inclusions, the hallmark of the disease. No reactive gliosis or other signs of toxicity were observed in the brain or internal organs. The performance of the SCA7(266Q/5Q) knock-in mice was significantly improved on two behavioural tests sensitive to cerebellar function: the Locotronic® Test of locomotor function and the Beam Walking Test of balance, motor coordination and fine movements, which are affected in patients with spinocerebellar ataxia 7. In addition to motor dysfunction, SCA7(266Q/5Q) mice present abnormalities in the retina as in patients: ataxin 7-positive neuronal intranuclear inclusions that were reduced by interferon beta treatment. Finally, since neuronal death does not occur in the cerebellum of SCA7(266Q/5Q) mice, we showed in primary cell cultures expressing mutant ataxin 7 that interferon beta treatment improves Purkinje cell survival.

C9ORF72 repeat expansions in the frontotemporal dementias spectrum of diseases: a flow-chart for genetic testing.

Frontotemporal dementia (FTD) refers to a disease spectrum including the behavioral variant FTD (bvFTD), primary progressive aphasia (PPA), progressive supranuclear palsy/corticobasal degeneration syndrome (PSP/CBDS), and FTD with amyotrophic lateral sclerosis (FTD-ALS). A GGGGCC expansion in C9ORF72 is a major cause of FTD and ALS. C9ORF72 was analyzed in 833 bvFTD, FTD-ALS, PPA, and PSP/CBDS probands; 202 patients from 151 families carried an expansion. C9ORF72 expansions were much more frequent in the large subgroup of patients with familial FTD-ALS (65.9%) than in those with pure FTD (12.8%); they were even more frequent than in familial pure ALS, according to estimated frequencies in the literature (23-50%). The frequency of carriers in non-familial FTD-ALS (12.7%) indicates that C9ORF72 should be analyzed even when family history is negative. Mutations were detected in 6.8% of PPA patients, and in 3.2% of patients with a clinical phenotype of PSP, thus enlarging the phenotype spectrum of C9ORF72. Onset was later in C9ORF72 (57.4 years, 95%CI: 55.9-56.1) than in MAPT patients (46.8, 95%CI: 43.0-50.6; p = 0.00001) and the same as in PGRN patients (59.6 years; 95%CI: 57.6-61.7; p = 0.4). ALS was more frequent in C9ORF72 than in MAPT and PGRN patients; onset before age 50 and parkinsonism were indicative of MAPT mutations, whereas hallucinations were indicative of PGRN mutations; prioritization of genetic testing is thus possible. Penetrance was age- and gender-dependent: by age 50, 78% of male carriers were symptomatic, but only 52% of females. This can also guide genetic testing and counseling. A flowchart for genetic testing is thus proposed.

The impact of familial structure on Parkinson's disease in Istanbul Medical School, Turkey.

The prevalence and family structure of idiopathic Parkinson disease (iPD) in Turkey is not known. Patients with iPD were recruited consecutively at the Medical School of Istanbul University over an 18-month period. Clinical details were assessed with standardized forms. Of the 219 iPD patients, 136 had sporadic iPD [26 with parental consanguinity (cs)], 20 autosomal recessive PD (9 with cs) and 63 autosomal dominant or pseudo-dominant inheritances (20 with cs). Age at onset was 49.1 ± 17.1 years (range 3-83) and age at examination 56.4 ± 16.5 years (range 4-93). Ages at examination and at clinical onset of PD were significantly greater in sporadic iPD than in familial iPD patients, but disease duration was similar. Patients with familial PD had significantly lower basal UPDRS III and Hoehn and Yahr scores than sporadic PD patients and brisk reflexes in the lower limbs were significantly more frequent, but they suffered less from mictional problems. The frequency of familial PD and consanguinity in Turkey is higher and age at onset of iPD earlier than in Western countries. Molecular diagnoses and genetic counseling will therefore have a very important impact on the medical, psychological, and familial handling of PD in Turkey.

Natural lipophilic inhibitors of mitochondrial complex I are candidate toxins for sporadic neurodegenerative tau pathologies.

