MARK3 and amyotrophic lateral sclerosis: MARK3 RNA expression was also significantly (P = 0.0124) elevated in the frontal cortex of 2 cohorts of ALS/FTD and FTLD-TDP patients; however, we found that MARK3 protein levels were unchanged in i3Neurons or iPSC-MNs upon TDP-43 knockdown and that MARK3 protein levels did not differ significantly between ALS/FTD and FTLD-TDP patients and unaffected controls in the frontal cortex.