SCA2 and SCA3 mutations in young-onset dopa-responsive parkinsonism.

In this study no one of our 85 patients of Serbian origin with young-onset (

Genetic and clinical analysis of spinocerebellar ataxia type 8 repeat expansion in Yugoslavia.

Spinocerebellar ataxia type 8 (SCA8) is a slowly progressive ataxia causally associated with untranslated CTG repeat expansion on chromosome 13q21. However, the role of the CTG repeat in SCA8 pathology is not yet well understood. Therefore, we studied the length of the SCA8 CTA/CTG expansions (combined repeats, CRs) in 115 patients with ataxia, 64 unrelated individuals with non-triplet neuromuscular diseases, 70 unrelated patients with schizophrenia, and 125 healthy controls. Only one patient with apparently sporadic ataxia was identified with an expansion of 100 CRs. He had inherited the expansion from his asymptomatic father (140 CRs) and transmitted the mutation to his son (92 CRs). Paternal transmission in this family produced contractions of 40 and 8 CRs, respectively. None of the subjects from other studied groups had an expansion at the SCA8 locus. In the control group the number of CRs at the SCA8 locus ranged from 14 to 34. Our findings support the notion that allelic variants of the expansion mutation at the SCA8 locus can predispose to ataxia.

CTG repeat polymorphism in DMPK gene in healthy Yugoslav population.

OBJECTIVES: Myotonic dystrophy type 1 (DM1) is caused by large expansions of cytosine-thymine-guanine (CTG)-repeats in myotonic dystrophy protein kinase (DMPK)-gene. This gene is highly polymorphic in healthy individuals. It has been proposed that expanded alleles originated from the group of large sized normal alleles. If this is correct, one should expect a positive correlation between the frequency of large sized normal alleles and a prevalence of this disorder in a population. In this paper we determined the distribution of alleles of DMPK gene in healthy Yugoslav population. MATERIAL AND METHODS: A sample of 235 healthy individuals of Yugoslav origin have been genotyped for the alleles of DMPK locus. RESULTS: We found 22 different alleles, ranging in size from 5 to 29 repeats. Among 470 chromosomes studied, 41 chromosomes had more than 18 repeats (8.72%). CONCLUSIONS: Relatively high frequency of large sized normal alleles found in our population, suggest that prevalence of DM1 in Yugoslavia should not be different from the prevalence in other European populations.

Yugoslav population data on nine STR loci.

Allele frequencies of nine short tandem repeats (TH01, TPOX, CSF1P0, vWA, FES/FPS, F13A01, D13S317, D7S820 and D16S539) were obtained in a sample of 111-125 unrelated Yugoslavs.

Is the 31 CAG repeat allele of the spinocerebellar ataxia 1 (SCA1) gene locus non-specifically associated with trinucleotide expansion diseases?

A number of human hereditary neuromuscular and neurodegenerative disorders are caused by the expansion of trinucleotide repeats within certain genes. The molecular mechanisms that underlie these expansions are not yet known. We have analyzed six trinucleotide repeat-containing loci [spinocerebellar ataxias (SCA1, SCA3, SCA8), dentatorubral-pallidoluysian atrophy (DRPLA), Huntington chorea (HD) and fragile X syndrome (FRAXA)] in myotonic dystrophy type 1 (DM1) patients (n = 52). As controls, we analyzed two groups of subjects: healthy control subjects (n =133), and a group of patients with non-triplet neuromuscular diseases (n = 68) caused by point mutations, deletions or duplications (spinal muscular atrophy, Charcot-Marie-Tooth disease, type 1A, hereditary neuropathy with liability to pressure palsies, and Duchenne and Becker muscular dystrophy). Allele frequency distributions for all tested loci were similar in these three groups with the exception of the SCA1 locus. In DM1 patients, the SCA1 allele with 31 CAG repeats account for 40.4% of all chromosomes tested, which is significantly higher than in two other groups (11.3% in healthy controls and 6.6% in the group of non-triplet diseased patients; P < 0.001, Fisher's exact test). This is consistent with our previous findings in HD patients. The absence of this association in non-triplet diseases as well as in healthy controls could indicate a possible role of this SCA1 allele with 31 repeats in triplet diseases. Here we discuss a possible role of the SCA1 region in pathological trinucleotide repeat expansions.

[Comparison of the number of CAG repeats in the gene for androgen receptors in a control Yugoslav population and in patients with schizophrenia]. / Poredjenje broja CAG-ponovaka u genu za androgeni receptor u kontrolnoj Jugoslovenskoj populacimi i kod bolesnika sa shizofrenijom.

