[Identification of people at the latent stage of Parkinson's disease (the PARKINLAR study): first results and an optimization of the algorithm].

AIM: To work out an optimal algorithm to identify people at the latent stage of neurodegenerative process of «parkinsonian¼ type in the Russian population. MATERIAL AND METHODS: Authors launched a two-step study aimed at identifying people at the latent stage of Parkinson's disease (PD) in the Russian population - the PARKINLAR (PARKINsonism, LAtent stage, Russia). As the first step, we formed a group of «primary risk¼ by the identification in neurologically healthy people of at least one of the following confirmed PD risk factors: a) the substantia nigra hyperechogenicity (ultrasound screening was performed in 193 people); b) mutations in «parkinsonian¼ genes (genetic screening was performed in 29 relatives of PD patients from families with LRRK2, PARK2 and GBA mutations). Thereby, 37 people comprised the «primary risk¼ group, of whom 23 agreed to continue further examination (44±10.2 years). A matched group of people without the aforementioned primary biomarkers of PD served as control. As the second step, we undertook in the prescreened groups a complex of investigations assessing the presence of secondary («minor¼) biomarkers of PD: Sniffin' Sticks olfactory testing; color visual evoked potentials; analysis of goal-directed eye-head-hand movements with the use of a special neuro-cybernetic system; assessment of motor and non-motor symptoms with the use of UPDRS and NMSS scales. RESULTS: When comparing the «primary risk¼ group with controls, maximal differences in the occurrence of symptoms were seen for goal-directed eye movements (43.5% vs. 20.0%) and color vision (39.1% vs. 26.7%). Among these individuals, we found two people with 4 secondary biomarkers and one with 3, and no such observations in controls. People with the combination of a primary biomarker with several secondary biomarkers of PD comprised a group of «high risk¼ in our study. CONCLUSION: Optimization of this algorithm of population screening of people predisposed to the development of PD may be done by expanding the spectrum of biomarkers and assessing their validity in a long-term prospective observational study.

Therapeutic efficacy of the neuroprotective plant adaptogen in neurodegenerative disease (Parkinson's disease as an example).

Therapeutic efficacy of the plant neuroprotector Phytomix-40 in Parkinson's disease was demonstrated. This preparation consists of the components from extracts of 40 plants, including some adaptogens (ginseng, eleutherococcus, Rhodiola rosea, etc.). The preparation normalized immune, antioxidant, and hormonal parameters in patients. The neuroprotective plant adaptogen can be used in complex therapy for Parkinson's disease for improving its efficacy.

A common leucine-rich repeat kinase 2 gene mutation in familial and sporadic Parkinson's disease in Russia.

A PARK8 form of Parkinson's disease (PD) is caused by a novel gene, leucine-rich repeat kinase 2 (LRRK2), and a single mutation G2019S was found in a proportion of LRRK2-associated cases of diverse ethnic origins. We performed the LRRK2 G2019S mutation analysis in 304 Russian patients with PD, including 291 sporadic and 13 autosomal dominant cases. The frequency of the LRRK2 G2019S was 0.7% amongst the sporadic patients (2/291) and 7.7% amongst familial PD (1/13). The mutation was also found in three unaffected relatives and absent in 700 control chromosomes. One patient carrying the LRRK2 G2019S was found earlier to have an additional mutation, a heterozygous duplication of exon 5 of the parkin gene. All patients carrying the LRRK2 G2019S exhibited typical levodopa-responsive parkinsonism, and severe levodopa-induced dyskinesia was observed in the patient carrying the LRRK2 and parkin mutations. There was notable variability in ages of the disease onset in G2019S carriers not explained by APOE genotypes. Two subsets of G2019S-positive patients had different PARK8 haplotypes suggesting that the LRRK2 G2019S in Russian patients had arisen independently on different chromosomes. Identification of common LRRK2 mutations in some PD patients without an overt family history has notable implications for genetic counseling.

Characteristics of learning voluntary control of posture in lesions of the pyramidal and nigrostriatal systems.

The aim of the study reported here was to investigate impairments on the learning of voluntary control of the center of pressures using visual feedback in patients with lesions of the corticospinal and nigrostriatal systems. Participants were 33 patients with Parkinson's disease and 20 patients with hemipareses due to circulatory lesions in the basin of the middle cerebral artery. Subjects stood on a stabilometric platform and used two computer games over 10 days to learn to shift the body relative to the foot to move the centre of pressures, indicated by the position of a cursor on the screen, with the target and to move the target to a specified part of the screen. The games differed in terms of the postural tasks. In one, the direction of movement of the center of pressures was not known to the subjects, and subjects learned a general strategy for posture control; the other formed a strictly defined postural coordination. Both groups of patients were found to have impairments of voluntary control of the position of the center of pressures. There were no differences between groups of patients, in terms of the severity of the initial performance deficit in the task involving shifts of the center of pressures in different directions (the general strategy for controlling the center of pressures), while learning of this task was more difficult for patients with Parkinson's disease. The initial deficit in the fine postural coordination task was more marked in patients with Parkinsonism, though learning in these patients was significantly better than in patients with hemipareses. It is suggested that the mechanisms of involvement of the nigrostriatal and corticospinal systems in learning the voluntary control of posture have elements in common as well as unique elements.

