Project description:Despite sharing much of their genomes, males and females are often highly dimorphic, reflecting at least in part the resolution of sexual conflict in response to sexually antagonistic selection. Sexual dimorphism arises owing to sex differences in gene expression, and steroid hormones are often invoked as a proximate cause of sexual dimorphism. Experimental elevation of androgens can lead to masculinization of behavior, physiology, and gene expression, but knowledge of the role of hormones remains incomplete, including how the sexes differ in their gene expression in response to exposure to hormones. We addressed these questions in a bird species with a long history of behavioral endocrinological and ecological study, the dark-eyed junco (Junco hyemalis), using a species-specific microarray. Focusing on two brain regions involved in sexually dimorphic behavior and regulation of hormone secretion, we identified 1,639 genes that differed in expression by sex in the ventromedial telencephalon and 768 in hypothalamus. In response to experimentally elevated testosterone, females exhibited a more “male-like” expression pattern than control females; unexpectedly, male expression patterns became more “female-like” rather than hyper-masculinized when compared to control males. This sex difference in pattern arose both because testosterone altered regulation of different genes in each sex and because testosterone altered regulation of the same genes differentially, i.e., up in one sex, down in the other. Hormonally regulated gene expression is a key genetic and physiological mechanism underlying sexual dimorphism, and further study should help to explain how it relates to the resolution of sexual conflict. Hypothalamus: 24 samples were analyzed, all were biological (not technical) replicates. 6 from males treated with testosterone [MT], 6 from control males [MC], 6 from females treated with testosterone [FT], and 6 from control females [FC]. All hybridizations were paired, and all treatment groups were compared, but no sample was analyzed more than once. Ventromedial telencephalon: 24 samples were analyzed, all were biological (not technical) replicates. 6 from males treated with testosterone [MT], 6 from control males [MC], 6 from females treated with testosterone [FT], and 6 from control females [FC]. All hybridizations were paired, and all treatment groups were compared, but no sample was analyzed more than once.

Project description:Purpose: In all vertebrates, the thymus is necessary and sufficient for production of classic adaptive T cells. The key components of the thymus are cortical and medullary thymic epithelial cells (cTECs and mTECs). Despite the capital role of TECs, our understanding of TEC biology is quite rudimentary. For instance, we ignore what might be the extent of divergence in the functional program of these two TECs populations. It also remains unclear why the number of TECs decreases rapidly with age, thereby leading to progressive thymic insufficiency. Methods: Systems level understanding of cell function begins with gene expression profiling, and the transcriptome is currently the only '-ome' that can be reliably tackled in its entirety in freshly harvested primary cells. In order to gain novel insights into TEC biology, we therefore decided to analyse the whole transcriptome of cTECs, mTECs and skin epithelial cells. We elected to analyse gene expression using RNA-seq rather microarrays because RNA-seq has higher sensitivity and dynamic range coupled to lower technical variations. Results: Our deep sequencing approach provides a unique perspective into the transcriptome of TECs. Consistent with their ability to express ectopic genes, we found that mTECs expressed more genes than other cell populations. Out of a total of 15,069 genes expressed in TECs, 25% were differentially expressed by at least 5-fold in cTECs vs. mTECs. Genes expressed at higher levels in cTECs than mTECs regulate numerous cell functions including cell differentiation, cell movement and microtubule dynamics. Almost all positive regulators of the cell cycle were overexpressed in skin ECs relative to TECs. Conclusions: Our RNA-seq data provide novel insights into the transcriptional landscape of TECs, highlight substantial divergences in the transcriptome of TEC subsets and suggest that cell cycle progression is differentially regulated in TECS and skinECs. We believe that our work will therefore represent a valuable resource and will be of great interest to readers working in biological sciences, particularly in the areas of immunology and systems biology. The mRNA profiles of cTEC, mTEC (from 14 thymi of 7-days old C57BL/6 mice) and skinEC (from the trunk and dorsum of seven newborn mice) were generated by RNA-sequencing using Illumina HiSeq2000.

