Detection of Cell Death in Spider Embryos Using TUNEL.

INTRODUCTIONThe spider Cupiennius salei, commonly known as the American Wandering Spider, is a particularly useful laboratory model for embryological studies because of the availability of tools to study and manipulate its embryonic development. Cupiennius is used to study axis formation, segmentation, appendage development, neurogenesis, and silk production. These studies contribute to our understanding of the evolution of these processes, but they also help us to understand the origin and diversification of evolutionary novelties. Comparisons between spiders and insects can show the degree of conservation and divergence of developmental mechanisms during arthropod evolution. Any embryological feature conserved between spiders and insects is likely to represent an ancestral feature for arthropods. Comparative molecular embryological work in insects and spiders should eventually allow us to define a molecular archetype for the phylum Arthropoda. This in itself will be a necessary cornerstone for comparing the different metazoan phyla, including chordates. A feature of apoptosis (i.e., cell death) is the cleavage or fragmentation of DNA that occurs in dead or dying cells. This protocol describes the detection of fragmented DNA in whole-mount Cupiennius embryos. The 3'-OH ends of these DNA fragments can be labeled with the terminal deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick-end labeling (TUNEL) technique. This protocol uses a terminal deoxynucleotidyl transferase to add labeled dUTP to the fragmented DNA, and this label is then detected by immunocytochemistry. The TUNEL technique is a relatively easy way to obtain a reliable picture of the cell death pattern during normal and abnormal development.