RESUMO
OBJECTIVE: To classify familial amyotrophic lateral sclerosis (FALS) on the base of family history, and to determine whether frequency of mutations in major amyotrophic lateral sclerosis (ALS) genes varies in different FALS categories. METHODS: Included in the study are 53 FALS families. Patients were classified as definite, probable and possible FALS, according to recently proposed criteria. Seven ALS-associated genes, including SOD1, TARDBP, FUS, ANG, ATXN2, OPTN and C9ORF72, were analysed. RESULTS: Thirteen patients (24.5%) were included in the definite group. The great majority of our FALS cases (40/53, 75.5%) were families with only two affected relatives; of these, 31 (58.5%) were included in the probable, and 9 (17%) in the possible FALS categories. The percentage of mutations was 61.5% in definite, 41.9% in probable and 11.1% in possible FALS. With respect to probable FALS, if cases with parent-to-child transmission of the disease were considered separately, the mutational load increased to 61.5%, as observed in definite FALS. CONCLUSIONS: Our findings provide evidence that frequency of mutations in currently known ALS genes varies widely among different FALS categories. Families with only two affected relatives have heterogeneous genetic components, the chance to detect mutations being higher in cases with parent-to-child transmission.
Assuntos
Esclerose Lateral Amiotrófica/classificação , Esclerose Lateral Amiotrófica/genética , Mutação , Adulto , Idoso , Ataxinas , Proteína C9orf72 , Proteínas de Ciclo Celular , Proteínas de Ligação a DNA/genética , Família , Feminino , Frequência do Gene , Humanos , Masculino , Proteínas de Membrana Transportadoras , Pessoa de Meia-Idade , Proteínas do Tecido Nervoso/genética , Proteínas/genética , Proteína FUS de Ligação a RNA/genética , Ribonuclease Pancreático/genética , Análise de Sequência de DNA , Superóxido Dismutase/genética , Superóxido Dismutase-1 , Fator de Transcrição TFIIIA/genéticaRESUMO
OBJECTIVES: To quantify the overall contribution of mutations in the currently known amyotrophic lateral sclerosis (ALS) genes in a large cohort of sporadic patients and to make genotype-phenotype correlations. METHODS: Screening for SOD1, TARDBP, FUS, ANG, ATXN2, OPTN, and C9ORF72 was carried out in 480 consecutive patients with sporadic ALS (SALS) and in 48 familial ALS (FALS) index patients admitted to a single Italian referral center. RESULTS: Mutations were detected in 53 patients, with a cumulative frequency of 11. Seven of them were novel. The highest frequencies of positive cases were obtained in TARDBP (2.7%), C9ORF72 (2.5%), and SOD1 (2.1%). The overall group of mutated patients was indistinguishable from that without mutations as no significant differences were observed with regard to age and site of onset, frequency of clinical phenotypes, and survival. However, by separately evaluating genotype-phenotype correlation in single genes, clinical differences were observed among different genes. Duration of disease was significantly shorter in patients harboring the C9ORF72 expansion and longer in the SOD1 group. A high frequency of predominant upper motor neuron phenotype was observed among patients with TARDBP mutations. Two patients, 1 with C9ORF72 and 1 with SOD1 mutation, had concurrent ANG mutations. Mutations were detected in 43.7% of patients with FALS. CONCLUSIONS: A considerable proportion of patients with SALS harbored mutations in major ALS genes. This result has relevant implications in clinical practice, namely in genetic counseling. The detection of double mutations in 2 patients raises the hypothesis that multiple mutations model may explain genetic architecture of SALS.