Several aspects of neural development and function rely on the regulated expression of specific glycans, but what are the mechanisms that govern neural-specific glycosylation during embryogenesis? On , Michael Tiemeyer and colleagues report that Sugar-free frosting (Sff) – the Drosophila homologue of SAD kinase, which regulates synaptic vesicle tethering and neuronal polarity in nematodes and vertebrates – drives neural-specific glycan expression in the Drosophila embryo prior to synaptogenesis. They performed a genetic screen for mutations that affect the expression of neural-specific N-linked glycans known as HRP-epitopes; neural expression of HRP-epitopes requires ectodermal expression of Tollo, a Drosophila Toll-like receptor. Analysis of the sff mutant recovered from this screen reveals that Sff modulates glycan complexity by altering Golgi dynamics in neurons that respond to Tollo transcellular signals. The researchers propose that multiple protein kinases facilitate flux through divergent Golgi processing pathways, thereby sculpting tissue-specific glycan expression patterns during development.