Annonacin, a natural lipophilic inhibitor of mitochondrial complex I has been implicated in the etiology of a sporadic neurodegenerative tauopathy in Guadeloupe. We therefore studied further compounds representing the broad biochemical spectrum of complex I inhibitors to which humans are potentially exposed. We determined their lipophilicity, their effect on complex I activity in submitochondrial particles, and their effect on cellular ATP levels, neuronal cell death and somatodendritic redistribution of phosphorylated tau protein (AD2 antibody against pS396/pS404-tau) in primary cultures of fetal rat striatum. The 24 compounds tested were lipophilic (logP range 0.9-8.5; exception: MPP(+) logP=-1.35) and potent complex I inhibitors (IC(50) range 0.9 nM-2.6 mM). They all decreased ATP levels (EC(50) range 1.9 nM-54.2 microM), induced neuronal cell death (EC(50) range 1.1 nM-54.5 microM) and caused the redistribution of AD2(+) tau from axons to the cell body (EC(5) range 0.6 nM-33.3 microM). The potency of the compounds to inhibit complex I correlated with their potency to induce tau redistribution (r=0.80, p<0.001). In conclusion, we propose that the widely distributed lipophilic complex I inhibitors studied here might be implicated in the induction of tauopathies with global prevalence.

Atlastin-1, the dynamin-like GTPase responsible for spastic paraplegia SPG3A, remodels lipid membranes and may form tubules and vesicles in the endoplasmic reticulum.

We examined the effects of wild-type and mutant atlastin-1 on vesicle transport in the endoplasmic reticulum (ER)-Golgi interface and vesicle budding from ER-derived microsomes using the temperature-sensitive reporter vesicular stomatitis virus glycoprotein (VSV-G), and the ability of purified atlastin-1 to form tubules or vesicles from protein-free phosphatidylserine liposomes. A GTPase domain mutation (T162P) altered the cellular distribution of the ER, but none of the mutations studied significantly affected transport from the ER to the Golgi apparatus. The mutations also had no significant effect on the incorporation of VSV-G into vesicles formed from ER microsomes. Atlastin-1, however, was also incorporated into microsome-derived vesicles, suggesting that it might be implicated in vesicle formation. Purified atlastin-1 transformed phosphatidylserine liposomes into branched tubules and polygonal networks of tubules and vesicles, an action inhibited by GDP and the synthetic dynamin inhibitor dynasore. The GTPase mutations T162P and R217C decreased but did not totally prevent this action; the C-terminal transmembrane domain mutation R495W was as active as the wild-type enzyme. Similar effects were observed in human embryonic kidney cells over-expressing mutant atlastin-1. We concluded that atlastin-1, like dynamin, might be implicated in membrane tubulation and vesiculation and participated in the formation as well as the function of the ER.

In vivo evidence for cerebral depletion in high-energy phosphates in progressive supranuclear palsy.

Indirect evidence from laboratory studies suggests that mitochondrial energy metabolism is impaired in progressive supranuclear palsy (PSP), but brain energy metabolism has not yet been studied directly in vivo in a comprehensive manner in patients. We have used combined phosphorus and proton magnetic resonance spectroscopy to measure adenosine-triphosphate (ATP), adenosine-diphosphate (ADP), phosphorylated creatine, unphosphorylated creatine, inorganic phosphate and lactate in the basal ganglia and the frontal and occipital lobes of clinically probable patients (N=21; PSP stages II to III) and healthy controls (N=9). In the basal ganglia, which are severely affected creatine in PSP patients, the concentrations of high-energy phosphates (=ATP+phosphorylated creatine) and inorganic phosphate, but not low-energy phosphates (=ADP+unphosphorylated creatine), were decreased. The decrease probably does not reflect neuronal death, as the neuronal marker N-acetylaspartate was not yet significantly reduced in the early-stage patients examined. The frontal lobe, also prone to neurodegeneration in PSP, showed similar alterations, whereas the occipital lobe, typically unaffected, showed less pronounced alterations. The levels of lactate, a product of anaerobic glycolysis, were elevated in 35% of the patients. The observed changes in the levels of cerebral energy metabolites in PSP are consistent with a functionally relevant impairment of oxidative phosphorylation.

Sporadic infantile epileptic encephalopathy caused by mutations in PCDH19 resembles Dravet syndrome but mainly affects females.

