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The dynactin p150glued subunit, encoded by the gene DCTN1 is part of the dynein-dynactin motor protein complex responsible for retrograde axonal transport. This subunit is a candidate modifier for neurodegenerative diseases, in particular motoneuron and extrapyramidal diseases. Based on an extensive screening effort of all 32 exons in more than 2,500 ALS/MND patients, patients suffering from Parkinsonian Syndromes and controls, we investigated 24 sequence variants of p150 in cell-based studies. We used both non-neuronal cell lines and primary rodent spinal motoneurons and report on cell biological abnormalities in five of these sequence alterations and also briefly report on the clinical features. Our results suggest the presence of biological changes caused by some p150 mutants pointing to a potential pathogenetic significance as modifier of the phenotype of the human disease.

The dynactin p150(Glued) subunit, encoded by the gene DCTN1, is part of the dynein-dynactin motor protein complex responsible for retrograde axonal transport in motor neurons. The p150 subunit is a candidate gene for neurodegenerative diseases, in particular motor neuron and extrapyramidal diseases. Tubulin-binding cofactors are believed to be involved in tubulin biogenesis and degradation and therefore to contribute to microtubule functional diversity and regulation. A yeast-two-hybrid screen for putative interacting proteins of dynactin p150(Glued) has revealed tubulin-folding cofactor B (TBCB). We analyzed the interaction of these proteins and investigated the impact of this complex on the microtubule network in cell lines and primary hippocampal neurons in vitro. We especially concentrated on neuronal morphology and synaptogenesis. Overexpression of both proteins or depletion of TBCB alone does not alter the microtubule network and/or neuronal morphology. The demonstration of the interaction of the transport molecule dynactin and the tubulin-regulating factor TBCB is thought to have an impact on several cellular mechanisms. TBCB expression levels have been found to have only a subtle influence on the microtubule network and neuronal morphology. However, overexpression of TBCB leads to the decreased localization of p150 to the microtubule network that might result in a functional modulation of this protein complex.

One of the major functional properties of the mature motoneuron is its ability to generate and conduct signals from the central nervous system (CNS) to the peripheral muscle cell in order to induce and control muscle contraction [1]. The molecular composition of the neuromuscular junction (NMj) is crucial for its function and maintenance whereas dysregulation of endplate physiology is considered to be involved in denervation of the muscle cells and subsequent motoneuron degeneration [2, 3]. At early developmental stages of the neuron-to-muscle synaptogenesis, a large number of spinal motoneurons die, presumably because they fail to form adequate connections with the target muscle. In fact, if the limb bud (the precursor of limb muscles) is removed before the formation of neuromuscular connections all the corresponding motoneurons eventually degenerate [4]. In vitro, various cell systems are utilized to search for developmental and functional characteristics of the motoneuron system. Both, primary cultures and stem cellderived motoneurons are used for various questions. Pluripotent embryonic stem cells [5] from mouse and human origin [6] had been shown to be able to generate motoneurons in vitro. Since the first discovery and invention of the induced pluripotent stem cell (iPSC) technology by Takahashi and Yamanaka [7], it is now possible to analyze and study cell development and differentiation on the basis of a gene defect in patient specific settings [8, 9]. For comparison all these studies are crucially dependent upon the analysis of human cell differentiation, morphology and protein expression under