Spinocerebellar ataxia type 1 in Russia. Received: 14 August 1995. Received in revised form: 28 December 1995'. Accepted: 11 January 1996. S. N. Illarioshkin ...
J Neurol (1996) 243 : 506-510 © SlJringer-Verlag 1996
Sergei N. Illarioshkin Pyotr A. Slominsky Igor V. Ovchinnikov Elena D. Markova Natalya I. Miklina Sergei A. Klyushnikov Marya Shadrina Nikolai V. Vereshchagin Svetlana A. Limborskaya Irina A. Ivanova-Smolenskaya
Received: 14 August 1995 Received in revised form: 28 December 1995' Accepted: 11 January 1996 S. N. Illarioshkin (YTI).I. V. Ovchinnikov E. D. Markova • N. I. Miklina S. A. Klyushnikov • N. V. Vereshchagin I. A. Ivanova-Smolenskaya Department of Neurogenetics, Institute of Neurology, Russian Academy of Medical Sciences, Volokolamskoye Shosse 80, Moscow 123367, Russia P. A. Slominsky - M. Shadrina S. A. Limborskaya Department of Molecular Basis of Human Genetics, Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov Square 46, Moscow 123182, Russia
Spinocerebellar ataxia type 1 in Russia
Abstract Spinocerebellar ataxia type 1 (SCA1) is one form of au(osomal dominant cerebellar ataxia (ADCA) caused by trinucleotide (CAG) repeat expansion within a mutant gene. We investigated 25 patients from 15 Russian A D C A families for SCA1 mutation and found an expanded CAG repeat in 5 families. Mutant chromosomes contained 41-51 C A G 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 pyrami-
Introduction The autosomal dominant cerebellar ataxias (ADCAs) represent a clinically and genetically heterogeneous group of neurodegenerative disorders primarily affecting the cerebellum. According to the widely accepted classification of Harding [13], A D C A s m a y be separated into three types: in A D C A type I progressive cerebellar ataxia is associated with a variable multisystem syndrome; patients with A D C A II have visual disturbances caused by retinal degeneration; A D C A III is characterized by a "pure" cerebellar syndrome. Recently, at least six different genes causing A D C A s have been shown to exist [1, 6, 8, 11, 22, 25, 26, 29]; this forms a strong ba-
dal 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 A D C A caused by expanded CAG repeat.
Key words Dominant ataxia. Trinucleotide repeat • Molecular analysis
sis for an accurate molecular genetic classification of these disorders. The gene for one form of A D C A I, spinocerebellar ataxia type 1 (SCA1), was assigned to chromosome 6p [14, 23, 28, 29]. In 1993 Orr et al. [20] found that this gene contains a (CAG)n repeat which is selectively expanded and unstable in SCA1 patients. During the last 2 years large series of SCA1 families from many countries have been investigated [3, 4, 9, 15, 18, 21]. A strong inverse correlation was shown between the number of CAG repeat units and age at onset [3, 4, 15, 20, 21], and the disease course was more severe in SCA1 patients with longer repeats [4, 15]. Also, a tendency of expanded repeats toward increase in size in paternal transmission was observed [3, 4, 15, 18]. Recently Kawaguchi et al. [16] have
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identified the analogous mutational m e c h a n i s m consisting of C A G repeat expansion in another form of A D C A s , Machado-Joseph disease (MJD). The discovery o f e x p a n d e d trinucleotide repeats in SCA1 and M J D m a d e it possible to introduce rapid m e t h o d s o f direct D N A diagnostics in A D C A families to identify these forms o f ataxia. Molecular analysis provides a means to investigate the distribution of repeat n u m b e r s on normal and mutant c h r o m o s o m e s in persons o f various ethnic backgrounds. Such a comparative study is o f great value, since it can help to establish firmly the status o f the e x a m i n e d persons carrying c h r o m o s o m e s with the particular C A G repeat sizes. It w o u l d be interesting also to c o m p a r e the frequencies and clinical features o f various forms o f dominantly inherited ataxias in different populations. In this paper we present the first results o f a clinico-molecular analysis in Russian A D C A families.
