Bone mesenchymal stem/ stromal cells (BMSC) reside in the marrow of bones and can give rise to several cell lineages, including adipocytes, myoblasts, chondroblasts and osteoblasts. A number of master regulators control the differentiation of BMSCs into the different lineages, with osteoblastic differentiation being controlled by Runx2. Osteoblastic differentiation is a key pathway for the development of healthy bone tissue and altered expression of osteogenic genes can lead to bone deficiencies such as Type I and II osteoporosis. Epigenetic mechanisms of gene regulation involve altering the expression of genes without changing the DNA sequence itself, and are abundant in the cells. DNA methylation (5mC) is one such major epigenetic mode of gene regulation that inhibits transcription with methylation status of genes in the genome being highly dynamic. Tet1 and Tet2 are 2 known epigenetic modifiers that have been found to be downregulated during osteoporosis, potentially implicating them in the onset and progression of the disease.
Hypothesis and approach
Deregulation through KO of Tet1 and Tet2 will lead a decreased bone density in aged mice (Type II).
Analysis of bone phenotype has shown effects such as trabecular bone loss as well as changes in cortical bone architecture in the KO animals at the 3 and 12 month age points, with the observed effects being more severe in the male cohort. Preliminary in vitro analysis has also shown decreased proliferation and changes in differentiation potential in cells taken from the same KO animals. This data will then be paired with sequencing analysis to assess the changes in global 5mC and 5hmC levels, as well as RNA seq to determine the changes in gene expression between the two cohorts in order to gain a deeper understanding of the pathways involved in bone development in the type II model.