Homeotic and nonhomeotic patterns in the tetrapod vertebral formula.

Vertebrate development and phylogeny are intimately connected through the vertebral formula, the numerical distribution of vertebrae along the body axis into different categories such as neck and chest. A key window into this relationship is through the conserved gene clusters. gene expression boundaries align with vertebral boundaries, and their manipulation in model organisms often results in the transformation of one vertebral type into its neighbor, a homeotic transformation.

CWL-Based Analysis Pipeline for Hi-C Data: From FASTQ Files to Matrices.

Over a decade has passed since the development of the Hi-C method for genome-wide analysis of 3D genome organization. Hi-C utilizes next-generation sequencing (NGS) technology to generate large-scale chromatin interaction data, which has accumulated across a diverse range of species and cell types, particularly in eukaryotes. There is thus a growing need to streamline the process of Hi-C data analysis to utilize these data sets effectively.

Embryonic genome instability upon DNA replication timing program emergence.

Faithful DNA replication is essential for genome integrity. Under-replicated DNA leads to defects in chromosome segregation, which are common during embryogenesis. However, the regulation of DNA replication remains poorly understood in early mammalian embryos.

Structure and dynamics of nuclear A/B compartments and subcompartments.

Mammalian chromosomes form a hierarchical structure within the cell nucleus, from chromatin loops, megabase (Mb)-sized topologically associating domains (TADs) to larger-scale A/B compartments. The molecular basis of the structures of loops and TADs has been actively studied. However, the A and B compartments, which correspond to early-replicating euchromatin and late-replicating heterochromatin, respectively, are still relatively unexplored.

A feedback loop that drives cell death and proliferation and its defect in intestinal stem cells.

Cell death and proliferation are at a glance dichotomic events, but occasionally coupled. Caspases, traditionally known to execute apoptosis, play non-apoptotic roles, but their exact mechanism remains elusive. Here, using intestinal stem cells (ISCs), we discovered that activation of caspases induces massive cell proliferation rather than cell death.

Replication dynamics identifies the folding principles of the inactive X chromosome.

Chromosome-wide late replication is an enigmatic hallmark of the inactive X chromosome (Xi). How it is established and what it represents remains obscure. By single-cell DNA replication sequencing, here we show that the entire Xi is reorganized to replicate rapidly and uniformly in late S-phase during X-chromosome inactivation (XCI), reflecting its relatively uniform structure revealed by 4C-seq.

Cell cycle dynamics and developmental dynamics of the 3D genome: toward linking the two timescales.

In the mammalian cell nucleus, chromosomes are folded differently in interphase and mitosis. Interphase chromosomes are relatively decondensed and display at least two unique layers of higher-order organization: topologically associating domains (TADs) and cell-type-specific A/B compartments, which correlate well with early/late DNA replication timing (RT). In mitosis, these structures rapidly disappear but are gradually reconstructed during G1 phase, coincident with the establishment of the RT program.

Highly rigid H3.1/H3.2-H3K9me3 domains set a barrier for cell fate reprogramming in trophoblast stem cells.

The placenta is a highly evolved, specialized organ in mammals. It differs from other organs in that it functions only for fetal maintenance during gestation. Therefore, there must be intrinsic mechanisms that guarantee its unique functions.

SAF-A promotes origin licensing and replication fork progression to ensure robust DNA replication.

The organisation of chromatin is closely intertwined with biological activities of chromosome domains, including transcription and DNA replication status. Scaffold-attachment factor A (SAF-A), also known as heterogeneous nuclear ribonucleoprotein U (HNRNPU), contributes to the formation of open chromatin structure. Here, we demonstrate that SAF-A promotes the normal progression of DNA replication and enables resumption of replication after inhibition.

Regulation of mammalian 3D genome organization and histone H3K9 dimethylation by H3K9 methyltransferases.

Histone H3 lysine 9 dimethylation (H3K9me2) is a highly conserved silencing epigenetic mark. Chromatin marked with H3K9me2 forms large domains in mammalian cells and overlaps well with lamina-associated domains and the B compartment defined by Hi-C. However, the role of H3K9me2 in 3-dimensional (3D) genome organization remains unclear.

Formation of a multi-layered 3-dimensional structure of the heterochromatin compartment during early mammalian development.