Peculiarities of carnosine metabolism in a patient with pronounced homocarnosinemia.

The article describes a case of homocarnosinemia with increased liquor and plasma content of homocarnosine, increased urinary excretion of homocarnosine, and low activity of serum carnosinase. These metabolic disturbances were accompanied by moderate neurological disorders. Changes in carnosine metabolism in family members were less pronounced and not accompanied by neuropathological symptoms.

Different phenotypes of Friedreich's ataxia within one 'pseudo-dominant' genealogy: relationships between trinucleotide (GAA) repeat lengths and clinical features.

We examined a large Turkmen family with 'pseudo-dominant' inheritance of Friedreich's ataxia resulting from consanguineous marriage of a Friedreich's ataxia patient to a heterozygote carrying an ancestral mutated allele. Two distinct phenotypes of the disease co-segregated within this genealogy. Two brothers from the younger generation exhibited 'classical' Friedreich's ataxia with onset of symptoms before 10 years and a rapidly progressive course. In contrast, three patients (two sisters from the younger generation and their father) had a more benign phenotype of late-onset Friedreich's ataxia with the onset at 26, 45 and 48 years and slow progression over decades. The patients with 'classical' Friedreich's ataxia were homozygous for a common ancestral expanded allele of the X25 gene containing 700-800 GAA repeats, while the patients with late-onset Friedreich's ataxia had two different mutated alleles, the shorter 250-repeat expansion of paternal origin and the longer 700-repeat expansion of maternal origin. One may conclude that clinical variability of Friedreich's ataxia in our patients is accounted for predominantly by a modifying effect of one of the two (shorter or longer) expanded alleles inherited from their affected father. Our observation clearly demonstrates the significance of variable-sized alleles for the phenotypic expression of the disease.

Identical dysferlin mutation in limb-girdle muscular dystrophy type 2B and distal myopathy.

Limb-girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy (MM) are autosomal recessive disorders caused by mutations in the dysferlin gene on chromosome 2p13. The authors studied a large Russian family with both LGMD2B and MM. All affected individuals, as well as one preclinical boy with dystrophic changes on muscle biopsy, were found to be homozygous for a novel dysferlin mutation, TG573/574AT (Val67Asp). This finding supports the view that additional factors (e.g., modifier genes) contribute to the phenotypic expression of causative mutations in dysferlinopathies.

A common 3-bp deletion in the DYT1 gene in Russian families with early-onset torsion dystonia.

Hereditary torsion dystonia represent a clinically and genetically heterogeneous group of movement disorders. The most severe and frequent form of hereditary torsion dystonia is early-onset generalized dystonia, DYT1. The DYT1 gene (Ozelius et al., 1997) encodes an ATP-binding protein torsin A. A unique 3-bp deletion (GAG) was found in the heterozygous state in almost all patients with early-onset dystonia from different populations. We observed 39 patients with early-onset generalized torsion dystonia belonging to 22 families from Russia. Seven families were of Ashkenazi Jewish (AJ) ethnic background, and other patients originated from the Slavonic population of Russia. The GAG deletion was identified in 24 affected persons from 15 families (68.2% of the families studied). In all the 7 families of AJ origin the disease was found to be caused by the deletion. In Slavs, the deletion was identified in 8 of 15 families (53%). In two deletion-positive families we observed the co-occurrence of typical early-onset generalized dystonia and atypical phenotypes-either isolated postural hand tremor or stutter.

A novel mutation in the GTP cyclohydrolase I gene associated with a broad range of clinical presentations in a family with autosomal dominant dopa-responsive dystonia.

We examined a large family of Ashkenazi Jewish origin with autosomal dominant dopa-responsive dystonia (DRD). Mutation analysis of the GTP cyclohydrolase I gene revealed in affected members a novel point mutation (a C/A change in exon 1) resulting in a threonine-to-lysine substitution at residue 94. The mutation was characterized by variable expressivity and was associated with either a 'classical' DRD phenotype or various atypical phenotypes, such as subtle transitory equinovarus postures of the feet or isolated hand tremor. This observation demonstrates the significance of the molecular testing in establishing the clinical diagnosis of DRD.

