Saif Shami
Pronouns: he/him
Research Mentor(s): Yadav Wagley
Research Mentor School/College/Department: Orthopaedic Surgery / Medicine
Program:
Authors: Saif Shami, Kurt D. Hankenson, Yadav Wagley
Session: Session 6: 3:40 pm – 4:30 pm
Poster: 87
Abstract
Osteoblast differentiation of human mesenchymal stem cells (hMSC) can be induced by Jagged1 and Bone Morphogenetic Proteins (BMP). Recent results from our laboratory have shown that the BMP signaling intersects with canonical Notch signaling via upregulation of JAG1 gene during osteoblastic differentiation of hMSC and that small interfering RNA (siRNA)-mediated knock-down of JAG1 impairs hMSC osteoblast differentiation1. However, the precise molecular mechanism involved in the transcriptional regulation of JAG1 after BMP-stimulation remains unknown. This study was designed to identify transcription factor(s) activated by BMP/SMAD signaling that facilitates the expression of JAG1. Functional classification of differentially upregulated genes in BMP2 stimulated hMSC showed a total of 130 transcription factors. The presence of binding sites of these transcription factors were computationally predicted in the promoter of JAG1 gene. Among several transcription factors that were predicted to bind within the JAG1 promoter, SNAI1 and SNAI2 were further interrogated in this study because these are known to regulate epithelial to mesenchymal transition. To validate that BMP stimulation enhanced the expression of SNAI1 and SNAI2, total RNA was prepared after stimulating hMSC with BMP2 for various lengths of time. We found that both SNAI1 and SNAI2 gene expression increased before measurable increase in JAG1 expression. In future works, we plan to evaluate the protein expression of these transcription factors upon BMP2 stimulation and examine whether their expression follows activation of canonical Notch signaling. Furthermore, we plan to knock-down the expression of SNAI1 and SNAI2 using small interfering RNA (siRNA) and utilize the gene silenced cells for JAG1 expression and osteoblast differentiation. To conclusively establish the role of SNAI1 and SNAI2 in the regulation of JAG1 expression and osteoblast differentiation, we aim to utilize chromatin immunoprecipitation assay to demonstrate enriched binding of these transcription factors within the JAG1 promoter. Since clinical utilization of BMP2 for bone regeneration is limited due to unwanted complications such as inflammation, understanding the precise downstream molecular mediators of BMP2-mediated osteoblast differentiation will be beneficial in assisting in the field of bone regenerative therapies. Reference: 1. Wagley, Y., Chesi, A., Acevedo, P. K. A. K., Lu , S., Wells, A. D., Johnson, M. E., Grant, S. F. A., & Hankenson , K. D. (2020). Canonical Notch signaling is required for bone morphogenetic protein-mediated human osteoblast differentiation (Issue 10, Vol. 38, Ser. Stem Cells). https://doi.org/10.1002/stem.3245
