Open Access Embargo
Date of Award
Molecular Biology and Genetics
Stephen A. Krawetz
Periconceptional environment, according to the Developmental Origins of Health and Disease (DOHaD) theory, influences offspring phenotype, primarily via epigenetic mechanisms. Although the paternal component in humans is poorly understood, both maternal and paternal peri-conceptional environment are now believed to contribute to this phenomenon. Manipulation of the early embryo for treating human infertility, is suspected of contributing to offspring abnormalities through epigenetic mechanisms. To directly address the effects of common assisted reproductive technology procedures on the offspring epigenome, the DNA methylation profiles of newborns conceived naturally, or through the use of intrauterine insemination (IUI), or in vitro fertilization (IVF) using Fresh or Cryopreserved (Frozen) embryo transfer, were compared. In addition to a reduction of epigenetic aberrations in the IVF conceptions using cryopreservation, metastable epialleles also exhibited altered methylation with fertility status. ART, embryo nutrition, and fertility status are thus suggested to have a lasting epigenetic effect of on the developing embryo. While the paternal contribution to the human embryo is uncertain, sperm deliver a collection of proteins and RNA to the zygote. To identify the entire cadre of intergenic spermatozoal RNAs, RNA Element (RE) discovery algorithm (REDa) was developed and applied to a spectrum of germline, embryonic, and somatic tissues. This highlighted extensive transcription throughout the human genome and yielded previously unidentified human RNAs. Human spermatogenesis was found to exhibit extensive intergenic transcription and pervasive repetitive sequence expression. By analyzing the collection of novel and annotated spermatozoal RNAs in sperm samples from the Mesalamine and Reproductive Health Study (MARS), the effect of endocrine disruptor exposure on human sperm RNA profiles was determined. Sperm RNA profiles among men and their relationship to di-butyl phthalate (DBP) was longitudinally assessed across binary (high or background) DBP crossover exposures. Numerous changes in the composition of sperm RNA elements were detected during the acute and recovery phases, which suggest that exposure to, or removal from high DBP, produces effects that require longer than one spermatogenic cycle to resolve, if at all. Overall, chronic phthalate exposure influences the male germline, and acts on the dynamic RNA expression during human spermiogenesis.
Estill, Molly, "Defining The Effect Of Environmental Perturbation On The Male Germline" (2019). Wayne State University Dissertations. 2238.
Available for download on Tuesday, August 31, 2021