RESUMEN
Mutations in the gene encoding the heavy chain subunit (DYNC1H1) of cytoplasmic dynein cause spinal muscular atrophy with lower extremity predominance, Charcot-Marie-Tooth disease and intellectual disability. We used the legs at odd angles (Loa) (DYNC1H1(F580Y)) mouse model for spinal muscular atrophy with lower extremity predominance and a combination of live-cell imaging and biochemical assays to show that the velocity of dynein-dependent microtubule minus-end (towards the nucleus) movement of EGF and BDNF induced signalling endosomes is significantly reduced in Loa embryonic fibroblasts and motor neurons. At the same time, the number of the plus-end (towards the cell periphery) moving endosomes is increased in the mutant cells. As a result, the extracellular signal-regulated kinases (ERK) 1/2 activation and c-Fos expression are altered in both mutant cell types, but the motor neurons exhibit a strikingly abnormal ERK1/2 and c-Fos response to serum-starvation induced stress. These data highlight the cell-type specific ERK1/2 response as a possible contributory factor in the neuropathological nature of Dync1h1 mutations, despite generic aberrant kinetics in both cell types, providing an explanation for how mutations in the ubiquitously expressed DYNC1H1 cause neuron-specific disease.
Asunto(s)
Dineínas Citoplasmáticas/genética , Sistema de Señalización de MAP Quinasas/genética , Atrofia Muscular Espinal/genética , Mutación/genética , Proteínas Proto-Oncogénicas c-fos/metabolismo , Animales , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Células Cultivadas , Medio de Cultivo Libre de Suero/farmacología , Modelos Animales de Enfermedad , Embrión de Mamíferos , Endosomas/efectos de los fármacos , Endosomas/metabolismo , Factor de Crecimiento Epidérmico/metabolismo , Humanos , Ratones , Ratones Transgénicos , Neuronas Motoras/efectos de los fármacos , Neuronas Motoras/metabolismo , Fosfoproteínas Fosfatasas/metabolismo , Transporte de Proteínas/efectos de los fármacos , Transporte de Proteínas/genética , TransfecciónRESUMEN
Mutations in the motor protein cytoplasmic dynein have been found to cause Charcot-Marie-Tooth disease, spinal muscular atrophy, and severe intellectual disabilities in humans. In mouse models, neurodegeneration is observed. We sought to develop a novel model which could incorporate the effects of mutations on distance travelled and velocity. A mechanical model for the dynein mediated transport of endosomes is derived from first principles and solved numerically. The effects of variations in model parameter values are analysed to find those that have a significant impact on velocity and distance travelled. The model successfully describes the processivity of dynein and matches qualitatively the velocity profiles observed in experiments.