Characterizing effects of sperm- and oocyte-derived epigenetic factors on early embryonic gene expression and offspring metabolic function

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PROJECT SUMMARY/ABSTRACT Metabolic diseases such as obesity have become significant health risks affecting one-third of the population worldwide and can have devastating complications. It is therefore imperative to understand the causes of metabolic disease predisposition in order to develop preventative strategies. Extensive genetic studies have failed to explain this ongoing epidemic. However, parents pass on not only genetic information, but also epigenetic factors, which can be modified in response to environmental stimuli, and can then affect gene expression. If information about parental environment can be recorded in the germline, it has the potential to be transmitted to the zygote and impact offspring health. This concept remains controversial in mammals and represents a large knowledge gap in the field of embryology. Previous work in the lab has demonstrated that sperm from fathers fed a low protein diet carry tRNA fragments and microRNAs that can modify gene expression in the embryo. Therefore, in Aim 1, sperm-derived RNAs will be purified and microinjected into parthenogenetically-activated oocytes, or parthenotes, which lack any paternal genetic content. Transcriptomic profiles of injected parthenotes will be acquired by single-embryo RNA-Seq to characterize resulting alterations to the embryonic transcriptome. Maternal transmission of epigenetic information has not been characterized to the same extent as the paternal side. Therefore, in Aim 2 a similar dietary paradigm will be utilized to address the question of whether information about maternal diet can be carried in oocytes and result in changes to the embryonic transcriptome. In vitro-fertilized embryos from mothers fed low protein, high fat, or control diet will be sequenced by single-embryo RNA-Seq. These embryos will be transferred to foster mothers to produce adult offspring, which will then be assessed for glucose tolerance and insulin resistance. The use of in vitro fertilization in this paradigm will ensure that any changes observed in the embryo originate from the oocyte and not from nutrient exchange during gestation. Completion of this research will elucidate effects of paternal and maternal epigenetic factors carried by gametes on the embryonic transcriptome. This work will be completed at the University of Massachusetts Medical School under the sponsorship of Dr. Oliver Rando. The fellowship training plan includes training in embryological techniques, such as microinjection and immunofluorescent staining of lineage markers, as well as metabolic phenotyping of adult mice. Opportunities to gain experience in science communication include participation in departmental seminars and local and national conferences. Furthermore, career development workshops are provided by the university, in addition to teaching and mentoring of first-year graduate students.