Aprataxin Gene Mutations in Tunisian Families
The authors report clinical and genetic study of 13 patients from three unrelated Tunisian families with an early onset cerebellar ataxia associated with oculomotor apraxia. Cerebellar ataxia with oculomotor apraxia 1 (AOA1) represents a clinically heterogeneous disease caused by mutations in the aprataxin gene. Two novel mutations were identified, the complete deletion of the gene, which seems to not correlate with an increased severity of the disease, and a splice mutation on the acceptor splice site of exon 7.
[Show abstract] [Hide abstract] ABSTRACT: Autosomal recessive cerebellar ataxias (ARCA) are a complex group of neurodegenerative disorders with great genetic and phenotypic heterogeneity, over 30 genes/loci have been associated with more than 20 different clinical forms of ARCA. Genetic heterogeneity combined with highly variable clinical expression of the cerebellar symptoms and overlapping features complicate furthermore the etiological diagnosis of ARCA. The determination of the most frequent mutations and corresponding ataxias, as well as particular features specific to a population, are mandatory to facilitate and speed up the diagnosis process, especially when an appropriate treatment is available. We explored 166 patients (115 families) refered to the neurology units of Algiers central hospitals (Algeria) with a cerebellar ataxia phenotype segregating as an autosomal recessive pattern of inheritance. Genomic DNA was extracted from peripheral blood samples and mutational screening was performed by PCR and direct sequencing or by targeted genomic capture and massive parallel sequencing of 57 genes associated with inherited cerebellar ataxia phenotypes. In this work we report the clinical and molecular results obtained on a large cohort of Algerian patients (110 patients/76 families) with genetically determined autosomal recessive ataxia, representing 9 different types of ARCA and 23 different mutations, including 6 novel ones. The five most common ARCA in this cohort were Friedreich ataxia, ataxia with isolated vitamin E deficiency, ataxia with oculomotor apraxia type 2, autosomal recessive spastic ataxia of Charlevoix-Saguenay and ataxia with oculomotor apraxia type 1. We report here a large cohort of patients with genetically determined autosomal recessive ataxia and the first study of the genetic context of ARCA in Algeria. This study showed that in Algerian patients, the two most common types of ataxia (Friedreich ataxia and ataxia with isolated vitamin E deficiency) coexist with forms that may be less common or underdiagnosed. To refine the genotype/phenotype correlation in rare and heteregeneous diseases as autosomal recessive ataxias, more extensive epidemiological investigations and reports are necessary as well as more accurate and detailed clinical characterizations. The use of standardized clinical and molecular protocols would thus enable a better knowledge of the different forms of ARCA.0Comments 2Citations
- "The nonsense mutation, c.837G > A; p.Trp279*, known as the most frequent mutation in the European population [44, 45], was present in 5 of our patients (2 families), while one patient was homozygous for a splice mutation on the acceptor splice site of exon 7, c.875-1G > A. A consanguineous context was noted in 5 patients (4 families) and two of these patients (from two unrelated families) had undergone neurological examination. The age at onset in our patients was 3 and 7 years old respectively, with gait-limb ataxia as a first sign for both patients, accordingly with the early-onset status of this form of ataxia [42, 46, 47]. Our patients had moderate cerebellar syndrome with dysarthria, but absence of nystagmus although this later feature accounts for one of the main clinical signs of AOA1 . "
[Show abstract] [Hide abstract] ABSTRACT: Background: Ataxia with oculomotor apraxia type 1 is an autosomal-recessive neurodegenerative disorder characterized by a childhood onset of slowly progressive cerebellar ataxia, followed by oculomotor apraxia and a severe primary motor peripheral axonal motor neuropathy. Ataxia with oculomotor apraxia type 1 is caused by bi-allelic mutations in APTX (chromosome 9p21.1). Case presentation: Our patient has a clinical presentation that is typical for ataxia with oculomotor apraxia type 1 with no particularly severe phenotype. Multiplex Ligation-dependent Probe Amplification analysis resulted in the identification of a homozygous deletion of all coding APTX exons (3 to 9). SNP array analysis using the Illumina Infinium CytoSNP-850 K microarray indicated that the deletion was about 62 kb. Based on the SNP array results, the breakpoints were found using direct sequence analysis: c.-5 + 1225_*44991del67512, p.0?. Both parents were heterozygous for the deletion. Homozygous complete APTX deletions have been described in literature for two other patients. We obtained a sample from one of these two patients and characterized the deletion (156 kb) as c.-23729_*115366del155489, p.0?, including the non-coding exons 1A and 2 of APTX. The more severe phenotype reported for this patient is not observed in our patient. It remains unclear whether the larger size of the deletion (156 kb vs 62 kb) plays a role in the phenotype (no extra genes are deleted). Conclusion: Here we described an ataxia with oculomotor apraxia type 1 patient who has a homozygous deletion of the complete coding region of APTX. In contrast to the patient with the large deletion, our patient does not have a severe phenotype. More patients with deletions of APTX are required to investigate a genotype-phenotype effect.0Comments 0Citations
- "Therefore, the size of the APTX deletion is unknown for their patient, neither do we know whether the two noncoding APTX exons are deleted in their patient. This is especially unsatisfactory because the typical AOA1 clinical presentation of our patient is similar to that reported for the patient of Amouri et al. . To our knowledge, a database with APTX genetic variants was not available when writing this report. "
[Show abstract] [Hide abstract] ABSTRACT: Ataxia, although rare, can be a symptom of many debilitating movement disorders. Hereditary ataxias are one subset of this condition and manifest when there is a genetic abnormality involved. Ataxia oculomotor apraxia type 1 (AOA1), an autosomal recessive ataxia, results from a mutation on the aprataxin gene (APTX). We characterized a novel homozygous deletion mutation (IVS4-12delT) on the APTX gene in a 14-year-old male born to consanguineous parents. This case report emphasizes the importance of investigating and increasing awareness of novel genetic mutations in order to help diagnose and further classify hereditary ataxias.0Comments 0Citations
- "This leads to oculomotor apraxia, a condition that is characterized by the inability to make side-to-side eye movements. The literature has described various types of genetic mutations associated with the APTX gene leading to AOA1 including substitution, missense and splicing mutations;[9–12] however, the IVS4-12delT mutation has never been specifically reported. This may play a major role in the observed oculomotor symptoms and may also be the cause of the abnormal visual evoked potentials seen in our patient. "