HNRNPK and amyotrophic lateral sclerosis: The purpose of including patient-relevant models (i.e., C9orf72 patient fibroblasts and iPSC-derived motor neurons) and post-mortem material in this study is to enable translation of the embryonic zebrafish screening to C9orf72 ALS in the clinic, and to assess the relevance of HNRNPK as a modifier of RNA toxicity in disease.