Identification of markers for migrasome detection

The migrasome is a newly discovered cellular organelle in migrating cells, first described in 2015 1 , 2 . Migrasomes have been proposed to mediate cell-cell communications and may exert physiological and pathological effects. In zebrafish embryos, generation of migrasomes has been observed during gastrulation, and migrasomes have been shown to be essential for organ morphogenesis during embryonic development (Personal communication). Although migrasome-like structures have been detected by transmission electron microscopy (TEM) in various organs including eye, lung and intestine, definitive evidence for the presence of migrasomes in vivo in mammals is still lacking. Exosomes are defined as 30–100 nm extracellular vesicles derived from the multivesicular body and are secreted by a variety of cell types. Exosomes have attracted great attention in clinical studies since they were detected in solid tissues, such as cartilage 3 , and in biological fluids, such as blood 4 . One of the most commonly used methods for detection of extracellular vesicles (EVs) is a biochemical approach using known marker proteins. This strategy allows researchers to identify EVs in complex biological samples such as body fluids and tissues, and thus provides great flexibility for detection of EVs in vivo. So far, there is no satisfactory marker for biochemical detection of migrasomes. TSPAN4 and integrin are known to be enriched on migrasomes 1 , 5 . However, both proteins are also present on exosomes 6 , making it difficult to distinguish the two structures biochemically based only on detection of these proteins. Imaging is the only approach for confirming the presence of migrasomes, but it is not compatible with most clinical samples. Thus, there is an urgent need to identify migrasome-specific markers.