Scott Baird (Committee Member), David Goldstein (Committee Chair), Mill Miller (Committee Member), Labib Rouhana (Advisor)
Master of Science (MS)
Evolutionarily conserved molecular processes involved in construction of the germline and embryonic development are essential for the procreation of many species. Infertility affects 15% of couples in the world and can be caused by dysfunctions during egg and sperm development, anatomic defects, as well as faulty embryonic development. Although there are some infertility disorders that are genetically defined, such as Turner and Klinefelter syndromes, many clinical infertility cases are diagnosed as idiopathic due to the lack of understanding of basic fertility mechanisms. Schmidtea mediterranea is a freshwater planarian species that has the ability to regenerate complete organisms, including germ cells and reproductive structures, from small tissue fragments containing pluripotent somatic stem cells. The developmental plasticity of planarians provides a wonderful opportunity to investigate the molecular mechanisms behind the differentiation and development of specialized cells, including gametes. Smed-boule encodes for an RNA-binding protein and is the most ancestral member of the Deleted in AZoospermia (DAZ) gene family. DAZ family genes function in different aspects of germ cell development and fertility in species ranging from sea anemone to humans. Whole-mount in situ hybridization experiments revealed Smed-boule expression is enriched in the testes and ovaries of planarian flatworms. Interestingly, Smed-boule RNA-interference (RNAi) planarians lost the ability to produce gametes, yet still were able to deposit sterile egg capsules. Virgin Smed-boule(RNAi) and control planarians maintained in isolation also continuously produced sterile egg capsules. Altogether these results demonstrate that egg capsule production in S. mediterranea occurs independently of ovulation, fertilization, and mating events. In addition, detailed analysis of gametogenesis defects revealed that Smed-boule functions at different stages during male and female germline development. These findings provide novel information about the evolution of boule and DAZ-family gene expression and function in sexual reproduction.
Department or Program
Department of Biological Sciences
Year Degree Awarded
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