Kikuë Tachibana-Konwalski

Kikuë Tachibana was educated in Austria, Japan and the UK. She obtained a PhD with Ron Laskey in cell cycle and cancer research from Cambridge University. She continued her postdoctoral research in Kim Nasmyth’s lab in Oxford, where she developed an assay that pioneered the use of TEV protease technology in the mouse to study cohesin in female germ cells. Since November 2011, Kikuë is a group leader at IMBA. 2013 she received an ERC Starting Grant for "Chromosome inheritance from mammalian oocytes to embryos” followed by election to the Young Academy of the Austrian Academy of Sciences in 2014. She was selected to the EMBO Young Investigator Programme (YIP) in 2016. Kikuë is the recipient of the 2017 Walther Flemming Award by the German Society for Cell Biology. In 2018, Kikuë Tachibana and three labs in Cambridge (USA), Kyoto (Japan) and Vienna (Austria) have been awarded a Project Grant from the Human Frontier Science Program (HFSP) to address the question of chromatin reprogramming to totipotency. They propose to overcome the existing limitations by several ground-breaking innovations and by combining the expertise from different disciplines in an unprecedented way. In May 2018, EMBO announced that Kikuë Tachibana was elected to its membership, joining the circle of the best researchers in Europe and around the world.

How chromatin is reorganized during zygotic reprogramming to totipotency

Chromatin is reprogrammed after fertilization to produce a totipotent zygote with the potential to generate all cell types. The maternal genome inherited from the oocyte and the paternal genome provided by sperm coexist as separate haploid nuclei in the zygote. How these two epigenetically distinct genomes are spatially organized is poorly understood. To study the 3D chromatin organization of zygotes, we developed a single-nucleus Hi-C (sn-Hi-C) protocol applicable to rare cell types. We show that chromatin architecture is uniquely reorganized during the oocyte-to-zygote transition and is distinct in zygotic paternal and maternal nuclei. Domains and loops, but not compartments, are present in zygotic maternal chromatin, suggesting that these are generated by different mechanisms. To gain insights into these mechanisms, we tested the hypothesis that chromatin conformations are generated by cohesin-dependent loop extrusion. Our simulations and experimental data provide evidence that loop extrusion organizes mammalian genomes from the one-cell embryo onwards.