thumb|The green and orange structures in this image are hemifusomes, newly discovered organelles that may represent a previously unrecognized pathway for recycling in human cells. Hemifusomes are intracellular organelles first described in 2025 by researchers at the National Institutes of Health and the University of Virginia School of Medicine. Discovered using in situ cryo-electron tomography, hemifusomes are heterotypic vesicular complexes consisting of a smaller translucent vesicle and a larger granular vesicle connected by an extended hemifusion diaphragm (HD)—a shared bilayer structure t
thumb|The green and orange structures in this image are hemifusomes, newly discovered organelles that may represent a previously unrecognized pathway for recycling in human cells. Hemifusomes are intracellular organelles first described in 2025 by researchers at the National Institutes of Health and the University of Virginia School of Medicine. Discovered using in situ cryo-electron tomography, hemifusomes are heterotypic vesicular complexes consisting of a smaller translucent vesicle and a larger granular vesicle connected by an extended hemifusion diaphragm (HD)—a shared bilayer structure that is remarkably stable and large (~0.9 nm diameter). These organelles account for up to 10% of vesicular structures at the cell periphery and are consistently associated with a 42-nanometer proteolipid nanodroplet (PND) embedded at the rim of the hemifusion diaphragm.
Hemifusomes exist in two primary conformations: direct hemifusomes, where the smaller vesicle is hemifused to the cytoplasmic side of the larger vesicle, and flipped hemifusomes, where the smaller vesicle is internal and hemifused to the luminal side. They frequently contain intraluminal vesicles but do not participate in conventional endocytic pathways, as demonstrated by gold nanoparticle uptake experiments.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).