[Leukemia-associated gene ASXL1 involved in paraspeckle formation]

Somatic mutations in the ASXL1 gene are commonly observed in myeloid neoplasms. Pathogenic ASXL1 mutations induce the expression of C-terminally truncated mutant ASXL1 protein. We have shown that wild-type ASXL1 is a phase-separating protein involved in the formation of paraspeckles, one of the best known membraneless organelles (MLOs). Mutant ASXL1 lacks the intrinsically disordered region, which is important for phase separation and fails to support paraspeckle formation. Additionally, paraspeckles are disrupted in hematopoietic cells derived from ASXL1-MT knockin mice. The disruption of paraspeckles in hematopoietic cells results in a dysfunction of the hematopoietic reconstitution capacity. Therefore, this review presents our findings and summarizes the knowledge of phase separation and MLOs as a hot topic in cell biology.