title: ATP-binding cassette (ABC) transporter expression and localization in sea urchin development.
abstract: BACKGROUND
  ATP-binding cassette (ABC) transporters are membrane proteins that regulate intracellular concentrations of myriad compounds and ions. There are >100 ABC transporter predictions in the Strongylocentrotus purpuratus genome, including 40 annotated ABCB, ABCC, and ABCG "multidrug efflux" transporters. Despite the importance of multidrug transporters for protection and signaling, their expression patterns have not been characterized in deuterostome embryos.
  
  
  RESULTS
  Sea urchin embryos expressed 20 ABCB, ABCC, and ABCG transporter genes in the first 58 hr of development, from unfertilized egg to early prism. We quantified transcripts of ABCB1a, ABCB4a, ABCC1, ABCC5a, ABCC9a, and ABCG2b, and found that ABCB1a mRNA was 10-100 times more abundant than other transporter mRNAs. In situ hybridization showed ABCB1a was expressed ubiquitously in embryos, while ABCC5a was restricted to secondary mesenchyme cells and their precursors. Fluorescent protein fusions showed localization of ABCB1a on apical cell surfaces, and ABCC5a on basolateral surfaces.
  
  
  CONCLUSIONS
  Embryos use many ABC transporters with predicted functions in cell signaling, lysosomal and mitochondrial homeostasis, potassium channel regulation, pigmentation, and xenobiotic efflux. Detailed characterization of ABCB1a and ABCC5a revealed that they have different temporal and spatial gene expression profiles and protein localization patterns that correlate to their predicted functions in protection and development, respectively.
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California 92093-0202, USA.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Shipp
authors.forename: Amro
authors.initials: A
authors.lastname: Hamdoun
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000367:Age Factors; D000818:Animals; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000096:biosynthesis; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D017403:In Situ Hybridization; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D047270:Strongylocentrotus purpuratus / Q000196:embryology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D017931:DNA Primers; D018076:DNA, Complementary