Rebuilding nuclei into mitotic chromosomes. William Earnshaw moved to Edinburgh in 1996 as a Wellcome Trust Principal Research Fellow, which he remained until his formal retirement from the University at the end of September 2025, assuming status as an emeritus professor. He graduated summa cum laude from Colby College in Waterville Maine in 1972, then completed a Ph.D. with Jonathan King at MIT in 1977 after a brief stint in the US Air Force. Postdoctoral training in Cambridge with Aaron Klug, Tony Crowther and Ron Laskey and in Geneva with Ulrich Laemmli was followed by 13 years at the Johns Hopkins School of Medicine. Bill Earnshaw Throughout his career, his studies focused on the packaging and segregation of chromosomes during cell division. Achievements of his team during his time in Edinburgh include identification of the chromosomal passenger complex, construction of the first human synthetic artificial chromosome and multidisciplinary studies of the organisation and formation of vertebrate mitotic chromosomes. He has been elected to EMBO, the Royal Society of Edinburgh, the Academy of Medical Sciences, the Royal Society of London and the National Academy of Science of the USA. He co-authored the textbook Cell Biology with Tom Pollard, Graham Johnson and Jennifer Lippincott-Schwartz (4th edition published in 2023). For more information see the Earnshaw lab website. Earnshaw Lab Website Lab members Moonmoon Deb, Natalia Kochanova, Bram Prevo, Caitlin Reid, Lucy Remnant, Itaru Samejima and Kumiko Samejima Research Rebuilding nuclei into mitotic chromosomesOur ongoing research focuses on structural dynamics in chromatin during the transition of cells from G2 phase into mitosis and the role of SMC proteins in mitotic chromosome formation and structure.A recent highlight was publication of the results of our long-running study of interactions between cohesin and condensin during mitotic chromosome formation. This was a truly interdisciplinary collaboration with the groups of Job Dekker, Leonid Mirny and Anton Goloborodko. We did the genetics, cell biology and imaging. They did Hi-C and polymer modelling, respectively. We discovered that cohesin has a significant effect on mitotic chromosome structure that has been previously overlooked and gained surprising new insights into the organisation of the chromatin fiber in chromosomes. Kumiko made many genomic knock-in cell lines, performed the cell synchrony and carried out extensive light microscopy analysis. Fernanda Cisneros-Soberanis and Nina Pučeková performed serial block face scanning electron microscopy with our collaborators Ian Prior and Alison Beckett in Liverpool. Itaru performed ChEP and Moonmoon has been doing ChIP - both to quantitate and map condensin and cohesin on the chromosomes during chromosome formation entry. These events begin before chromatin condensation is visible, and the study was only possible using the chemical-genetic system for synchronous mitotic entry developed by Kumiko.Ongoing studies involve mapping all nucleosomes in the nuclear volume adjacent to the nuclear envelope as prophase chromosome formation occurs with Ohad Medalia (University of Zürich), mapping mitotic chromosomes to ask if particular genomic regions occupy preferred positions in the interior and exterior of chromosomes with Magda Bienko (Milan, Italy), making and analysing structure-informed mutants to characterise condensin regulation with Kyle Muir (Edinburgh), and using robotic high-throughput super-resolution microscopy to trace the path of the chromatin fiber as mitotic chromosomes form with Alistair Boettiger (Stanford University). Our ongoing work is supported by a Wellcome Principal Research Fellowship. Following its completion at the end of March 2026, the lab will be funded by a Wellcome Discovery Award for five more years. Figure legendThree-dimensional reconstruction of an anaphase human RPE1 cell. Left, projection of the three-dimensional reconstruction superimposed on an orthoslice from the electron microscopy map. Corresponding sister chromatids have the same colours. Right, partial karyotype with individual sister chromatids (identified by size and centromere position) extracted from the map and displayed next to their sisters. Sample preparation and modeling in AMIRA by Fernanda Cisneros-Soberanis. Serial block face scanning electron microscopy by Alison Beckett and Ian Prior, University of Liverpool Selected publications K. Samejima†, J.H. Gibcus†, S. Abraham‡, F. Cisneros-Soberanis‡, I. Samejima‡, A.J. Beckett, N. Pučeková, M. Alba Abad, C. Spanos, B. Medina-Pritchard, J.R. Paulson, L. Xie, A.A. Jeyaprakash, I.A. Prior, L.A. Mirny*, J. Dekker*, A. Goloborodko*, W.C. Earnshaw*. (2025). Rules of engagement for condensins and cohesins guide mitotic chromosome formation. Science 388, eadq1709. PMID: 40208986; PMCID: 12118822; DOI: https://doi.org/10.1126/science.adq1709.Cisneros-Soberanis, F.†, E. Simpson†, A.J. Beckett, N, Pucekova, S. Corless, N.Y. Kochanova, I.A. Prior, D.G. Booth*, W.C. Earnshaw*. (2024). Near Millimolar Concentration of Nucleosomes in Mitotic Chromosomes from Late Prometaphase into Anaphase, J. CELL BIOL. 223: e202403165 PMID: 39186086; PMCID: 11346515; DOI: https://doi.org/10.1083/jcb.202403165.Sacristan,C.†*, K. Samejima†, L.A. Ruiz, M. Deb, M.L.A. Lambers, A. Buckle, C.A. Brackley, D. Robertson, T. Hori, S. Webb, R. Kiewisz, T. Bepler, E. van Kwawegen, P. Risteski, K. Vukušić, I.M Tolić, T. Müller-Reichert, T. Fukagawa, N. Gilbert, D. Marenduzzo, W.C. Earnshaw* & G.J.P.L. Kops*. (2024). Condensin reorganizes centromeric chromatin during mitotic entry into a bipartite structure stabilized by cohesin, CELL 187: 3006-3023. PMID: 38744280; PMCID: PMC11164432; DOI: https://doi.org/10.1016/j.cell.2024.04.014. This article was published on 2026-04-23
