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.

[A PARK8 form of Parkinson's disease: a mutational analysis of the LRRK2 gene in Russian population]

A recently described form of Parkinson's disease - PARK8 - is caused by mutations in the novel LRRK2 gene on chromosome 12q12. The most common mutation in this gene is the substitution G2019S and we studied it for the first time in a large group of Russian Slavonic patients (311 patients) with Parkinson's disease including 295 sporadic and 16 familial cases. The mutation LRRK2-G2019S was identified in 1% of patients examined (3 cases) and was not found in a group of population control. The clinical picture of all patients with the LRRK2-G2019S mutation was typical for levodopa-responsive parkinsonism and age of disease onset varied widely (from 39 to 71 years). Two different PARK8-linked haplotypes were found in carriers of the mutation that suggested the independent origin of the G2019S mutation on different chromosomes. The identification of mutations in the LRRK2 gene in patients with "ordinary" sporadic Parkinson's disease has serious implications for medical genetic counseling and prognosis in respective families.

[7-year experience in usage of mirapex in patients with different forms of primary parkinsonism]

The results of mirapex (pramipexol) treatment of 402 patients with Parkinson's disease and juvenile parkinsonism during the period from 6 months to 7 years are summarized. Mirapex was used in monotherapy as well as in combination with levadopa and other antiparkinsonic drugs. The drug was well tolerated and effective in rest tremor, hypokinesia, muscle rigidity and depression, the more pronounced effect being seen at the early stage of the disease. The use of mirapex allows an effective control of motor fluctuations developing during long-term continuous levodopa therapy. The results obtained characterize mirapex as a drug of choice in the treatment of juvenile parkinsonism. In case of a break in mirapex treatment, the recommencement of treatment usually is not accompanied by reduced sensitivity to drug effect.

[Molecular genetic analysis of hereditary neurodegenerative diseases]

The review summarizes the results of a decade of molecular genetic studies of several high-incidence hereditary neurodegenerative diseases, including primary parkinsonism, various forms of hereditary dystonia and ataxia, polyglutamine disorders, hepatolenticular degeneration, essential tremor, etc. Various relevant mutations were studied. The character and frequencies of particular mutations and the corresponding genetic disorders were established for the Russian population. Particular genotypes were associated with various clinical variants of the diseases. Genetic loci were identified for several unique hereditary diseases of the nervous system (X-linked cerebellar hypoplasia, an atypical form of autosomal recessive muscular dystrophy, etc.). Nosological positions of the relevant clinical forms were clarified on the basis of the molecular genetic data. Protocols were developed for direct or indirect DNA diagnostics of the diseases under study to improve medical genetic counseling and prevention of new disease cases in affected families.

[Voluntary postural control learning with a use of visual bio-feedback in patients with spinocerebellar degenerations]

The study aimed at evaluation of possibility and features of voluntary postural control learning using biofeedback from a force platform in patients with spinocerebellar ataxias. Thirty-seven patients with different forms of spinocerebellar degenerations and 13 age-matched healthy subjects were trained to shift the center of pressure (CP) during several stabilographic computer games which tested an ability to learn 2 different types of voluntary postural control: general strategy and precise coordination of CP shifting. Despite the disturbances of static posture and ability for voluntary control of CP position, patients with spinocerebellar degenerations can learn to control a vertical posture using biofeedback on stabilogram. In contrast to healthy subjects, improvement of coordination in the training process does not exert a significant influence on the static posture characteristics, in particular on lateral CP oscillations. The results obtained suggest involvement of the cerebellum in both types of postural control that distinguishes them from pathology caused by motor cortex and nigro-striatal system involved only in one type of postural control.

[Clinical and genetic analysis of juvenile parkinsonism in Russia]

Clinical and genetic analysis of juvenile parkinsonism was performed in 26 sibs from 20 families. Heterogeneity of the disorder was observed. Mutations in the parkin gene (locus PARK2, chromosome 6q25.2-27), with the prevalence of deletions over point mutations, have been identified in 41%. The comparative clinical analyses of patients examined confirmed the phenotypical polymorphism of "parkinopathy". We also showed the absence of asymmetric manifestation--an important and underestimated so far sign of the disease. The results of the study may be considered as a valuable clue to the clinical diagnosis of parkin-related juvenile parkinsonism in Russian population and implemented for mutation screening and medico-genetic counseling of affected families.

