Anabela Ferro

A survey of spinocerebellar ataxia in South Brazil : 66 new cases with Machado-Joseph disease, SCA7, SCA8, or unidentified disease-causing mutations

Background The autosomal dominant spinocerebellar ataxias (SCAs) are a clinical and genetically heterogeneous group of debilitating, neurodegenerative diseases, related to fourteen different loci– SCAs 1, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13 and 14, Machado-Joseph disease (MJD/SCA 3), and DRPLA. Objectives (1) to verify the frequency of SCA1, SCA2, MJD, DRPLA, SCA6, SCA7 and SCA8 in a series of new SCA patients from South Brazil and (2) to compare their molecular and clinical characteristics with other patients previously described. Methods sixty-six cases were included in the present study: 52 were familial and 14 sporadic. Molecular analysis of the trinucleotide repeat loci were performed according to methods in the literature. Results 92 % of families with autosomal dominant inheritance segregated the MJD1 mutation, 2 % of families segregated the SCA7 mutation and 6 % remained undiagnosed. Among 14 isolated cases, one showed the SCA8 mutation. Clinical and molecular findings were similar to those already described in the literature, but revealed (1) one SCA7 patient with eyelid retraction, a sign usually related to MJD; and (2) one sporadic case of SCA8. Conclusions The proportion of MJD cases was very high, probably reflecting an Azorean founder effect. The estimated frequency of affected individuals with MJD, in our region, was 1.8 / 100,000, and of SCAs other than MJD, 0.2/100,000.

Inherited and acquired risk factors and their combined effects in pediatric stroke

The aim of this study was to identify hereditary and acquired risk-factors as they are related to the occurrence of stroke in children. We identified 21 children with stroke. A search of the Factor V Leiden mutation, the Factor II G20210A variant, and the thermolabile variant of methylenetetrahydrofolate reductase was performed in patients and in a control group (n = 115). We identified risk factors of acquired and/or hereditary nature for stroke in 19 of 21 children. Eleven children had three or more risk factors, seven had two risk factors, and one child had only one risk factor. We found three carriers (14.3%) of the Factor V Leiden mutation, two carriers (9.5%) of the Factor II G20210A variant, eleven (52.4%) thermolabile variant of methylenetetrahydrofolate reductase heterozygote carriers, and one (4.8%) homozygotes for this variant. Frequencies of the Factor V Leiden mutation and the Factor II variant were higher in patients than in controls, suggesting that these variants are associated with an increased risk of stroke in childhood. Homozygosity for the thermolabile variant of methylenetetrahydrofolate reductase was equally frequent amongst patients and controls. Our study confirms that stroke in children is commonly associated with a combination of multiple risk factors, both genetic and acquired, and that the Factor V Leiden mutation and the Factor II G20210A variant are predisposing factors for this situation.

Nonsense mutation in TITF1 in a Portuguese family with benign hereditary chorea

Benign hereditary chorea (BHC) is an autosomaldominant disorder of early onset characterized by a slowly progressing or nonprogressing chorea, without cognitive decline or other progressive neurologic dysfunction, but also by the existence of heterogeneity of the clinical presentation within and among families. The genetic cause of BHC is the presence of either point mutations or deletions in the thyroid transcription factor 1 gene (TITF1). We studied a Portuguese BHC family composed of two probands: a mother and her only son. The patients were identified in a neurology out-patient clinic showing mainly involuntary choreiform movements since childhood, myoclonic jerks, falls, and dysarthria. We performed magnetic resonance imaging (MRI), electroencephalogram (EEG), nerve conduction studies, thyroid ultrasound scan, biochemical thyroid tests, and electrocardiogram (ECG). We excluded Huntington disease by appropriate genetic testing and sequenced the entire TITF1 gene for both patients. The patients showed MRI alterations: (1) in the mother, abnormal hyperintense pallida and cortical cerebral/cerebellar atrophy; and (2) in the son, small hyperintense foci in the cerebellum and subtle enlargement of the fourth ventricle. Sequence analysis of the TITF1 gene in these patients revealed the presence of a heterozygous C > T substitution at nucleotide 745, leading to the replacement of a glutamine at position 249 for a premature stop codon. A previously undescribed nonsense mutation in the TITF1 gene was identified as being the genetic cause of BHC in this family.

