Investigating gene expression pattern during early sea urchin embryo development

Background: The sea urchin embryo model is a beneficial tool to understand signaling events during human embryo development. Early embryo development requires apoptosis of unwanted cells. This study aims to measure apoptotic gene expression at different stages of sea urchin embryo development to study when apoptotic events occur. This study also measures apoptotic gene expression in the presence of PAF, a signaling molecule that modulates apoptosis. Methods: Gametes were collected from gravid sea urchins (Lytechinus variegatus) following the injection of 0.5 M KCl. Oocytes were fertilized with spermatozoa and cultured to the 2-cell stage in filtered sea water and were subsequently cultured for up to 24-hours. Individual microdrops were collected at each progressing cell stage (from 2 Cell to Pluteus) and stored at -20oC until assayed. The test group of embryos were treated with 10-7M PAF which was added after an hour of normal culture. RNA was purified from the different stage sea urchin embryos. Real-time PCR was used to assess expression of apoptotic genes. Genes showing differential expression were further assessed in other embryo samples using gene specific TaqMan primers. Results: Initial results revealed that caspase gene expression in the control group spiked at around 2 hours and maintained a sinusoidal pattern over time. Conclusions: Apoptotic gene expression varies during early sea urchin embryo development. This initial study uncovered a fluctuating pattern of caspase gene expression during sea urchin development. Further research will focus on assessing the expression of other apoptotic genes identified in the gene array study.