Fig. 5. Identification of a Xenopus tropicalis LPA receptor that is similar to mammalian LPA₂. (A) Alignment of X. tropicalis XLPA₂ with mouse and human LPA₂. Putative transmembrane domains (TMD) are indicated above the sequence. Residues important for LPA binding and specificity in other species are highlighted in red. X. tropicalis XLPA₂ is 62% identical and 16% similar to murine LPA₂. (B) Expression using real-time RTPCR of XLPA₁ and XLPA₂ mRNA during early development. Each bar represents the amount of mRNA present, normalized to the loading control ornithine decarboxylase. As reported previously, XLPA₁ is abundant maternally and continues to be expressed at a low level throughout development. Expression of XLPA₂ begins at the mid-blastula stage and continues to at least stage 45. St.2, two-cell stage; St.9, late blastula; St.10, early gastrula; St.12, late gastrula; St.15, early neurula; St.20, late neurula; St.35, tail-bud; St.45, swimming tadpole.