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My group has studied a broad range of questions relating to the development of neurogenic placodes and the neural crest, two embryonic cell populations in vertebrates that together build the entire peripheral nervous system. Neurogenic placodes - paired patches of thickened surface ectoderm in the embryonic head - give rise to the paired peripheral sense organs and most of the neurons in cranial sensory ganglia. Current work in the lab focuses on the formation of lateral line electroreceptors, as a model for sensory cell-type diversification in development and evolution. Mechanosensory hair cells in the inner ear, arising from the otic placode, detect fluid movement for hearing and balance. In fishes and aquatic-stage amphibians, almost identical hair cells are also found in lateral line placode-derived neuromasts, distributed in lines over the head and trunk, which detect local water movement. In electroreceptive species (e.g. skates, sturgeons, salamanders), some or all of the cranial neuromast lines are flanked by fields of electrosensory ampullary organs that detect weak, low-frequency electric fields around other animals in water (primarily used for detecting prey/predators). We and others have shown that lateral line placodes form ampullary organs as well as neuromasts, and that electroreceptors are closely related to mechanosensory hair cells. Electroreception was lost in the lineages leading to teleost fishes and to frogs, so electroreceptor development cannot be studied in the standard lab models, i.e., the teleost zebrafish and the frog Xenopus. However, electroreception evolved at least twice independently within teleost fishes, most likely from neuromast hair cells - a superb example of convergent evolution. We are investigating the embryological origins of electroreceptors and the genes underlying their formation, in a wide range of vertebrate groups including lamprey (jawless fish), skate (cartilaginous fish), axolotl (amphibian), sturgeon and paddlefish (non-teleost ray-finned bony fishes), and catfish (a teleost with independently evolved electroreceptors).
Paddlefish larval lateral line organs
Lateral line organs on the head in a larval paddlefish (skinmount stained with Sytox green). Rosette-like electrosensory organs flank lines of mechanosensory neuromasts.