A novel H101Q mutation causes PKCγ loss in spinocerebellar ataxia type 14

AbstractSpinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disorder, first described in a Japanese family, showing linkage to chromosome 19q13.4-qter. Recently, mutations have been identified in the PRKCG gene in families with SCA14. The PRKCG gene encodes the protein kinase Cγ (PKCγ), a member of a serine/threonine kinase family involved in signal transduction important for several cellular processes, including cell proliferation and synaptic transmission. To identify the disease-causing mutation in a large group of ataxia patients, we searched for mutations in the PRKCG gene. We ascertained 366 unrelated patients with spinocerebellar ataxia, either pure or with associated features such as epilepsy, mental retardation, seizures, paraplegia, and tremor. A C-to-G transversion in exon 4, resulting in a histidine-to-glutamine change at codon 101 of the PKCγ protein, was identified in patients from a family with slowly progressive pure cerebellar ataxia. Functional studies performed in HEK293 cells transfected with normal or mutant construct showed that this mutation affects PKCγ stability or solubility, verified by time-dependent decreased protein levels in cell culture. In conclusion, the H101Q mutation causes slowly progressive uncomplicated ataxia by interfering with PKCγ stability or solubility, which consequently may cause in either case a decrease in the overall PKCγ-dependent phosphorylation.

Use of fluoxetine for treatment of Machado‐Joseph disease: an open‐label study

Context – Machado‐Joseph Disease (MJD/SCA3) is an autosomal dominant spinocerebellar degeneration that evolves to disability and death. Experimental data have shown that serotonin is an important cerebellar neurotransmitter and that impairment of the serotoninergic cerebellar system can induce cerebellar ataxia.

Machado-Joseph disease in South Brazil : clinical and molecular characterization of kindreds

Objective– To examine the clinical, genetic, and molecular characteristics of a group of MJD patients recently identified in the southernmost state of Brazil, and compare these data with studies from the literature. Methods– Some 62 individuals from 35 families, mostly of Azorean ancestry, had their clinical data and their MJD1 expanded regions examined. Results– The present patients had an earlier age of onset, on average, than Portuguese–Azorean cases. Their survival, proportion of types, average anticipation, proportion of affected versus non‐affected siblings, neurological signs and molecular findings are similar to those observed in patients previously described. Type 1 patients with male transmission showed worse anticipations than type 1 patients with female transmission. Patients with type 1 had also larger CAG expansions than other patients. Conclusions– The Brazilian origin seemed to affect the age of onset. We also noted that there were no differences other than the neurological between types 2 or 3, since both are similar in age of onset, disease duration and length of CAG repeats. We addressed the question of maintaining or not subtypes 2 and 3 separated, among patients with genetic and geographical backgrounds like the presented patients here.

Population Genetics of Wild-Type CAG Repeats in the Machado-Joseph Disease Gene in Portugal

Objective: To gain insights on the molecular mechanisms of mutation that led to the emergence of expanded alleles in the MJD gene, by studying the behavior of wild-type alleles and testing the association of its distribution with the representation of the disease. Methods: The number of CAG motifs in the MJD gene was determined in a representative sample of 1000 unrelated individuals. Associations between the repeat size and the epidemiological representation of MJD were tested. Results: The allelic profile of the total sample was in the normal range (13–41 repeats), with mode (CAG)23. No intermediate alleles were present. Allelic size distribution showed a negative skew. The correlation between the epidemiological representation of MJD in each district and the frequency of small, medium and large normal alleles was not significant. Further correlations performed grouping the districts also failed to produce significant results. Conclusions: The absence of association between the size of the repeats and the representation of MJD demonstrates that prevalence is not an indirect reflection of the frequency of large normal alleles. Globally the results obtained are in accordance with a model that postulates the occurrence of a few mutations on the basis of most of the MJD cases worldwide.

Spinocerebellar ataxias in 114 Brazilian families: clinical and molecular findings.

