EAPSI: Characterizing Regenerative Cells during Central Nervous System Regeneration in Marine Acorn Worms

Luttrell Shawn M, Friday Harbor WA

Investigators

Abstract

Central nervous system (CNS) regeneration remains on the forefront of scientific research after decades of study. Progress and advances have been made, however, many of the cellular mechanisms controlling CNS regeneration continue to be elusive. Millions of people suffer from debilitating neurological defects, like Alzheimer?s and Parkinson?s disease, spina bifida, epilepsy, and spinal cord injuries, to name a few. Furthermore, aging and age related diseases eventually affect everyone. Regeneration may slow the aging process and stem cells, which have the potential to become any type of cell in the body, including nerve cells, present one feasible way to combat neural diseases and injuries. The goal of this project is to determine whether bona fide stem cells are elaborating missing tissue during regeneration in marine acorn worms. Some species of acorn worms, like Ptychodera flava, completely regenerate their entire CNS after amputation. Understanding the mechanisms for regeneration in acorn worms may yield clues to unlocking regeneration in other animals with limited CNS regeneration, including humans. I will be working with Dr. Yi-Hsien Su at the Institute of Cellular and Organismic Biology at Academia Sinica in Taiwan on this project. She routinely collects and uses this animal for biological studies. Her lab specializes in gene networks regulating animal body plan evolution, development, and patterning using molecular techniques that target specific genes and cell types. This project may be a springboard that could give insights for new stem cell therapies and nerve regeneration in humans. Acorn worms, also known as hemichordates, are marine, invertebrate deuterostomes and sister group to the echinoderms. Acorn worms have a tripartite body plan with an anterior proboscis, a middle collar region, and a long posterior trunk. As deuterostomes, hemichordates share several morphological and developmental features with the chordates. The solitary hemichordate, Ptychodera flava, has a hollow, dorsal neural tube that develops in a very similar fashion to the chordate neural tube. Upon amputation, P. flava reliably regrows their entire neural tube and anterior head-like structure in about two weeks. No chordate has been shown to have this ability. Our lab has shown that extensive cell death and cell proliferation are activated during anterior regeneration in P. flava. It is not known whether bona fide stem cells are proliferating in this animal or whether somatic cells are de-differentiating and then becoming multi-potent to generate new structures. To help confirm the origin and identity of proliferating cells in P. flava, I will stain non-regenerating animals with antibodies raised against a hemichordate vasa protein. Vasa is a marker for germline stem cells across numerous animal phyla. Vasa is also expressed in some non-germline, multi-potent stem cells. I will also use in situ hybridization with the stem cell markers, c-Myc, pax6, and alkaline phosphatase. If expression of these markers co-localize with staining of vasa protein in non-germ cells, this will support a hypothesis of bona fide stem cells in P. flava. If this is confirmed, P. flava presents an exciting model to study the molecular mechanisms of stem cell recruitment and specification during central nervous system regeneration in the deuterostomes. Further experiments will be required to prove that the stem cells can self renew and also differentiate into other cell types during regeneration. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Ministry of Science and Technology of Taiwan.