Patients and methods We examined 25 patients from 15 families with dominantly inherited ataxias. The families examined originated from different regions of Russia, being predominantly of East European ethnic background. All patients were evaluated by the same examiner at the Department of Neurogenetics, Moscow Institute of Neurology. Diagnosis of ADCAs was based on (1) clear autosomal dominant mode of inheritance; (2) progressive, unremitting cerebellar ataxia, usually in association with one or more of the additional clinical signs, such as supranuclear ophthalmoplegia, optic atrophy, dysarthria, dementia, pyramidal signs, peripheral neuropathy, decreased vibration sense, extrapyramidal features; (3) cerebellar atrophy on CT and/or MRI. Pathological confirmation was obtained in one case. From the clinical viewpoint, 12 families could be assigned to ADCA I, one family represented ADCA II, and in two families the neurological findings were compatible with ADCA III. Genomic DNA for molecular genetic analysis was extracted from venous blood by standard procedures [19]; all persons examined gave informed consent. Polymerase chain reactions (PCR) were performed using the Repl and Rep2 primers for SCA1 [20], and MJD52 and MJD25 primers for MJD [16]. PCR conditions for amplification of CAG repeats in SCA1 and MJD locus were as previously described [16, 20]. PCR products were analysed by electrophoresis through a 6% polyacrylamide gel and autoradiography. Allele sizes were determined by comparing migration relative to an M13 sequencing ladder. As controls the shorter (normal) alleles of the affected or "at risk" persons were studied, giving us a series of 46 normal chromosomes.
Results In 11 patients from 5 families (one third o f the examined families) we found that one allele o f SCA1 locus contained an increased n u m b e r of C A G repeat units (41-51, mean 46.1, SD 3.1); that strongly suggests C A G repeat expansion and corresponds to the SCA1 mutation (Fig. 1). Repeat sizes o f the second allele in these patients, as well as repeat numbers in patients from other families, fell in the normal range (21-27, mean 24.7, SD 1.3). We did not
Fig. 1 Analysis of the CAG repeat in patients from spinocerebellar ataxia type 1 families. Lanes 3-5, 10, 14, 15 Normal individuals; lanes 1, 2, 6, 9, 11, 13 clinically affected individuals; lanes 7, 8, 12 clinically unaffected carriers of the SCA1 mutation. Number of CAG repeats is indicated on the right (M13 sequencing ladder)
observe any "intermediate" numbers of C A G repeats in the persons examined. In three cases o f paternal transmission of the expanded allele we observed a minimal increase in the repeat length in children (of 1-2 C A G repeat units). In contrast, no changes in the expanded repeat length between generations were found in two mother-child pairs. The normal alleles were always meiotically stable in both maternal and paternal transmission. Clinical features of our SCA1 patients are summarized in Table 1. Affected individuals exhibited a rather uniform clinical phenotype with cerebellar ataxia, dysarthria, pyramidal signs, dysphagia and ocular motor abnormalities as predominant symptoms irrespective of the particular number of C A G repeats. N o n e of the SCA1 patients in our cohort had any specific neurological s y m p t o m s that were not observed in the n o n - S C A 1 group. It is noteworthy that two SCA1 patients who carried the longest C A G repeat tracts (51 and 48 repeats) had the earliest age of onset of the disease in our series (23 and 20 years, respectively). Moreover, the disease course in these cases was relatively fast, so that both patients exhibited severe, disabling ataxia and prominent dysphagia 5 years after the disease onset (the latter s y m p t o m was u n c o m m o n in other patients and was usually observed only at the very late stage o f the disorder). It was possible to perform presymptomatic D N A testing for five "at risk" persons from SCA1 families between the ages of 19 and 25 years following their urgent requests and under informed consent. In three cases (see Fig. 1,
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Table 1 Clinical features of spinocerebellar ataxia type 1 patients Affected examined (n)
11
Men/women (n)
4/7
Age at onset (years)
33+7 (range 22-45)
Disease duration (years)
6+3 (range 3-14)
Clinical features
Number of cases
Percentage
11 6 3 6 11 10 3
100 55 27 55 100 91 27
1 3 4 8
9 27 36 73
Ataxia Ocnlar movement abnormalities Optic atrophy Dysphagia Dysarthria Pyramidal signs Extrapyramidal rigidity/ hyperkinesias Depressed/absent reflexes Decreased vibration sense Sphincter abnormalities Cognitive impairment
lanes 7, 8, 12) we found an expanded CAG repeat (49, 48 and 42 copies), while two other persons (Fig. 1, lanes 3, 10) had both alleles with CAG repeats in the normal range (21-26 copies). A molecular analysis in our series has not revealed CAG repeat expansion in the MJD gene. All examined patients and control persons had two alleles with repeat lengths of < 35 repeat units, which unambiguously corresponded to the normal range [16].
