Early embryonic apoptosis in the purple sea urchin, Strongylocentrotus purpuratus: Developmental timing, control, and responses to environmental disruption

This dissertation characterizes a novel link between apoptosis and efflux transporters in early sea urchin development. Using a cell biological framework I have demonstrated that while embryos of the sea urchin Strongylocentrotus purpuratus are highly resistant to stress-induced apoptosis, disruption of the efflux transporter system circumvents or directly abolishes this resistance. In addition this dissertation has demonstrated that while apoptosis is stage dependent, occurs in low frequency, and is unnecessary for normal urchin development, it is advantageous during times of stress, providing urchin embryos a sensitive pathway to eliminate damaged cells in early development. This study also found that inducible apoptosis occurs in a temporally predictable fashion, peaking around the hatching stage. These findings confirm that chemo-sensitization via transporter inhibition has real embryological consequences. In addition, I have shown for the first time that small subtle variations in transporter substrate sensitivity significantly affect embryo toxin susceptibility, a result that has important implications for embryo health and survivorship.