[Clinical and stabilometric analysis of postural instability in Parkinson's disease]

A disturbance of postural control is one of the most invalidating symptoms of Parkinson's disease (PD), and mechanisms underlying its development have not been so far elucidated. To specify the postural control features in different PD forms, clinico-neurophysiological analysis was conducted in 61 patients divided into 3 groups according to PD forms: tremor-rigid, rigid-tremor and akinetic-rigid. Dissociation between clinical expression of postural instability and its stabilometric reflection--the square of statokinesogram was found, indicating importance of differentiated approach in performance of stabilometric analysis in patients with different PD forms. The square of statokinesogram may be regarded as a neurophysiological marker of postural instability only in patients with rigid forms, in tremor parkinsonian phenotypes an increased square of stabilogram being mainly a stabilometric reflection of tremor. The importance of stabilometric test performance with cognitive loading, allowing switching out of voluntary posture control, is shown. Possible neuromediator mechanisms involved in postural instability in PD are discussed.

[Cytochemical activity of mitochondrial enzymes in Parkinson's disease]

Using cytochemical computerized morphometric method, activity of the key enzymes of energetic metabolism (succinate dehydrogenase, alpha-glycerophosphate dehydrogenase, malate dehydrogenase, glutamate dehydrogenase and lactate dehydrogenase) was studied in blood lymphocytes of 75 patients with Parkinson's disease and 15 healthy controls. The signs of systemic mitochondrial insufficiency, which correlated with the disease duration and severity, were found in all the patients, including those with juvenile parkinsonism. These data may provide a basis for introducing cytochemical monitoring as well as for administration of modern "mitochondrial" drugs (yantavit, coenzyme Q10, L-carnitine, etc).

[Molecular genetic analysis of essential tremor]

Essential tremor (ET) is the most common extrapyramidal disorder of the central nervous system with autosomal dominant transmission in the majority of cases and age-dependent penetrance of the mutant gene. In a number of cases, it shares some phenotypic features with autosomal dominant idiopathic torsion dystonia (locus DYT1 on chromosome 9q32-34) and is genetically heterogeneous: distinct variants of ET were mapped to chromosomes 3q13 (ETM1) and 2p22-25 (ETM2). We performed studies of candidate loci in a group of Slavonic (11 patients) and Tajik (19 patients) families with ET. Mutational analysis of the DYT gene in probands did not reveal the major deletion 946-948delGAG characteristic of idiopathic torsion dystonia, which allows one to genetically distinguish the studied hereditary forms of ET and torsion dystonia. Based on analysis of genetic linkage in informative Tajik pedigrees with ET, linkage to locus ETM1 on chromosome 3q13 was established in four families. Maximum pairwise Lod score was 2.46 at recombination fraction of theta = 0.00; maximum combined multipoint Lod score was 3.35 for marker D3S3720 and a common "mutant" haplotype for markers D3S3620, D3S3576, and D3S3720 allowed us to locate a mutant gene in a relatively narrow chromosome region spanning 2 cM. In one informative pedigree with ET, both candidate loci ETM1 and ETM2 were definitely excluded on the basis of negative Lod scores obtained by linkage estimations, which testifies to the existence of another distinct gene for autosomal dominant ET.

[Nervous tissue protein autoantibodies in hepatolenticular degeneration]

Two novel protein antigens-Hbmp-1 and Hbmp-2 have been isolated from human brain tissue. Test-systems for determining auto-antibodies (a-Ab) to above mentioned proteins, as well as to basic myelin protein, S-100 beta and glial fibrillary acid protein have been developed. Sixty-three HLD patients have been examined. Increased a-Ab levels to the novel proteins has been shown in HLD patients; no difference between HLD patients and control groups being found for a-Ab levels to other proteins. Correlation has been observed between a type and course of the disease, on the one hand, and a-Ab levels to Hbmp-1 and to Hbmp-2, on the other hand.

[Regularities of fixation of brain serum antibodies from patients with lateral amyotrophic sclerosis in rabbit CNS]

Kuhns' indirect immunofluorescent test was used to study fixation of serum brain antibodies (Ab) of patients with bulbar, cervicothoracic, lumbosacral lateral amyotropic sclerosis (LAS) on brain sections of rabbits. The disease is characterized by formation of brain Ab complementary to various structures of nervous and glial cells, myelin of fibers from different conducting systems, vessels which exhibit both common and individual antigenic properties. It was found that fixation of antineuronal, antimyelin brain Ab of patients with bulbar, cervicothoracic and lumbosacral LAS in different CNS structures varies.

