Functional Analysis of Genes Involved in Regulating Stem Cell Maintenance and Differentiation in the Freshwater Planarian Schmidtea Mediterranea
Guo, Tingxia
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/86310
Description
Title
Functional Analysis of Genes Involved in Regulating Stem Cell Maintenance and Differentiation in the Freshwater Planarian Schmidtea Mediterranea
Author(s)
Guo, Tingxia
Issue Date
2007
Doctoral Committee Chair(s)
Joseph Henry
Department of Study
Cell and Developmental Biology
Discipline
Cell and Developmental Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Cell
Language
eng
Abstract
Freshwater planarians have been a classic model for regeneration studies for more than 250 years. The great regenerative abilities of planarians rely on neoblasts, adult stem cells maintained throughout the animal's life. This thesis reports an analysis of genes that regulate stem cell maintenance and differentiation in planarian Schmidtea mediterranea. A member of the Bruno-like family of RNA binding proteins was found to be critical for neoblast self-renewal in the planarian Schmidtea mediterranea. Smed-bruno-like (bruli) mRNA and protein are expressed in the neoblasts and in the central nervous system. Immunofluorecense with antibodies recognizing SMEDWI-1 and Historie H4 (monomethyl-K20) and other cell cycle markers showed that the neoblast population was eliminated from both regenerating and intact planarians following smed-bruli RNA interference, leading to the death of the animals. These results suggest that Bruli is required for stem cell maintenance. We further characterized expression of SMEDWI-1 in somatic stem cells and germ cells. SMEDWI-1 protein is expressed in neoblasts and their differentiating progeny in both asexual and sexual planarians. In sexual planarians, SMEDWI-1 expression is detected in spermatogonia and spermatocytes as well as oogonia. SMEDWI-1 antibodies also recognize the presumptive germ cells in asexual planarians that reproduce exclusively by fission. However, SMEDWI-1 protein is dispensable for the development, maintenance and regeneration of testes in sexual planarians, probably due to the redundancy of other PIWI family members expressed in germ cells. Finally, we examined the differentiation of neoblasts in intact and Smed-slit RNAi planarians. BraU incorporation and immunofluorescent labeling with cell type-specific markers were used to label proliferating neoblasts and follow the fates of their progeny into various differentiated cell types, including marginal gland cells, photoreceptors, and neurons. In slit RNAi animals, neoblasts differentiate into ectopic neural tissues that form ganglia-like structures along the midline. Thus, Smed-slit may function to regulate neoblast differentiation in addition to acting as a repulsive cue in axon guidance.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
