RESUMEN
OBJECTIVE: To improve understanding of TRPV4-associated axonal Charcot-Marie-Tooth (CMT) neuropathy phenotypes and their debated pathologic mechanism. METHODS: A total of 17 CMT2C phenotypic families with vocal cord and diaphragmatic involvement and 36 clinically undifferentiated CMT2 subjects underwent sequencing analysis of the coding region of TRPV4. Functional studies of mutant proteins were performed using transiently transfected cells for TRPV4 subcellular localization, basal and stimulated Ca(2+) channel analysis, and cell viability assay with or without channel blockade. RESULTS: Two TRPV4 mutations R232C and R316H from 17 CMT2C families were identified in the ankyrin repeat domains. The R316H is a novel de novo mutation found in a patient with CMT2C phenotype. The family with R232C mutation had individuals with and without vocal cord and diaphragm involvement. Both mutant TRPV4 proteins had normal subcellular localization in HEK293 and HeLa cells. Cells transfected with R232C and R316H displayed increased intracellular Ca(2+) levels and reversible cell death by the TRPV channel antagonist, ruthenium red. CONCLUSION: TRPV4 ankyrin domain alterations including a novel de novo mutation cause axonal CMT2. Individuals with the same mutation may have nondistinct CMT2 or have phenotypic CMT2C with vocal cord paresis. Reversible hypercalcemic gain-of-function of mutant TRPV4 instead of loss-of-function appears to be pathologically important. The reversibility of cell death by channel blockade provides an attractive area of investigation in consideration of treatable axonal degeneration.
Asunto(s)
Axones/patología , Enfermedad de Charcot-Marie-Tooth , Diafragma/patología , Hipercalcemia/etiología , Mutación/genética , Canales Catiónicos TRPV/genética , Adulto , Aminoácidos/genética , Animales , Calcio/metabolismo , Línea Celular Transformada , Supervivencia Celular , Enfermedad de Charcot-Marie-Tooth/complicaciones , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/patología , Salud de la Familia , Humanos , Hipercalcemia/genética , Líquido Intracelular/metabolismo , Masculino , Rojo de Rutenio/farmacología , Transfección/métodosRESUMEN
OBJECTIVE: Amyotrophic lateral sclerosis (ALS) is a progressive paralytic disorder caused by degeneration of motor neurons. Mutations in the FUS gene were identified in patients with familial ALS (FALS) and patients with sporadic ALS (SALS) from a variety of genetic backgrounds. This work further explores the spectrum of FUS mutations in patients with FALS and patients with FALS with features of frontotemporal dementia (FALS/FTD) or parkinsonism and dementia (FALS/PD/DE). METHODS: All exons of the FUS gene were sequenced in 476 FALS index cases negative for mutations in SOD1 and TARDBP. A total of 561-726 controls were analyzed for genetic variants observed. Clinical data from patients with FUS mutations were compared to those of patients with known SOD1 and TARDBP mutations. RESULTS: We identified 17 FUS mutations in 22 FALS families, 2 FALS/FTD families, and 1 FALS/PD/DE family from diverse genetic backgrounds; 11 mutations were novel. There were 4 frameshift, 1 nonsense, and 1 possible alternate splicing mutation. Patients with FUS mutations appeared to have earlier symptom onset, a higher rate of bulbar onset, and shorter duration of symptoms than those with SOD1 mutations. CONCLUSIONS: FUS gene mutations are not an uncommon cause in patients with FALS from diverse genetic backgrounds, and have a prevalence of 5.6% in non-SOD1 and non-TARDBP FALS, and approximately 4.79% in all FALS. The pathogenicity of some of these novel mutations awaits further studies. Patients with FUS mutations manifest earlier symptom onset, a higher rate of bulbar onset, and shorter duration of symptoms.
Asunto(s)
Empalme Alternativo/genética , Esclerosis Amiotrófica Lateral/genética , Codón sin Sentido/genética , Mutación del Sistema de Lectura/genética , Demencia Frontotemporal/genética , Trastornos Parkinsonianos/genética , Proteína FUS de Unión a ARN/genética , Adolescente , Adulto , Anciano , Esclerosis Amiotrófica Lateral/diagnóstico , Estudios de Casos y Controles , Estudios de Cohortes , Femenino , Demencia Frontotemporal/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Linaje , Adulto JovenAsunto(s)
Sustitución de Aminoácidos , Enfermedad de Charcot-Marie-Tooth , Proteínas de la Membrana/genética , Proteínas Mitocondriales/genética , Enfermedad de la Neurona Motora/genética , Mutación , Adolescente , Adulto , Secuencia de Aminoácidos , Animales , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/fisiopatología , GTP Fosfohidrolasas , Humanos , Masculino , Datos de Secuencia Molecular , Enfermedad de la Neurona Motora/fisiopatología , Alineación de SecuenciaRESUMEN
Rasmussen encephalitis (RE) sera were screened for antibodies to human alpha7 nicotinic acetylcholine receptors (nAChRs) using electrophysiology, calcium imaging, and ligand binding assays. Sera from two of nine patients with RE blocked ACh-induced currents through alpha7 nAChRs and the ACh-induced rise in intracellular free calcium ([Ca2+]i) and inhibited (125)I-alpha-bungarotoxin binding in cells expressing alpha7 nAChRs. Thus, the alpha7 nAChR is a potential target for pathogenic antibodies in patients with RE.