Chromatin remodeling in early embryogenesis
Abstract
The development of a live organism is a tightly regulated process. During the first phase of development, two specialized cells (the gametes) undergo a dramatic re-arrangement of their genetic material in order to form the zygote. The zygotic genome is considered totipotent, that is, totally unrestricted in its developmental potential. Such a peculiar state is attained through a process called epigenetic reprogramming. The epigenetic settings of the parental genome are remodeled to acquire totipotency. Epigenetic reprogramming is achieved by means of covalent chemical modification at the chromatin level, including histone tail modifications and DNA methylation. Another method by which epigenetic reprogramming is accomplished includes non covalent remodeling of the chromatin architecture. The basic unit of chromatin is the nucleosome; the nucleosome is constituted by 146 base pairs of DNA wrapped around an octamer of histone proteins. Eukaryotic cells possess a family of remodeling complexes that are able to actively reassemble the nucleosome onto the DNA template; these are called the SNF2-type ATP dependent chromatin remodeling complexes. These ATP-dependent chromatin remodeling complexes contain an ATPase subunit that belongs to the SNF2 superfamily. Relatively little is known about the role of these complexes during early embryonic development. The objective of this dissertation was to investigate the role played by SNF2-type ATP dependent chromatin remodeling complexes in nuclear reprogramming during porcine cleavage development. The purpose of this dissertation was also to test the hypothesis that mis-regulation of ATP dependent chromatin remodeling enzymes may be detrimental for correct embryogenesis. We tested our hypothesis via mis-regulation of SNF2-type chromatin remodeling ATPases brahma and Brg1. We showed that altering the transcript levels of brahma and Brg1 resulted in impaired embryonic development. Moreover we characterized how mis-regulation of brahma and Brg1 has a deep impact on the expression pattern of key developmental genes. We also linked SNF2-type chromatin remodeling to epigenetic reprogramming following somatic cell nuclear transfer (SCNT). Our results showed possible beneficial applications for manipulation of the SNF2-type chromatin remodeling repertoire prior to SCNT.
Degree
Ph.D.
Advisors
Cabot, Purdue University.
Subject Area
Molecular biology|Animal Physiology
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