Date of Award

11-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Cancer and Developmental Biology

Research Advisor

Susan A. Miranda, Ph.D.

Committee

Weikuan Gu, PhD Gustavo A. Miranda-Carboni, PhD Megan K. Mulligan, PhD Edwards A. Park, PhD Claire L. Simpson, PhD

Keywords

Bone; ERα; Osteoblasts; SNPs; WNT

Abstract

Osteoporosis is the most common bone metabolic disorder, affecting over 200 million people globally. It is characterized by bone mass depletion and microarchitectural deterioration, leading to bone fragility and susceptibility to bone fracture. Genetic factors, estrogen deficiency, and dysregulation of the WNT signaling pathway contribute to the development of this disease. Genome-wide association studies have predicted that the single nucleotide polymorphisms (SNPs) rs2887571 and rs9921222 associate with low bone mass, but the mechanism of these SNPs has remained unknown. Analysis of osteoblasts from 112 different joint replacement patients reveals that the genotype of rs2887571 correlates with WNT5B expression, and the genotype of rs9921222 correlates with AXIN1 expression. Mechanistically, SNP rs2887571 has less binding of ERα and NFATc1 to allele A than allele G, resulting in more expression of WNT5B in homozygous AA than homozygous GG. Furthermore, WNT5B exhibits distinct effects from other WNTs on osteoblastogenesis. WNT5B increases mesenchymal stem cell proliferation, promotes adipogenesis, and suppresses osteoblast differentiation via ROR1/2, then activates DVL2/3, Rac1/Cdc42, JNK, and SIN3A signaling, as well as inhibits ROCK2 and β-catenin activity. For SNP rs9921222, homozygous TT has a higher expression of AXIN1 than homozygous CC. Molecular analysis shows that GATA4 favors binding at rs9921222 allele T to promote AXIN1 expression; in contrast, ERα prefers to bind at allele C to suppress the expression, resulting in more expression of AXIN1 in homozygous TT than homozygous CC. Functionally, the level of AXIN1 negatively correlates with the level of active β-catenin, which enhances osteoblast differentiation. Taken together, the biological mechanisms of SNPs rs2887571 and rs9921222, which are associated with osteoporosis via the WNT signaling pathway, are revealed, as well as the inhibitory effect of WNT5B on osteoblastogenesis. These data will be the fundamental knowledge for the development of osteoporosis prediction and therapeutic strategies.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

http://orcid.org/0000-0002-6943-4013

DOI

10.21007/etd.cghs.2021.0548

Additional Files
2021-019-Suthon-DOA.pdf (193 kB)
Declaration of Authorship
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