[Analysis of mutations in ATP7B gene and experience with direct DNA-diagnosis in hepato-lenticular degeneration]

Hepatolenticular degeneration (HLD) is a severe autosomal-recessive disorder of the copper metabolism. It is characterized by excessive accumulation of copper in the brain and in viscera and is conditioned by the damage in the gene of copper ATP-ase (ATP7B). The paper presents the results of screening of ATP7B gene mutation in 42 patients with HLD from Russian population. The regions of ATP7B gene that are the most frequently exposed to the mutation have been studied (the exzones 14, 15, 16, 18). It is demonstrated that A-->C mutation in the 14-th exzone that led to the change of histidine1069 amino acid for glutamine, was found in more than 60% of patients--Slavs from the European Russia. This mutation was observed in both homo- and heterozygous states. The deletion of (CCC-->CC) nucleotide in the 15-th exzone of the gene was observed in 2 cases. The detailed analysis of the clinical-genetic correlations was performed in patients with the determined damages of ATP7B gene. In Russia the experience of the direct DNA-diagnosis of HLD is described for the first time. It is significant for early evaluation of the patients in preclinical state and for prescription of the preventive copper-eliminating therapy.

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.

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.

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.

[Molecular-genetic analysis of torsion dystonia in Russia]

For the first time in Russia, analysis of the GCH-I and DYT1 genes was carried out for the purpose of direct DNA diagnostics in families with various forms of hereditary torsion dystonia (TD). Four new missense mutations (Met102Lys, Thr94Lys, Cys141Trp, and Ser176Thr) in the GCH-I gene were found in patients with dopa-responsive dystonia (DRD), testifying to a genetic heterogeneity of this clinical form of TD. The distribution of the major del GAG mutation in exon 5 of the DYT1 gene was studied in patients with non-dopa-responsive dystonia (NDRD). In total, the mutation was found in 68% of the patients. The frequency of this mutation in Ashkenazi Jews with NDRD was 100% (twice higher than in Slavonic families), suggesting the founder effect reported for NDRD in this ethnic group. Mutations of the GCH-I and DYT1 genes were also found in patients with atypical and questionable cases of TD, which are difficult to diagnose with methods other than DNA analysis. The data obtained made it possible to extend the spectrum of clinical signs of DRD and NDRD and to revise the views on true penetrance of the corresponding mutant genes, which is important for medical genetic counseling in affected families.

[Acoustic brain stem and cognitive evoked potentials (P300) in patients with hepatolenticular degeneration]

18 patients with hepatolenticular degeneration (Wilson's disease, WD) aged 15-38 years were subjected to an overall clinical and neurophysiologic examinations. As a result, the data obtained enable to evaluate functional reserves of CNS of the WD patients in correlation with the illness duration and severity of neurologic symptoms. Correlation between an increase of interpeak I-V and the degree of neurological deficit and, also, level of ceruloplasmin was established (r = -0.45; p < 0.05). Correlation between an increase of latency P300 and the degree of manifestation of neurologic symptoms was identified as well (r = 0.63; p < 0.05). Positive dynamics of evoked potentials was followed in 4 WD patients during copper-eliminative drugs treatment.

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.

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.

[Friedreich's disease: a real spectrum of clinical manifestations in terms of direct DNA diagnosis]

Friedreich's disease (FD) is autosomal-recessive form of hereditary ataxias conditioned by expansion of the trinucleotide GAA-repetitions in a new X25 gene. The study was performed in 20 patients from 13 families of different ethnic origin (Slavs, Turkmen, Moldavians, etc) with a suspicion to FD as well as in their 24 relatives who were clinically healthy. Direct DNA-diagnosis confirmed FD diagnosis in patients from 11 families; besides, a number of GAA-repetitions in the patients was in the range from 100 till 1200 (680 +/- 350). A molecular analysis revealed that FD severity was determined by a character of the mutation in each case: a classic form of the disease was characterized by the highest degree of the expansion of GAA-repetitions (more than 400), meanwhile atypic FD cases with late debut and slow progression were conditioned by either a small degree of the expansion of GAA-repetitions or by the presence of point mutations in one of the gene's alleles. A direct DNA-diagnosis permitted to determine a heterozygous carriage of the mutation in 3 clinically healthy individuals. Such cases are necessary to take into consideration in medico-genetic consultations.

