Gametogenesis (spermatogenesis and oogenesis) is accompanied by the acquisition of gender-specific epigenetic marks, such as DNA methylation and histone modifications to form highly differentiated, but transcriptionally silent cell-types in preparation for fertilization. Upon fertilization, extensive global epigenetic reprogramming takes place to remove the previously acquired epigenetic marks and produce totipotent zygotic states. It has become increasingly evident that sperm carry genetic and epigenetic information to the next generation. It is thus critical to understand the mechanisms underlying both paternal and material inheritance, which is highly relevance to a wide range of genetic diseases in humans. In this K99/R00 application, I propose to systematically attack the problem in the regulation of protamine-to-histone exchange in mammalian zygotes and the role of this transition for zygotic gene activation (ZGA) and intergenerational inheritance. I propose three aims, two of which will be pursued in the K99 phase and the last one will be my goals in the R00 phase: 1. Establish a key role of SRPK1 in regulating the protamine-to-histone transition in fertilized egg. 2. Identify the molecular basis for asymmetric epigenetic reprogramming of paternal and maternal genomes. 3. Determine the contribution of paternal genome epigenetic reprogramming to ZGA and intergenerational inheritance. These three aims take independent, yet intertwined approaches, which are designed to uncover the molecular basis for chromatin dynamics and epigenetic reprogramming in early life. I have been pursuing several related projects as a postdoctoral fellow in Dr. Xiang-Dong Fu?s lab at UCSD, which has led to publication of several impactful papers, including one recently appeared in Cell. Importantly, I have generated a series of unpublished data, showing that the splicing kinase SRPK1 is indeed essential for paternal DNA decondensation in fertilized egg. This has laid a critical foundation for the proposed experiments. The proposed research will greatly benefit from the outstanding research environment on the UCSD campus, particularly from the advisory committee I have assembled. Several committee members will not only mentor my research and career development, but also collaborate with me on the proposed project by providing complementary expertise on embryo manipulation and analysis of epigenetic reprogramming. This mentorship will greatly accelerate my career development towards an independent investigator.
This proposal seeks to uncover the mechanism for a highly specialized chromatin remodeling event (protamine-to-histone transition) prior to zygotic gene activation in fertilized eggs. The proposed project will link the protamine-to-histone transition to the formation of paternal pronucleus and asymmetric epigenetic reprogramming of both paternal and maternal genomes, which will provide key insight into fundamental aspects in reproductive medicine.
