Show simple item record

dc.contributor.authorSugathan, Aarathien_US
dc.date.accessioned2015-09-29T16:01:40Z
dc.date.available2015-09-29T16:01:40Z
dc.date.issued2013
dc.identifier.urihttps://hdl.handle.net/2144/13139
dc.description.abstractSex differences in mammalian gene expression result from differences in genotypic sex as well as in hormonal regulators between males and females. In rat, mouse and human liver, ~1000 genes are expressed in a sex-dependent manner, and contribute to sex differences in metabolism of drugs, steroids and lipids, and in liver and cardiovascular disease risk. In rats and mice, sex-biased liver gene expression is primarily dictated by the sexually dimorphic pattern of pituitary growth hormone (GH) release and its STAT5-dependent transcriptional activities. Studies presented in this thesis include the following. (1) A computational approach based on DNA sequence and phylogenetic conservation was developed and used to identify novel functional STAT5 binding sites - both consensus and non-consensus STAT5 sequences - near prototypic GH-responsive genes. (2) Global gene expression analysis of livers from pituitary-ablated male and female mice identified four major classes of sex-biased genes differing in their profiles of GH dependence. (3) Sex-differences in DNase-hypersensitive sites (DHS, corresponding to open chromatin regions) were identified genome-wide in mouse liver. These sex-differential DHSs were enriched for association with sex-biased genes, but a majority was distant from sex-biased genes. Furthermore, many were responsive to GH treatment, demonstrating that GH-mediated regulation involves chromatin remodeling. Analysis of sequence motifs enriched at sex-biased DHSs implicated STAT5 and novel transcription factors such as PBX1 and TAL1 in sex-biased gene regulation. (4) Genome-wide mapping of histone modifications revealed distinct mechanisms of sex-biased gene regulation in male and female liver: sex-dependent K27me3-mediated repression is an important mechanism of repression of female-biased, but not of male-biased, genes, and a sex-dependent K4me1 distribution, suggesting nucleosome repositioning by pioneer factors, is observed at male-biased, but not female-biased, regulatory sites. STAT5-mediated activation was most strongly associated with sex-biased chromatin modifications, while BCL6-mediated repression primarily occurs in association with sex-independent chromatin modifications, both at binding sites and at target genes. The relationships between sex-dependent chromatin accessibility, chromatin modifications and transcription-factor binding uncovered by these studies help elucidate the molecular mechanisms governing sex-differential gene expression, and underscore the utility of functional genomic and epigenetic studies as tools for elucidating transcriptional regulation in complex mammalian systems.en_US
dc.language.isoen_US
dc.subjectBioinformaticsen_US
dc.subjectChIP-seqen_US
dc.subjectDNase-seqen_US
dc.subjectEpigenomicsen_US
dc.subjectLiver sexual dimorphismen_US
dc.titleRole of growth hormone and chromatin structure in regulation of sex differences in mouse liver gene expressionen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2015-09-23T22:19:26Z
etd.degree.nameDoctor of Philosophyen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplineBioinformaticsen_US
etd.degree.grantorBoston Universityen_US


This item appears in the following Collection(s)

Show simple item record