Driesch's Conditional Isolation of Blastomeres

Students: Laura Smith, Sanaya Roberts

Faculty Mentor: Lisa Hua

Biology

College of Science, Technology, and Business

The objective of this experiment was to investigate the plasticity of cell fate during early embryonic development and demonstrate that cellular outcomes are not predetermined but can be influenced by environmental factors and intercellular interactions. To explore this, we separated the blastomeres of developing sea urchin embryos and observed whether they would continue their developmental progression from cleavage to gastrulation. Sea urchin eggs were fertilized with diluted sperm, and once 90% of the embryos exhibited the formation of a fertilization envelope, we applied two distinct treatments. One group of embryos was treated with Calcium-Free Seawater and ATAZ (a polyspermy-blocking drug) to dissolve the hyaline layer of the envelope, while the other was treated with only Calcium-Free Seawater. The former group, referred to as "Naked" embryos, would undergo isolation of their blastomeres, whereas the latter, termed "Control," represented the standard developmental process. Both groups were incubated at 15°C, and their cleavage progress was monitored at 24 and 48 hours. By the 48-hour mark, the "Control" embryos successfully progressed to various cleavage stages, ranging from 2-cell to gastrulation. Unfortunately, all "Naked" embryos failed to survive, likely due to experimental or environmental errors. However, analysis of a control sample provided by our TA revealed that the embryos from that sample reached gastrulation, confirming the robustness of the developmental process under normal conditions. This experiment highlights the capacity of embryonic cells to continue development despite environmental or structural alterations early in the process, supporting the idea of cellular plasticity in developmental fate determination.