Maria Thereza Drummond Gama’s research while affiliated with Federal University of São Paulo and other places

Previous studies using whole exome sequencing (WES) have shown that a significant proportion of adult patients with undiagnosed ataxia in European and North American cohorts have a known genetic cause. Little is known about the diagnostic yield of WES in non-Caucasian ataxic populations. Herein, we used WES to investigate a Brazilian cohort of 76 adult patients with idiopathic ataxia previously screened for trinucleotide expansions in known ataxia genes. We collected clinical and radiological data from each patient. WES was performed following standard procedures. Only variants labeled as pathogenic or likely pathogenic according to American college of medical genetics and genomics (ACMG) criteria were retrieved. We determined the diagnostic yield of WES for the whole cohort and also for subgroups defined according to presence or not of pyramidal signs, peripheral neuropathy, and cerebellar atrophy. There were 41 women and 35 men. Mean age at testing was 48 years. Pyramidal signs, peripheral neuropathy, tremor, and cerebellar atrophy were found in 38.1%, 13.1%, 10.5%, and 68.3% of all subjects, respectively. Diagnostic yield of WES was 35.5%. Thirty-six distinct mutations were found in 20 different genes, determining the diagnosis of 18 autosomal recessive and 9 autosomal dominant ataxias. SACS and SPG7 were the most frequently found underlying genes. WES performed better in the subgroup with vs the subgroup without spasticity (p = 0.005). WES was diagnostic in 35.5% of cases of the Brazilian cohort of ataxia cases. These results have implications for diagnosis, genetic counseling and eventually treatment.

Background The gene SYNE1 is highly expressed in the cerebellum and its dysfunction is related to an autosomal recessive ataxia (SYNE1-ataxia). The disease was firstly considered a pure cerebellar ataxia however, recent studies have described a broader clinical presentation, including motor neuron disease symptoms. Objectives To investigate cerebellar and potential extra-cerebellar changes in SYNE1-ataxia using multimodal neuroimaging analyses. Methods Six patients completed clinical and imaging exams, and were compared to age-gender-matched healthy controls. Gray matter was analyzed using FreeSurfer and CERES for brain and cerebellum, respectively. White matter was analyzed with DTI-TBSS while we used SpineSeg for spinal cord analysis. Results We found significantly reduced cortical thickness (p < 0.05, FDR-corrected) in primary and association cortices, and volume reduction in subcortical structures, brainstem and cerebellum. White matter was found disrupted in both brain and cerebellum (p < 0.05, FWE-corrected). These results are consistent with the expression of the SYNE1 mRNA and its encoded protein in the brain. We failed to demonstrate spinal cord changes. Conclusions SYNE1-ataxia is, therefore, a relatively common cause of recessive ataxia characterized by complex multisystemic neurostructural changes consistent with the phenotypic heterogeneity and neuroimaging configures a potential marker of the disease.