We are interested in understanding how the epigenome is established during human development and stem cell differentiation, and how epigenetic information changes over the life course of a person.
To research these topics, we use different types of stem cell (primarily human pluripotent stem cells), stem cell-based embryo models (blastoids and gastruloids), and donated human embryos, in combination with a variety of molecular and genetic approaches to investigate their epigenomes.
This research is important because establishing our epigenomes correctly during development is vital for establishing a healthy pregnancy, and has long lasting consequences on our health. We therefore need to know more about how it happens and why it sometimes goes wrong. Our work also provides new avenues for improving the epigenetic stability of human pluripotent stem cells, and our ability to drive their specialisation towards useful cell types, which are essential requirements to fulfill their promise in regenerative medicine.
Chinese hamster ovary (CHO) cells are the leading mammalian system for recombinant therapeutic protein production. However, optimizing transgene expression remains challenging due to the limited understanding of the regulatory mechanisms controlling gene expression in CHO cells. Towards overcoming this barrier, here we provide a systematic characterization of cis-regulatory elements in CHO cells. Using genome-wide STARR-seq, a high-throughput method for quantifying enhancer strength, we identified regions with enhancer activity in the CHO cell genome. By integrating these data with ATAC-seq and histone modification profiles, we were able to characterize the chromatin state of these regions. Our analysis revealed thousands of newly identified enhancer sequences. The most active sequences could drive transgene expression at levels similar to or higher than strong viral enhancers. Notably, half of the regions found to have enhancer activity were within inaccessible chromatin in their native context. We observed that accessible enhancers were primarily near to transcriptional start sites and associated with ubiquitously-expressed genes, whereas inaccessible enhancers were predominantly intergenic and associated with tissue-specific genes. Additionally, through a deep-learning-based approach ETS and YY1 transcription factor (TF) binding motifs were identified as key determinants of enhancer identity and strength. Disrupting YY1 binding motifs led to reduced enhancer activity, thereby highlighting the importance of YY1 as a transcriptional activator in CHO cells. Our study demonstrates the first comprehensive map of functionally-validated enhancers in CHO cells and generates new insights into gene regulation and the role of TFs in determining enhancer strength. This study helps to lay the foundation for strategic engineering of CHO cell transcriptional networks to achieve enhanced biopharmaceutical production.
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.
Human stem cell-based embryo models (SCBEMs) are a research technology with the potential to facilitate our understanding of human embryogenesis, improve assisted reproductive technology outcomes, elucidate the causes of early pregnancy failure, and provide a clearer understanding of the developmental origins of disease. Given that human SCBEMs are designed to model specific phenotypic features and developmental processes of human embryos, they raise distinct concerns from other stem cell models, such as organoids. The International Society for Stem Cell 51在线 (ISSCR) Guidelines for Stem Cell 51在线 and Clinical Translation, published in 2021, made recommendations for research oversight of SCBEMs and established different categories of review based on involvement of embryonic and extraembryonic lineages. However, recent progress has enabled unexpected ways to create increasingly complex models, as well as more efficient means of doing so without including all major extraembryonic lineages. A working group was tasked by the ISSCR executive to undertake a thorough reexamination of the guidelines in the light of these advances. The three main recommendations of the working group are that all research involving organized 3-dimensional human SCBEMs (1) should be subject to appropriate review, (2) must have a clear scientific rationale, and (3) must be subject to limited timelines. The proposed modifications to the ISSCR guidelines are intended to bring more clarity to the field, help guide the deliberations of researchers, oversight committees and other relevant stakeholders, and ensure continued public confidence.