 Sincitin is a fusion protein that plays a key role in mediating intercellular transfer of cargo between cells. It was discovered that when sincitin is present in both donor and recipient cells, it can create an open-ended connection between them, allowing for efficient transfer of cargo such as Cas9 protein. This finding suggests that sincitin may be the primary factor responsible for the formation of these open-ended connections. This article was authored by Tsongyang Zhong and Randy Skeekman.