VPS4A and amyotrophic lateral sclerosis: To test this, we overexpressed GFP tagged wildtype VPS4 or a GFP tagged dominant negative variant of VPS4 (VPS4E228Q) that has previously been shown to impair ESCRT dependent release events [31] and performed SIM and immunostaining for POM121 in nuclei isolated from control and ALS iPSNs.