Coelomocyte Proliferation and the Search for their Source in the Purple Sea Urchin

The number of immune cells (coelomocytes) in the purple sea urchin, Stronglyocentrotus purpuratus, increases four-fold upon immune challenge with heat-killed marine bacteria, Vibrio diazotrophicus. It is unclear whether the increase results from either the proliferation of new immune cells, the release of pre-existing cells into the coelomic fluid (CF), or both. The SpShapeshifter (SpShsh) immune proteins, which are encoded by Sp185/333 genes and may be coelomocyte markers, show highest expression in the axial organ, suggesting that it may be a hematopoietic tissue. Therefore, we measured coelomocyte proliferation using ethynyl deoxyuridine incorporation into newly synthesized DNA in response to either challenge with Vibrio or simulation of immune challenge by removal of CF. Both treatments account for up to 10% of newly proliferated coelomocytes in the CF, suggesting that the remaining 90% were pre-existing coelomocytes that appear in the CF after challenge. Levels of proliferated coelomocytes increase by ~1.5% within 24 hours and continue to increase thereafter, presumably replacing cells responding to immune challenge or lost due to CF removal. After CF removal, levels of proliferated cells are unchanged in the axial organ, but higher in gut and esophagus. Additionally, these three tissues have elevated levels of proliferated cells expressing SpShsh, implying coelomocyte proliferation. Hematopoietic transcription factors expression in coelomocytes and tissues was used to identify the source of coelomocytes. Transcription factors SpGataC, SpScl, SpGcm, and SpE2A, and transcription regulators SpLmo2, SpId, SpPU.1, and SpTCF are expressed at high levels in pharynx, followed by the axial organ. These results suggest that the pharynx and the axial organ may participate in production of coelomocytes and their release into the CF.

Author

• Golconda, Preethi

Language

• en

Keyword

• Hematopoietic Tissue
• EdU
• Echinoderm
• Transcription Factors

Date created

• 2015

Type of Work

• Master's Thesis

License

• All rights reserved

Rights statement

• In Copyright

GW Unit

• Biological Sciences

Degree

• M.S.

Advisor

• Smith, L. Courtney

Committee Member(s)

• Donaldson, Robert P
• Eleftherianos, Ioannis

Persistent URL

•  https://scholarspace.library.gwu.edu/etd/fn106x97k