Introduction 1 1, 2, 4, 6, 11–14 2 1 11 12 13 4 6 2 14 1 2 3 4 5 6 9 1 10 1 12 1 12 1 1, 2, 4, 6, 11 12–14 1 4 12 11 12 13 1 6 14 12 Fig. 1 2 10 12 framed 1 2  12 Discovery and deorphanization of group members 12 12 13 14 1 1 lyso 12 Table 1 12 Receptor G protein coupling Natural agonist Tissue expression 12 i ADP, CysLT-E4, phosphoribosyl pyrophosphate 19 13 i ADP, diadenosine triphosphate 22 45 14 i N 15 16 71 GPR87 i n.k 28 29 GPR171 n.k n.k n.k GPR34 i lyso 27 31 34 72 GPR82 n.k n.k Testes, epididymis (unpublished own results) 1 n.k 12 14 15 16 17 14 12 18 21 12 12 + Xenopus 19 2+ 12 21 13 12 22 24 12 N 1 12 13 25 26 27 28 29 30 12 1 lyso 31 12 The evolutionary origins 12 1 2 12 12 13 14 2 12 13 14 12 14 12 32 12 Fig. 2 12 12  12 14 Mustelus manazo Carcharodon carcharias Callorhinchus milii 12 Petromyzon marina Strongylocentrotus purpuratus 12 Gnathostomata 12 13 14 12 13 12 13 12 14 14 Xenopus 14 14 14 12 12 Anolis carolinensis 12 12 33 12 2 12 Comparison of transcript and genomic sequences provides information on intron/exon structure of a GPCR gene. Since the gain or loss of spliceosomal introns are unique events in evolution, they can serve as markers for phylogenetic analysis. Further, such analyses may reveal splice variants and may be informative about the promoter structure and gene regulation. Introns are the basis of alternative splicing, exon skipping, and RNA editing events and, therefore, can contribute to receptor diversity at a supragenomic level. 12 2 34 Table 2 12 n.a. Member Number of introns in the 5′ non-coding region Number of introns in the coding region a 12  Human 1–2 − 47 kbp (2 different transcript starts)  Mouse 4 − 46.5 kbp  Chicken n.a. b n.a. (>1 kbp)  African clawed frog − 1 (N terminus) 4 kbp  Zebrafish n.a. b n.a. (>1 kbp)  Stickleback 1 1 (TMD2) 2 kbp  Pufferfish n.a. 1 (TMD2) >2 kbp 13  Human − 1 (rare transcript, N terminus, NM_176894)  3.2 kp (2 different transcript starts)  Mouse 1 − 3 kbp  Chicken n.a. b n.a. (>1 kbp)  African clawed frog − 1 (N terminus) 14–19 kbp 14  Human 2 − 66 kbp (2 different transcript starts)  Mouse 1–2 − 16 kbp  Chicken n.a. b n.a. (>1 kbp) GPR87  Human 1 1 (N terminus) 22.7 kbp  Mouse 1 1 (N terminus) 16 kbp  Chicken 2 1 (N terminus) 9.5 kbp  African clawed frog n.a. b n.a. (>1 kbp) 14  Zebrafish n.a. b n.a. (>1 kbp)  Pufferfish n.a. b n.a. (>1 kbp) GPR171  Human 2 − 5 kbp  Mouse 1 − 4.5 kbp  Chicken 1 − 2.3 kbp  Zebrafish n.a. b n.a. (>1 kbp) GPR82  Human 2 − 4 kbp  Mouse 2–3 − 6 kbp  Chicken n.a. b n.a. (>1 kbp)  African clawed frog n.a. b n.a. (>1 kbp)  Zebrafish n.a. b n.a. (>1 kbp) GPR34  Human 3–4 1 cryptic (N terminus) 8.2 kbp  Mouse 3–4 − 9.1 kbp  Chicken 1 − 2.5 kbp  African clawed frog 2 − 5.2 kbp  Zebrafish   Type 1 1 − 7.3 kbp   Type 2 − − 1.2 kbp  Pufferfish n.a. b n.a. (>1 kbp) 12 a b 12 2 12 33 35 12 12 12 36 37 It is of interest to note that both genes, GPR34 and GPR82, are located in antisense orientation within a large intron of the CASK gene. This position is conserved during vertebrate evolution. The CASK gene encodes a calcium/calmodulin-dependent serine protein kinase that is a member of the membrane-associated guanylate kinase (MAGUK) protein family. Since GPR34 and GPR82 transcripts are antisense orientated to CASK one can speculate that transcripts may regulate expression of CASK or vice versa. Such hypotheses will be addressed in receptor-deficient mouse models (see below) in the future. Key residues defining the individual member 12 1 11 38 39 33 40 42 12 12 13 14 12 3 12 12 13 12 12 K a K s 12 3 12 K a K s 12 Fig. 3 12 12 13 14 12 73 1.39 1.57 2.43 2.50 2.58 3.33 3.50 4.50 6.47 6.50 7.49 7.50 TMD  Table 3 12 Receptor K a K s Pi (mean ± SD) (mean ± SD) 12 0.049 ± 0.018 0.145 ± 0.022 13 0.141 ± 0.070 0.187 ± 0.023 14 0.103 ± 0.036 0.190 ± 0.024 GPR87 0.046 ± 0.027 0.134 ± 0.018 GPR171 0.078 ± 0.012 0.158 ± 0.021 GPR34 0.082 ± 0.037 0.137 ± 0.026 GPR82 0.202 ± 0.049 0.167 ± 0.034 12 K a K s K a K s 12 Bos taurus, Equus caballus, Canis familiaris, Pteropus vampyrus, Ornithorhynchus anatinus, Monodelphis domestica, Callithrix jacchus, Pan troglodytes, Homo sapiens, Macaca mulatta, Microcebus murinus, Pongo pygmaeus, Tarsius syrichta, Cavia porcellus, Mus musculus, Rattus norvegicus, Tursiops truncates, Gallus gallus 3 12 1.57 2.43 4.50 6.50 7.49 7.50 12 13 12 13 12 3 3.53 5.59 13 7.48 6.44 7.57 7.52 12 6.52 6.55 7.35 7.36 7.39 38 12 12 12 12 i 22 i 13 22 24 14 43 lyso 31 33 12 15 16 44 16 13 45 q i Δ6qi4 46 i 47 qi4 12–14 lyso 25 33 48 12 lyso 33 12 4 12 14 14 14 Fig. 4 12 12 12 i 12 Δ6qi4 46  Saccharomyces cerevisiae 49 5 50 51 12 52 14 53 lyso 6 12 Fig. 5 i 49 Gpa Ste4 Ste18 Ste12 Far1  Fig. 6 12 a 12 4 b 12 − − 12 115 177 224 115  12 1 54 12 12 12 12 115 177 224 115 6 12 12 12 12 2 12 1 12 12 18 55 12 12 Mus musculus castaneus 12 12 M. m. castaneus 41 12 12 M. m. castaneus 12 12 13 Xenopus 12 12 12 12 12 56 12 57 12 1 258 256 265 19 58 60 12 12 12 61 12 62 63 64 65 4 6 12 182 12 182 12 330 12 12 59 158 13 158 158 Tursiops truncates 35 240 14 19 58 283 283 283 46 179 355 205 205 313 296 34 66 12 67 70 Conclusion 12 12