Meeting Abstract
Understanding the mechanisms that generate new/novel cell types remains a fundamental challenge in the advancement of cell biology. Because they are among the few clearly novel cell types, cnidocytes (the stinging cells in cnidarians) provide a valuable model for studies of novelty. We manipulated in vivo gene expression to assess the effect of several key transcription factors on the differentiation of cnidocytes in embryos of Nematostella vectensis, a model sea anemone. Morpholino knockdown of the homeobox transcription factor paxA resulted in loss of cnidocytes and knockdown of soxB2 resulted in both loss of cnidocytes and in reduction of paxA expression in N. vectensis. Interestingly, neither of these transcription factors has yet been identified in the regulatory network of medusozoan cnidocytes. Because of the challenges associated with acquiring and manipulating embryos in these lineages, studies of medusozoan cnidocyte differentiation have largely utilized regenerating adult tissue. Using in situ hybridization, we have further identified paxA and soxB2 transcripts in the ectoderm of the tentacle tips of N. vectensis polyps undergoing cnidocyte replacement, suggesting these genes may regulate differentiation of this novel cell type in both developmental and regenerative contexts among anthozoans. Importantly, amassing evidence from across cnidarian lineages suggests that several conserved families of transcription factors (e.g., bHLH, HMG, Sox, and both PRD-class and SIN-class homeobox genes) are required for the development of cnidocytes. Considering the structural elements of cnidocytes are encoded by lineage-specific genes, this system provides a unique opportunity to assess how conserved regulatory genes become integrated into networks of novel structural genes to regulate the development of novel cells.