[The surgical results in patients with different forms of torsion dystonia]

The paper describes stereotactic operations made in 278 patients with different forms of torsion dystonia during 20 years. Late outcomes were studied and assessed in 130 patients. The duration of follow-ups was 3 to 23 years. The patients' mean age at surgery was 30.5 years. The indications for surgical treatment were ineffective medical treatment and progressive disease. Positive early and late postoperative outcomes were achieved in 93 and 70% of patients, respectively. Complications developed in 3.2 and 12.3% of patients after the first and second operations, respectively. The positive outcome depends on the form, etiology, the destructible structure or a complex of structures. Surgical treatment of patients with torsion dystonia by stereotactic operations on basal ganglia is an effective treatment that provides a steady-state positive result in 70% of patients in the late period.

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.

[Molecular genetic testing in the diagnosis of sporadic cases of Huntington's chorea]

Huntington's disease is characterized by autosomal dominant transmission and a complete penetrance of the mutant gene. Mutation in Huntington's disease consists in expansion of the unstable tandem CAG-trinucleotide repeats. This discovery allowed to perform a precise DNA diagnosis of the mutant gene carriers. Direct DNA diagnosis has a special importance in sporadic cases of the disease. We performed direct DNA diagnosis in 4 patients with sporadic choreic hyperkinesis, and elaborated a modified protocol for DNA amplification. The obtained results are discussed from the viewpoint of current knowledge about the nature of the Huntington's disease gene.

[A new form of hereditary ataxia: X-linked congenital cerebellar hypoplasia (a clinical and molecular genetic analysis)]

There was performed the examination of a family with innate cerebellar hypoplasia. The disease was manifested in 7 males from 3 generations. X-linked recessive type of transmission of mutant gene was established. Clinical syndrome was characterized by delay of motor development during the first year of child's living as well as by ataxia, dysarthria, external ophthalmoplegia and nonprogressive course too. The signs of pronounced hypoplasia of hemispheres and vermis were found by means of computer and magneto-resonance investigation. Molecular genetic study (linkage-analysis) revealed that the gene of the disease was localized in proximal part of long X-chromosome's shoulder, exactly in XpII 21-q24 interval (38 centimorgan genetic distance). That was the first example of successful genetic mapping of the disease from the group of hereditary cerebellar hypoplasias.

[Mapping of the gene for autosomal-recessive progressive muscular dystrophy in an isolate from a highland region of Dagestan to chromosome 2-13]

A unique inbred Avar family from an isolate of the Dagestan highland was studied. Unusual phenotypic expression of autosomal recessive progressive muscular dystrophy was revealed in 12 members of this family from three generations. Limb-girdle (proximal) muscular dystrophy (LGMD) was detected in nine patients, while the other three patients displayed typical distal myopathy (DM). Genetic linkage analysis with several candidate loci determining various forms of muscular dystrophy allowed a gene for this polymorphic syndrome to be assigned to chromosome 2p13. In spite of the difference in clinical manifestation, all patients appeared to be homozygous for a unique haplotype. This implies the founder effect and proves the same genetic basis of LGMD and DM in the family. Recombination analysis showed that the centromeric and telomeric ends of the gene region are marked with D2S2111 and D2S327, respectively (genetic distance < 1 cM). This region is overlapped by two larger regions in which the genes for LGMD type 2B (LGMD2B) and Miyoshi myopathy were recently mapped. Complex analysis of clinical and genetic data indicated that LGMD2B, Miyoshi myopathy, and the revealed polymorphic syndrome may represent allelic variants of 2p13-linked autosomal recessive muscular dystrophy.

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.

[Presymptomatic DNA diagnosis of spinocerebellar ataxia type 1]

Hereditary autosomal dominant ataxias is a clinically and genetically heterogeneous group of diseases characterized by a progressive ataxia combined with the signs of multisystem involvement of the brain and spinal cord. The modern classification of these disorders of the central nervous system is based on recent advances in molecular genetics. In a form of dominant ataxia, spinocerebellar ataxia type 1 (SCA1), the mutation consists of an increased number of copies (expansion) of trinucleotide repeats within the causative gene. This mutational mechanism is characteristic of a group of hereditary neurodegenerative diseases. Revealing this phenomenon provided a tool for direct DNA diagnosis of SCA1 at any stage of the disease, including the preclinical one. This is the first reported case of a direct DNA diagnosis of SCA1 in Russia. The diagnosis was performed in five healthy persons from the risk group, i.e., relatives of patients with a molecularly proven SCA1. Three persons were diagnosed to be presymptomatic carriers of the mutant SCA1 gene; in two persons, the mutation was not found. A complex of moral, ethical, medical, and social problems connected with the application of direct DNA testing of SCA1 in genetic counselling is discussed.