Studies of the candidate genes in X-linked congenital cerebellar hypoplasia.

A gene for X-linked congenital cerebellar hypoplasia was recently localized to chromosome Xp11.21-q24. This region comprises several brain-specific genes responsible for various neurological disorders, including the proteolipid protein (PLP), doublecortin, and PAK3 genes. We screened these genes for mutations in patients with X-linked congenital cerebellar hypoplasia and found no pathogenic nucleotide changes or gene dose alterations. These findings allow the ruling out of PLP, doublecortin, and PAK3 as the disease-causing genes in this hereditary neurological syndrome.

De novo mutations (GAG deletion) in the DYT1 gene in two non-Jewish patients with early-onset dystonia.

The DYT1 gene recently has been cloned and shown to contain a three nucleotide (GAG) deletion responsible for most cases of autosomal dominant early-onset torsion dystonia. This deletion results in the loss of one of a pair of glutamic acids in a conserved region of a novel ATP-binding protein (torsinA). Previous haplotype analysis revealed that this same deletion had arisen at least two different times in history, suggesting independent mutational events. This deletion is the only sequence change found thus far to be associated uniquely with the disease status, regardless of ethnic origin. Here we describe two patients with typical early-onset torsion dystonia of Swiss-Mennonite and non-Jewish Russian origin, respectively, that both carry this same mutation as a de novo GAG deletion. This finding proves that this 3 bp deletion in the DYT1 gene is indeed a mutation that causes early-onset torsion dystonia. The DYT1 mutation is one of the rare examples of the same recurrent mutation causing a dominantly inherited condition. The sequence surrounding the GAG deletion contains an imperfect 24 bp tandem repeat, suggesting a possible mechanism for the high frequency of this mutation.

The GTP cyclohydrolase I gene in Russian families with dopa-responsive dystonia.

OBJECTIVE: To search for mutations in the GTP cyclohydrolase I (GCH-I) gene in a set of Russian families with dopa-responsive dystonia (DRD). DESIGN: Six large families with 54 affected family members and 2 patients with sporadic DRD were examined. Mutation screening was performed using single-strand conformation polymorphism analysis followed by direct sequencing of the presumably mutated exons, in patients whose results showed a normal pattern on single-strand conformation polymorphism analysis, the entire coding region of the GCH-I gene was sequenced. RESULTS: Three new heterozygote point mutations located within exons 1, 2, and 4 of the GCH-I gene were identified in 3 families with autosomal-dominant inheritance. All these mutations are predicted to cause amino acid changes in the highly conserved regions of the gene. In patients from 3 other families and in both patients with sporadic DRD, no alterations in the translated portion of the GCH-I gene were observed. CONCLUSIONS: Mutations in the coding region of the GCH-I gene account for a significant fraction (up to half) of the patients with a typical clinical picture of DRD. None of the mutations in the GCH-I gene described so far were detected more than once, which precludes the possibility of creating simple DNA testing procedures for routine clinical practice.

Identification and analysis of mutations in the Wilson disease gene (ATP7B): population frequencies, genotype-phenotype correlation, and functional analyses.

Wilson disease (WD) is an autosomal recessive disorder characterized by toxic accumulation of copper in the liver and subsequently in the brain and other organs. On the basis of sequence homology to known genes, the WD gene (ATP7B) appears to be a copper-transporting P-type ATPase. A search for ATP7B mutations in WD patients from five population samples, including 109 North American patients, revealed 27 distinct mutations, 18 of which are novel. A composite of published findings shows missense mutations in all exons-except in exons 1-5, which encode the six copper-binding motifs, and in exon 21, which spans the carboxy-terminus and the poly(A) tail. Over one-half of all WD mutations occur only rarely in any population sample. A splice-site mutation in exon 12 accounts for 3% of the WD mutations in our sample and produces an in-frame, 39-bp insertion in mRNA of patients homozygous, but not heterozygous, for the mutation. The most common WD mutation (His1069Glu) was represented in approximately 38% of all the WD chromosomes from the North American, Russian, and Swedish samples. In several population cohorts, this mutation deviated from Hardy-Weinberg equilibrium, with an overrepresentation of homozygotes. We did not find a significant correlation between His1069Glu homozygosity and several clinical indices, including age of onset, clinical manifestation, ceruloplasmin activity, hepatic copper levels, and the presence of Kayser-Fleischer rings. Finally, lymphoblast cell lines from individuals homozygous for His1069Glu and 4 other mutations all demonstrated significantly decreased copper-stimulated ATPase activity.

