CSR has alsomade significant contributions to clinical research, as demonstratedby its application to Pelizaeus–Merzbacher disease (PMD), ahypomyelination leukodystrophy disorder.163 Using sparse-SIM, researchers investigated PLP1 mutations associatedwith PMD, identifying three distinct cellular phenotypes linked toclinical subtypes (Figure 8(d)): severe phenotypes resulting from ER retention, intermediatephenotypes involving lysosomal missorting, and mild phenotypes relatedto vesicle trafficking defects. The gene discussed is PLP1; the disease is Pelizeaus-Merzbacher spectrum disorder.