Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder originally described in families of Portuguese-Azorean ancestry. The cloning of the MJD1 gene allowed identification of the disease in many other populations, and MJD is now known to be the most common cause of dominant spinocerebellar ataxia. The hypothesis that its present world distribution could result from the spread of an original founder mutation has been raised, both at historical and molecular levels. In the present study, we tested this hypothesis by linkage-disequilibrium analysis of tightly linked polymorphisms and by haplotype comparison, in 249 families from different countries. We typed five microsatellite markers surrounding the MJD1 locus (D14S1015, D14S995, D14S973, D14S1016, and D14S977), and three intragenic single-base-pair polymorphisms (A(669)TG/G(669)TG, C(987)GG/G(987)GG, and TAA(1118)/TAC(1118)). The results show two different haplotypes, specific to the island of origin, in families of Azorean extraction. In families from mainland Portugal, both Azorean haplotypes can be found. The majority of the non-Portuguese families also share the same intragenic haplotype seen in the families coming from the island of Flores, but at least three other haplotypes were seen. These findings suggest two introductions of the mutation into the Portuguese population. Worldwide, the sharing of one intragenic haplotype by the majority of the families studied implies a founder mutation in MJD.

Intergenerational instability is one of the most important features of the disease-associated trinucleotide expansions, leading to variation in size of the repeat among and within families, which manifests as variable age at onset and severity, and is probably the basis for the occurrence of anticipation. Several factors are known to affect the degree of instability, namely the type of repeated sequence, its initial size, the presence or absence of interruptions in the repetitive tract and the gender of the transmitting parent. A recent study demonstrated the effect of an intragenic polymorphism (C 987 GG/G 987 GG) in the Machado-Joseph disease causative gene, immediately downstream of the CAG repeat, on the intergenerational instability of the expanded repeat. Surprisingly, there was an effect not only of the specific allele in cis to the disease chromosome, but also of the allele on the normal chromosome, suggesting the existence of an interaction between the normal and expanded alleles that affects the fidelity of replication of the (CAG) n tract. This effect could be a direct effect of the polymorphism studied or, alternatively, this polymorphism could be in disequilibrium with some other flanking sequence which affects the instability of the repetitive (CAG) n tract. In order to confirm the previous results in a different population and to distinguish between a direct and indirect effect of the CGG/GGG polymorphism, we typed 70 parent-progeny pairs for which the variation in the (CAG) n length in the MJD1 gene was known, for three intragenic polymorphisms: C European Journal of Human Genetics (1999) 7, 147-156 © 1999 Stockton Press All rights reserved 1018-4813/99 $12.00 t http://www.stockton-press.co.uk/ejhg suggestive of an instability-predisposing effect of the repeat-flanking sequences, which could have led to the origin of the MJD mutation in the human population. We confirmed the effect of the C 987 GG/G 987 GG polymorphism on intergenerational instability when present in trans. Our results suggest that this effect is restricted to a small region of the gene, immediately downstream of the CAG repeat, which includes this particular nucleotide substitution and the stop codon of the MJD1 cDNA, and is not a more widespread chromosomal effect. The lack of a significant association of any specific intragenic haplotype with larger CAG repeats in normal chromosomes, together with the absence of an effect of the intragenic haplotype in cis on the intergenerational instability of the expanded (CAG) n in MJD families does not indicate the existence of an instability-predisposing haplotype.

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An urban survey of Lisbon, the largest city in Portugal, was carried out to investigate its environmental burden, emphasizing metallic elements and their public health impacts. This paper examines the geochemistry of lead and its influence on human health data. A total of 51 soil samples were collected from urban recreational areas used by children to play outdoors. The semi-quantitative analysis of lead was carried out by inductively coupled plasma mass spectrometry after an acid digestion. X-ray diffraction was used to characterise the soil mineralogy. The solid phase distribution of lead in the urban soils was investigated on a sub-set of 7 soils, out of a total of 51 samples, using a non-specific sequential extraction method coupled with chemometric analysis. Oral bioaccessibility measurements were obtained using the Unified BARGE Method developed by the Bioaccessibility Research Group of Europe. The objectives of the study are: (i) investigation of lead solid-phase distribution; (ii) interpretation of lead oral bioaccessibility measurements; (iii) integration of metal geochemistry with human health data; (iv) understanding the influence of geochemistry and mineralogy on oral bioaccessibility. The results show that the bioaccessible fraction of Pb is lower when major metal fractions are associated to less soluble soil phases such as Fe-oxyhydroxides, and more elevated when the metal is in the highly soluble carbonate phase. However, there is some evidence that the proportion of carbonates in the soil environment is also a key control over the oral bioaccessibility of Pb, irrespective of its solid phase fractionation.