Discussion Previously SCA1 has been described in various European populations [4, 9; 15, 18, 20], Caucasian and Black American kindreds [21, 28], families of South African [2], Malaysian, Jamaican, Bangladeshi [9], Indian [4], and Iakut [10] ethnic origin. Our study revealed SCA1 mutation in a third of the dominant-ataxia families from different regions and ethnic groups of Russia. The frequency of SCA1 we found in our series of ADCA is higher than in the studies of Dubourg et al. [4] (16%) and Ranum et al. [21] (14%), but similar to the frequency of SCA1 (26%) among a number of ADCA families of British and Italian origin [9]. We agree with Giunti et al. [9] that SCA1 i s one of the commonest subtypes of autosomal dominant ataxias, at least in some European populations. The distribution of CAG repeat numbers on normal and SCA1 chromosomes in our sample was virtually identical to that described by other authors [3, 4, 15, 18, 20, 21]. These data may serve as further confirmation of sim-
ilarities of molecular mechanisms underlying multiple origins of dynamic SCA1 mutations in different racial groups, analogous to the situation observed in Huntington's disease. We found a clear-cut and wide separation of normal and mutant alleles, with a gap of 14 repeat units between the upper end of the normal range and the lower end of the expanded range. This finding is very valuable from the practical viewpoint for making an accurate, correct clinical and presymptomatic diagnosis of SCA1. Since the latter has very serious ethical and legal implications, such analysis should always be performed using a strong counselling protocol as in Huntington's disease [27]. Following these international guidelines, we have tested five at risk subjects above the age of 18 years and diagnosed three of them as carriers of the SCA1 mutation. One of the most difficult and confusing questions is a characterization of the specific clinical findings and phenotypes associated with different ADCA genes. Our study confirmed that pyramidal signs and dysarthria may be commonly seen in SCA1 patients in any stage of the disease [7, 9, 21]. It is of particular interest that we observed three patients from one SCA1 family (Table 1) in whom a typical optic atrophy with a marked bitemporal pallor and vascular paucity manifested several years after the onset of neurological disorder, so that the diagnosis of multiple sclerosis was initially made in two patients by a district neurologist. Although optic atrophy has occasionally been seen in ADCA I [11], to our knowledge it has never been described in the genetically proven cases of SCA1 [4, 5, 7, 21]. Our observation demonstrates that the clinical picture in SCAI patients may include optic atrophy. Since this sign may be found in the early stage of the disease [ 12], optic atrophy does not seem to depend on the disease duration. In general, however, we could not see any specific clinical differences between SCA1 and other dominantly inherited ataxias, which could serve as criteria to confirm the diagnosis of SCA1 in individual patients and families. We would agree, therefore, with a majority of authors who consider that in practice various forms of ADCA are clinically indistinguishable [4, 5, 9, 17, 21, 24]. One may conclude that dominantly inherited ataxias can be accurately diagnosed only on the basis of the molecular genetic analysis [24]. In our series of ADCA families we did not identify the MJD mutation, possibly because of the relatively small sample size. Another explanation might be the fact that our families originated predominantly from the European part of Russia, as in Europe (except for certain populations) MJD is assumed to be uncommon compared with SCA1 [9]. Further data collection will help to resolve the question whether a low frequency of MJD is a characteristic feature of the ADCA group in Russia. Acknowledgements We are deeply grateful to the ADCA families who participated in this research.