Refined genetic location of the chromosome 2p-linked progressive muscular dystrophy gene.

Autosomal recessive progressive muscular dystrophies may be clinically subclassified into limb-girdle muscular dystrophy (LGMD) and distal myopathy (DM), each clinical form being genetically heterogeneous. Genes for LGMD type 2B and Miyoshi myopathy (a form of DM) have been mapped to essentially the same region on chromosome 2p. We described recently a large inbred family with autosomal recessive muscular dystrophy in which the LGMD and the DM phenotypes were manifested in separate affected members, and we assigned the gene for this condition to the same locus as in LGMD2B and Miyoshi myopathy. Here we report extended haplotypes in this family generated from 15 markers located at the region of interest on chromosome 2p13. Key recombinants allowed us to reduce further the candidate region for this polymorphic condition and defined the loci D2S327 and D2S2111 as the most likely boundaries of the mutant gene.

Fine localization of the torsion dystonia gene (DYT1) on human chromosome 9q34: YAC map and linkage disequilibrium.

The DYT1 gene, which maps to chromosome 9q34, appears to be responsible for most cases of early-onset torsion dystonia in both Ashkenazic Jewish (AJ) and non-Jewish families. This disease is inherited in an autosomal dominant mode with reduced penetrance (30%-40%). The abnormal involuntary movements associated with this disease are believed to be caused by unbalanced neural transmission in the basal ganglia. Previous linkage disequilibrium studies in the AJ population placed the DYT1 gene in a 2-cM region between the loci D9S62a and ASS. A YAC contig has now been created spanning 600 kb of this region including D9S62a. The location of the DYT1 gene has been refined within this contig using several new polymorphic loci to expand the linkage disequilibrium analysis of the AJ founder mutation. The most likely location of the DYT1 gene is within a 150 kb region between the loci D9S2161 and D9S63.

Clinical and molecular analysis of a large family with three distinct phenotypes of progressive muscular dystrophy.

We describe a unique six-generation, highly consanguineous family originating from an isolated mountainous village in the Russian province of Daghestan. Three separate clinical phenotypes of progressive muscular dystrophy were identified in this large family. Seven patients developed a classical limb-girdle variant of muscular dystrophy (LGMD), with disease onset at 15-30 years and loss of ambulation within a 25-year course. The second group included three patients with a slowly progressive distal myopathy first manifested in the late teens and confined to the tibial and calf muscles. Each of these two phenotypes segregated independently as an autosomal recessive trait, and muscle biopsies showed non-specific myopathic changes. Lastly, two male siblings exhibited an atypical variant of Duchenne muscular dystrophy confirmed by detection of a deletion in the dystrophin gene. To clarify the molecular basis of the polymorphic autosomal recessive form of muscular dystrophy in this kindred, we performed molecular genetic studies on 67 family members and obtained significant evidence for linkage to chromosome 2p. A maximum pairwise lod (logarithm of odds) score of 5.64 was achieved at the zero recombination fraction (i.e. at theta = 0.00) for locus D2S291; multipoint linkage analysis confirmed the most likely location of a mutant gene near D2S291. The patients with LGMD and those with the distal muscular dystrophy phenotype share a common affected homozygous haplotype associated with the same founder chromosome; key recombinants defined D2S286 and D2S292 to be the closest loci flanking the mutant gene. Remarkably, two clinically distinct forms of autosomal recessive muscular dystrophy, LGMD type 2B (LGMD2B) and Miyoshi myopathy, were recently mapped to the same locus. We suggest that all three chromosome 2p-linked conditions may represent allelic disorders, i.e. different phenotypic expressions of a single gene.

Spinocerebellar ataxia type 1 in Russia.

Spinocerebellar ataxia type 1 (SCA1) is one form of autosomal dominant cerebellar ataxia (ADCA) caused by trinucleotide (CAG) repeat expansion within a mutant gene. We investigated 25 patients from 15 Russian ADCA families for SCA1 mutation and found an expanded CAG repeat in 5 families. Mutant chromosomes contained 41-51 CAG repeats (mean 46.1, SD 3.1), and normal chromosomes displayed 21-27 repeat units (mean 24.7, SD 1.3). Progressive cerebellar ataxia in our series of SCA1 patients was very commonly associated with dysarthria (in all cases) and pyramidal signs (in 10 of 11 cases). In three patients from one family we found optic atrophy, which has never been described before in genetically proven cases of SCA1. We observed no specific clinical features distinguishing SCA1 from non-SCA1 patients. In contrast to the high frequency of SCA1 in our series, we found no patients with Machado-Joseph disease, another form of ADCA caused by expanded CAG repeat.