The LMB is thrilled to welcome Edith Heard, CEO of the Francis Crick Institute, to deliver the 2026 César Milstein Lecture. Edith’s talk, titled ‘Life with two X chromosomes: mechanisms of silencing and escape during X-chromosome inactivation’ will begin at 11am (BST) on the 11th May 2026. External attendees are advised to arrive at least ten minutes in advance to allow time to register at LMB Reception.
Edith Heard joined the Francis Crick Institute in 2025. In addition to serving as Chief Executive Officer, she leads a research group focussed on developmental epigenetics. More specifically, she uses multi-disciplinary approaches to investigate how X-chromosome inactivation is initiated and maintained in developing female embryos.
She is responsible for several breakthroughs in this field, including uncovering how the RNA molecule Xist silences one of the X chromosomes. Her work has also identified the protein complexes and chromatin architecture which underpins this process, highlighting key developmental timing, plasticity and epigenetic reprogramming events which occur in early embryogenesis. More recently, her group has shown that modifying Xist levels causes inactivation of genes which normally escape X chromosome silencing, extending into later stages of development, illustrating that Xist is not only important at the very early stages of embryo growth.
Edith began her career in science at the University of Cambridge, where her undergraduate studies specialised in genetics. After graduating in 1986, she pursued a PhD investigating gene amplification mechanisms in the context of cancer at the Imperial Cancer Research Fund before turning her attention to X-chromosome inactivation as a postdoc at the Pasteur Institute in Paris. She later spent a year as a visiting scientist at Cold Spring Harbor Laboratory, USA, before she joined the Institut Curie, France as Director of the Department for Genetics and Developmental Biology. In 2019, she was appointed Directed General of EMBL and oversaw operations across its six sites during the Covid-19 pandemic.
Edith became a member of EMBO in 2005 and was elected a Fellow of the Royal Society in 2013. Her work has been recognised with the CNRS Silver Medal in 2008, the CNRS Gold Medal in 2024 and the Croonian Medal and Lecture from the Royal Society in 2025.
Lecture abstract
Dosage compensation is essential to balance gene expression between the sexes, as females carry two X chromosomes while males carry only one. In mammals, this balance is achieved through X-chromosome inactivation, a process by which one X chromosome is transcriptionally silenced in female cells to prevent a potentially deleterious double dose of X-linked gene products. X inactivation has long been viewed as a stable and irreversible mechanism established early in development and faithfully maintained throughout life. However, it is now clear that this process is far more dynamic than previously thought. During early embryogenesis, X inactivation can be reversed, resetting epigenetic states before being re-established in a lineage-specific manner. Moreover, a substantial number of genes can escape silencing in somatic tissues, leading to variable expression from the inactive X chromosome.
My group has contributed to this revised paradigm by investigating the extent and regulation of escape from X inactivation, and by demonstrating the transient nature of silencing during early development. My talk will focus on the molecular mechanisms that underlie both gene silencing and escape, including the roles of chromatin organization, long non-coding RNAs and nuclear architecture. I will highlight how these findings contribute to our understanding of epigenetic stability and plasticity, with implications for sexual dimorphism and disease.
Background information
The César Milstein Lecture is named in honour of César Milstein, an LMB Nobel Laureate. This named lecture is one of a series of named lectures organised by the LMB and given by eminent scientists from around the world. These talks are supported financially by AstraZeneca and the Max Perutz Fund.
César was born in Argentina in 1927. After completing PhDs in both Buenos Aires and Cambridge, he embarked on a brief spell of research in Argentina before he joined the LMB in 1963. César then spent the rest of his career and his life here.
César developed an early interest in immunology, with his research concentrated on antibody structure and diversity. In the early 1970s, he and his postdoc, Georges Köhler, developed the technique used to produce monoclonal antibodies. This work led to them being jointly awarded the 1984 Nobel Prize in Physiology or Medicine. The technique developed by César and Georges has since been developed further by LMB colleagues for therapeutic applications, leading to the creation of several MRC spin-out companies. César continued his research on how somatic mutation arises in immunoglobulin genes. He died in Cambridge on 24th March 2002.
