Mutations of FUS gene in sporadic amyotrophic lateral sclerosis.

BACKGROUND: Mutations in the FUS gene have recently been discovered to be a major cause of familial amyotrophic lateral sclerosis (FALS). OBJECTIVE: To determine the identity and frequency of FUS gene mutations in a large cohort of Italian patients enriched in sporadic cases (SALS). METHODS: Exons 5, 6, 14 and 15 of the FUS gene were screened for mutations in 1009 patients (45 FALS and 964 SALS). The genetic analysis was extended to the entire coding sequence of FUS in all the FALS and 293 of the SALS patients. RESULTS: Seven missense mutations (p.G191S, p.R216C, p.G225V, p.G230C, p.R234C, p.G507D and p.R521C) were identified in nine patients (seven SALS and two FALS), and none in 500 healthy Italian controls. All mutations are novel except for the p.R521C mutation identified in one SALS and one FALS case. Both patients showed a similar unusual presentation, with proximal, mostly symmetrical, upper limb weakness, with neck and axial involvement. With the exception of p.G507D and p.R521C, the mutations identified in SALS patients are all localised in the glycine-rich region encoded by exon 6. In addition, eight different in-frame deletions in two polyglycine motifs were detected, the frequency of which was not significantly different in patients and controls. CONCLUSIONS: The results show that FUS missense mutations are present in 0.7% of Italian SALS cases, and confirm the previous mutational frequency reported in FALS (4.4%). An unusual proximal and axial clinical presentation seems to be associated with the presence of the p.R521C mutation.

Natural history of upper motor neuron-dominant ALS.

A new amyotrophic lateral sclerosis (ALS) category named 'UMN-dominant ALS' and defined as 'due predominantly to UMN signs but with minor electromyogram (EMG) denervation or LMN signs on examination' has been proposed. The clinical and laboratory features of 20 patients with UMN-dominant ALS are described here, their disease course is analysed longitudinally according to their disability progression, and all these parameters are compared with those of typical ALS patients. Ten women and 10 men diagnosed with UMN-dominant ALS were evaluated. Their mean age at disease onset was 58.6 years. At the most recent evaluation, after a mean disease duration of 7.7 years, all patients progressed to a tetrapyramidal syndrome with pseudobulbar features of varying degree. No patient had respiratory problems. Cognitive impairment was observed in eight patients. The differences in disease progression between the UMN-dominant ALS and typical ALS patients proved significant (p <0.02) both with regard to the total ALSFRS-R score at six months and to each single region subscore at 12 months. Our findings suggest that there is both a different pattern of disability and longer survival in UMN-dominant ALS compared to classic ALS patients.

TDP-43 in skeletal muscle of patients affected with amyotrophic lateral sclerosis.

TAR DNA binding protein (TDP-43) is the pathologic substrate of neuronal and glial aggregates in amyotrophic lateral sclerosis (ALS). Pathologic TDP-43 is hyperphosphorylated and cleaved to generate abnormal protein species that accumulate in the cytoplasm. To assess the hypothesis of TDP-43 pathology as a systemic disorder in ALS we analysed the immunohistochemical and biochemical profile of TDP-43 in muscle biopsies of 30 ALS patients and 30 controls. In all ALS muscle biopsies we observed that TDP-43 was constantly present in an intranuclear localization and TDP-43 Western blotting showed only a 43-KDa band as controls. Our results suggest that TDP-43 pathology is probably confined to the central nervous system in ALS.