Project description:PGCs undergo two distinct stages of demethylation before reaching a hypomethylated ground state at E13.5. Stage 1 occurs between E7.25- E9.5 in which PGCs experience a global loss of cytosine methylation. However, discreet loci escape this global loss of methylation and between E10.5-E13.5, stage 2 of demethylation takes place. In this stage these loci are targeted by Tet1 and Tet2 leading to the loss of the remaining methylation and resulting in the epigenetic ground state. Our data shows that Dnmt1 is responsible for maintaining the methylation of loci that escape stage 1 demethylation, and that it functions in a UHRF1 independent manner. Our data further demonstrates that when these loci lose methylation prior to stage 2 it results in early activation of the meiotic program, which leads to precocious differentiation of the germ line resulting in a decreased pool of PGCs in the embryo and subsequent infertility in adult mice.
Project description:A polyclonal mouse model of breast tumor heterogeneity using model cell line 4T1 was developed previously. It was shown that 4T1 cells were composed of mixed subpopulations with specializations, including dominating the primary tumor, contributing to metastatic populations, etc. Here in a different angle, we reveal that each 4T1 cells can switch between 2 distinct states, which could be easily misclassified into 2 subpopulations, as the 2 states can be distinguished by distinct patterns of gene expression, dramatic difference of metastatic competence, stem-cell like feature or not, etc. The event for each 4T1 cell to exhibit one state or another is stochastic and the metastatic competence of clones generated from a single 4T1 cell is variable rather than stable. Further, given that metastatic competence of 4T1 cells is not stable, classification of clones based on metastatic competence is highly biased. Similarly, the classification of 4T1 clones based on gene expression profiles is also highly biased. Taken together, our data support that the exhibition of metastatic competence depends on the state of 4T1 cells and do not support the existence of subpopulations with specialization. To the best of our knowledge, no similar work has ever been reported.
