Our lab is interested in epigenetic gene regulation in mammalian development and in ageing. Global epigenetic reprogramming occurs at fertilisation and fundamentally remodels the epigenomes of sperm and egg. We are working to understand the mechanisms of reprogramming and also how it may be linked with zygotic genome activation, the sudden transcriptional springing to life of the genome in the early embryo.
Soon after implantation of the embryo in the maternal uterus there is a major programme of cell fate decisions which establishes the three primary germ layers, the ectoderm (which gives rise to brain and skin), the mesoderm (giving rise to muscle and heart), and the endoderm (which gives rise to the gut amongst other tissues).
These three lineages are the foundations of all organs in the adult body and we are interested in the transcriptional and epigenetic events that underlie their emergence from the undifferentiated epiblast. Finally, we are studying how the epigenome degrades during ageing potentially in a programmed fashion, and whether there are approaches by which this degradation can be slowed down or reversed.
The development of complex tissues relies on the precise assignment of cell identity. At the molecular scale, this process depends on the deposition of epigenetic modifications-such as methylation-that are regulated by complex biochemical networks and occur at specific regions on the DNA and chromatin. Here we show that despite the complexity of epigenetic regulation, dynamical scaling and self-similarity of DNA methylation marks emerge in embryonic development. Drawing on single-cell multi-omics experiments, super-resolution microscopy and statistical physics, we demonstrate that these phenomena originate in dynamical feedback between DNA methylation and the formation of nanoscale dynamic chromatin aggregates. These nanoscale processes lead to genome-wide increase in DNA methylation marks following a power law and self-similar correlation functions. Using this framework, we identify methylation patterns that precede gene expression changes in embryonic symmetry breaking. Our work identifies linear sequencing measurements as a laboratory to study mesoscopic biophysical processes in vivo.
Aging is a complex multifactorial process that affects cellular function and tissue homeostasis over time. Despite substantial research, the molecular mechanisms driving cellular aging remain poorly understood. Many studies focused on changes in DNA methylation as an indicator of aging. In particular, methylation at polycomb CpG islands was shown to be predictive of phenotypic changes associated with aging. Since many age-related pathological processes are thought to originate from single cells, we asked whether polycomb CpG island methylation occurs preferentially in a subset of cells within a population. Using single-cell whole-genome methylation data across ages and tissues, we identify polycomb CpG methylation as a hallmark of cellular aging. This revealed that aging occurs at varying rates, with faster proliferating cells showing accelerated gain of methylation. Differential gene expression analysis identified changes in immune response, translation, tumorigenesis and neurodegeneration. These results challenge traditional models of homogeneous cellular aging and suggest that aging is a highly individualized process at the single-cell level, that may be driven by programmed changes in polycomb CpG island DNA methylation.
Profiling combinations of histone modifications identifies gene regulatory elements in different states and discovers features controlling transcriptional and epigenetic programs. However, efforts to map chromatin states in complex, heterogeneous samples are hindered by the lack of methods that can profile multiple histone modifications together with transcriptomes in individual cells. Here, we describe single-cell multitargets and mRNA sequencing (scMTR-seq), a high-throughput method that enables simultaneous profiling of six histone modifications and transcriptome in single cells. We apply scMTR-seq to uncover dynamic and coordinated changes in chromatin states and transcriptomes during human endoderm differentiation. We also use scMTR-seq to produce lineage-resolved chromatin maps and gene regulatory networks in mouse blastocysts, revealing epigenetic asymmetries at gene regulatory regions between the three embryo lineages and identifying Trps1 as a potential repressor in epiblast cells of trophectoderm-associated enhancer networks and their target genes. Together, scMTR-seq enables investigation of combinatorial chromatin landscapes in a broad range of heterogeneous samples, providing insights into epigenetic regulatory systems.