[Tunneling nanotubes (TNTs): An essential yet overlooked modality of inter-cellular communication]

Tunneling nanotubes (TNTs) are open membranous protrusions that allow direct communication between distant cells. Recent research has revealed their significant biological roles, prompting a reassessment of many physiological and pathological processes, especially in the nervous system where TNT properties could play a key physiological role. TNT-like connections have been observed in the developing brain and are implicated in neurodegenerative diseases, brain cancers, as well as in other diseases, underscoring their importance in pathophysiological events. This review covers the key features of TNTs, including their structural properties, formation mechanisms, and detection challenges. We also explore their functions, focusing on the nervous system. The discovery of TNTs may lead to a reconsideration of brain function as a physically connected neuronal network, as proposed by Golgi, complementing Cajal's theory of neurons as separate entities.