Dravet syndrome (DS) is a genetically determined epileptic encephalopathy mainly caused by de novo mutations in the SCN1A gene. Since 2003, we have performed molecular analyses in a large series of patients with DS, 27% of whom were negative for mutations or rearrangements in SCN1A. In order to identify new genes responsible for the disorder in the SCN1A-negative patients, 41 probands were screened for micro-rearrangements with Illumina high-density SNP microarrays. A hemizygous deletion on chromosome Xq22.1, encompassing the PCDH19 gene, was found in one male patient. To confirm that PCDH19 is responsible for a Dravet-like syndrome, we sequenced its coding region in 73 additional SCN1A-negative patients. Nine different point mutations (four missense and five truncating mutations) were identified in 11 unrelated female patients. In addition, we demonstrated that the fibroblasts of our male patient were mosaic for the PCDH19 deletion. Patients with PCDH19 and SCN1A mutations had very similar clinical features including the association of early febrile and afebrile seizures, seizures occurring in clusters, developmental and language delays, behavioural disturbances, and cognitive regression. There were, however, slight but constant differences in the evolution of the patients, including fewer polymorphic seizures (in particular rare myoclonic jerks and atypical absences) in those with PCDH19 mutations. These results suggest that PCDH19 plays a major role in epileptic encephalopathies, with a clinical spectrum overlapping that of DS. This disorder mainly affects females. The identification of an affected mosaic male strongly supports the hypothesis that cellular interference is the pathogenic mechanism.

A locus for bilateral occipital polymicrogyria maps to chromosome 6q16-q22.

We describe the clinical, radiographic, and genetic features of a large consanguineous Moroccan family in which bilateral occipital polymicrogyria segregated as an autosomal recessive trait. Six affected members of the family had partial complex seizures often associated with behavioral abnormalities. On MRI, three patients had a thickened irregular cortex in the lateral occipital lobes with small gyri. A high-density genome-wide scan with 10,000 SNPs established linkage by homozygosity mapping to a 14-Mb region on chromosome 6q16-q22. Candidate genes by function (TUBE1, GRIK2, GPRC6A, GPR6, NR2E1, MICAL1, and MARCKS) in this locus were screened for mutations.

The PSP-associated MAPT H1 subhaplotype in Guadeloupean atypical parkinsonism.

The aim of this study was to determine whether the H1 subhaplotype in MAPT associated with progressive supranuclear palsy (PSP) in Caucasians confers risk for PSP-like atypical parkinsonism in Guadeloupe, a tauopathy. Guadeloupean controls and patients with atypical and idiopathic parkinsonism and ethnically and age-matched controls were genotyped for H1 and H2 alleles, then for the H1 subhaplotype associated with PSP in Caucasians, using previously described haplotype-tagging single nucleotide polymorphisms (Ht-SNPs) in linkage disequilibrium at the MAPT locus. Most Guadeloupean controls and patients were homozygous for the H1 allele; only 5% were heterozygous for the H2 allele, consistent with the European contribution to the racial admixture in Guadeloupe, but equivalent to the frequency found in Caucasian PSP patients. The frequencies of the Ht-SNPs used to determine the PSP-associated H1 subhaplotype in both Guadeloupean controls and parkinsonians were similar, indicating that the H1 subhaplotype associated with PSP in Caucasians was not a risk factor for PSP-like atypical parkinsonism in Guadeloupe. Interestingly, they were also similar to the frequencies in Caucasian PSP patients. The major H1 subhaplotype in Guadeloupe, determined by analysis of linkage desequibrium, differed from the major Caucasian subhaplotype, but corresponded to minor alleles previously described.

Atypical parkinsonism in the Caribbean island of Guadeloupe: etiological role of the mitochondrial complex I inhibitor annonacin.

On the French West Indian island of Guadeloupe, atypical parkinsonian patients represent two-thirds of all cases of parkinsonism, which is exceptionally frequent compared to epidemiological data from European countries where atypical parkinsonism accounts for only approximately 5% of all cases. The clinical entity was a unique combination of levodopa-resistant parkinsonism, tremor, myoclonus, hallucinations, REM sleep behavior disorder and fronto-subcortical dementia. Based on the presence or the absence of supranuclear gaze palsy, two subgroups of patients were distinguished. In patients with oculomotor signs that came to autopsy, neuronal loss was found to predominate in the substantia nigra and the striatum but other brain areas were also affected, including the frontal cortex. In addition, tau-containing lesions were detected throughout the brain. Epidemiological data suggested a close association of the disease with the regular consumption of soursop, a tropical annonaceous plant. Experimental studies performed in midbrain cell cultures identified annonacin, a selective mitochondrial complex I inhibitor contained in the fruit and leaves of soursop, as a probable etiological factor. Consistent with this view, chronic administration of annonacin to rats through Alzet osmotic minipumps showed that annonacin was able to reproduce the brain lesions characteristic of the human disease.

Recent advances in the genetics of spastic paraplegias.