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.

[Immunochemical correlates of the severity of Parkinson's disease]

The serum samples from 29 patients with Parkinson's disease were analysed for the levels of the autoantibodies (a-AB) and antiidiotype antibodies (AIAB) to the proteins of nervous system S-100, GFAP, NKP and MP-65. High levels of a-AB or AIAB to at least 3 proteins were seen in patients with severe course of the disease. No significant changes of these levels were observed in patients with light course of the disease. The plasmapheresis was carried out to some patients with severe course of the disease. After this procedure the decrease of neurological deficit from number 21 +/- 2 to 8 +/- 1 on Webster's scale and decrease of a-AB and AIAB levels to normal values (in some cases it became lower than normal values) were observed. It can be concluded that the levels of the a-AB to the nervous tissue proteins correlate with clinical condition of the patient.

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.

[Search for expansion of CAG-repeats in DNA sequences expressed in the brain of humans with psychiatric and neurological diseases]

Dynamic mutations due to trinucleotide repeat expansion are a new class of human genome mutations. CAG repeat expansion in the coding region of associated genes is the molecular genetic basis of the several diseases of nervous system. Eight DNA sequences with CAG repeats expressed in human brain were chosen from the GenBank database. The search of CAG expansion was carried out for patients with schizophrenia (brain and blood) and essential tremor. CAG repeat expansion has not been found for the loci. The distribution of allelic sizes is similar in the patients and control samples. Locus HS0073 has shown the polymorphism of the length for CAG repeat alleles. Statistically reliable excess of the homozygotes has been found for schizophrenic patients.

X-linked nonprogressive congenital cerebellar hypoplasia: clinical description and mapping to chromosome Xq

We examined a large family in which an X-linked recessive congenital ataxia manifested in 7 males from three generations. The affected boys first exhibited a marked delay of early developmental motor milestones. A neurological syndrome became evident by 5 to 7 years of age and included cerebellar ataxia, dysarthria, and external ophthalmoplegia; there were no symptoms of mental retardation, spastic paraparesis, or sensory loss. Neuroimaging studies revealed hypoplasia of cerebellar hemispheres and vermis. The disease showed no progression beyond early childhood. The unique heredity and clinical features clearly distinguish this new entity from a variety of previously described familial ataxias. Pairwise linkage analysis and haplotype reconstruction allowed us to map the gene responsible for this disorder to a 38-cM interval on chromosome Xp11.21-q24 flanked by the loci DXS991 and DXS1001. Upon multipoint linkage analysis, the disease gene was determined to be located most likely in the proximal part of chromosome Xq, with the maximal lod score of 4.66 at the locus DXS1059 (Xq23). This is the first example of the genetic mapping of a pure congenital cerebellar hypoplasia syndrome.

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.

[Genetic study of idiopathic torsion dystonia in Russia]

Inheritance of idiopathic torsion dystonia (ITD) was studied in 41 Russian families including 41 probands with generalized, focal, and segmental dystonia and 140 recurred cases. Affected relatives appeared in two or more generations in 31 families analyzed. It was shown that in 76% of segregated cases, ITD was inherited as an autosomal dominant trait with a penetrance of 40% and varying expression. An autosomal recessive type was observed in 24% of the cases. Approximately 10% of the cases of disease could be caused by a new mutation and 14.6% by a nongenetic phenotype similar to genetic forms in its clinical symptoms. ITD with the X-linked recessive type of inheritance did not occur in the families studied. The recurrence risk was 20% in autosomal dominant forms. The risk correlated with age the relative's: clinical symptoms developed in 98.4% of patients by the age of 30.

