Meeting Abstract
Sea anemones have hair cells bearing hair bundles on their tentacles which are used to detect nearby prey. Hair bundles in sea anemones are similar in morphology and physiology to those in the ears and lateral line system of vertebrates. The Delta-Notch pathway has been implicated in regulating hair cell differentiation in vertebrates. We tested whether this pathway was involved in differentiation of hair cells in adult anemones. We tested three groups of anemones: seawater control, 0.1% DMSO in seawater, and 20uM DAPT in 0.1% DMSO seawater. DAPT is an inhibitor of the Delta-Notch pathway. Anemones were incubated in solutions for 48 h, and then tentacles were excised and processed for phase-contrast microscopy. Hair bundles were counted and surface areas measured from digital images. Hair bundle density was expressed as the number of hair bundles per 50 microns of tentacle surface. Our average hair bundle density for the seawater control was 4.60+1.2, for DMSO control was 4.46+0.8, and for DAPT treatment was 6.86+1.7. There was no statistically significant difference between the seawater control and DMSO control groups, indicating no effect of DMSO alone on hair bundles, but there was a significant increase in hair bundle density when the anemone tentacles were treated with DAPT dissolved in 0.1% DMSO. These results support our hypothesis that Delta-Notch regulates differentiation of cells forming hair bundles in anemone tentacles. Because each hair bundle in anemones is formed from a multicellular complex of 2-4 hair cells surrounding a single sensory neuron, ongoing experiments are investigating whether neuronal density increases with the inhibition of the Delta-Notch Pathway in addition to hair bundle density.
