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Title: Transcribed germline-limited coding sequences in Oxytricha trifallax
Authors: Miller, Richard Vincent
Advisors: Landweber, Laura F
Contributors: Molecular Biology Department
Keywords: ciliate
DNA copy number
genome rearrangement
Subjects: Molecular biology
Issue Date: 2020
Publisher: Princeton, NJ : Princeton University
Abstract: The germline-soma distinction is a fundamental and recurring theme in developmental biology. The germline and somatic lineages are the first to diverge in multicellular organisms, and the two lineages often express radically different genes with different roles. Some multicellular organisms even encode germline-specific DNA containing germline-limited protein-coding sequences that are expressed during critical periods during the organism’s life. The ciliate Oxytricha trifallax contains germline and somatic genomes in the same cell. Previous research showed that the germline genome of O. trifallax encodes a set of germline-limited protein-coding sequences that are expressed during the organism’s sexual life cycle. I studied the set of germline-limited protein-coding sequences in O. trifallax, which I dubbed “transcribed germline-limited open reading frames (TGLOs). In the second chapter, I specifically focused on TGLO DNA dynamics and expression during genome rearrangement. Like earlier work on germline-limited genes, TGLOs were shown to be transcribed during the organism’s sexual life cycle. Computational and in vivo research showed that TGLOs are progressively eliminated from the developing somatic nucleus during the sexual life cycle. In the third chapter, I used synthetic biology to investigate the RNA-guided pathway that relegates TGLOs to the germline genome. Interestingly, RNA microinjection could program the heritable somatic retention of TGLOs in subsequent generations, and somatically encoded TGLOs were transcribed outside the sexual life cycle. In the final chapter, I uncovered an example of a strain-specific TGLO that is somatically encoded by some progeny after mating to a parent with a low somatic copy level of the strain-specific TGLO. The epigenetic inheritance of this locus offers tantalizing glimpses at how somatic copy number is regulated in O. trifallax. This project enhances our understanding of germline-encoded protein-coding sequences in a unicellular system. Moreover, this unicellular system provides interesting opportunities to study the germline-soma divide.
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Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Molecular Biology

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