The ceramide synthase 2b gene mediates genomic sensing and regulation of sphingosine levels during zebrafish embryogenesis
Karen Mendelson,
Suveg Pandey,
Yu Hisano,
Frank Carellini,
Bhaskar C Das,
Timothy Hla,
Todd Evans
Affiliations
Karen Mendelson
Department of Surgery, Weill Cornell Medical College, Cornell University, New York, United States; Center for Vascular Biology, Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, Cornell University, New York, United States
Suveg Pandey
Department of Surgery, Weill Cornell Medical College, Cornell University, New York, United States
Yu Hisano
Vascular Biology Program, Department of Surgery, Boston Children’s Hospital, Boston, United States; Harvard Medical School, Boston, United States
Frank Carellini
Department of Surgery, Weill Cornell Medical College, Cornell University, New York, United States
Bhaskar C Das
Department of Medicine, Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, United States
Timothy Hla
Vascular Biology Program, Department of Surgery, Boston Children’s Hospital, Boston, United States; Harvard Medical School, Boston, United States
Sphingosine-1-phosphate (S1P) is generated through phosphorylation of sphingosine by sphingosine kinases (Sphk1 and Sphk2). We show that sphk2 maternal-zygotic mutant zebrafish embryos (sphk2MZ) display early developmental phenotypes, including a delay in epiboly, depleted S1P levels, elevated levels of sphingosine, and resistance to sphingosine toxicity. The sphk2MZ embryos also have strikingly increased levels of maternal transcripts encoding ceramide synthase 2b (Cers2b), and loss of Cers2b in sphk2MZ embryos phenocopies sphingosine toxicity. An upstream region of the cers2b promoter supports enhanced expression of a reporter gene in sphk2MZ embryos compared to wildtype embryos. Furthermore, ectopic expression of Cers2b protein itself reduces activity of the promoter, and this repression is relieved by exogenous sphingosine. Therefore, the sphk2MZ genome recognizes the lack of sphingosine kinase activity and up-regulates cers2b as a salvage pathway for sphingosine turnover. Cers2b can also function as a sphingolipid-responsive factor to mediate at least part of a feedback regulatory mechanism.