INTRODUCTION: Dynamic mutations were recently discovered causing hereditary non polyposis colon cancer. Soon almost 15 hereditary neurological diseases were described caused by the expansion of trinucleotide repeats in target genes. These mutations are unstable: the number of trinucleotide repeats is increasing from generation to generation. These mutations do not obey Mendelian low. There is a positive correlation between the number of repeats and the severity of clinical symptoms, as well as with the age of onset. This fact explains the genetical basis of anticipation. Since schizophrenia is showing non-Mendelian way of inheritance and anticipation, it is believed that it might be caused by trinucleotide repeats in some gene(s). We analysed the number of CAG triplets in the gene for androgen receptor (AR) where expansions are causing spinal and bulbar muscular atrophy in healthy and schizophrenic subjects. The aim of this study was to see if the androgen receptor gene in schizophrenic patients shows instability in the number of trinucleotide repeats. PATIENTS AND METHODS: In healthy Yugoslav population we analysed 85 X chromosomes from 52 non-related individuals (33 females and 19 males) from healthy Yugoslav population and 84 X chromosomes (41 females and 2 males) from patients with schizophrenia. DNA was isolated from peripheral blood leukocytes and used for further PCR amplification of the segment of AR gene containing CAG repeats. The exact number of these repeats was determined by electrophoresis on a 5% denaturing polyacrilamide gel stained by silver. RESULTS: In healthy Yugoslav population we detected 16 different AR alleles in which the number of CAG triplets was from 14 to 29. The most common alleles were with 23 repeats (14.1%) and with 22 repeats (12.9%). The average number of CAG triplets per allele was 20.91. In patients with schizophrenia we detected 13 AR different alleles. The number of triplets was from 17 to 30. The most common allele was with 22 repeats (25%). The average number of CAG triplets per allele was 22.1.

The status of SCA1, MJD/SCA3, FRDA, DRPLA and MD triplet containing genes in patients with Huntington disease and healthy controls.

A number of human hereditary neuromuscular and neurodegenerative disorders are caused by the expansion of trinucleotide repeats within certain genes. Here we report the results of the analysis of five trinucleotide repeats containing genes (SCA1, MJD/SCA3, DRPLA, FRDA and MD) in HD patients and in a group of healthy controls. Allelic frequency distributions for SCA1 and FRDA genes were shifted toward larger alleles in the group of unrelated HD patients, compared to healthy controls. This linkage disequilibrium suggests a possible existence of a common mechanism of trinucleotide repeats expansion in these loci.

[Clinico-genetic study of type I spinocerebelllar ataxia]. / Klinicko-genetska studija spinocerebelarne ataksije, tip jedan.

Inherited, autosomal-dominant cerebellar ataxia (ADCA) comprises a genetically and clinically heterogenous group of neurodegenerative disorders. Clinical classification of these disorders was an important step [2] in differentiation among several types, the most common one being ADCA-I, accompanied with supranuclear ophthalmoplegia, optic nerve atrophy, symptoms of the basal ganglia lesions, dementia and amyotrophia. Molecular-genetic studies indicated genetic heterogeneity of ADCA-I with mutations of genetic loci on chromosome 6p (spinocerebellar ataxia type 1; SCA1), 12q (SCA2), 14q (SCA3), 19p (SCA6) and 16q (SCA4) [3]. Spinocerebellar ataxia type 1 (SCA1) is characterized by cerebellar ataxia, ophthalmoplegia and pyramidal signs [4], but also with other neurological findings that tend to prevent clinical differentiation among patients with SCA1, SCA2 and SCA3. The mutation inducing SCA1 is an instable expansion of trinucleotide (CAG) repeats in the coding region on chromosome 6 [5]. Herein, we report clinical features in patients from two families with SCA1: family I with 15 and family II with 8 affected members in 4 consecutive generations. The acceptable data (history, examination and/or insight into medical records) were obtained for 9 patients in family I and 7 patients in family II. The age at the onset of the disease was 37.8 +/- 11.3 years (mean value +/- SD) (range: 27-60) for all the patients, or 31.8 +/- 10.7 years (range: 7-60) for family I and 45.0 +/- 8.4 years (range: 35-55) for family II. Duration of the disease was 8.9 +/- 4.6 years (range: 3-15); 10.8 +/- 4.1 (range 5-15) and 5.7 +/- 3.8 years (range: 3-10) for families I and II, respectively. The mean number of CAG repeats in the mutated allele for SCA1 of the affected individuals was 50.5 +/- 6.2 (range 45-64). A significant inverse correlation (p < 0.05) was noted between the number of CAG repeats and the age at the onset of the disease (Figure 3). Similarity of initial symptoms in SCA1 was noted. They include simultaneous gait-related problems and dysarthria (usually slurred speech). Occurrence of other neurological signs (Table 3) was also predictable in most cases and depended on the phase of SCA1 at the time of examination. Generally, it is believed that intra- and interfamilial phenotypic heterogeneity in SCA1 is lower than in SCA2 and SCA3 [12]). In conclusion, typical clinical manifestations of SCA1, at least in early phases of the disease, according to our study, include gait ataxia, dysarthria, brisk muscle reflexes and marked hand ataxia; the age at the onset of the disease was inverse, and clinical progression was directly related to the number of CAG repeats in the mutated allele on chromosome 6. Nevertheless, significant differences in clinical properties of this inherited disease are possible among different affected families.

