We propose an improved protocol for molecular testing for MJD. These strategies, developed to overcome the practical difficulties mostly in the presymptomatic and prenatal diagnosis of MJD, should prove useful for other polyglutamine-related disorders.

The autosomal dominant spinocerebellar ataxias (SCAs) are a group of late-onset, neurodegenerative disorders for which 10 loci have been mapped (SCA1, SCA2, SCA4-SCA8, SCA10, MJD, and DRPLA). The mutant proteins have shown an expanded polyglutamine tract in SCA1, SCA2, MJD/SCA3, SCA6, SCA7, and DRPLA; a glycine-to-arginine substitution was found in SCA6 as well. Recently, an untranslated (CTG)n expansion on chromosome 13q was described as being the cause of SCA8. We have now (1) assessed the repeat size in a group of patients with ataxia and a large number of controls, (2) examined the intergenerational transmission of the repeat, and (3) estimated the instability of repeat size in the sperm of one patient and two healthy controls. Normal SCA8 chromosomes showed an apparently trimodal distribution, with classes of small (15-21 CTGs), intermediate (22-37 CTGs), and large (40-91 CTGs) alleles; large alleles accounted for only0.7% of all normal-size alleles. No expanded alleles (>/=100 CTGs) were found in controls. Expansion of the CTG tract was found in five families with ataxia; expanded alleles (all paternally transmitted) were characterized mostly by repeat-size contraction. There was a high germinal instability of both expanded and normal alleles: in one patient, the expanded allele (152 CTGs) had mostly contraction in size (often into the normal range); in the sperm of two normal controls, contractions were also more frequent, but occasional expansions into the upper limit of the normal size range were also seen. In conclusion, our results show (1) no overlapping between control (15-91) and pathogenic (100-152) alleles and (2) a high instability in spermatogenesis (both for expanded and normal alleles), suggesting a high mutational rate at the SCA8 locus.

Machado-Joseph disease (MJD) is the most common dominant spinocerebellar ataxia. MJD is caused by a CAG trinucleotide expansion in the ATXN3 gene, which encodes a protein named ataxin-3. Ataxin-3 has been proposed to act as a deubiquitinating enzyme in the ubiquitin-proteasome pathway and to be involved in transcriptional repression; nevertheless, its precise biological function(s) remains unknown. To gain further insight into the function of ataxin-3, we have identified the Caenorhabditis elegans orthologue of the ATXN3 gene and characterized its pattern of expression, developmental regulation, and subcellular localization. We demonstrate that, analogous to its human orthologue, C. elegans ataxin-3 has deubiquitinating activity in vitro against polyubiquitin chains with four or more ubiquitins, the minimum ubiquitin length for proteasomal targeting. To further evaluate C. elegans ataxin-3, we characterized the first known knockout animal models both phenotypically and biochemically, and found that the two C. elegans strains were viable and displayed no gross phenotype. To identify a molecular phenotype, we performed a large-scale microarray analysis of gene expression in both knockout strains. The data revealed a significant deregulation of core sets of genes involved in the ubiquitin-proteasome pathway, structure/motility, and signal transduction. This gene identification provides important clues that can help elucidate the specific biological role of ataxin-3 and unveil some of the physiological effects caused by its absence or diminished function.

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RESUMO Introdução: Com o envelhecimento populacional e melhoria dos cuidados de saúde, constata-se um aumento de pessoas dependentes que requerem maior apoio para a satisfação das suas necessidades. O cuidador familiar (CF) é fundamental para garantir a continuidade de cuidados, apesar de ser um processo desgastante e com consequências na saúde. Um programa de intervenção de enfermagem (PIE), devidamente estruturado, revela-se importante neste contexto. Objetivo: Desenvolver e implementar um PIE de apoio e capacitação aos CF de pessoas dependentes. Métodos: Foi realizada uma revisão integrativa da literatura (RIL) que permitiu evidenciar as principais necessidades cuidadores. Depois foi estruturado um PIE, nos domínios do apoio emocional e instrumental, validado por peritos da área, com recurso à técnica de Delphi. Este foi implementado e avaliado, com recurso a um estudo quase experimental, com avaliação pré e pós intervenção. Resultados: Da RIL evidenciaram-se 21 artigos, que destacaram as principais necessidades manifestadas pelos CF. Da técnica de Delphi obteve-se um PIE com 93 intervenções de enfermagem. Da sua implementação, obteve-se uma melhoria geral do estado de saúde do CF, uma diminuição da sobrecarga manifestada e um maior recurso a estratégias de coping. Conclusões: Intervenções de Enfermagem estruturadas e contextualizadas, direcionadas para o apoio e capacitação dos CF, são facilitadoras da transição para este papel, com impacto na sua saúde e nos cuidados prestados.

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