Characterization Of Pigment Cell Specific Genes In The Sea Urchin Embryo (strongylocentrotus Purpuratus)

In sea urchin development, cell fate specification appears by the 60-cell stage embryo when several embryonic territories are recognized: the small micromeres, the large micromeres which will generate primary mesenchyme cells, the vegetal2 layer that will give rise to pigment cells, immunocytes, and muscle cells, the vegetal1 layer, as well as the oral and aboral ectoderm. A Delta-Notch signaling event is required for the differential specification of mesodermal cells that will give rise to secondary mesenchyme cells (SMCs). SMCs produce four cell types: pigment cells, blastocoelar cells, circumesophageal muscle cells, and coelomic pouch cells. Pigment cells are the first to be specified. During primary invagination at the gastrula stage, eight pigment cell progenitors delaminate from the archenteron into the blastocoel. By the pluteus stage, approximately 30 pigment cells are embedded in the ectoderm. Pigment cells produce echinochrome, a napthoquinone pigment. Previously, several genes in the sea urchin embryo were isolated that are expressed specifically in pigment cell precursors during the blastula stage. The goal of this research was to characterize a subset of these genes, which are highly similar to: the polyketide synthase gene (Pks), a sulfotransferase gene (Sult), three different members of the flavin-containing monooxygenase gene family (Fmo), and the transcription factor glial cells missing (Gcm). Polyketide synthases (PKSs) are a large family of multifunctional proteins mainly found in bacteria, fungi, and plants. They are responsible for the biosynthesis of a variety of polyketide compounds including antibiotics and mycotoxins. In the sea urchin, SpPks is required for echinochrome biosynthesis. Flavin-containing monooxygenases (FMOs) are NADPH-dependent flavoproteins mainly found in bacteria, plants, and higher metazoan. They are responsible for catalyzing the oxidation of several compounds including the detoxification of xenobiotics and activation of numerous metabolites. It is known that SpFmo1 is required for echinochrome biosynthesis. Sulfotransferases are found from bacteria through higher eukaryotes. These enzymes catalyze the sulfate conjugation of several substrates resulting in either compound detoxification or bioactivation