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Date of Award

Spring 2026

Rights

Access restricted for 2 years to EWU users with an active EWU NetID

Date Available to Non-EWU Users

2028-06-29

Document Type

Thesis: EWU Only

Degree Name

Master of Science (MS) in Biology

Department

Biology

First Advisor

Dr. Jason Ashley

Second Advisor

Dr. Andrea Castillo

Third Advisor

Dr. Ashley Lamm

Abstract

Osteoporosis is characterized by excessive bone resorption and impaired skeletal remodeling, resulting in increased fracture risk, particularly in postmenopausal populations. This imbalance is largely driven by osteoclasts, which are the primary bone resorbing cells responsible for breaking down bone tissue during remodeling. Current treatments, including bisphosphonates and denosumab, suppress osteoclast activity, but prolonged inhibition of remodeling can reduce bone quality. Notch signaling is an important regulator of osteoclastogenesis, and its modulation may provide a novel strategy to reduce bone resorption while maintaining bone integrity. The Fringe family of glycosyltransferases includes Lunatic Fringe (LFNG), Manic Fringe (MFNG), and Radical Fringe (RFNG), which modify Notch receptors and influence downstream signaling. Overexpression of Fringe proteins in primary bone marrow derived macrophages increased osteoclast size and tartrate resistant acid phosphatase (TRAP) activity. However, primary macrophage cultures are limited by low cell yields from mouse bone marrow. To overcome this, the ER-Hoxb8 conditional immortalization system was used to generate a renewable myeloid progenitor population. RNA sequencing verified stable transgene expression and characterized downstream transcriptional changes in female myeloid progenitor cell derived osteoclasts. Increased osteoclast differentiation, TRAP activity, and preliminary resorptive activity were associated with elevated RFNG expression in female myeloid progenitor cells. Actin ring formation also remained consistent with mature osteoclast formation, indicating that Fringe overexpression did not prevent cytoskeletal organization. Male myeloid progenitor cells showed increased TRAP activity in RFNG overexpressing populations, but TRAP positive area and morphology were reduced compared with controls. This suggests a potential sex dependent effect, which may inform alternative therapeutic approaches for postmenopausal osteoporosis. These findings further support the role of Fringe proteins in regulating osteoclastogenesis and highlight their utility in studying bone remodeling.

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