Simon Walker

Simon Walker
Simon Walker
Simon Walker
Head of Imaging Facility
Simon Walker

Simon obtained his first degree in Biochemistry at Heriot-Watt University in Edinburgh before moving to the John Innes Centre in Norwich where he studied for his PhD under the supervision of Allan Downie looking at the role of calcium signalling during legume symbiosis.

Simon then went to work as a postdoc for four years in Pete Cullen's lab in the Department of Biochemistry at Bristol University where he investigated the GAP1 family of ras GTPase-activating proteins.

​Having become interested in the application of imaging technologies to answer biological quesions Simon moved to the Babraham Institute in 2004 where he helped establish the core Imaging Facility.

Simon now manages the Facility which has over 100 registered users based within the Institute and an increasing number of commercial users based both on and off campus.

Latest Publications

Orozco G, Schoenfelder S, Walker N, Eyre S, Fraser P Epigenetics

Genome sequencing has revealed over 300 million genetic variations in human populations. Over 90% of variants are single nucleotide polymorphisms (SNPs), the remainder include short deletions or insertions, and small numbers of structural variants. Hundreds of thousands of these variants have been associated with specific phenotypic traits and diseases through genome wide association studies which link significant differences in variant frequencies with specific phenotypes among large groups of individuals. Only 5% of disease-associated SNPs are located in gene coding sequences, with the potential to disrupt gene expression or alter of the function of encoded proteins. The remaining 95% of disease-associated SNPs are located in non-coding DNA sequences which make up 98% of the genome. The role of non-coding, disease-associated SNPs, many of which are located at considerable distances from any gene, was at first a mystery until the discovery that gene promoters regularly interact with distal regulatory elements to control gene expression. Disease-associated SNPs are enriched at the millions of gene regulatory elements that are dispersed throughout the non-coding sequences of the genome, suggesting they function as gene regulation variants. Assigning specific regulatory elements to the genes they control is not straightforward since they can be millions of base pairs apart. In this review we describe how understanding 3D genome organization can identify specific interactions between gene promoters and distal regulatory elements and how 3D genomics can link disease-associated SNPs to their target genes. Understanding which gene or genes contribute to a specific disease is the first step in designing rational therapeutic interventions.

+view abstract Frontiers in cell and developmental biology, PMID: 36340032 2022

Novo CL, Wong EV, Hockings C, Poudel C, Sheekey E, Wiese M, Okkenhaug H, Boulton SJ, Basu S, Walker S, Kaminski Schierle GS, Narlikar GJ, Rugg-Gunn PJ

Heterochromatin maintains genome integrity and function, and is organised into distinct nuclear domains. Some of these domains are proposed to form by phase separation through the accumulation of HP1ɑ. Mouse heterochromatin contains noncoding major satellite repeats (MSR), which are highly transcribed in mouse embryonic stem cells (ESCs). Here, we report that MSR transcripts can drive the formation of HP1ɑ droplets in vitro, and modulate heterochromatin into dynamic condensates in ESCs, contributing to the formation of large nuclear domains that are characteristic of pluripotent cells. Depleting MSR transcripts causes heterochromatin to transition into a more compact and static state. Unexpectedly, changing heterochromatin's biophysical properties has severe consequences for ESCs, including chromosome instability and mitotic defects. These findings uncover an essential role for MSR transcripts in modulating the organisation and properties of heterochromatin to preserve genome stability. They also provide insights into the processes that could regulate phase separation and the functional consequences of disrupting the properties of heterochromatin condensates.

+view abstract Nature communications, PMID: 35725842 20 Jun 2022

Mikulasova A, Kent D, Trevisan-Herraz M, Karataraki N, Fung KTM, Ashby C, Cieslak A, Yaccoby S, van Rhee F, Zangari M, Thanendrarajan S, Schinke C, Morgan GJ, Asnafi V, Spicuglia S, Brackley CA, Corcoran AE, Hambleton S, Walker BA, Rico D, Russell LJ Immunology

Chromosomal translocations are important drivers of hematological malignancies whereby proto-oncogenes are activated by juxtaposition with super-enhancers, often called enhancer hijacking. We analysed the epigenomic consequences of rearrangements between the super-enhancers of the immunoglobulin heavy locus () and proto-oncogene that are common in B cell malignancies. By integrating BLUEPRINT epigenomic data with DNA breakpoint detection, we characterised the normal chromatin landscape of the human locus and its dynamics after pathological genomic rearrangement. We detected an H3K4me3 broad domain (BD) within the locus of healthy B cells that was absent in samples with translocations. The appearance of H3K4me3-BD over in the latter was associated with overexpression and extensive chromatin accessibility of its gene body. We observed similar cancer-specific H3K4me3-BDs associated with super-enhancer hijacking of other common oncogenes in B cell (, and /) and in T-cell malignancies (, and ). Our analysis suggests that H3K4me3-BDs can be created by super-enhancers and supports the new concept of epigenomic translocation, where the relocation of H3K4me3-BDs from cell identity genes to oncogenes accompanies the translocation of super-enhancers.

+view abstract Genome research, PMID: 34933939 21 Dec 2021

Group Members

Simon Walker

Head of Imaging Facility

Kirsty MacLellan-Gibson

Senior Electron Microscopy Specialist

Hanneke Okkenhaug

Imaging Facility Deputy Manager