Neurons in crayfish brains can be replaced throughout adult life. The brain neurons are formed by a process that begins when an immature cell, or stem cell, divides and then goes through a process of development that converts the stem cell to a mature neuron. Interestingly, the source of the neuron stem cells is not known in the crayfish. The Principal Investigator proposes that cells in the crayfish?s immune system may be the source of the stem cells. This is a novel idea because it requires that adult cells with a very different function (immunity) change into immature cells with the ability to develop into neurons. The researcher has found evidence to support this idea and will carry out studies to confirm her findings and learn how these potential source cells get from the crayfish circulatory system into the brain. The project will provide research training opportunities for female undergraduates and for students from underrepresented groups. Student experiences will be assessed using institutional and curricular surveys. Outreach activities will be carried out at local K-12 schools, for alumni associations, and for senior citizens in the Older, Wiser Lifelong Learning (OWLLS) program to teach neuroscience and explain the value of using invertebrate animal model systems to study lifelong plasticity in the nervous system.
The innate immune system of crayfish is composed of two distinct tissues that contain different cell types with characteristic cell cycle times and properties. In vitro and adoptive transfer methods will be used to identify regions involved in producing putative neuronal precursor cells. Crayfish will be injected with bromodeoxyuridine to label cells that are in the cell cycle. Hemolymph containing BrdU-labeled cells will then be extracted from these donor crayfish, and hemocyte types separated using Percoll gradients. Each hemocyte class will then be tested for its attraction to the niche in vitro, as well as injected into live crayfish for long-term studies that will test whether particular immune-derived cell types do transition into neuron progenitors that then develop into neurons. The neuronal phenotype will be confirmed by labeling for appropriate neurotransmitters and tract-tracing to reveal cellular morphology.
