The leucine-rich repeat receptor family and its interactions in zebrafish. (a) Zebrafish LRR proteins were phylogenetically clustered into subfamilies using MegAlign (DNASTAR, Madison, WI, USA), and are shown as a phylogenetic tree, together with a schematic representation of their protein architecture. All the proteins shown were included in the protein-protein interaction screen. Protein domain abbreviations: LRR = leucine-rich repeat; LRRNT = leucine-rich repeat amino-terminal domain; LRRCT = leucine-rich repeat carboxy-terminal domain; IG = immunoglobulin superfamily domain; FN = fibronectin type III domain; TIR = Toll/interleukin-1 receptor homology domain; TM = transmembrane region; GPI = glycophosphatidylinositol anchor. (b) A binding grid showing all tested reciprocal interactions between the extracellular LRR proteins using AVEXIS. The baits are vertically ordered in correspondence to the tree shown in (a) and numbered as described in Additional data file 4. The preys are similarly ordered horizontally such that homophilic interactions are on the diagonal from top left to bottom right. Interactions identified by a red square were positive in both screens; blue squares were detected only once, but reciprocated. Baits 7, 8, 26 and 50 and prey 43 were expressed below the threshold required for the assay and were therefore not included in the screen. (c) A binding grid showing the interaction screen between the zebrafish LRR and IgSF receptor families. The 97 IgSF proteins are ordered horizontally according to their phylogenetic relationships and numbered as described in Additional data file 5; the 52 LRR proteins are similarly arranged vertically. Red and yellow squares indicate high and lower confidence interactions, respectively, as detailed in Additional data file 6.