Tubers from patients with tuberous sclerosis complex are characterized by changes in microtubule biology through ROCK2 signalling.

Most patients with tuberous sclerosis complex (TSC) develop cortical tubers that cause severe neurological disabilities. It has been suggested that defects in neuronal differentiation and/or migration underlie the appearance of tubers. However, the precise molecular alterations remain largely unknown. Here, by combining cytological and immunohistochemical analyses of tubers from nine TSC patients (four of them diagnosed with TSC2 germline mutations), we show that alteration of microtubule biology through ROCK2 signalling contributes to TSC neuropathology. All tubers showed a larger number of binucleated neurons than expected relative to control cortex. An excess of normal and altered cytokinetic figures was also commonly observed. Analysis of centrosomal markers suggested increased microtubule nucleation capacity, which was supported by the analysis of an expression dataset from cortical tubers and control cortex, and subsequently linked to under-expression of Rho-associated coiled-coil containing kinase 2 (ROCK2). Thus, augmented microtubule nucleation capacity was observed in mouse embryonic fibroblasts and human fibroblasts deficient in the Tsc2/TSC2 gene product, tuberin. Consistent with ROCK2 under-expression, microtubule acetylation was found to be increased with tuberin deficiency; this alteration was abrogated by rapamycin treatment and mimicked by HDAC6 inhibition. Together, the results of this study support the hypothesis that loss of TSC2 expression can alter microtubule organization and dynamics, which, in turn, deregulate cell division and potentially impair neuronal differentiation.

Revisiting genotype-phenotype overlap in neurogenetics: triplet-repeat expansions mimicking spastic paraplegias.

Hereditary spastic paraplegias (HSPs) constitute a heterogeneous group of neurological disorders, characterized primarily by progressive spasticity and weakness of the lower limbs. HSPs are caused by mutations in multiple genes (at least 48 loci and 28 causative genes). The clinical spectrum of HSPs is wide and important differences have been reported between patients with distinct mutations in the same gene, or even between different family members bearing the same mutation. Many patients with HSP present clinical deficits related to the involvement of neuronal systems other than corticospinal tracts, namely, peripheral nerves, sensory, or cerebellar pathways. These cases may be difficult to differentiate from other neurological diseases (e.g., hereditary ataxias), also genetically and clinically heterogeneous. As an illustration of how overlapping this genotype-phenotype relationship is, and the difficulties that it brings upon the development of neurogenetic algorithms and databases, we review the main clinical and genetic features of HSPs, and summarize reports on cases of triplet-repeat spinocerebellar ataxias that can mimic HSP phenotypes. This complex scenario makes the necessity of high-quality, curated mutation databases even more urgent, in order to develop adequate diagnostic guidelines, correct interpretation of genetic testing, and appropriate genetic counseling.

The effects of parkin suppression on the behaviour, amyloid processing, and cell survival in APP mutant transgenic mice.

Parkin suppression induces accumulation of beta-amyloid in mutant tau mice. We studied the effect of parkin suppression on behaviour and brain pathology in APP(swe) mutant mice. We produced double mutant mice with human mutated APP(swe)+partial (hemizygote) or total (homozygote) deletion of Park-2 gene. We studied the development, behaviour, brain histology, and biochemistry of 12- and 16-month-old animals in 6 groups of mice, with identical genetic background: wild-type (WT), APP(swe) overexpressing (APP), hemizygote and homozygote deletion of Park-2 (PK(+/-) and PK(-/-), respectively), and double mutants (APP/PK(+/-) and APP/PK(-/-)). APP mice have reduced weight gain, decreased motor activity, and reduced number of entrances and of arm alternation in the Y-maze, abnormalities which were partially or completely normalized in APP/PK(+/-) and APP/PK(-/-) mice. The double mutants had similar number of mutant human APP transgene copies than the APP and levels of 40 and 80 kDa proteins; but both of them, APP/PK(+/-) and APP/PK(-/-) mice, had less plaques in cortex and hippocampus than the APP mice. APP mutant mice had increased apoptosis, proapoptotic Bax/Bcl2 ratios, and gliosis, but these death-promoting factors were normalized in APP/PK(+/-) and APP/PK(-/-) mice. APP mutant mice had an increased number of tau immunoreactive neuritic plaques in the cerebral cortex as well as increased levels of total and phosphorylated tau protein, and these changes were partially normalized in APP/PK(+/-) heterozygotic and homozygotic APP/PK(-/-) mice. Compensatory protein-degrading systems such as HSP70, CHIP, and macroautophagy were increased in APP/PK(+/-) and APP/PK(-/-). Furthermore, the chymotrypsin- and trypsin-like proteasome activities, decreased in APP mice in comparison with WT, were normalized in the APP/PK(-/-) mice. We proposed that partial and total suppression of parkin triggers compensatory mechanisms, such as chaperone overexpression and increased autophagy, which improved the behavioural and cellular phenotype of APP(swe) mice.

