Scientists from the University of Virginia and the U.S. National Institutes of Health have identified a previously unknown cellular structure. Named the “hemifusome,” this transient organelle plays a crucial role in how cells manage internal cargo. Detailed in a study in Nature Communications, the research used advanced imaging to capture the structure, revealing a new pathway for sorting materials within the cell.

Advanced cryo-electron tomography allowed scientists to visualize the delicate hemifusome in its natural state without damaging it.

(Tavakoli et al., 2025)

The hemifusome forms when two transport vesicles partially merge, creating a stable bridge called a hemifusion diaphragm. This structure acts as a dynamic platform for creating multivesicular bodies (MVBs), which are essential for sorting cellular cargo. This process operates independently of the well-known ESCRT protein complex, suggesting cells have an alternate system for internal logistics.

The discovery was made possible by in situ cryo-electron tomography (cryo-ET), a technique that flash-freezes cells to preserve them in a near-native state. This avoided the use of chemical fixatives that could alter delicate cellular components. By revealing this ESCRT-independent pathway, the finding introduces a previously unknown biological mechanism for how cells maintain themselves.

Understanding this new pathway reshapes our fundamental knowledge of how cells function and manage their internal logistics.

(Photo by JC Gellidon on Unsplash)

This fundamental discovery has significant implications for a range of inherited disorders linked to faulty cellular transport, such as Hermansky-Pudlak syndrome. This rare genetic condition can cause albinism, lung disease, and bleeding problems. By providing a new blueprint for these essential processes, the identification of the hemifusome offers a fresh avenue for research into these and other diseases.