[Analysis of trinucleotide repeat expansion as a new mechanism of mutation in Huntington's chorea: theoretical and applied aspects]

The Huntington's chorea mutation consists of expansion of trinucleotide CAG repeats in the recently discovered gene IT-15. In this work, for the first time in a population of Russian patients, correlations between the number of copies of CAG repeats and various clinical characteristics of the disease are investigated. It is established that the degree of triplet expansion determines the age of onset of the disease and the rate of progression of the neurological and mental symptoms of Huntington's chorea, and it is also shown that the genetic instability of the mutant allele is considerably higher upon transmission of the disease gene along the paternal line. We obtained direct confirmation of the possibility of genetic instability of a normal allele inherited paternally. In this work, the first successful direct (including preclinical) DNA diagnosis in Russia of Huntington's chorea was obtained.

[A new mechanism of mutation in man: expansion of trinucleotide repeats]

An analysis of a novel, recently discovered class of mutations in man - an expansion, i.e., an increase of the copy number of intragenic unstable trinucleotide repeats - is presented. The expansion of trinucleotide repeats causes the development of at least seven hereditary diseases which damage the nervous system: the fragile X chromosome syndrome (two separate variants of the disease - FRAXA and FRAXE), myotonic dystrophy, spinal and bulbar Kennedy's amyotrophy, Huntington's chorea, type 1 spinocerebellar ataxia, and dentatorubral-pallidolyusian atrophy. The discovery of triplet expansion allows a satisfactory explanation on the molecular level of a series of unusual clinical genetic phenomena, such as anticipation, the ¿paternal transmission¿ effect, the ¿Sherman paradox¿, and others. The common properties and the distinctions of unstable trinucleotide mutations in the above-mentioned nosologic forms are analyzed comprehensively among for the mechanism by which these mutations cause disease, the time of their appearance in ontogenesis, and various clinical genetic correlations. The evolutionary origin of this class of mutations and, in particular, the role of alleles with an ¿intermediate¿ triplet number, which are the persistent reservoir of mutations arising de novo in a population, are also discussed. The possible implication of unstable trinucleotide repeats for a series of other hereditary diseases, such as spinocerebellar ataxia of type 2, Machado-Joseph disease, hereditary spastic paraplegia, essential tremor, schizophrenia and others, is also suggested.

Trinucleotide repeat length and rate of progression of Huntington's disease

The Huntington's disease gene contains an expanded unstable (CAG)n repeat, and the repeat lengths have been shown to correlate with the age of onset. Using detailed clinical scales, we evaluated the rate of progression of Huntington's disease and its relationship to the number of triplet repeats. We found significant positive correlation between the rate of progression of clinical symptoms (both neurological and psychiatric) and CAG repeat length. These data suggest an important role of expanded trinucleotide repeat length in affecting the pathological process during the entire course of Huntington's disease.

[Comparative study of human erythrocyte membranes in normal people and in Huntington's chorea patients]

Erythrocytes of healthy volunteers and of patients with hereditary chorea were studied. Evaluation of the state of cellular membrane was carried out by measuring osmotic resistance, activity of Na+, K(+)-ATPase and protein composition. In the patients osmotic resistance of erythrocytes was distinctly decreased down to 66.3 +/- 3.3, while the Na+, K(+)-ATPase activity was increased 4-fold as compared with controls. Protein composition of erythrocyte membranes, studied by means of two-dimensional electrophoresis, was similar both in healthy persons and in patients with hereditary chorea when the electrophoretograms were analyzed visually. An additional protein with Mr = 30,000 and r-1-0.25 was detected in one of the patients. Slowly sedimenting fraction of erythrocytes was found in almost all the patients with hereditary chorea when erythrocytes aging was studied by means of fractionation in Ficoll density gradient. The fraction was not observed in healthy persons. These data suggest that the cell membranes in Huntington's chorea are altered as compared with normal state.

[Protective effect rendered by human ceruloplasmin on erythrocytes in hepatocerebral dystrophy]

In order to elucidate the protective effect of human ceruloplasmin (CP) on erythrocytes in patients with hepatocerebral dystrophy (HCD), the parameters reflecting the interaction of CP from the blood of healthy donors (n-CP) and of HCD patients (h-CP) with erythrocytes from healthy donors (n-ER) and from HCD patients (h-ER) were estimated. The protective effects of n-CP and h-CP on n-ER and h-ER during the Cu2+-induced lysis were compared. It was shown that the ability of h-CP to prevent the human ER breakdown upon Cu2+-induced lysis is much lower (approximately 3-fold) than that of n-CP. The differences in the protective effect of n-CP and h-CP are manifested in a greater degree during the n-ER lysis than during the h-ER lysis.