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References 1. Benomar A, Krols L, Stevanin G, Cancel G, LeGuem E, David G, Ouhabi H, Martin J-J, Durr A, Zaim A, Ravise N, Busque C, Penet C, Van Regemorter N, Weissenbach J, Yahyaoui M, Chkili T, Agid Y, Van Broeckhoven C, Brice A (1995) The gene for autosomal dominant cerebellar ataxia with pigmentary macular dystrophy maps to chromosome 3p12-p21.1. Nature Genet 10: 84-88 2. Bryer A, Martell RW, duToit ED, Beighton P (1992) Adult onset spinocerebellar ataxia linked to HLA in a large South African kindred of mixed ancestry. Tissue Antigens 40:111-115 3. Chung M, Ranum LP, Duvick LA, Servadio A, Zoghbi HY, Orr HT (1993) Evidence for a mechanism predisposing to intergenerational CAG repeat instability in spinocerebellar ataxia type 1. Nature Genet 5:254-258 4. Dubourg O, Durr A, Cancel G, Stevanin G, Chneiweiss H, Penet C, Agid Y, Brice A (1995) Analysis of the SCA1 CAG repeat in a large number of families with dominant ataxia: clinical and molecular correlations. Ann Neurol 37:176-180 5. Durr A, Chneiweiss H, Khati C, Stevanin G, Cancel G, Feingold J, Agid Y, Brice A (1993) Phenotypic variability in autosomal dominant cerebellar ataxia type I is unrelated to genetic heterogeneity. Brain 116:1497-1508 6. Gardner K, Alderson K, Galster B, Kaplan C, Leppert M, Ptasek L (1994) Autosomal dominant spinocerebellar ataxia: clinical description of a distinct hereditary ataxia and genetic localization to chromosome 16 (SCA4) in a Utah kindred (abstract). Neurology 44 [Suppl 2]: A361 7. Genis D, Matilla T, Volpini V, Rosell J, Davalos A, Ferrer I, Molins A, Estivill X (1995) Clinical, neuropathologic, and genetic studies of a large spinocerebellar ataxia type 1 (SCA1) kindred: (CAG)n expansion and early premonitory signs and symptoms. Neurology 45:24-30
8. Gispert S, Twells R, Orozco G, Brice A, Weber J, Heredero L, Scheufler K, Riley B, Allotey R, Nothers C, Hillermann R, Lunkes A, Khati C, Stevanin G, Hemandez A, Magarino C, Klockgether T, Durr A, Chneiweiss H, Enczmann J, Farall M, Beckmann J, Mullan M, Wernet P, Agid Y, Freund H-Y, Williamson R, Auburger G, Chamberlain S (1993) Chromosomal assignment of the second locus for autosomal dominant cerebellar ataxia (SCA-2) to chromosome 12q23-24.1. Nature Genet 4:295-299 9. Giunti P, Sweeney MG, Spadaro M, Jodice C, Novelletto A, Malaspina P, Frontali M, Harding AE (1994) The trinucleotide repeat expansion on chromosome 6p (SCA1) in autosomal dominant cerebellar ataxias. Brain 117: 645-649 10. Goldfarb LG, Chumakov MP, Petrov PA, Fedorova NI, Gajdusek DC (1989) Olivopontocerebellar atrophy in a large Iakut kinship in eastern Siberia. Neurology 39:1527-1530 11. Haberhausen G, Damian MS, Leweke F, Mtiller U (1995) Spinocerebellar ataxia, type 3 (SCA3) is genetically identical to Machado-Joseph disease (MJD). J Neurol Sci 132:71-75 12. Harding AE (1982) The clinical features and classification of the late onset autosomal dominant cerebellar ataxias: a study of 11 families, including descendants of the "Drew family of Walworth". Brain 105:1-28 13. Harding AE (1993) Clinical features and classification of inherited ataxias. Adv Neurol 61:1-14 14. Jackson JF, Currier RD, Terasaki P[, Morton NE (1977) Spinocerebellar ataxia and HLA linkage: risk prediction by HLA typing. N Engl J Med 296:1138-1141 15. Jodice C, Malaspina P, Persichetti F, Noveletto A, Spadaro M, Giunti P, Morocutti C, Terrenato L, Harding AE, Frontali M (1994) Effect of trinucleotide repeat length and parental sex on phenotypic variation in spinocerebellar ataxia 1. Am J Hum Genet 54: 959-965 16. Kawaguchi Y, Okamoto T, Taniwaki M, Aizawa M, Inoue M, Katayama S, Kawakami H, Nakamura S, Nishimura M, Akiguchi I, Kimura J, Narumiya S, Kakizuka A (1994) CAG expansions in a novel gene from Machado-Joseph disease at chromosome 14q32.1. Nature Genet 8:221-228
