sphingosine-1-phosphate and Heart-Defects--Congenital

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are second-generation lysophospholipid mediators that exert multiple biological functions through their own cognate receptors. They are both present in the blood stream, activate receptors with similar structures (endothelial differentiation gene receptors), have similar roles in the vasculature and are vasoactive. However, it is unclear whether these lysophospholipid mediators cross-talk downstream of each receptor. Here, we provide in vivo evidence that LPA signaling counteracted S1P signaling. When autotaxin (Atx), an LPA-producing enzyme, was overexpressed in zebrafish embryos by injecting atx mRNA, the embryos showed cardia bifida, a phenotype induced by down-regulation of S1P signaling. A similar cardiac phenotype was not induced when catalytically inactive Atx was introduced. The cardiac phenotype was synergistically enhanced when antisense morpholino oligonucleotides (MO) against S1P receptor (s1pr2/mil) or S1P transporter (spns2) was introduced together with atx mRNA. The Atx-induced cardia bifida was prominently suppressed when embryos were treated with an lpar1 receptor antagonist, Ki16425, or with MO against lpar1. These results provide the first in vivo evidence of cross-talk between LPA and S1P signaling.

Topics: Animals; Down-Regulation; Embryo, Nonmammalian; Heart Defects, Congenital; HEK293 Cells; Humans; Isoxazoles; Lysophospholipids; Phenotype; Phosphoric Diester Hydrolases; Propionates; Receptors, Lysophosphatidic Acid; RNA, Messenger; Signal Transduction; Sphingosine; Zebrafish

Sphingosine-1-phosphate (S1P) is a secreted lipid mediator that functions in vascular development; however, it remains unclear how S1P secretion is regulated during embryogenesis. We identified a zebrafish mutant, ko157, that displays cardia bifida (two hearts) resembling that in the S1P receptor-2 mutant. A migration defect of myocardial precursors in the ko157 mutant is due to a mutation in a multipass transmembrane protein, Spns2, and can be rescued by S1P injection. We show that the export of S1P from cells requires Spns2. spns2 is expressed in the extraembryonic tissue yolk syncytial layer (YSL), and the introduction of spns2 mRNA in the YSL restored the cardiac defect in the ko157 mutant. Thus, Spns2 in the YSL functions as a S1P transporter in S1P secretion, thereby regulating myocardial precursor migration.

Topics: Animals; Animals, Genetically Modified; Blastomeres; Carrier Proteins; Cell Movement; CHO Cells; Cricetinae; Cricetulus; Embryo, Nonmammalian; Embryonic Development; Heart; Heart Defects, Congenital; Humans; Lysophospholipids; Membrane Proteins; Mesoderm; Mice; Molecular Sequence Data; Mutation; Oligonucleotides, Antisense; Organogenesis; Signal Transduction; Somites; Sphingosine; Zebrafish; Zebrafish Proteins