Project description:Purpose: In all vertebrates, the thymus is necessary and sufficient for production of classic adaptive T cells. The key components of the thymus are cortical and medullary thymic epithelial cells (cTECs and mTECs). Despite the capital role of TECs, our understanding of TEC biology is quite rudimentary. For instance, we ignore what might be the extent of divergence in the functional program of these two TECs populations. It also remains unclear why the number of TECs decreases rapidly with age, thereby leading to progressive thymic insufficiency. Methods: Systems level understanding of cell function begins with gene expression profiling, and the transcriptome is currently the only '-ome' that can be reliably tackled in its entirety in freshly harvested primary cells. In order to gain novel insights into TEC biology, we therefore decided to analyse the whole transcriptome of cTECs, mTECs and skin epithelial cells. We elected to analyse gene expression using RNA-seq rather microarrays because RNA-seq has higher sensitivity and dynamic range coupled to lower technical variations. Results: Our deep sequencing approach provides a unique perspective into the transcriptome of TECs. Consistent with their ability to express ectopic genes, we found that mTECs expressed more genes than other cell populations. Out of a total of 15,069 genes expressed in TECs, 25% were differentially expressed by at least 5-fold in cTECs vs. mTECs. Genes expressed at higher levels in cTECs than mTECs regulate numerous cell functions including cell differentiation, cell movement and microtubule dynamics. Almost all positive regulators of the cell cycle were overexpressed in skin ECs relative to TECs. Conclusions: Our RNA-seq data provide novel insights into the transcriptional landscape of TECs, highlight substantial divergences in the transcriptome of TEC subsets and suggest that cell cycle progression is differentially regulated in TECS and skinECs. We believe that our work will therefore represent a valuable resource and will be of great interest to readers working in biological sciences, particularly in the areas of immunology and systems biology.

Project description:Despite sharing much of their genomes, males and females are often highly dimorphic, reflecting at least in part the resolution of sexual conflict in response to sexually antagonistic selection. Sexual dimorphism arises owing to sex differences in gene expression, and steroid hormones are often invoked as a proximate cause of sexual dimorphism. Experimental elevation of androgens can lead to masculinization of behavior, physiology, and gene expression, but knowledge of the role of hormones remains incomplete, including how the sexes differ in their gene expression in response to exposure to hormones. We addressed these questions in a bird species with a long history of behavioral endocrinological and ecological study, the dark-eyed junco (Junco hyemalis), using a species-specific microarray. Focusing on two brain regions involved in sexually dimorphic behavior and regulation of hormone secretion, we identified 1,639 genes that differed in expression by sex in the ventromedial telencephalon and 768 in hypothalamus. In response to experimentally elevated testosterone, females exhibited a more “male-like” expression pattern than control females; unexpectedly, male expression patterns became more “female-like” rather than hyper-masculinized when compared to control males. This sex difference in pattern arose both because testosterone altered regulation of different genes in each sex and because testosterone altered regulation of the same genes differentially, i.e., up in one sex, down in the other. Hormonally regulated gene expression is a key genetic and physiological mechanism underlying sexual dimorphism, and further study should help to explain how it relates to the resolution of sexual conflict. Males and females can be highly dimorphic in metabolism and physiology despite sharing nearly identical genomes, and males and females both respond phenotypically to elevated testosterone, a steroid hormone that alters gene expression. Only recently has it become possible to learn how a hormone like testosterone affects global gene expression in non-model systems, and whether it affects the same genes in males and females. To investigate the transcriptional mechanisms by which testosterone exerts its metabolic and physiological effects on the periphery, we compared gene expression by sex and in response to experimentally elevated testosterone in a well-studied bird species, the dark-eyed junco (Junco hyemalis). We identified 324 genes in the liver, and 733 in the pectoralis muscle that were differentially expressed between males and females. In addition, we identified 1,872 genes that were differentially expressed between testosterone-treated and control individuals in at least one tissue and sex. Testosterone-treatment altered the expression of only130 genes in both males and females in the same tissue. These substantial differences in transcriptional response to testosterone suggest that males and females may employ different pathways when responding to elevated testosterone, despite the fact that many phenotypic effects of experimentally elevated testosterone are similar in the sexes. In contrast, of the 130 genes that were affected by testosterone-treatment in both sexes, 78% were regulated in the same direction (e.g. either higher or lower in testosterone-treated than control males and females). Thus, it appears that testosterone acts through both unique and shared transcriptional pathways in males and females, suggesting multiple mechanisms by which sexual conflict can be mediated.

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Sex hormones have pervasive effects on thymic epithelial cells

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