Hereditary spastic paraplegias (HSPs) are genetically heterogeneous mendelian disorders characterized by weakness and spasticity in the lower limbs associated with additional neurologic signs in "complex" or "complicated" forms. Major advances have been made during the past two decades in our understanding of their molecular bases. The mapping of 34 genes (17 of which have been identified) involved in this clinically diverse group of disorders has highlighted their great genetic heterogeneity. From the combined genetic and clinical information obtained, a new classification is now emerging that will help to better diagnose this condition, evaluate disease progression, guide follow-up, and permit genetic counselling. Evidence is now accumulating that at least part of the physiopathology results from abnormal intracellular trafficking, as well as from altered cell recognition and signaling, oligodendroglial dysfunction, mitochondrial defects, and impaired cholesterol and/or neurosteroid metabolism.

Composite cerebellar functional severity score: validation of a quantitative score of cerebellar impairment.

Reliable and easy to perform functional scales are a prerequisite for future therapeutic trials in cerebellar ataxias. In order to assess the specificity of quantitative functional tests of cerebellar dysfunction, we investigated 123 controls, 141 patients with an autosomal dominant cerebellar ataxia (ADCA) and 53 patients with autosomal dominant spastic paraplegia (ADSP). We evaluated four different functional tests (nine-hole pegboard, click, tapping and writing tests), in correlation with the scale for the assessment and rating of cerebellar ataxia (SARA), the scale of functional disability on daily activities (part IV of the Huntington disease rating scale), depression (the Public Health Questionnaire PHQ-9) and the EQ-5D visual analogue scale for self-evaluation of health status. There was a significant correlation between each functional test and a lower limb score. The performance of controls on the functional tests was significantly correlated with age. Subsequent analyses were therefore adjusted for this factor. The performances of ADCA patients on the different tests were significantly worse than that of controls and ADSP patients; there was no difference between ADSP patients and controls. Linear regression analysis showed that only two independent tests, the nine-hole pegboard and the click test on the dominant side (P < 0.0001), accounted for the severity of the cerebellar syndrome as reflected by the SARA scores, and could be represented by a composite cerebellar functional severity (CCFS) score calculated as follows: [Formula: see text]. The CCFS score was significantly higher in ADCA patients compared to controls (1.12 +/- 0.18 versus 0.85 +/- 0.05, P(c) < 0.0001) and ADSP patients (1.12 +/- 0.18 versus 0.90 +/- 0.08, P(c) < 0.0001) and was correlated with disease duration (P < 0.0001) but independent of self-evaluated depressive mood in ADCA. Among genetically homogeneous subgroups of ADCA patients (Spinocerebellar ataxia 1, 2, 3), SCA3 patients had significantly lower (better) CCFS scores than SCA2 (P(c) < 0.04) and the same tendency was observed in SCA1. Their CCFS scores remained significantly worse than those of ADSP patients with identified SPG4 mutations (P < 0.0001). The pegboard and click tests are easy to perform and accurately reflect the severity of the disease. The CCFS is a simple and validated method for assessing cerebellar ataxia over a wide range of severity, and will be particularly useful for discriminating paucisymptomatic carriers from affected patients and for evaluating disease progression in future therapeutic trials.

REM sleep behavior disorder in patients with guadeloupean parkinsonism, a tauopathy.

STUDY OBJECTIVE: To describe sleep characteristics and rapid eye movement (REM) sleep behavior disorder in patients with Guadeloupean atypical parkinsonism (Gd-PSP), a tauopathy resembling progressive supranuclear palsy that mainly affects the midbrain. It is possibly caused by the ingestion of sour sop (corossol), a tropical fruit containing acetogenins, which are mitochondrial poisons. DESIGN: Sleep interview, motor and cognitive tests, and overnight videopolysomnography. PATIENTS: Thirty-six age-, sex-, disease-duration- and disability-matched patients with Gd-PSP (n = 9), progressive supranuclear palsy (a tauopathy, n = 9), Parkinson disease (a synucleinopathy, n = 9) and controls (n = 9). SETTINGS: Tertiary-care academic hospital. RESULTS: REM sleep behavior disorder was found in 78% patients with Gd-PSP (43% of patients reported having this disorder several years before the onset of parkinsonism), 44% of patients with idiopathic Parkinson disease, 33% of patients with progressive supranuclear palsy, and no controls. The percentage of muscle activity during REM sleep was greater in patients with Gd-PSP than in controls (limb muscle activity, 8.3%+/-8.7% vs 0.1%+/- 0.2%; chin muscle activity, 24.3%+/- 23.7% vs 0.7%+/-2.0%) but similar to that of other patient groups. The latency and percentage of REM sleep were similar in patients with Gd-PSP, patients with Parkinson disease, and controls, whereas patients with progressive supranuclear palsy had delayed and shortened REM sleep. CONCLUSION: Although Gd-PSP is a tauopathy, most patients experience REM sleep behavior disorder. This suggests that the location of neuronal loss or dysfunction in the midbrain, rather than the protein comprising the histologic lesions (synuclein versus tau aggregation), is responsible for suppressing muscle atonia during REM sleep. Subjects with idiopathic REM sleep behavior disorder should avoid eating sour sop.