On the diagnosis of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a genetic arteriopathy related to Notch3 mutations, is difficult to diagnosis. The goal of this study was to determine the value of clinical, immunohistochemical, and molecular techniques for the diagnosis of CADASIL. Clinical features and the immunohistochemical and molecular findings in 200 subjects with suspected CADASIL in whom 93 biopsies and 190 molecular studies are reported. Eighteen pathogenic mutations of the Notch3 gene, six of them previously unreported, were detected in 67 patients. The clinical features did not permit differentiation between CADASIL and CADASIL-like syndromes. The sensitivity and specificity of the skin biopsies was 97.7% and 56.5%, respectively, but increased to 100% and 81.5%, respectively, in cases with proven family history. In conclusion, a clinical diagnosis of CADASIL is difficult to determine and confirmatory techniques should be used judiciously.

Parkin deletion causes cerebral and systemic amyloidosis in human mutated tau over-expressing mice.

Deposition of proteins leading to amyloid takes place in some neurodegenerative diseases such as Alzheimer's disease and Huntington's disease. Mutations of tau and parkin proteins produce neurofibrillary abnormalities without deposition of amyloid. Here we report that mature, parkin null, over-expressing human mutated tau (PK(-/-)/Tau(VLW)) mice have altered behaviour and dopamine neurotransmission, tau pathology in brain and amyloid deposition in brain and peripheral organs. PK(-/-)/Tau(VLW) mice have abnormal behaviour and severe drop out of dopamine neurons in the ventral midbrain, up to 70%, at 12 months and abundant phosphorylated tau positive neuritic plaques, neuro-fibrillary tangles, astrogliosis, microgliosis and plaques of murine beta-amyloid in the hippocampus. PK(-/-)/Tau(VLW) mice have organomegaly of the liver, spleen and kidneys. The electron microscopy of the liver confirmed the presence of a fibrillary protein deposits with amyloid characteristics. There is also accumulation of mouse tau in hepatocytes. These mice have lower levels of CHIP-HSP70, involved in the proteosomal degradation of tau, increased oxidative stress, measured as depletion of glutathione which, added to lack of parkin, could trigger tau accumulation and amyloidogenesis. This model is the first that demonstrates beta-amyloid deposits caused by over-expression of tau and without modification of the amyloid precursor protein, presenilins or secretases. PK(-/-)/Tau(VLW) mice provide a link between the two proteins more important for the pathogenesis of Alzheimer disease.

Risk factors for dementia of Alzheimer type and aging-associated cognitive decline in a Spanish population based sample, and in brains with pathology confirmed Alzheimer's disease.

We investigated the environmental and genetic factors for Alzheimer's disease (AD) in Spain and performed a door to door study of a cohort of more than 500 subjects, over 70 years old, from Leganés, a suburban area near Madrid. The cohort was followed for 6 years by neurologists and other health workers and was divided in three groups: normal controls, subjects with aging-associated cognitive decline (AACD) and probable AD or dementia of Alzheimer's type (DAT). Biological variables and polymorphisms of different genes, important in neurodegeneration or reported to be associated with AD, were investigated as putative risk modifiers. These polymorphisms have also been analyzed in 94 brains, 39 from patients with pathologically confirmed AD and 55 controls. The statistical investigation included the evaluation of different individual risks and a multinomial logistic regression analysis to detect predictive factors. The risk of AACD and AD increased with age, feminine gender and history of stroke and decreased with education. The allele ApoE4 increased the risk of AD but not of AACD. When the impact of ApoE4 was added to the model, the effect of education and stroke disappeared as risk modifiers.

Parkin polymorphisms in progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) is a mostly sporadic disorder of unknown pathogenesis. Familial PSP have been reported related to mutations of microtubule-associated protein tau (MAPT). Mutations of the Park2 gene cause autosomal recessive parkinsonism with neuropathological findings consistent with neurofibrillary tangles and tau immunoreactive lesions. We analysed the presence of MAPT and Park2 mutations and polymorphisms in sporadic and familial PSP. No patients had mutations of Park2 or MAPT but there was genetic association for the polymorphism Val380Leu in sporadic and familial PSP. Leu380 is associated with less risk of familial or sporadic PSP.