17. Khati C, Stevanin G, Durr A, Chneiweiss H, Belal S, Seck A, Cann H, Brice A, Agid Y (1993) Genetic heterogeneity of autosomal dominant cerebellar ataxia type 1: clinical and genetic analysis of 10 French families. Neurology 43:1131-1137 18. Matilla T, Volpini V, Genis D, Rosell J, Corral J, Davalos A, Molins A, Estivill X (1993) Presymptomatic analysis of spinocerebellar ataxia type 1 (SCA1) via the expansion of the SCA1 CAG-repeat in a large pedigree displaying anticipation and parental male bias. Hum Mol Genet 2:2123-2128 19. Miller SA, Dykes DD, Polesky HF (1988) A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res 16:1215 20. Orr HT, Chung M, Banff S, Kwiatkowski TJ, Servadio A, Beaudet AL, McCall AE, Duvick LA, Ranum LP, Zoghbi HY (1993) Expansion of an unstable trinucleotide CAG repeat in spinocerebellar ataxia type 1. Nature Genet 4:221-226 21. Ranum LP, Chung M, Banff S, Bryer A, Schut LJ, Ramesar R, Duvick LA, McCall A, Subramony SH, Goldfarb L, Gomez C, Sandkuijl LA, Orr HT, Zoghbi HY (1994) Molecular and clinical correlations in spinocerebellar ataxia type 1: evidence for familial effects on the age at onset. Am J Hum Genet 55:244-252 22. Ranum LP, Schut LJ, Lundgren JK, Orr HT, Livingston DM (1994) Spinocerebellar ataxia type 5 in a family descended from the grandparents of President Lincoln maps to chromosome 11. Nature Genet 8:280-284 23. Rich SS, Wilkie P, Schut L, Vance G, Orr HT (1987) Spinocerebellar ataxia: localization of an autosomal dominant locus between two markers on human chromosome 6. Am J Hum Genet 41: 524-531 24. Rosenberg RN (1995) Autosomal dominant cerebellar phenotypes: the genotype has settled the issue. Neurology 45:1-5 25. Stevanin G, LeGuern E, Ravise N, Chneiweiss H, Durr A, Cancel G, Vignal A, Boch A-L, Ruberg M, Penet C, Pothin Y, Lagroua I, Haguenan M, Rancurel G, Weissenbach J, Agid Y, Brice A (1994) A third locus for autosomal dominant cerebellar ataxia type 1 maps to chromosome 14q24.3-qter: evidence for the existence of a fourth locus. Am J Hum Genet 54:11-20
510
26. Takiyama Y, Nishizawa M, Tanaka H, Kawashima S, Sakamoto H, Karube Y, Shimazaki H, Soutome M, Endo K, Ohta S, Kagawa Y, Kanazawa I, Mizuno Y, Yoshida M, Yuasa T, Horikawa Y, Oyanagi K, Nagai H, Kondo T, Inuzuka T, Onodera O, Tsuji S (1993) The gene for Machado-Joseph disease maps to human chromosome 14q. Nature Genet 4:300-304
27. World Federation of Neurology: Research Committee. Research Group on Huntington's disease (1989) Ethical issues policy statement on Huntington's disease molecular genetics predictive tests. J Neurol Sci 94:327-32 28. Zoghbi HY, Pollack MS, Lyons LA, Ferrell RE, Daiger SP, Beaudet AL (1988) Spinocerebellar ataxia: variable age of onset and linkage to human leukocyte antigen in a large kindred. Ann Neurol 23:580-584
29. Zoghbi HY, Jodice C, Sandkuijl LA, Kwiatkowski TJ, McCall AE, Huntoon SA, Lulli P, Spadaro M, Litt M, Cann HM, Frontali M, Terrenato L (1991) The gene for autosomal dominant spinocerebellar ataxia (SCA1) maps telomeric to the HLA complex and is closely linked to the D6S89 locus in three large kindreds. Am J Hum Genet 49:23-30
