NimA promotes cell adhesion at the blood brain barrier of Drosophila nervous system

Glial cells are crucial for nervous system development and function, by clearing debris, protecting neurons, and ensuring neuronal survival. In Drosophila, glia also form the blood-brain barrier (BBB), which regulates neural stem cell proliferation and shields the nervous system while maintaining organism-wide communication. To uncover glial-specific roles, we compared their transcriptome with that of neurons and macrophages.

Our study identifies NimA, an uncharacterized member of the Nimrod scavenger receptor family, as a glial-specific protein consistently expressed during development. Unlike other family members, i.e. NimC1 (macrophage-specific), Draper (shared by glia and macrophages), and NimC4/Simu (restricted to embryonic stages), NimA is not involved in phagocytosis. Instead, it regulates cell-cell interactions and adhesion, crucial for maintaining the tight septate junctions of the larval BBB. Loss of NimA compromises BBB integrity, delays development, reduces brain size and impairs neural stem cell proliferation.

Altogether, the identification of a novel molecular player and more in general, of the glial-specific molecular landscape, are key to understand the contribution of glia to the construction and the function of the nervous system.