The SAD-1 kinase regulates SYD-2/Liprin-α phase separation and active zone formation.

(A, B) HSN synapse formation phenotypes visualized with Airyscan superresolution imaging of endogenous fluorescent tags in the indicated mutants. Pegl-6::SAD-1(T202E) is the expression of constitutively active SAD-1 kinase in HSN. Scale bar, 5 μm. (B) Quantification of HSN intensity in (A). ****, p sad-1Δ background at embryonic nerve ring synapses to measure dynamics. Wild-type SYD-2 is present in dynamic phase-separated condensates and loss of sad-1 inhibits condensate formation. Scale bars, 5 μm. (D) Quantification of FRAP in (C). (E) Airyscan superresolution image of endogenous GFP-SAD-1 at HSN presynapses. Scale bar, 5 μm. Underlying data is available in S1 Data. FRAP, fluorescence recovery after photobleaching; HSN, hermaphrodite-specific neuron.