Project description:Sex chromosomes evolved many times independently in many different organisms. According to the currently accepted model, X- and Y-chromosomes evolve from a pair of autosomes via a series of inversions leading to step-wise expansion of a non-recombining region on the Y chromosome (NRY) and the consequential degeneration of genes trapped in the NRY. Our results suggest that plants represent an exception to this rule due to their unique life-cycle that includes alteration of diploid and haploid generations and widespread haploid expression of genes in plant gametophytes. Using a new high-throughput approach we identified over 400 new genes expressed from X- and Y- chromosomes in Silene latifolia, a plant that evolved sex chromosomes about 10 million years ago. Y-linked genes show faster accumulation of amino-acid replacements and loss of expression, compared to X-linked genes. These degenerative processes are significantly less pronounced in more constrained genes and genes that are likely exposed to haploid-phase selection. This may explain why plants retain hundreds of expressed Y-linked genes despite millions of years of Y-chromosome degeneration, while animal Y-chromosomes are almost completely degenerate.
Project description:Sperm are highly differentiated and the activities that reprogram them for embryonic development during fertilization have historically been considered unique to the oocyte. We here challenge this view and demonstrate that mouse embryos in the mitotic cell cycle can also directly reprogram sperm for full term development. Developmentally incompetent haploid embryos (parthenogenotes) injected with sperm developed to produce healthy offspring at up to 24% of control rates, depending when in the embryonic cell cycle injection took place. This implies that most of the first embryonic cell cycle can be bypassed in sperm genome reprogramming for full development. Remodeling of histones and genomic 5'- methylcytosine and 5'-hydroxymethylcytosine following embryo injection were distinct from remodeling in fertilization and the resulting 2-cell embryos consistently possessed abnormal transcriptomes. These studies demonstrate plasticity in the reprogramming of terminally differentiated sperm nuclei and suggest that different epigenetic pathways or kinetics can establish totipotency. phICSI vs ICSI
Project description:Sex chromosomes evolved many times independently in many different organisms. According to the currently accepted model, X- and Y-chromosomes evolve from a pair of autosomes via a series of inversions leading to step-wise expansion of a non-recombining region on the Y chromosome (NRY) and the consequential degeneration of genes trapped in the NRY. Our results suggest that plants represent an exception to this rule due to their unique life-cycle that includes alteration of diploid and haploid generations and widespread haploid expression of genes in plant gametophytes. Using a new high-throughput approach we identified over 400 new genes expressed from X- and Y- chromosomes in Silene latifolia, a plant that evolved sex chromosomes about 10 million years ago. Y-linked genes show faster accumulation of amino-acid replacements and loss of expression, compared to X-linked genes. These degenerative processes are significantly less pronounced in more constrained genes and genes that are likely exposed to haploid-phase selection. This may explain why plants retain hundreds of expressed Y-linked genes despite millions of years of Y-chromosome degeneration, while animal Y-chromosomes are almost completely degenerate. We used a combination of Illumina sequencing of cDNA (RNAseq) and segregation analysis of SNPs identified from RNAseq to identify sex-linked genes in plant Silene latifolia. The experiment involved RNAseq from male and female parents and F1 progeny for two genetic crosses. We submit raw data in fastq format for 11 samples. Four of these samples are single end Solexa reads (a single file per sample) and seven samples were sequenced with paired end Solexa sequencing (two fastq files per sample) - 18 files in total.
Project description:Sperm are highly differentiated and the activities that reprogram them for embryonic development during fertilization have historically been considered unique to the oocyte. We here challenge this view and demonstrate that mouse embryos in the mitotic cell cycle can also directly reprogram sperm for full term development. Developmentally incompetent haploid embryos (parthenogenotes) injected with sperm developed to produce healthy offspring at up to 24% of control rates, depending when in the embryonic cell cycle injection took place. This implies that most of the first embryonic cell cycle can be bypassed in sperm genome reprogramming for full development. Remodeling of histones and genomic 5'- methylcytosine and 5'-hydroxymethylcytosine following embryo injection were distinct from remodeling in fertilization and the resulting 2-cell embryos consistently possessed abnormal transcriptomes. These studies demonstrate plasticity in the reprogramming of terminally differentiated sperm nuclei and suggest that different epigenetic pathways or kinetics can establish totipotency.
Project description:Cancer incidence increases in the elderly, although the underlying reasons for this association are unknown. We show that B-progenitors in old mice exhibit profound signaling and metabolic defects, and that expression of BCR-ABL, NRASV12 and MYC reverses these fitness defects, leading to selection of oncogenically-initiated cells and leukemogenesis in old hematopoietic backgrounds. Aging is associated with increased inflammation in the BM microenvironment, and inducing inflammation in young mice phenocopies aging B-lymphopoiesis. Importantly, reducing inflammation in aged mice preserves the function of B-progenitors and prevents NRasV12-mediated oncogenesis. We conclude that chronic microenvironments in old age lead to reductions in the fitness of hematopoietic stem and progenitor cell populations. This reduced progenitor pool fitness leads to selection for cells harboring oncogenic mutations in part due to their ability to correct aging-associated functional defects. Aging B-lymphopoiesis is accompanied by significant reductions in purine and pyrimidine metabolism. Microarray experiment results also indicated that mitochondrial dysfunction accompanied aging B-lymphopoiesis.
Project description:Mammalian haploid embryonic stem cells (haESCs) provide new possibilities for large-scale genetic screens because they bear only one copy of each chromosome. However, haESCs are prone to spontaneous diploidization through unknown mechanisms. Here, we report that a small molecule combination could restrain mouse haESCs from diploidization by impeding exit from naïve pluripotency and by shortening the S-G2/M phases. Combined with 2i and PD166285, our chemical cocktail could maintain haESCs in the haploid state for at least five weeks without fluorescence-activated cell sorting (FACS) enrichment of haploid cells. Taken together, we established an effective chemical approach for long-term maintenance of haESCs, and highlighted that proper cell cycle progression was critical for the maintenance of haploid state.
Project description:Diploid and haploid strains often exhibit different tolerance to variety of stresses. Transcriptome of acclimation to ethanol stress in diploid and haploid strain of Saccharomyces cerevisiae was analyzed. We analyzed transcriptome profiles of diploid and haploid strains in the presence of ethanol.
Project description:Haploid pluripotent stem cells, such as haploid embryonic stem cells (haESCs), facilitate the genetic study of recessive traits. In vitro, fish haESCs maintain haploidy in both undifferentiated and differentiated states, but whether mammalian haESCs can preserve pluripotency in the haploid state has not been tested. Here, we report that mouse haESCs can differentiate in vitro into haploid epiblast stem cells (haEpiSCs), which maintain an intact haploid genome, unlimited self-renewal potential, and durable pluripotency to differentiate into various tissues in vitro and in vivo. Mechanistically, the maintenance of self-renewal potential depends on the Activin/bFGF pathway. We further show that haEpiSCs can differentiate in vitro into haploid progenitor-like cells.