Autosomal dominant cerebellar ataxias in the Kinki area of Japan

Calpain Inhibition Is Protective in Machado-Joseph Disease Zebrafish Due to Induction of Autophagy

The neurodegenerative disease Machado-Joseph disease (MJD), also known as spinocerebellar ataxin-3, affects neurons of the brain and spinal cord, disrupting control of the movement of muscles. We have successfully established the first transgenic zebrafish (Danio rerio) model of MJD by expressing human ataxin-3 protein containing either 23 glutamines (23Q, wild-type) or 84Q (MJD-causing) within neurons. Phenotypic characterization of the zebrafish (male and female) revealed that the ataxin-3-84Q zebrafish have decreased survival compared with ataxin-3-23Q and develop ataxin-3 neuropathology, ataxin-3 cleavage fragments and motor impairment. Ataxin-3-84Q zebrafish swim shorter distances than ataxin-3-23Q zebrafish as early as 6 days old, even if expression of the human ataxin-3 protein is limited to motor neurons. This swimming phenotype provides a valuable readout for drug treatment studies. Treating the EGFP-ataxin-3-84Q zebrafish with the calpain inhibitor compound calpeptin decreased levels of ataxin-3 cleavage fragments, but also removed all human ataxin-3 protein (confirmed by ELISA) and prevented the early MJD zebrafish motor phenotype. We identified that this clearance of ataxin-3 protein by calpeptin treatment resulted from an increase in autophagic flux (indicated by decreased p62 levels and increased LC3II). Cotreatment with the autophagy inhibitor chloroquine blocked the decrease in human ataxin-3 levels and the improved movement produced by calpeptin treatment. This study demonstrates that this first transgenic zebrafish model of MJD is a valuable tool for testing potential treatments for MJD. Calpeptin treatment is protective in this model of MJD and removal of human ataxin-3 through macro-autophagy plays an important role in this beneficial effect.SIGNIFICANCE STATEMENT We have established the first transgenic zebrafish model of the neurodegenerative disease MJD, and identified relevant disease phenotypes, including impaired movement from an early age, which can be used in rapid drug testing studies. We have found that treating the MJD zebrafish with the calpain inhibitor compound calpeptin produces complete removal of human ataxin-3 protein, due to induction of the autophagy quality control pathway. This improves the movement of the MJD zebrafish. Artificially blocking the autophagy pathway prevents the removal of human ataxin-3 and improved movement produced by calpeptin treatment. These findings indicate that induction of autophagy, and removal of ataxin-3 protein, plays an important role in the protective effects of calpain inhibition for the treatment of MJD.

The hereditary adult-onset ataxias in South Africa

There is little data on the spectrum and frequencies of the autosomal dominant spinocerebellar ataxias (SCAs) from the African continent. We undertook a large prospective population-based study over a 10-year period in South Africa (SA). Affected persons were clinically evaluated, and the molecular analysis for the SCA1, 2, 3, 6 and 7 expansions was undertaken. Of the 54 SA families with dominant ataxia, SCA1 accounted for 40.7%, SCA2 for 13%, SCA3 for 3.7%, SCA6 for 1.9%, SCA7 for 22.2% and 18.5% were negative for all these mutations. The frequency of the SCA1 and SCA7 expansions in SA represents one of the highest frequencies for these expansions reported in any country. In this study, the SCA7 mutations have only been found in SA families of Black ethnic origin.

Autosomal dominant cerebellar ataxias in ethnic Bengalees in West Bengal - an Eastern Indian state

BACKGROUND

Phenotypic and genotypic patterns of a hereditary disease in a large multiethnic country like India need to be studied in relation to geographical location and ethnicity of the population. The few reported studies from India on dominant ataxias (ADCA) have mostly been conducted on multiethnic populations and hence may not reflect the patterns observed in specific ethnic groups or geographical locations. The present study attempted to look into the patterns of ADCA amongst ethnic Bengalee patients hailing from the eastern Indian state of West Bengal.

MATERIAL AND METHODS

Between mid-1996 and mid-2000, in a clinic based study, 37 cases (from 14 families) with ADCA were studied. This included 33 affected and four asymptomatic members with abnormal physical signs. Genotypic analyses were performed on more than one affected member from each family. Clinical, neuroradiological and electrophysiological aspects were studied.

OBSERVATIONS

Genotype analysis revealed: two families with SCA-1,4 families with SCA2,5 families with SCA3 and three families with undetermined genotype. Of the latter, phenotypically 2 were of ADCA 1 and one of ADCA 2 type. No clear preponderance of one particular genotype over another was observed. We noted significant intra- and interfamily variations in phenotype within the same genotype form as well as overlapping of clinical signs between different genotypes. Slow saccadic eye movements and peripheral neuropathy were not seen consistently in our ethnic Bengalee subjects with SCA2 genotypes. Similarly, extrapyramidal features, ophthalmoplegias and distal amyotrophy were seen in some but not in all families with SCA3 mutation. A peculiar form of abduction lag during slow pursuit movement of eyes was observed in an asymptomatic girl in an SCA3 family.

CONCLUSIONS

Although SCA2 has been claimed to be the commonest form of ADCA in India, this does not appear to be so in our ethnic Bengalee subjects. Phenotypic expression of the genotype also appears to be variable amongst families and individuals. Hence, phenotypic expression appears to be an inconsistent marker of the SCA genotype in our patients.

CAG repeat expansions in patients with sporadic cerebellar ataxia

CAG repeat expansions cause spinocerebellar ataxia type 1 (SCA1), SCA2, SCA3, SCA6 and dentatorubral-pallidoluysian atrophy (DRPLA). So far these expansions have been examined mainly in ataxia patients with a family history. However, some sporadic cases with SCA have recently been reported. To elucidate the frequency and characteristics of sporadic SCAs, we screened 85 Japanese ataxia patients without a family history for the SCA1, SCA2, SCA3, SCA6 and DRPLA mutations. As a result, 19 patients (22%) were found to have expanded CAG repeats. Among sporadic SCAs, the SCA6 mutation was most frequently observed. The sporadic SCA6 patients had smaller CAG repeats and a later age of onset than SCA6 patients with an established family history. We also identified one father-child pair in which intermediate sized CAG repeats expanded into the SCA2 disease range during transmission. These findings suggest that patients with ataxia even without a family history should be examined for a CAG repeat expansion.