Using PGCLCs as a model system for early germ cell development to characterize the roles of histone marks and their readers in DNA methylation homeostasis and transcriptional regulation

点击翻译按钮获取中文摘要

At a fundamental level, the field of epigenetics involves the study of chemical marks on DNA and the proteins associated with DNA that either promote or inhibit the turning on or off of genes encoded in DNA. One of these marks, which is widely studied in the field, is called "methylation". Our interest is in studying the interplay between the methylation on DNA and the methylation on proteins that interact with DNA, specifically in the cells that give rise to sperm and egg, using the mouse as a model system. So-called "primordial germ cells", the precursors to sperm and egg, emerge in the early embryo, when these epigenetic marks are quite dynamic. Using embryonic stem cells as a starting point and a novel cell culture system that mimics this essential developmental time window, we will specifically study whether disrupting the methylation on DNA-associated proteins via genetic engineering of the enzymes that deposit this mark, or a related set of proteins that recognize such marks in the cell, leads to the aberrant "turning on" of target germ cell genes, and/or parasitic elements, that are normally enriched for these marks in the genome and "turned off". These experiments will shed light on the fundamental role of epigenetic marks in primordial germ cell development as well as the molecular basis of "transgenerational inheritance", a phenomenon whereby changes in the marks on DNA or the proteins associated with DNA unrelated to changes in the sequence of the DNA itself in one generation lead to heritable alterations in the next generation. While the molecular basis of such heritable changes remain largely uncharacterized, they likely are dependent on epigenetic marks, established in the gametes, such as those under study here. As mechanistic studies of such epigenetic phenomena are difficult to study in living animals, given that these cells are present in only small numbers, development and application of a tissue culture model of germ cell development is an essential step in this line of basic research.