Doctor of Philosophy (PhD)
Genomic imprinting is a mechanism that targets epigenetic modifications to regulate gene transcription to express a gene from only one of its two parental alleles. Imprinted genes are typically clustered together and are involved in developmental regulation of the fetus. The paternally expressed gene 3 (Peg3) domain represents one such imprinted gene cluster involved in fetal growth regulation and maternal caring behavior. The transcription and imprinting control of the Peg3 domain requires the transcription factor Yin-Yang 1 (YY1), a protein that plays important roles throughout development. The first part of this work explores evidence for the hypothesis that half a dosage of YY1 may be involved in controlling the transcription and imprinting of Peg3 in vivo. The results reveal that Yy1 most likely functions as a transcriptional repressor in this domain. The results also provide new evidence for bi-allelic expression of Peg3 in the mouse brain. Altogether, this indicates that the maternal allele of Peg3 is expressed and functional in specific areas of the brain, including the choroid plexus, paraventricular nucleus (PVN), and the supraoptic nucleus (SON). The observed bi-allelic expression pattern indicates either de-repression of the maternal allele of the known promoter or the presence of alternative promoters for the Peg3 locus. Therefore, the second part of this work demonstrates that several alternative promoters exist for Peg3. The results reveal that these alternative promoters display allele-, tissue-, and developmental stage-specific expression patterns. This suggests that the activity of these alternative promoters have been functionally selected features for the Peg3 imprinted domain during mammalian evolution. The third part of this work develops a novel methodology that detects alternative promoters for Peg3 by incorporating both 5’ rapid amplification of cDNA ends (5’RACE) and next-generation sequencing (NGS) techniques. The results indicate that this NGS-based 5’RACE protocol is a sensitive and reliable method for detecting low-abundant transcripts and promoters. Overall, the research presented in this dissertation advances our understanding of how the YY1 transcription factor is involved in controlling the Peg3 imprinted domain and how alternative promoters may contribute to the allele-, tissue- and developmental stage-specific, Peg3 expression patterns observed in the mouse.
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Perera, Bambarendage Pinithi Upekka, "Yy1 Gene Dosage Effect and Allele-Specific Expression Analysis of Peg3" (2016). LSU Doctoral Dissertations. 3968.