Unraveling the role of primary cilia in the pathogenesis of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting upper and lower motoneurons. So far, more than 30 causative genes have been associated to ALS, including the major C9ORF72 and the minor NEK1 genes. Dysfunctions in primary cilia, non-motile organelles acting as a sensory-hub in post-mitotic cells, are recently emerging as a possible pathomechanism in ALS. Here we investigated the role of primary cilia in ALS pathogenesis, in particular related to mutations in NEK1 and C9ORF72 genes, using patient-derived fibroblasts and motoneurons differentiated from human induced-pluripotent stem cells (iPSC-MNs) as disease models. iPSC-MNs used for the study include two lines carrying heterozygous loss-of-function mutations in NEK1 gene (p.R540X and p.R1044X) together with a wild-type (WT) isogenic control, as well as two iPSC lines carrying repeat expansions in C9ORF72 gene and two WT controls. Primary cilia in iPSC-MNs were analysed for their number and length by staining for Arl13b and pericentrin markers. Moreover, cilia functionality was assessed by investigating the sonic hedgehog (Shh) pathway, the main one associated to cilia functioning. Partial cilia defects were identified in both NEK1 and C9ORF72 mutant iPSC-MNs and treatment with tubacin A is ongoing to see if these defects can be rescued. Finally, analysis of cilia number, length and functioning is ongoing also in C9ORF72 fibroblasts, that could be exploited as an alternative screening platform.