Leukodystrophies are a broad spectrum of neurological disorders that are characterized primarily by deficiencies in myelin formation. Clinical manifestations of leukodystrophies usually appear during childhood and common symptoms include lack of motor coordination, difficulty with or loss of ambulation, issues with vision and/or hearing, cognitive decline, regression in speech skills, and even seizures. Many cases of leukodystrophy can be attributed to genetic mutations, but they have diverse inheritance patterns (e.g., autosomal recessive, autosomal dominant, or X-linked) and some arise from de novo mutations. In this review, we provide an updated overview of 35 types of leukodystrophies and focus on cellular mechanisms that may underlie these disorders. We find common themes in specialized functions in oligodendrocytes, which are specialized producers of membranes and myelin lipids. These mechanisms include myelin protein defects, lipid processing and peroxisome dysfunction, transcriptional and translational dysregulation, disruptions in cytoskeletal organization, and cell junction defects. In addition, non-cell-autonomous factors in astrocytes and microglia, such as autoimmune reactivity, and intercellular communication, may also play a role in leukodystrophy onset. We hope that highlighting these themes in cellular dysfunction in leukodystrophies may yield conceptual insights on future therapeutic approaches.

Oligodendrocytes have elaborate arbors of microtubules that extend toward axons and spiral around myelin sheaths. Oligodendrocytes rely on satellite organelles called Golgi outposts to nucleate new microtubules at sites far from the cell body. We now show that the Golgi outpost marker TPPP (tubulin polymerization promoting protein) forms liquid condensates that co-partition with tubulin in order to nucleate microtubules. In oligodendrocytes, TPPP forms either dynamic puncta or aberrant microtubule-associated aggregates. In Multiple System Atrophy (MSA), a sequela of histological events initiates with TPPP aggregation in myelin sheaths and terminates in perinuclear TPPP co-aggregation with alpha-synuclein (aSyn). Finally, recombinant TPPP aggregates are toxic to primary oligodendrocytes. Thus, while the liquid condensate property of TPPP facilitates microtubule nucleation, it also predisposes TPPP to aggregate in disease.