Association in alcoholic patients between psychopathic traits and the additive effect of allelic forms of the CNR1 and FAAH endocannabinoid genes, and the 3' region of the DRD2 gene.

Little is known about the genetic factors that underlie the comorbidity between alcohol use disorder and antisocial personality disorder. Previous studies have associated both, dopaminergic and endocannabinoid systems to severe alcoholism with non-adaptive disrupted behaviours. In this work we have examined some gene variants involved in such systems in a sample of alcoholic patients to test whether there is a relationship with antisocial traits. The genetic analysis involved the genotyping of the single nucleotide polymorphism (SNP) TaqIA located nearby the DRD2 gene, the 10-repeat allele of a variable number tandem repeats (VNTR) of the SLC6A3 gene, the C385A FAAH SNP and the 3'-UTR microsatellite of CNR1 gene. The clinical study was performed in 137 Spanish alcohol dependent males. Antisocial Personality Disorder (DSM-IV) diagnosis was made by applying the International Personality Disorder Examination, and psychopathic traits were evaluated by the Hare's Psychopathy Checklist revised (PCL-R). The genotype distribution indicates there is a relationship between the TaqIA SNP, CNR1 and FAAH genes and PCL-R's Factor 1 in alcoholic patients. This relationship seems to be additive and independent and might be responsible for 11.4% of the variance in this PCL-R subscale. Our results suggest the implication of the dopaminergic and endocannabinoid systems in those processes leading to the comorbidity of alcoholism and antisocial behaviour.

(AAT)n repeat in the cannabinoid receptor gene, CNR1: association with schizophrenia in a Spanish population.

The cannabinoid receptor 1 gene (CNR1) has been associated with addictive disorders and schizophrenia in different studies. We have compared the frequencies of the alleles for the 3'-UTR CNR1 microsatellite in a sample of 113 Spanish schizophrenic patients, including 68 with comorbid substance abuse, and 111 healthy controls. We report that the frequency of the allele 4 of this microsatellite is significantly lower in schizophrenia patients when compared with controls (chi(2) = 7.858; df 1; P = 0.005). No differences have been found with respect to substance abuse.Thus, the allele 4 represents, in our sample, a protective factor against schizophrenia (odds ratio 0.468, 95% confidence interval (CI) 0.27-0.79). The population attributable genetic risk for the allele 4 absence is 30% (95% CI = 17-41%) and the attributable risk for the allele 4 absence in those with schizophrenia is 53% (95% CI = 20-73%). Our results suggest that, independent of substance abuse, differences in the cannabinoid system function could be involved in the vulnerability to schizophrenia in Spanish population.

Genetic linkage of autosomal dominant progressive supranuclear palsy to 1q31.1.

Progressive supranuclear palsy (PSP) is a disorder of unknown pathogenesis. Familial clusters of PSP have been reported related to mutations of protein tau. We report the linkage of a large Spanish family with typical autosomal dominant PSP to a new locus in chromosome 1. Four members of this family had typical PSP, confirmed by neuropathology in one case. At least five ancestors had similar disease. Other members of the family have incomplete phenotypes. The power of the linkage analysis was increased by detecting presymptomatic individuals with 18F-fluoro-dopa and 18F-deoxyglucose positron emission tomography. We screened the human genome with 340 polymorphic markers and we enriched the areas of interest with additional markers. The disease status was defined according to the clinical and positron emission tomography data. We excluded linkage to the tau gene in chromosome 17. PSP was linked, in this family, to one area of 3.4 cM in chromosome 1q31.1, with a maximal multipoint < OD score of +3.53. This area contains at least three genes, whose relevance in PSP is unknown. We expect to further define the gene responsible for PSP, which could help to understand the pathogenesis of this disease and to design effective treatment.

