Project description:During embryogenesis, haematopoietic and endothelial lineages emerge closely in time and space. It is thought that the first blood and endothelium derive from a common clonal ancestor, the haemangioblast. However, investigation of candidate haemangioblasts in vitro has revealed a mesenchymal differentiation potential, a feature more compatible with an earlier mesodermal precursor. To date, no evidence for an in vivo haemangioblast has been discovered. Using single cell RNA-Sequencing and in vivo cellular barcoding, we have unraveled the ancestral relationships that give rise to the haematopoietic lineages of the yolk sac, the endothelium, and the mesenchyme. We show that the mesodermal derivatives of the yolk sac are produced by three distinct bipotential precursors: the haemangioblast, mesenchymoangioblast, and a novel cell type: the haematomesoblast. Between E6.5 and E7.5, this trio of precursors seeds haematopoietic, endothelial, and mesenchymal trajectories.
Project description:We establish an experimental and bioinformatic pipeline using 3SEQ to quantitatively measure mRNA expression and reliably determine 3' end formation by sequencing polyadenylated transcripts. When applied to purified mouse embryonic skin stem cells direct differentiation lineages, we identify 15,651 UTRs representing 10,442 distinct mRNAs that are abundantly expressed in the skin. We determine that ~80% of UTRs are formed by using canonical A[A/U]UAAA polyadenylation signals, whereas ~20% of UTRs utilize alternative signals. We demonstrate that comparing with qPCR, our RNA-Seq approach can precisely measure mRNA fold-change and accurately determine the expression of mRNAs over four orders of magnitude. We also reported 453 out of 10,442 genes (4.3%) show differential 3' end usage between skin stem cells and their direct differentiation lineages. Among them, core components of the miRNA pathway, including Dicer, Dgcr8, Xpo5 and Ago2, show dynamic 3' UTR formation patterns, indicating a self-regulatory mechanism. Together, our quantitative analysis reveals a dynamic picture of mRNA 3' end formation in closely related somatic stem cell lineages. Perform 3SEQ in E14 epidermal basal cells and E14 epidermal suprabasal cells.
Project description:Low copy number plasmids must encode maintenance mechanisms, such as partitioning systems, to ensure that the plasmid is sustained through host generations. Plasmid partition systems segregate sister plasmid copies and are subdivided into different types based on the NTPase they encode. The characterisation and distribution of partition system types is well understood in Enterobacteriaceae plasmids. However, how these systems maintain plasmids and are distributed across wider bacterial diversity is poorly understood. We searched a large and diverse plasmid database to identify the distribution of partition system types and found that plasmids encoding multiple partition systems are more widespread than previously realised, composing ~19% of all plasmids predicted to encode partition systems. Many of these plasmids were predicted to encode multiple partition systems of the same type, which had never been studied previously. We used the Streptomyces coelicolor A3(2) plasmid SCP1, which encodes two type Ia partition systems, as a model to investigate this. Sequence analysis of the SCP1 partition systems revealed that both ParB proteins contain less conserved CTP-binding pockets, suggesting one or both proteins may not behave like canonical ParB proteins. However, using a combination of chromatin immunoprecipitation with deep sequencing (ChIP-seq), biochemistry and mutagenesis we show that both ParB proteins behave like bone fide ParB proteins: they bound to distinct parS sites on SCP1, both proteins bound and hydrolysed CTP and both proteins required CTP and their cognate parS site to accumulate, or spread, on DNA. Intriguingly, however, only ParB1 was critical for SCP1 stability. Together, our findings further our understanding of Streptomyces plasmid maintenance by providing the first functional characterisation of two type Ia partition systems coexisting on a single plasmid and offer new insights into the diversity and distribution of plasmid partition systems.
Project description:Low copy number plasmids must encode maintenance mechanisms, such as partitioning systems, to ensure that the plasmid is sustained through host generations. Plasmid partition systems segregate sister plasmid copies and are subdivided into different types based on the NTPase they encode. The characterisation and distribution of partition system types is well understood in Enterobacteriaceae plasmids. However, how these systems maintain plasmids and are distributed across wider bacterial diversity is poorly understood. We used the Streptomyces coelicolor A3(2) plasmid SCP1, which encodes two type Ia partition systems, as a model to investigate this. Sequence analysis of the SCP1 partition systems revealed that both ParB proteins contain less conserved CTP-binding pockets, suggesting one or both proteins may not behave like canonical ParB proteins. However, using a combination of chromatin immunoprecipitation with deep sequencing (ChIP-seq) we demonstrate that both the SCP1 ParB proteins, ParB1 and ParB2, bound to distinct parS sites on SCP1, and accumulate, or spread, on DNA approximately 20 kb away from their initial parS loading site. Together, our findings further our understanding of Streptomyces plasmid maintenance by providing the first functional characterisation of two type Ia partition systems coexisting on a single plasmid and offer new insights into the diversity and distribution of plasmid partition systems.
Project description:We identify distinct murine brown adipocytes lineages using bioinformatics analysis of gene expression profiles generated by RNAseq. Further comparison with established-database for human and mouse brown fat genes enables us to sort and determine three genes to distinguish different lineages.