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6 th International Charcot‐Marie‐Tooth and Related Neuropathy Consortium (CMTR) Meeting
Author(s) -
Colecchia, D,
Stasi, M,
Leonardi, M,
Manganelli, F,
Nolano, M,
Veneziani, BIANCA MARIA,
Santoro, L,
Chiariello, M,
Bucci, C.
Publication year - 2016
Publication title -
journal of the peripheral nervous system
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 67
eISSN - 1529-8027
pISSN - 1085-9489
DOI - 10.1111/jns.12181
Subject(s) - citation , library science , medicine , computer science
Background: Spinal muscular atrophy with lower extremity predominance (SMA-LED) is an autosomal dominant congenital motor neuron disease. The condition presents with distal limb weakness and muscle atrophy, further compounded with intellectual disability. The most common cause are mutations in dynein cytoplasmic 1 heavy chain 1 (DYNC1H1; OMIM:600112), which encodes the largest subunit of cytoplasmic dynein 1. Dynein is defined by its role as a retrogradely oriented molecular motor but it is also fundamental to other cellular processes including growth cone dynamics and regulation of the Golgi apparatus. Moreover, mutations in dynactin 1 (DCTN1; OMIM: 601143) encoding p150 (Glued) subunit of the dynactin complex, which regulates cytoplasmic dynein function, cause autosomal dominant distal hereditary motor neuronopathy. Objective: To dissect common molecular mechanisms underlying motor neuron degeneration caused by R399G and D338N mutations in DYNC1H1. Methods: Immunofluorescence was performed on patient fibroblasts harbouring the R399G or D338N DYNC1H1 mutation to assess the integrity of the Golgi apparatus and the localization of dynein to the organelle. Modifications of microtubules and the interaction of dynein with golgin-160 were investigated using biochemical analysis. Results: Decreased a-tubulin acetylation was a common molecular phenotype in patient fibroblasts harbouring the R399G (p50.05, N=3) or D338N (p50.01, N=5) mutation in comparison to wild-type fibroblasts (N=3 and N=5, respectively). However, only the R399G mutant fibroblasts (N=20) exhibited a significant (p50.0001) decrease of dynein at the Golgi apparatus in comparison to wild-type cells (N=21). Uniquely, the R399G mutation also caused a significant and inherent fragmentation of the Golgi apparatus, which correlated with the zygosity of the mutation (+/R339G p50.01 N=4, R399G/R399G p50.0001 N=4). A consequent compensational response was measured as an increased interaction between the dynein intermediate chain and golgin-160 in the R399G mutant cells. Excitingly, the treatment of R399G mutant fibroblasts with tubacin (N=32), an HDAC6 inhibitor, caused a striking statistically significant (p50.0001) amelioration of the Golgi apparatus integrity by increasing microtubule acetylation in comparison to untreated R399G mutant fibroblasts (N=33). Discussion and conclusions: Using DYNC1H1 mutations we illustrate a dynein-dependent acetylation of the microtubule network, which if aberrant and compounded by a decrease in the amount of dynein present on the Golgi membranes results in the fragmentation of the organelle. Intriguingly, a-tubulin acetylation, is significantly reduced in motor neurons harbouring ALS associated mutant TUBA4A (OMIM: 191110). These data suggest a tentative link between genetic variations in DYNC1H1 and the microtubule cytoskeleton, which could contribute to aberrant tubulin modification, Golgi integrity, and axonal transport and consequently susceptibility to ALS. Importantly, we show that ameliorating the microtubule acetylation is sufficient to rescue the Golgi integrity, thereby providing a potential therapeutic target for this pathology.