Phylogenetic relationship of LDLRR-GPCR/LGR-like members of Ciona with those of Snail and Human LGRs and their domain organization. A) Maximum likelihood tree of the TM regions of the 14 Ciona LDLRR-GPCRs, the Ciona INSL3/relaxin receptor-like and the Snail and Human LGRs. The tree is rooted using a human LHCGR and a Ciona orphan LGR (ci0100151424) that are distantly related to these sequences. Support values are indicated in percentages. Taxons represented in numerals refer to Ciona GPCRs as per information in Additional data file 2. Ciona GPCRs that deviate from the predicted 7TM structure are marked using a '#' symbol. B) Schematic diagram representing the modular domain organization corresponding to the clusters identified in the phylogenetic tree.