Document Type

Dissertation - Open Access

Award Date

2021

Degree Name

Doctor of Philosophy (PhD)

Department / School

Chemistry and Biochemistry

First Advisor

Jianning Tao

Keywords

Congenital, Epigenetic, Musculoskeletal, Notch, Oncogene, Proteomic

Abstract

Notch signaling is an evolutionarily conserved signaling pathway involved in cell fate decisions and cell renewal of multiple systems, including skeletal and muscle homeostasis. As the multifunctional nuclear complex of Notch1 is essential for its pathological function, identifying these interacting partners represents a potentially broad range of druggable vulnerabilities. We have completed a BioID proteomics study and found a large set of nuclear proteins associated with NOTCH1, including transcriptional regulators and epigenetic modulators, of which Histone Deacetylase 1 (HDAC1) is a promising interacting partner of Notch1. Our Cytoscape analysis predicted HDAC1 to be a top critical node in an activated Notch state. Pathological Notch super-activation in committed osteoblasts of the skeletal system can stimulate their proliferation, but simultaneously inhibit their differentiation into mature osteoblasts. This phenotype is consistent with studies of human OS samples, which show that the Notch signaling is frequently upregulated in human OS. Considering its role in osteoblasts, we hypothesize that suppression of HDAC1 in a NOTCH1 activated OS may ameliorate the proliferative hallmark of the disease. We assessed efficacy and mode of action of a novel class I histone deacetylase inhibitor, 4SC-202, on the SJSA-1 osteosarcoma cell line and hFOB1.19, an immortalized fetal osteoblast cell line. Preclinical treatment of an SJSA-1 xenograft mouse model validates the effects seen in vitro. A common mechanism of action, indicated by an increase in H3K27Ac protein expression upon 4SC-202 treatment, implicates epigenetic regulation gene expression in this context. RNA-seq transcriptome analysis reveals Notch signaling, as a top altered molecular network from 4SC-202 treatment. We also continued our study on the effects of an HDACi in vivo in a Notch3 gain-of-function murine model for Lateral Meningocele Syndrome (LMS). Our findings reveal a pharmacological prevention of the kyphosis phenotype in a murine model of LMS, which may translate to a potential strategy for mitigating pathological musculoskeletal phenotypes for patients. Overall, our findings indicate an unappreciated positive regulation of Notch signaling by HDACs in bone disease, which may help guide future therapies for Notch gain of function musculoskeletal disease.

Number of Pages

283

Publisher

South Dakota State University

Available for download on Sunday, December 15, 2024

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Rights Statement

In Copyright