To the Editor: Dominant spinocerebellar ataxias (SCAs) are a group of neurodegenerative diseases that affect the cerebellum, brain stem, and spinocerebellar tracts. SCA1, SCA2, SCA3, SCA6, SCA7, SCA12, SCA17 and dentatorubral pallidoluysian atrophy (DRPLA) are caused by CAG trinucleotide repeat expansions (1). SCA8 has a CTG expansion in the causative gene. SCA10 has been found to represent a large expansion of a pentanucleotide (ATTCT) repeat (2). The frequency of each SCA varies between regions and ethnic groups. Machado–Joseph disease (MJD/SCA3) is the most common SCA among populations with Portuguese and Azorean background and populations in Japan and Germany (3–10). SCA2 is common in Cuba, India, Korea, and Italy (11– 14). SCA10 has been only described in the New World (15–19). Our aim was to determine the frequency of the SCA1, SCA2, SCA3, SCA6, SCA7, SCA10, SCA17 and DRPLA among SCA families who have the same geographic origin, namely southern Brazil (Rio Grande do Sul). Clinical, epidemiological, and molecular features are also described herein. Cases were recruited based on the following inclusion criteria: (1) ataxia, often associated with other neurological signs; and (2) inheritance as an autosomal dominant trait. Neurological examination followed a standard examination already published (19). Presence and gradation of several neurological findings were evaluated as numeric ordinal variables. Peripheral blood was collected, and genomic DNA was isolated from peripheral blood leukocytes, using the salting-out technique, as previously described (20). Molecular analyses of the repeat loci were performed by molecular tests specific to each ataxia by PCR amplification. Southern blot was performed to SCA10 locus. Patients were stratified according to their molecular diagnosis. Clinical variables were then compared between these groups. Comparisons were performed using analysis of variance (ANOVA), when the variable was parametric, or the Kruskal–Wallis test (KW test), when the variable was nonparametric. A Bonferroni procedure was done, in order to correct for multiple testing. This study was approved by the ethics committee of the institution where it was conducted; informed consent forms were filled out by all patients. A total of 114 families with autosomal dominant trait were investigated during an 8-year period (up to 2004). Diagnosis, ethnicity, and main clinical features are presented in Tables 1 and 2. SCA3 was the most prevalent, comprising 84.2% of all SCAs. The other SCAs were far less common and represented from one to five pedigrees each. The number of clinically examined patients with the diverse molecular diagnoses was variable. Due to this, some statistical comparisons could not be done: SCA1 and SCA10 patients were excluded from comparisons. Neurological findings that showed statistical differences among groups were (1) nystagmus, less frequent in cases with SCA2 and SCA7 than in the general sample; (2) limb ataxia, more severe in SCA6 patients; and (3) pyramidal findings and optic atrophy, more common in SCA7 patients than in other groups (p , 0.0025, 0.0025, 0.041 and 0.0411, respectively; KW test). Most of the present families were of mixed ancestry but Portuguese surnames prevailed. In our region, the main Portuguese ancestry was Azorean in origin, dating from circa 1750 (7). The Amerindians are another important ancestry. The composition of mitochondrial Amerindian markers in urban Brazilian populations is high and varies between 22% and 54% (26). This finding shows the importance of this Brazilian ancestry. So far, SCA10 has only been described in American families (15–18, 27). The finding of two SCA10 kindreds is in line with the hypothesis that this mutation is somehow restricted to patients with an Amerindian ancestry. Although some of the present families have already been described (7, 18, 19, 28), they had never been compared. We made these comparisons

ATX-3, CDC-48 and UBXN-5: a new trimolecular complex in Caenorhabditis elegans.

Ataxin-3 is the protein involved in Machado-Joseph disease, a neurodegenerative disorder caused by a polyglutamine expansion. Ataxin-3 binds ubiquitylated proteins and acts as a deubiquitylating enzyme in vitro. It was previously proposed that ataxin-3, along with the VCP/p97 protein, escorts ubiquitylated substrates for proteasomal degradation, although other players of this escort complex were not identified yet. In this work, we show that the Caenorhabditis elegans ataxin-3 protein (ATX-3) interacts with both VCP/p97 worm homologs, CDC-48.1 and CDC-48.2 and we map the interaction domains. We describe a motility defect in both ATX-3 and CDC-48.1 mutants and, in addition, we identify a new protein interactor, UBXN-5, potentially an adaptor of the CDC-48-ATX-3 escort complex. CDC-48 binds to both ATX-3 and UBXN-5 in a non-competitive manner, suggesting the formation of a trimolecular complex. Both CDC-48 and ATX-3, but not UBXN-5, were able to bind K-48 polyubiquitin chains, the standard signal for proteasomal degradation. Additionally, we describe several common interactors of ATX-3 and UBXN-5, some of which can be in vivo targets of this complex.

The C677T Polymorphism in MTHFR Is Not Associated with Migraine in Portugal

Migraine is a debilitating disorder affecting a large proportion of the population. The effect of methylenetrathydrofolate reductase (GeneID: 4524) polymorphisms in migraine etiology and development has been a theme of great interest. Several populations were evaluated with contradictory results. In this case-control study, we investigated the effect of the C677T polymorphism in MTHFR, as a genetic risk factor for migraine, in the Portuguese population. We observed that, overall, there was no significant difference in the frequencies of MTHFR C677T genotypes or of the T-allele among the Portuguese migraineurs when compared to controls. There was also no association of migraine with aura with MTHFR genotypes or with the T-allele, in contrast with previous studies. Regarding the risk of the T-allele homozygote carriers, there was an equal probability to develop migraine with aura over migraine without aura in our patients. Thus, we conclude that the C677T MTHFR polymorphism, responsible for a reduction of the MTHFR activity in folate metabolism, is not a major genetic susceptibility factor for migraine in the Portuguese population.