Hemifusomes: Biologists Discover Previously Unknown Organelle Complexes inside Human Cells
Hemifusomes constitute up to 10% of vesicular organelles on the periphery of cells but do not engage in canonical endocyte routes, according to a team of biologists from the University of Virginia and the National Institutes of Health.
Image of Cryo-electron microscopy representative of the attack edge of a Rat-1 cell cultivated on cryo-EM grids. Lamellipodes and filopods in the upper right corner delimit the cell border, separating the cytoplasm (CYT) from the extracellular space (EXT). Vesicular organelles are highlighted in color: early endosome type vesicles (in, pink), multifacecular body (MVB, blue), hemifusomes (HF, yellow) and inverted hemifusomes (FHF, Green). Scale bar – 0.5 µm. Image credit: Tavakoli and al., DOI: 10.1038 / S41467-025-59887-9.
“It’s like discovering a new recycling center inside the cell,” said the co-ennior, Dr. Seham Ebrahim, researcher at the University of Virginia.
“We believe that the hemifusoma helps to manage how cells pack and treat the material, and when it goes wrong, it can contribute to diseases that affect many systems of the body.”
“Such a condition is Hermansky-Pudlak syndrome, a rare genetic disorder that can cause albinism, vision problems, pulmonary diseases and blood clotting problems.”
“The problems with the way the cells manage the cargo are the cause of many disorders of this type.”
“We are just starting to understand how this new organel is integrated into the situation in its health and cellular disease set.”
“It’s exciting because finding something really new inside the cells is rare – and it gives us a whole new path to explore.”
Using cryo-electron tomography (cryo-and), the researchers created striking images of hemifusomes.
They believe that these organelles facilitate the formation of vesicles, tiny bags in the shape of blisters which act like bowls and organelles made up of several vesicles.
This process is essential for cell sorting, recycling and the elimination of debris.
“You can think of vesicles like small delivery trucks inside the cell,” said Dr. Ebrahim.
“The hemifusoma is like a loading care station where they connect and transfer the cargo. This is a step in the process that we did not know.”
Although hemifusomes have escaped detection so far, they are surprisingly common in certain parts of our cells.
Scientists are impatient to better understand their importance for good cellular function and learn how problems with them could contribute to the disease.
Such ideas could lead to targeted treatments for a range of serious genetic disorders.
“This is only the start,” said Dr. Ebrahim.
“Now that we know that hemifusomes exist, we can start asking how they behave in healthy cells and what is happening when things go wrong.”
“This could lead us to new strategies to treat complex genetic diseases.”
The team’s article was published in the newspaper Nature communications.
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A. Tavakoli and al. 2025. Hemifusomes and nanodroplet proteolipids interacting dumbfilling the formation of multi-vœsicular bodies. Common nat 16, 4609; DOI: 10.1038 / S41467-025-59887-9