During embryogenesis in mammals, the 3-dimensional (3D) genome organization changes globally in parallel with transcription changes in a cell-type specific manner. This involves the progressive formation of heterochromatin, the best example of which is the inactive X chromosome (Xi) in females, originally discovered as a compact 3D structure at the nuclear periphery known as the Barr body. The heterochromatin formation on the autosomes and the Xi is tightly associated with the differentiation state and the developmental potential of cells, making it an ideal readout of the cellular epigenetic state.

Mapping replication timing domains genome wide in single mammalian cells with single-cell DNA replication sequencing.

Replication timing (RT) domains are stable units of chromosome structure that are regulated in the context of development and disease. Conventional genome-wide RT mapping methods require many S-phase cells for either the effective enrichment of replicating DNA through bromodeoxyuridine (BrdU) immunoprecipitation or the determination of copy-number differences during S-phase, which precludes their application to non-abundant cell types and single cells. Here, we provide a simple, cost-effective, and robust protocol for single-cell DNA replication sequencing (scRepli-seq).

Microrheology for Hi-C Data Reveals the Spectrum of the Dynamic 3D Genome Organization.

The one-dimensional information of genomic DNA is hierarchically packed inside the eukaryotic cell nucleus and organized in a three-dimensional (3D) space. Genome-wide chromosome conformation capture (Hi-C) methods have uncovered the 3D genome organization and revealed multiscale chromatin domains of compartments and topologically associating domains (TADs). Moreover, single-nucleosome live-cell imaging experiments have revealed the dynamic organization of chromatin domains caused by stochastic thermal fluctuations.

Multifaceted Hi-C benchmarking: what makes a difference in chromosome-scale genome scaffolding?

Background: Hi-C is derived from chromosome conformation capture (3C) and targets chromatin contacts on a genomic scale. This method has also been used frequently in scaffolding nucleotide sequences obtained by de novo genome sequencing and assembly, in which the number of resultant sequences rarely converges to the chromosome number. Despite its prevalent use, the sample preparation methods for Hi-C have not been intensively discussed, especially from the standpoint of genome scaffolding.

The Eleanor ncRNAs activate the topological domain of the ESR1 locus to balance against apoptosis.

MCF7 cells acquire estrogen-independent proliferation after long-term estrogen deprivation (LTED), which recapitulates endocrine therapy resistance. LTED cells can become primed for apoptosis, but the underlying mechanism is largely unknown. We previously reported that Eleanor non-coding RNAs (ncRNAs) upregulate the ESR1 gene in LTED cells.

DNA Replication Timing Enters the Single-Cell Era.

In mammalian cells, DNA replication timing is controlled at the level of megabase (Mb)-sized chromosomal domains and correlates well with transcription, chromatin structure, and three-dimensional (3D) genome organization. Because of these properties, DNA replication timing is an excellent entry point to explore genome regulation at various levels and a variety of studies have been carried out over the years. However, DNA replication timing studies traditionally required at least tens of thousands of cells, and it was unclear whether the replication domains detected by cell population analyses were preserved at the single-cell level.

Practical Analysis of Hi-C Data: Generating A/B Compartment Profiles.

Recent advances in next-generation sequencing (NGS) and chromosome conformation capture (3C) analysis have led to the development of Hi-C, a genome-wide version of the 3C method. Hi-C has identified new levels of chromosome organization such as A/B compartments, topologically associating domains (TADs) as well as large megadomains on the inactive X chromosome, while allowing the identification of chromatin loops at the genome scale. Despite its powerfulness, Hi-C data analysis is much more involved compared to conventional NGS applications such as RNA-seq or ChIP-seq and requires many more steps.

Srf destabilizes cellular identity by suppressing cell-type-specific gene expression programs.

Multicellular organisms consist of multiple cell types. The identity of these cells is primarily maintained by cell-type-specific gene expression programs; however, mechanisms that suppress these programs are poorly defined. Here we show that serum response factor (Srf), a transcription factor that is activated by various extracellular stimuli, can repress cell-type-specific genes and promote cellular reprogramming to pluripotency.

Epigenetic differences between naïve and primed pluripotent stem cells.

It has been 8 years since the concept of naïve and primed pluripotent stem cell states was first proposed. Both are states of pluripotency, but exhibit slightly different properties. The naïve state represents the cellular state of the preimplantation mouse blastocyst inner cell mass, while the primed state is representative of the post-implantation epiblast cells.