The emergence of E-Cadherin spot junctions between germline and somatic cells facilitates late stage oogenesis in Drosophila

Coordinated tissue morphogenesis relies on precise interactions between distinct cell lineages. During development of the Drosophila oocyte, interactions between di_erent somatic follicle cell types and the germline-derived nurse cells and the future oocyte are crucial for coordinating oogenesis. However, the molecular basis of their interaction throughout enormous morphological changes remains largely unexplored. During late oogenesis, nurse cells transfer their cytoplasmic content into the oocyte, while anterior follicle cells (AFCs) must closely envelop the nurse cells to induce phagoptosis and remove their remnants. We identify E-cadherin-based spot junctions as novel adhesive complexes at this essential soma-germline interface. AFCs reorganize their E-cadherin from intraepithelial adherens junctions to their apical surface to form interlineage spot junctions with nurse cells, representing a switch in adhesive and thus mechanical coupling. The distribution and density of these junctions is stably organized, even as the interface undergoes dramatic size changes. Additionally, we show that these junctions integrate into a microvilli-rich nurse cell surface, influencing microvilli architecture. Importantly, disruption of E-cadherin spot junctions impairs nurse cell enveloping. Our findings reveal a switch from intra-lineage to inter-lineage mechanical coupling that is driven by the formation of E-Cadherin spot junctions and highlights their essential role in ensuring robust soma-germline coupling and coordination during nurse cell dumping in late oogenesis.