Revisión del significado clínico del polimorfismo TaqI a en la dependencia alcohólica / Clinical significance of taqI a on alcohol dependence: a review

El gen para el receptor de dopamina D2 ha sido uno de los más investigados en neuropsiquiatría. Después de que en 1990 se estableciese la asociación del alelo Taql A con el alcoholismo se han publicado un gran número de trabajos. El principal problema de estos estudios reside en la heterogeneidad de los resultados sobre la asociación con la dependencia y en la diversidad de fenotipos relacionados. En este trabajo se revisan todos los estudios recogidos en MEDLINE desde 1990 hasta diciembre de 2003 en los que se haya estudiado la asociación del alelo A1 en dependientes del alcohol. Se ha intentado establecer las relaciones de dicho alelo con las características fenotipicas y endofenitípicas presentes en dependientes del alcohol. Los resultados de la revisión indican que el alelo A1 se asocia con el alcoholismo, especialmente con sus formas más graves. Los alcohólicos portadores de dicho alelo tienen tres veces más riesgo para la enfermedad que la población control. Las características fenotipicas de los pacientes con dicho alelo son la edad de inicio más temprano, la presencia de más complicaciones y de conductas antisociales. Los hallazgos endofenotípicos indican la relación del Taql A con una hipofunción de receptores dopaminérgicos D2. En conclusión, a pesar de que el Taql no tenga expresión genética, los hallazgos apuntan a que dicho polimorfismo está asociado a otras variantes genéticas implicadas en la función dopaminérgica mesolímbica (AU)

The new mutation, E46K, of alpha-synuclein causes Parkinson and Lewy body dementia.

Familial parkinsonism and dementia with cortical and subcortical Lewy bodies is uncommon, and no genetic defect has been reported in the previously described sibships. We present a Spanish family with autosomal dominant parkinsonism, dementia, and visual hallucinations of variable severity. The postmortem examination showed atrophy of the substantia nigra, lack of Alzheimer pathology, and numerous Lewy bodies which were immunoreactive to alpha-synuclein and ubiquitin in cortical and subcortical areas. Sequencing of the alpha-synuclein gene showed a novel, nonconservative E46K mutation in heterozygosis. The E46K mutation was present in all affected family members and in three young asymptomatic subjects, but it was absent in healthy and pathological controls. The novel mutation, that substitutes a dicarboxylic amino acid, glutamic acid, with a basic amino acid such as lysine in a much conserved area of the protein, is likely to produce severe disturbance of protein function. Our data show that, in addition to the previously described hereditary alpha-synucleinopathies, dementia with Lewy bodies is related to mutation of alpha-synuclein.

Steele-Richardson-Olszewski syndrome in a patient with a single C212Y mutation in the parkin protein.

Steele-Richardson-Olszewski syndrome (SROS) is a neurodegenerative disorder of unknown aetiology, most frequently sporadic. Familial cases of SROS have been described. An intronic polymorphism of the tau gene is associated with sporadic SROS and mutations of the tau gene are present in atypical cases of SROS. The role of tau has been excluded in other families with pathology proven SROS, suggesting that this syndrome may have multiple causes. An 82-year-old patient, father of 3 children with autosomal recessive juvenile parkinsonism due to combined heterozygous mutations of the parkin gene, developed clinical features of SROS 2 years before death. The diagnosis was confirmed by pathology. He carried the C212Y mutation of the parkin gene and was homozygous for the A0 polymorphism and for the H1 haplotype. The role of parkin in the processing of tau is discussed.

Molecular findings in familial Parkinson disease in Spain.

BACKGROUND: Several genetic errors in alpha-synuclein (Park1) and ubiquitin carboxyl-terminal-hydrolase L1(Park5) genes cause autosomal dominant familial Parkinson disease. Mutations in the parkin gene (Park2) are the major cause of autosomal recessive Parkinson disease. OBJECTIVE: To analyze the clinical and molecular data of 19 Spanish kindreds (13 with recessive, 4 with dominant, and 2 with uncertain inheritance) who have familial Parkinson disease. METHODS: We searched for the previously described mutations in Park1 and Park5 genes and for new or described mutations in Park2. We used single-strand conformation polymorphism, direct sequencing, and restriction digestion of polymerase chain reaction (PCR)-amplified genomic DNA for this study. RESULTS: None of these families have either Park1 or Park5 mutations. We found 5 different mutations in Park2 gene in 5 of the families with recessive inheritance. To our knowledge, 2 of these mutations, V56E and C212Y, have not been previously reported. The other mutations found (deletion of exons 3 and 5 and 225delA) have been described in other ethnic groups. Heterozygous carriers of a single Park2 mutation either were asymptomatic or developed clinical symptoms in late adulthood or after brief exposure to haloperidol therapy. CONCLUSIONS: Mutations in Park2 gene account for 38% of the families with recessive parkinsonism in Spain. We found 2 cases of simple heterozygous Park2 mutation carriers that developed clinical symptoms, either in late adulthood or after brief exposure to parkinsonizing agents. Thus, hereditary Parkinson disease has more variable clinical phenotype and molecular defects than previously thought since heterozygous mutations could be a risk factor for parkinsonism.