Correlation between triplet repeat expansion and computed tomography measures of caudate nuclei atrophy in Huntington's disease.

Huntington's disease (HD) is an autosomal dominant, progressive disorder characterized by choreic movements, cognitive decline, and psychiatric manifestations. Eleven patients with HD were retrospectively selected from a larger group of 42 patients based on the similar, early onset of the disease (between 21 and 30 years) and the same duration of HD at the moment of computed tomography (CT) examination (5 years). A significant correlation between the number of CAG trinucleotides and the bicaudate index or the frontal horn index, two indices of caudate atrophy, was found in this group of patients. Our results, although in a small number of patients, suggest that the striatal degeneration, assessed by CT measures, is primarily regulated by the size of expanded CAG repeats.

[Importance of the number of trinucleotide repeat expansions in the clinical manifestations of Huntington's chorea]. / Znacaj povecanja broja trinukleotidnih ponovaka za klinicka ispoljavanja Hantigtonove horeje.

INTRODUCTION: In 1993 the gene responsible for Huntington's disease (IT15) was isolated [5]. It was mapped to the tip of the short arm of chromosome 4 and within its coding sequence, near the 5' end, it contained a certain number of trinicleotide (CAG)n (cytosine-adenine-guanine) repeats (Figure 1). This gene codes for a protein (348 kd) called "huntington" that is widely expressed, and its sequence is not related to any protein [6]. The normal range of (CAG)n repeat numbers within IT15 was reported to be between 6 and 37 [6]. Mutation responsible for Huntington's disease implied expansion of (CAG)n repeats: in patients with Huntington's disease the pathologic range was determined to be between 35 and 121 repeats [7-10]. PATIENTS AND METHODS: In this study we correlated the age at onset, rate of progression and initial symptoms of Huntington's disease with the number of trinucleotide (CAG)n repeats in IT15. DNA was isolated from peripheral blood leukocytes of patients fulfilling clinical criteria for definite and probable Huntington's disease [2]. Genetic verification of Huntington's disease was made by the previously described and modified PRC (polymerase chain reaction) technique [17, 18]. In our laboratory a gene with 40 or more repeats was considered as a marker of Huntington's disease. RESULTS: The study comprised 26 patients (11 women and 15 men). At the onset of Huntington's disease they were between 19 and 66 years old (36.6 12.8 years), with the duration of the disease between 1 and 15 years (5.8 4.3 years). The number of (CAG)n, repeats in IT15 ranged between 40 and 95 (49.9 14.1). The negative correlation between the (CAG)n, count in the expanded allele and the age at onset of the disease has been confirmed. Regression analysis showed the correlation coefficient of -0.54 (p = 0.012). The effect of trinucleotide (CAG)n, repeats on the initial clinical manifestations and rate of progression of Huntington's disease is only one of the growing group of "CAG-repeat" disorders that also include entities such as spinocerebellar ataxia-type 1 and 3, spinobulbar muscular atrophy and dentato-rubo-pallidoluysian atrophy [6].

Improved polymerase chain reaction conditions for quick diagnostics of Huntington disease.

Huntington disease (HD) belongs to a growing list of neurodegenerative disorders (fragile X syndrome [6], myotonic dystrophy [1], spino-bulbar muscular atrophy [2] etc.) characterized by unstable expanded trinucleotide repeats (so-called 'dynamic mutations'). The dynamic mutation causing HD represents the expansion of CAG triplets in the first exon of a gene IT15 (chromosome 4) coding for huntington. This trinucleotide stretch is varying in the range of 11-34 in normal chromosomes and 39-121 in HD chromosomes. The most direct diagnostic approach is to amplify the proximal region of IT15 gene (from patients genomic DNA) by polymerase chain reaction (PCR) and estimate the number of CAG triplets. All protocols published to date are difficult to reproduce because amplification is inefficient giving additional non-specific products. The strategy of our experiment is shown in Fig. 1. We designed one new primer, primer No. 2 (another primer was primer No. 1) and novel PCR conditions. Primer No. 2 is located closer to CAG triplets and its extension is not including the GC rich region. PCR amplified products, using primer Nos. 1 and 2, thus do not include the GC rich region and, therefore, are much more efficiently amplified (compared to the products of amplification with primer Nos. 1 and 3).