In our lab

We are interested in mechanisms of cell fate decisions in the early mouse embryo and their application to the maintenance and differentiation of embryo-derived stem cells.

We combine tools of genetic manipulation, live imaging, proteomics and single cell expression analysis to explore the fundamental aspects of lineage development. For example, we are investigating epigenetic and regulatory differences between pluripotency and the extraembryonic stem cell state, since this is the key switch that marks loss of totipotency. We are also applying our developmental knowledge to the differentiation of human iPS cells into cell types suitable for exploring new aspects of human biology and disease.

We recently developed a CRISPR/Cas9-based genome editing method that allows for highly efficient, precise insertion of large DNA fragments into the mouse embryo genome. Two-cell homologous recombination (2C-HR)-CRISPR, is based on introducing CRISPR reagents into embryos at the two-cell stage, taking advantage of the open chromatin structure and the likely increase in homologous-recombination efficiency during the long G2 phase. We are currently exploiting this method to generate a number of mouse lines carrying fluorescent reporters, inducible protein degradation systems, optogenetic constructs and other synthetic biology tools.

Current research

Embryo PictureUtilization of Preimplantation embryos is a fundamental system, which allows us to study embryo development in vivo. Our research focuses on characterizing embryo development and understanding the underlying molecular mechanisms of cell fate determination.

Embryo Projects

Stem Cells growing in a plateWe utilize a variety of embryo derived stem cell lines to model lineage establishment in vitro. We study the maintenance of pluripotency as well as cell fate changes through driving differentiation and cell conversion.

Stem Cell Projects

Recent publications

Genetic control of early cell lineages in the mammalian embryo. Rossant J. Annual Review of Genetics. 2018 Nov 23;52:185-201.

Gene editing in human development: ethical concerns and practical applications. Rossant J. Development. 2018 Jul 25;145(16).

Efficient generation of targeted large insertions by microinjection into two-cell-stage mouse embryos. Gu B, et al., Nature Biotechnology. 2018 Jun 11.

AIRE is a critical spindle-associated protein in embryonic stem cells. Gu B, et al., Elife. 2017 Jul 25;6.

Position- and Hippo signaling-dependent plasticity during lineage segregation in the early mouse embryo. Posfai E, et al., Elife. 2017 Feb 22;6.

Identification of RSK and TTK as Modulators of Blood Vessel Morphogenesis Using an Embryonic Stem Cell-Based Vascular Differentiation Assay. Hammoud L, et al., Stem Cell Reports. 2016 Oct 11;7(4):787-801.

Depending on maternal Yap. Posfai E, Rossant J. Cell Research. 2016 Apr;26(4):393-4.

What Is Trophoblast? A Combination of Criteria Define Human First-Trimester Trophoblast. Lee CQ, et al., Stem Cell Reports. 2016 Feb 9;6(2):257-72.

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Our work