The spinocerebellar ataxias (SCAs) are clinically and genetically a heterogeneous group of neurodegenerative disorders. To date, eight different loci causing SCA have been identified: SCA1, SCA2, Machado-Joseph disease (MJD)/SCA3, SCA4, SCA5, SCA6, SCA7, and dentatorubropallidoluysian atrophy (DRPLA). Expansion of a CAG repeat in the disease genes has been found in five of these disorders. To estimate the relative frequencies of the SCA1, DRPLA, MJD, SCA2, and SCA6 mutations among Portuguese ataxia patients, we collected DNA samples from 48 ataxia families and performed polymerase chain reaction (PCR) amplification of the CAG repeat mutations on chromosomes 6p, 12p, 14q, 12q, and 19p, respectively. Fifty-five individuals belonging to 34 dominant families (74%) had an expanded CAG repeat at the MJD gene. In five individuals from two kindreds with a dominant pattern of inheritance (4%), an expanded CAG repeat at the SCA2 gene was found. In MJD patients, the normal allele size ranged from 13 to 41, whereas the mutant alleles contained 65 to 80 repeats. For the SCA2 patients, normal alleles had 22 or 23, while expanded alleles had between 36 and 47 CAG units. We did not find the SCA1, DRPLA, or SCA6 mutations in our group of families. The MJD mutation remains the most common cause of SCA in Portugal, while a small number of cases are caused by mutations at the SCA2 gene, and 22% are due to still unidentified genes.

Article history: Available online xxxx a b s t r a c tTo assess the impact of potentially harmful elements in soil/dust on the health of children that use urban recreational areas to play outdoors, an urban survey of Lisbon, the largest city in Portugal was carried out, collecting soils and dusts from public gardens, parks, playgrounds and schoolyards. An exposure and risk assessment study for the incidental soil/dust ingestion of lead was carried out based on US EPA guidelines using a sub-set of 19 topsoil and 8 outdoor dusts, out of a total of 51 samples, incorporating oral bioaccessibility measurements using the Unified BARGE Method developed by the Bioaccessibility Research Group of Europe. The objectives are: (i) interpretation of soil and dust oral bioaccessibility measurements; (ii) assessment of site-specific exposure and non-carcinogenic risk posed by lead; (iii) hazard assessment for urban soil and dust with respect to children playing in outdoor recreational areas. The results show that significant fractions of Pb occur in bioaccessible forms, 24-100% in soils and 35-100% in dusts and the associated risk is greater for dust ingestion than for soil ingestion in Lisbon city recreational areas.

Soil quality in urban areas is affected by anthropogenic activities, posing a risk to human health and ecosystems. Since the pseudo-total concentrations of potentially toxic elements may not reflect their potential risks, the study of element mobility is very important on a risk assessment basis. This study aims at characterising the distribution and major sources of 34 elements in two Portuguese urban areas (Lisbon and Viseu), with different geological characteristics, industrial and urban development processes. Furthermore, the potential availability of As, Co, Cr, Cu, Ni, Pb and Zn was assessed, by measuring the fraction easily mobilised. Lisbon is enriched in elements of geogenic and anthropogenic origin, whereas in the smaller city, the high levels observed are mainly related to a geogenic origin. Background values can be more relevant than the dimension of the city, even when anthropogenic components may be present, and this parameter should be considered when comparing results from different cities. Regarding the potential available fraction, a high variability of results was observed for elements and for sampling sites with an influence of the soil's general characteristics. Elements showing very high concentrations due to geological reasons presented, in general, a low mobility and it was not dependent on the degree of contamination. For elements with major anthropogenic origin, only Zn was dependent on the pseudo-total content. Yet, the highest available fractions of some elements, both with major geogenic and anthropogenic origin, were observed in specific contaminated samples. Therefore, a site-specific evaluation in urban soils is important due to the high spatial variability and heterogeneity.

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