Developmental Biology & Disease Mechanisms | Genetics, Epigenetics & Gene Regulation | Nucleus & Chromosome Biology
Transcriptional Regulation during Early Embryonic Development
Every mammal starts out as one cell, the zygote. This cell already carries all the information that is necessary to form a whole individual. However, the actual developmental process occurs one step at a time in a highly reproducible fashion. At any given developmental time point environmental cues such as growth factors induce a response in the cell that depends on the cellular identity. Every cell state reacts differently to the same growth factor since downstream effectors...more
Every mammal starts out as one cell, the zygote. This cell already carries all the information that is necessary to form a whole individual. However, the actual developmental process occurs one step at a time in a highly reproducible fashion. At any given developmental time point environmental cues such as growth factors induce a response in the cell that depends on the cellular identity. Every cell state reacts differently to the same growth factor since downstream effectors of growth factors converge with the existing, cell type specific transcription factor landscape to drive cell type specific gene expression patterns.
But when and how is a cell able to react to specific cues and how is the differentiation set into motion? In order to study these fundamental questions about development we have established and extensively characterized a differentiation strategy based on mouse embryonic stem cells that allows us now to closely follow a cell fate transition in vitro. Using this highly reproducible and dynamic system we can ask how cell fate decisions are driven and manifested during early embryonic development.
We specifically focus on transcriptional enhancer, short stretches of DNA sequences that drive cell type specific gene expression pattern and that integrate cellular identity with growth factor signaling. We have mapped and identified changes in the enhancer landscape during our differentiation strategy and are now dissecting the contributions of single enhancer elements to the activation of a target gene.
The expression of a gene is often regulated by multiple single enhancer element that together form a sometimes called super enhancer. However, it is still unclear what the contributions of each element is to the overall expression of the target gene: are all single elements equally important, are they working additively or can loss of a single element be tolerated? In order to further understand the inner workings of super enhancers we are employing CRISPR/Cas9 to delete, mutate and invert single enhancer elements and study the effect of these changes during differentiation on the expression of a target gene.
Even though most embryonic stem cells will eventually differentiate, the rate at which differentiation is initiated is not the same throughout a population. To determine the causes for these differences we employ a combination of single cell methods such as RNA-FISH, life imaging and single cell ATAC-seq. Understanding why heterogeneity arises during differentiation will guide us to develop cleaner and more efficient differentiation strategies for clinical applications in the future.close
Buecker, Christa; Srinivasan, Rajini; Wu, Zhixiang; Calo, Eliezer; Acampora, Dario; Faial, Tiago; Simeone, Antonio; Tan, Minjia; Swigut, Tomasz; Wysocka, Joanna (2014). Reorganization of enhancer patterns in transition from naive to primed pluripotency. Cell stem cell.;14(6):838-53. PMID: 24905168
Buecker, Christa; Wysocka, Joanna (2012). Enhancers as information integration hubs in development: lessons from genomics. TRENDS GENET;28(6):276-84. PMID: 22487374
Buecker, Christa; Chen, Hsu-Hsin; Polo, Jose Maria; Daheron, Laurence; Bu, Lei; Barakat, Tahsin Stefan; Okwieka, Patricia; Porter, Andrew; Gribnau, Joost; Hochedlinger, Konrad; Geijsen, Niels (2010). A murine ESC-like state facilitates transgenesis and homologous recombination in human pluripotent stem cells. Cell stem cell.;6(6):535-46. PMID: 20569691