Meeting Abstract

53.4  Jan. 6  Amino Acid Transporter Gene Expression During Sea Urchin Development MEYER, E.*; MANAHAN, D. T.; Univ. Southern California; Univ. Southern California elishame@usc.edu

The mechanisms that regulate transport of organic nutrients during early animal development are not fully understood. Several amino acid transporter genes were cloned from a cDNA library of 4-cell-stage embryos of the sea urchin Strongylocentrotus purpuratus. Two of these genes (spAT2 and spAT17) have sequence similarities with transporters of organic solutes characterized in other animals. Heterologous expression of these sea urchin genes in frog oocytes (Xenopus laevis) showed that spAT2 and spAT17 encode novel, functional alanine transporters. Transport rates by sea urchin larvae of alanine from seawater decreased in the presence of a specific antibody raised against spAT2, demonstrating the in vivo alanine transport function of this gene. During sea urchin development, alanine transport rates increased 6-fold between 5-hr-old embryos and 4-d-old larvae. Corresponding changes in gene expression were measured during this developmental period. The high initial transcript abundance of spAT2 in eggs decreased 24% in 4-d-old larvae. In contrast, the transcript abundance of spAT17 was very low in eggs, and increased 1,100% in 4-d-old larvae. Ontogenetic patterns of expression of these two alanine transporter genes, each with different amino acid sequences, suggest the possibility that known physiological changes in capacities and affinities of amino acid transport during development are regulated by differential gene expression. These findings represent a functional characterization of amino acid transporter genes in marine invertebrate larvae and provide new tools for investigating long-standing questions regarding the mechanisms of dissolved organic nutrient transport by marine animals.