Project description:Sexual dimorphism can evolve through sex-specific regulation of the same gene set. However, sex chromosomes can also facilitate this by directly linking gene expression to sex. Moreover, heteromorphic sex chromosomes often exhibit different gene content, which contributes to sexual dimorphism. Understanding patterns of sex-biased gene expression across organisms is important for gaining insight about the evolution of sexual dimorphism and sex chromosomes. Moreover, studying gene expression in species with recently established sex chromosomes can help understand the evolutionary dynamics of gene loss and dosage compensation. The threespine stickleback is known for its strong sexual dimorphism, especially during the reproductive period. Sex is determined by a young XY sex chromosome pair with three non-recombining regions that have started to degenerate. Using the high multiplexing capability of 3′ QuantSeq to sequence the sex-biased transcriptome of liver, gills and brain, we provide the first characterization of sex-specific transcriptomes from ~80 stickleback (40 males and 40 females) collected from a natural population during the reproductive period. We find that the liver is extremely differentiated (36% of autosomal genes) and reflects ongoing reproduction, while the brain shows very low levels of differentiation (0.78%) with no particular functional enrichment. Finally, the gills exhibit high levels of differentiation (5%), suggesting that sex should be considered in physiological and ecotoxicological studies of gill responses in fishes. We also find that sex-biased gene expression in X-linked genes is mainly driven by a lack of dosage compensation. However, sex-biased expression of genes that have conserved copies on both sex chromosomes is likely driven by the degeneration of Y allele expression and a down-regulation of male-beneficial mutations on the X chromosome.
Project description:Environmental sex determination (ESD) occurs in divergent, phylogenetically unrelated taxa, and in some species co-occurs with genetic sex determination (GSD) mechanisms. Although epigenetic regulation in response to environmental effects has long been proposed to be associated with ESD, a systemic analysis on epigenetic regulation of ESD is still lacking. Using half-smooth tongue sole (Cynoglossus semilaevis) as a model – a marine fish which has both ZW chromosomal GSD and temperature-dependent ESD – we investigated the role of DNA methylation in transition from GSD to ESD by comparing gonadal DNA methylomes of parental females, parental pseudo-males, F1 females, F1 pseudo-males and normal males. To assess the gonadal DNA methylome patterns across different sexual types of tongue sole, we carried out BS-seq on bisulfite converted DNA extracted from adult gonads of parental females, parental pseudo-males, and F1 pseudo-males and females from a cross between a parental pseudo-male and a normal female. We also sampled normal male individuals as a control for the normal male DNA methylation pattern. For each of the five samples, two biological replicates were utilized, with each replicate being pooled by five fish. The phenotype and genotype of each selected fish was identified by the histological analysis and PCR validation using the W chromosome specific marker. DNA were isolated from five pooled gonads of the same replicate, then 5 ?g DNA was used to do the bisulfite conversion and BS-seq. The bisulfite conversion of sample DNA was carried out using a modified NH4HSO3-based protocol (Hayatsu et al. 2006). The paired-end library construction and sequencing were carried out using Illumina HiSeq 2000, according to the manufacturer’s instructions (Illumina). We also mixed 25 ng cl857 Sam7 Lambda DNA in each sample to use as conversion quality control for each library.
Project description:Sexual dimorphism in mammals is mostly attributable to sex-related hormonal differences in fetal and adult tissues; however, this may not be the sole determinant. Though genetically-identical for autosomal chromosomes, male and female preimplantation embryos could display sex-specific transcriptional regulation which can only be attributted to the differences in sexual chromosome dosage. We used microarrays to analyze sex-related transcriptional differences at the blastocyst stage.
Project description:Environmental sex determination (ESD) occurs in divergent, phylogenetically unrelated taxa, and in some species co-occurs with genetic sex determination (GSD) mechanisms. Although epigenetic regulation in response to environmental effects has long been proposed to be associated with ESD, a systemic analysis on epigenetic regulation of ESD is still lacking. Using half-smooth tongue sole (Cynoglossus semilaevis) as a model – a marine fish which has both ZW chromosomal GSD and temperature-dependent ESD – we investigated the role of DNA methylation in transition from GSD to ESD by comparing gonadal DNA methylomes of parental females, parental pseudo-males, F1 females, F1 pseudo-males and normal males.
Project description:Sexual dimorphism of the skeleton is well documented. At maturity, the male skeleton is typically larger and has a higher bone density than the female skeleton. However, the underlying mechanisms for these differences are not completely understood. In this study, we examined sexual dimorphism in the formation of osteoclasts between cells from female and male mice. We found that the number of osteoclasts in bones was greater in females. Similarly, in vitro osteoclast differentiation was accelerated in female osteoclast precursor (OCP) cells. To further characterize sex differences between female and male osteoclasts, we performed gene expression profiling of cultured, highly purified, murine bone marrow OCPs that had been treated for 3 days with M-CSF and RANKL. We found that 125 genes were differentially regulated in a sex-dependent manner. In addition to genes that are contained on sex chromosomes, transcriptional sexual dimorphism was found to be mediated by genes involved in innate immune and inflammatory response pathways. Furthermore, the NFκB-NFATc1 axis was activated earlier in female early osteoclasts, which partially explains the differences in transcriptomic sexual-dimorphism in these cells. Collectively, these findings identify a sex-dependent intrinsic difference in early osteoclasts, which results from an altered response to osteoclastogenic stimulation. In humans these differences could contribute to the lower peak bone mass and increased risk of osteoporosis that females demonstrate relative to males.
Project description:Sexual dimorphism in mammals is mostly attributable to sex-related hormonal differences in fetal and adult tissues; however, this may not be the sole determinant. Though genetically-identical for autosomal chromosomes, male and female preimplantation embryos could display sex-specific transcriptional regulation which can only be attributted to the differences in sexual chromosome dosage. We used microarrays to analyze sex-related transcriptional differences at the blastocyst stage. Day 7 bovine in vitro produced bovine blastocysts produced with sorted semen from 3 different bulls. Pooled RNA from 60 blastocysts of one sex and produced with one bull was used per chip. Three replicates of each sex per bull. In total, 18 Bovine GeneChip (Affymetrix) were used (3 replicates X 3 bulls X 2 sexes).
Project description:Due to its hemizygous mode of inheritance and role in sex determination, the X chromosome is expected to play an important role in the evolution of sexual dimorphism, and to be enriched for sexually antagonistic genetic variation. By forcing the X chromosome to only be expressed in males over many generations, we changed the selection pressures on the X to become similar to those experienced by the Y chromosome. This releases the X from any constraints arising from selection in females, and is predicted to lead to specialization for male fitness, including masculinization of phenotypes that normally experience sexually antagonistic selection. Indeed, we found evidence of this via upregulation of male-benefit sexually antagonistic genes, and downregulation of X-linked female benefit genes. Interestingly, we could detect evidence of microevolutionary changes consistent with previously documented patterns of macroevolutionary change, such as changes in expression consistent with previously established patterns of sexual dimorphism, an increase in the expression of metabolic genes related to mitonuclear conflict, and evidence that dosage compensation constitutes a constraint for male-benefit genes. These results confirm the importance of the X in the evolution of sexual dimorphism and as a source for sexually antagonistic genetic variation, and demonstrate that experimental evolution can be a fruitful method for testing theories of sex chromosome evolution. Microarray data was used to detect differences in gene expression as result of experimental evolution.