Mesenchymal Stem Cells And B Lymphocyte Leukemia Epigenetics Research

In recent yeas, epigenetics has become an increasingly important research field, It is the study of heritable changes in genome that occur without alterations to DNA sequences, including three aspects:DNA methylation. histone modification and noncoding microRNAs. Epigenetic regulation mechanisms are involved in many important biological processes such as X-chromosome inactivation and genome imprint. Emerging evidences suggest that epigenetic abnormality plays as important a role as genetic abnormality during cancer initiation and progression.Stem cells are defined by two common characteristics:self-renewal which can maintain the stem cell population and pluripotence which can give rise to a wide range of differentiated cells. There are two types of stem cells:embryonic stern cells and adult stem cells. Embryonic stem cells have unlimited self-renewal and totipotent differentiation potential. They are the ideal cellular model for the study of development and differentiation. However their application in clinical research is still in trouble due to ethical and law problems as well as some unresolved issues related to safety and technology. Mesenchymal stem cells are adult stem cells isolated from bone marrow or adipose tissue. They can differentiate into chondrocytes, osteoblasts and adipocytes. Since mesenchymal stem cells are ideal seed cells in tissue engineer and regenerative medicine, it is very important to understand the mechanisms underlying their self-renewal and pluripotency.The first part of the study mainly focuses on some key signal pathways and epigenetic changes during MSC osteogenic differentiation. We examined the protein expression changes of key signal pathway and histone modification during differentiation, then we explored the whole genome state of histone modification of H3K4me3. H3K9me3. H3K27me3in MSC by using the Chromatin immunoprecipitation and sequencing (ChIP-seq). We found that (3catenin of classical WNT pathway was upregulated and the activiated form of ERK1/2was increased during the osteogenic differentiation. This indicated that classical WNT and MEK/ERK pathway played a positive role in the osteogenic differentiation. Smad2/3expression was decreased in protein level which indicated a negative effect. Our ChIP-seq results indicated that bivalent modification of H3K4me3and H3K27has nearly2000targed genes and played important role in maintaining MSC multi-differentiation.Acute lymphoblastic leukemia is a common malignacy in hematopoietic system whose pathogenesis is still not fully understood. The second part of the work mainly focused on polycomb protein EZH2and histone modification in B-ALL. First we compared the protein expression level in the normal B and Nalm-6cell lines, and found that tumor surpressor gene PTEN was absent and polycomb protein EZH2was upregulated in Nalm-6. Then we performed Chromatin Immunoprecipitation using EZH2and H3K27me3antibodies and found that EZH2and H3K27me3were bound to the promoter region of PTEN. Then we treated the Nalm-6cells with HDAC inhibitor TSA and checked the protein expression changes with Western blot. TSA treatment decreased EZH2and H3K27me3in protein level. Our results indicated that polycomb protein EZI12may be involved in the B-ALL pathogenesis by inhibiting the tumor surpressor gene PTEN and that EZH2can be inhibited by HDAC inhibitor TSA.