@phdthesis{Sivadasan2016,
  author    = {Sivadasan, Rajeeve},
  title     = {The role of RNA binding proteins in motoneuron diseases},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-141907},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2016},
  abstract  = {Motoneuron diseases form a heterogeneous group of pathologies characterized by the progressive degeneration of motoneurons. More and more genetic factors associated with motoneuron diseases encode proteins that have a function in RNA metabolism, suggesting that disturbed RNA metabolism could be a common underlying problem in several, perhaps all, forms of motoneuron diseases. Recent results suggest that SMN interacts with hnRNP R and TDP-43 in neuronal processes, which are not part of the classical SMN complex. This point to an additional function of SMN, which could contribute to the high vulnerability of spinal motoneurons in spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). The current study elucidates functional links between SMN, the causative factor of SMA (spinal muscular atrophy), hnRNP R, and TDP-43, a genetic factor in ALS (amyotrophic lateral sclerosis). In order to characterize the functional interaction of SMN with hnRNP R and TDP-43, we produced recombinant proteins and investigated their interaction by co-immunoprecipitation. These proteins bind directly to each other, indicating that no other co-factors are needed for this interaction. SMN potentiates the ability of hnRNP R and TDP-43 to bind to ß-actin mRNA. Depletion of SMN alters the subcellular distribution of hnRNP R in motoneurons both in SMN-knockdown motoneurons and SMA mutant mouse (delta7 SMA). These data point to functions of SMN beyond snRNP assembly which could be crucial for recruitment and transport of RNA particles into axons and axon terminals, a mechanism which may contribute to SMA pathogenesis and ALS. ALS and FTLD (frontotemporal lobar degeneration) are linked by several lines of evidence with respect to clinical and pathological characteristics. Both sporadic and familial forms are a feature of the ALS-FTLD spectrum, with numerous genes having been associated with these pathological conditions. Both diseases are characterized by the pathological cellular aggregation of proteins. Interestingly, some of these proteins such as TDP-43 and FUS have also common relations not only with ALS-FTLD but also with SMA. Intronic hexanucleotide expansions in C9ORF72 are common in ALS and FTLD but it is unknown whether loss of function, toxicity by the expanded RNA or dipeptides from non ATG-initiated translation is responsible for the pathophysiology. This study tries to characterize the cellular function of C9ORF72 protein. To address this, lentiviral based knockdown and overexpression of C9ORF72 was used in isolated mouse motoneurons. The results clearly show that survival of these motoneurons was not affected by altered C9ORF72 levels, whereas adverse effects on axon growth and growth cone size became apparent after C9ORF72 suppression. Determining the protein interactome revealed several proteins in complexes with C9ORF72. Interestingly, C9ORF72 is present in a complex with cofilin and other actin binding proteins that modulate actin dynamics. These interactions were confirmed both by co-precipitation analyses and in particular by functional studies showing altered actin dynamics in motoneurons with reduced levels of C9ORF72. Importantly, the phosphorylation of cofilin is enhanced in C9ORF72 depleted motoneurons and patient derived lymphoblastoid cells with reduced C9ORF72 levels. These findings indicate that C9ORF72 regulates axonal actin dynamics and the loss of this function could contribute to disease pathomechanisms in ALS and FTLD.},
  subject      = {Motoneuron},
  language  = {en}
}
@article{YadavSelvarajBenderetal.2016,
  author    = {Yadav, Preeti and Selvaraj, Bhuvaneish T. and Bender, Florian L. P. and Behringer, Marcus and Moradi, Mehri and Sivadasan, Rajeeve and Dombert, Benjamin and Blum, Robert and Asan, Esther and Sauer, Markus and Julien, Jean-Pierre and Sendtner, Michael},
  title     = {Neurofilament depletion improves microtubule dynamics via modulation of Stat3/stathmin signaling},
  series = {Acta Neuropathologica},
  volume    = {132},
  journal   = {Acta Neuropathologica},
  number    = {1},
  doi       = {10.1007/s00401-016-1564-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188234},
  pages     = {93-110},
  year      = {2016},
  abstract  = {In neurons, microtubules form a dense array within axons, and the stability and function of this microtubule network is modulated by neurofilaments. Accumulation of neurofilaments has been observed in several forms of neurodegenerative diseases, but the mechanisms how elevated neurofilament levels destabilize axons are unknown so far. Here, we show that increased neurofilament expression in motor nerves of pmn mutant mice, a model of motoneuron disease, causes disturbed microtubule dynamics. The disease is caused by a point mutation in the tubulin-specific chaperone E (Tbce) gene, leading to an exchange of the most C-terminal amino acid tryptophan to glycine. As a consequence, the TBCE protein becomes instable which then results in destabilization of axonal microtubules and defects in axonal transport, in particular in motoneurons. Depletion of neurofilament increases the number and regrowth of microtubules in pmn mutant motoneurons and restores axon elongation. This effect is mediated by interaction of neurofilament with the stathmin complex. Accumulating neurofilaments associate with stathmin in axons of pmn mutant motoneurons. Depletion of neurofilament by Nefl knockout increases Stat3-stathmin interaction and stabilizes the microtubules in pmn mutant motoneurons. Consequently, counteracting enhanced neurofilament expression improves axonal maintenance and prolongs survival of pmn mutant mice. We propose that this mechanism could also be relevant for other neurodegenerative diseases in which neurofilament accumulation and loss of microtubules are prominent features.},
  language  = {en}
}