Annonacin, a natural mitochondrial complex I inhibitor, causes tau pathology in cultured neurons.

A neurodegenerative tauopathy endemic to the Caribbean island of Guadeloupe has been associated with the consumption of anonaceous plants that contain acetogenins, potent lipophilic inhibitors of complex I of the mitochondrial respiratory chain. To test the hypothesis that annonacin, a prototypical acetogenin, contributes to the etiology of the disease, we investigated whether annonacin affects the cellular distribution of the protein tau. In primary cultures of rat striatal neurons treated for 48 h with annonacin, there was a concentration-dependent decrease in ATP levels, a redistribution of tau from the axons to the cell body, and cell death. Annonacin induced the retrograde transport of mitochondria, some of which had tau attached to their outer membrane. Taxol, a drug that displaces tau from microtubules, prevented the somatic redistribution of both mitochondria and tau but not cell death. Antioxidants, which scavenged the reactive oxygen species produced by complex I inhibition, did not affect either the redistribution of tau or cell death. Both were prevented, however, by forced expression of the NDI1 nicotinamide adenine dinucleotide (NADH)-quinone-oxidoreductase of Saccharomyces cerevisiae, which can restore NADH oxidation in complex I-deficient mammalian cells and stimulation of energy production via anaerobic glycolysis. Consistently, other ATP-depleting neurotoxins (1-methyl-4-phenylpyridinium, 3-nitropropionic, and carbonyl cyanide m-chlorophenylhydrazone) reproduced the somatic redistribution of tau, whereas toxins that did not decrease ATP levels did not cause the redistribution of tau. Therefore, the annonacin-induced ATP depletion causes the retrograde transport of mitochondria to the cell soma and induces changes in the intracellular distribution of tau in a way that shares characteristics with some neurodegenerative diseases.

Frequency of the LRRK2 G2019S mutation in siblings with Parkinson's disease.

BACKGROUND: Mutations in the LRRK2 gene, the most frequent of which is the G2019S mutation in exon 41, cause familial and sporadic Parkinson's disease (PD) with reduced penetrance. OBJECTIVES: To assess the frequency of the LRRK2 G2019S mutation in families thought to have autosomal recessive PD (siblings but not their parents were affected) and to determine the clinical features of LRRK2 mutation carriers. METHODS: We sequenced both strands of exon 41 of the LRKK2 gene in 90 index cases from French and North African families in which PD might have been inherited as a recessive trait. Patients with mutations underwent detailed clinical evaluations. RESULTS: We found heterozygous G2019S mutations in 1 Algerian and 1 French family (overall relative frequency = 2.2%). Four LRRK2-positive patients had typical PD, but their Mini Mental State Examination (MMSE) scores were lower than those of patients without this mutation. CONCLUSION: The LRRK2 G2019S mutation is as frequent in families with possible autosomal recessive PD (2.2%) as in the sporadic cases published elsewhere (1.9%). The clinical features in the LRRK2-positive patients were those of typical PD, except for lower MMSE scores.

A de novo SPAST mutation leading to somatic mosaicism is associated with a later age at onset in HSP.

SPG4/SPAST, the gene-encoding spastin, is responsible for the most frequent form of autosomal dominant hereditary spastic paraplegia (HSP). SPG4-HSP is a heterogeneous disorder characterized by both interfamilial and intrafamilial variation, especially regarding the severity and the age at onset. In this study, we investigated the origin of the mutation and the factors involved in intra-familial heterogeneity in a family with a SPG4 mutation. We demonstrated that the mutation occurred de novo and show evidence of somatic mosaicism in the grandfather, who was the only affected member of six siblings. His disease began at age 55, much later than in his daughter, who had onset at age 18, and his grandson, in whom onset was at age 5. These observations indicate that de novo mutations can occur in SPG4, and that somatic mosaicism might account for intra-familial variation in SPG4-linked HSP.