Blebology

blebology.com is a public reference on cellular blebs, the rounded bulges that animal cells push out of their surface when the membrane comes away from the cortex beneath it.

It is written for scientists who are not bleb specialists, from cell biologists and physicists to engineers, clinician-scientists and students. We explain the basic concepts and go into enough depth that bleb specialists will also find it a useful resource.

What this site is

Blebs have been described for almost three centuries, under many names and in many organisms, but knowledge of them is scattered across cell biology, biophysics, developmental biology, cancer research and the study of cell death. This site brings it together and explains it, from how blebs form and retract to what remains unknown. It expands and updates the review “Blebology: principles of bleb-based migration”, by Juan Manuel García-Arcos, Ankita Jha, Clare M. Waterman and Matthieu Piel, published in Trends in Cell Biology in 2024 (García-Arcos et al., 2024a ◆), and is also an experiment in new ways of compiling and sharing scientific reviews. The pages rest on a systematic reading of the literature, described in the Meta-review, and every statement points to its source. We update the site as new work appears, discuss a recent paper each month in a journal club, and welcome corrections (About).

What is a bleb?

The surface of an animal cell has two layers. The plasma membrane lies on top of the cortex, a thin network of actin filaments pulled taut by myosin motors and attached to the membrane by linker proteins. Because the cortex is under tension, the cytoplasm it encloses is under pressure. A bleb forms where the membrane loses the support of the cortex, either because the links between them fail or because the cortex itself tears. The pressure then pushes the freed membrane outward, and cytoplasm flows in to fill a rounded protrusion within seconds (Charras et al., 2005; Tinevez et al., 2009). A new cortex assembles under the bleb membrane and stops its growth, and myosin then usually pulls the bleb back (Cunningham, 1995; Charras et al., 2006).

The bleb cycle. (1) The cortex is under tension and the cytoplasm under pressure. (2) A bleb starts where the membrane detaches from the cortex (2a) or the cortex breaks (2b). (3) Cytosol flows into a bleb without cortex. (4) A new cortex…
The bleb cycle. (1) The cortex is under tension and the cytoplasm under pressure. (2) A bleb starts where the membrane detaches from the cortex (2a) or the cortex breaks (2b). (3) Cytosol flows into a bleb without cortex. (4) A new cortex assembles and myosin pulls the bleb back. Source: blebology.com, adapted from García-Arcos et al., 2024a ◆, Trends Cell Biol, Box 2.

This simple cycle hides much variety. Some blebs last seconds and others hours; some stay in place, some travel around the cell, and some leave it altogether. Cells bleb when they migrate, divide and die, and blebs can also act as small compartments that organize signaling.

A guide to the site

Kinds of blebsTransient, circus and stable blebs, leader blebs, and the blebs of dividing, dying and squeezed cells: what distinguishes them.Physics of blebsPressure, tension, membrane–cortex attachment and cortex assembly, from everyday objects up to the equations.Blebs by the numbersSizes, lifetimes, speeds, tensions and pressures, each with its cell type, conditions and measurement method.A long history of blebbingFrom a “little Proteus” drawn in 1755 to blebs rebuilt from purified proteins: how the ideas developed.MilestonesTwenty pieces of work that changed how blebs are understood.MigrationHow blebs move cells in embryos, amoebae, tumors and the immune system, and why confinement makes many cells switch to blebs.Signaling hubsHow the curved membrane at the edges of blebs can gather signaling proteins that keep detached cancer cells alive.FragmentsPieces that leave the cell, from blebs that detach as cytoplasts to apoptotic bodies, platelets and large oncosomes, and how far blebbing is involved in each.Dying and injured cellsBlebbing during apoptosis and injury: how it is driven and what it does and does not tell us.Meta-reviewA curated, semi-automated review of the bleb literature: trends since the nineteenth century and what reviews predicted.GlossaryThe terms used on the site and how their meaning has changed.AboutWho writes the site, how to read it, and how to suggest a paper or a correction.

How to read the pages

Each page reads as connected text, with details in the Milestones and in the reference list at the bottom, which opens with a click. Author–year citations link to the paper, and specialist terms link to the glossary at first use. Central claims carry a discreet italic label for the state of the evidence, from established to open question, explained on the About page. Our own papers are marked ◆.

References (5)
  • Charras GT, Hu CK, Coughlin M et al. (2006) Reassembly of contractile actin cortex in cell blebs. J Cell Biol 175:477–490. doi:10.1083/jcb.200602085
  • Charras GT, Yarrow JC, Horton MA et al. (2005) Non-equilibration of hydrostatic pressure in blebbing cells. Nature 435:365–369. doi:10.1038/nature03550
  • Cunningham CC (1995) Actin polymerization and intracellular solvent flow in cell surface blebbing. J Cell Biol 129:1589–1599. doi:10.1083/jcb.129.6.1589
  • ◆ García-Arcos JM, Jha A, Waterman CM et al. (2024a) Blebology: principles of bleb-based migration. Trends Cell Biol 34:838–853. doi:10.1016/j.tcb.2024.02.009
  • Tinevez JY, Schulze U, Salbreux G et al. (2009) Role of cortical tension in bleb growth. Proc Natl Acad Sci USA 106:18581–18586. doi:10.1073/pnas.0903353106