fig2

Figure 2. A schematic diagram showing the biogenesis pathway of microvesicles and exosomes. Microvesicles are formed by direct budding from the plasma membrane and are capable of encapsulating multiple forms of molecular cargo including proteins and nucleic acids. The biogenesis of exosomes begins with internalization of the cell membrane leading to the formation of early endosomes. Intraluminal vesicles (ILVs) are formed by the inward invagination of endosomal membranes, resulting in the formation of multivesicular bodies (MVBs). During this process, cytosolic constituents, including nucleic acids and proteins, can be sorted into ILVs. Upon fusion of MVBs with the plasma membrane, ILVs are released as exosomes into the extracellular milieu. Exosomes can include many different types of exRNA as listed in Table 1. ER: endoplasmic reticulum; MLV: multivesicular body; ILV: intraluminal vesicle; miRNA: microRNA; piRNA: piwi-interacting RNA; tRF: tRNA-derived RNA fragments; snoRNA: small nucleolar RNA; lncRNA: long non-coding RNA