Prmt5 Negatively Regulates Erythropoiesis By Multiple Mechanisms, Including Controlling DNA Methyltransferase 3A Protein Levels

The shift in sites of hematopoiesis during embryonic development leads to primitive hematopoiesis within the fetal liver at E12.5, which generates primarily erythrocytes. Definitive hematopoiesis, which occurs within the bone marrow, follows at birth. During the erythroid differentiation of fetal hematopoiesis, progenitor cell maturation is accompanied by global DNA demethylation, a process necessary for fetal liver erythrocyte formation and accompanied by diminishing expression of the de novo DNA methyltransferases, Dnmt3a and Dnmt3b.

In our current study of hematopoietic cell specific Prmt5 knockout mice, we have identified Prmt5 as a master regulator of erythropoiesis; the cell-specific deletion of Prmt5 in fetal liver cells is embryonic lethal as Prmt5-null embryos have severe anemia and increased expression of Dnmt3a and Dnmt3b proteins. RNA-seq and pathway analysis studies revealed profound defects in several critical pathways that regulate normal hematopoiesis, including the tumor suppressor p53 pathway. Methyl-seq studies are currently being conducted to determine the effects of the enforced expression of key DNA methyltransferases on global DNA methylation and gene expression in erythroid progenitors and how it leads to a block in erythrocyte maturation. To decipher the extent of Dnmt3a or p53's involvement in the observed phenotypes, we have generated double knockout mouse models that are being analyzed. Mechanistically, p53 has been shown to be directly methylated by Prmt5, a modification that affects its tumor suppressor activity. Here we have found that Dnmt3a is also a substrate of Prmt5 and the effects of the di methylation of Dnmt3a on its function are currently under investigation. Thus, we have uncovered a potential functional interaction between DNA methylation and protein arginine methylation triggered by Prmt5 that regulates primitive erythropoiesis.