Life Sciences Research for Lifelong Health

Rachael Walker

Head of Flow Cytometry: Dr Rachael Walker
Building 580, Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT
rachael.walker@babraham.ac.uk
01223 496559

Rachael has over a dozen years of experience in flow cytometry and cell sorting and nearly 10 years of working in flow cytometry core facilities. Rachael joined the core in September 2012, following 7 years running Flow Cytometry Core Facilities at the University of Cambridge.

Rachael has extensive experience in analysis and sorting cells of differing types including; immunology, cell biology, stem cell biology, large cells such as cardiomyocytes, c. elegans eggs; organelles such as nuclei. Rachael can provide expertise in experimental setup, optimisation and analysis. She can help with optimal instrument set up, post-acquisition analysis of data and preparing figures for papers.

Education:
2005- PhD in Tissue Engineering, Department of Clinical Engineering, University of Liverpool
2001- BMedSc (Honours), Biomedical Materials Science, University of Birmingham

Flow Cytometry community
Rachael is very involved with the flow cytometry community on a local, national and international level.

Rachael’s work includes:
  • Awarded International Society for Advancement of Cytometry (ISAC) Scholarship 2012-2014
  • Awarded ISAC ‘Emerging Leader in Shared Resource Laboratory’ Scholarship 2014-2016
  • Co-chair of ISAC Membership Services Committee
  • Member of ISAC Program committee for CYTO conferences since 2010
  • Secretary and organiser of local Mid-Anglia Cytometry (MACC) meetings
  • Secretary of flowcytometryUK, also one of main organisers of flowcytometryUK national annual meetings
  • Fellow and Secretary of Royal Microscopical Society (RMS) Cytometry Section
  • Lecturer at RMS Annual Flow Cytometry Course
  • ​Regular contributor to ‘Flow Cytometry’ Channel on Bitesize Bio website.

Latest Publications

Comprehensive Cell Surface Protein Profiling Identifies Specific Markers of Human Naive and Primed Pluripotent States.
Collier AJ, Panula SP, Schell JP, Chovanec P, Plaza Reyes A, Petropoulos S, Corcoran AE, Walker R, Douagi I, Lanner F, Rugg-Gunn PJ

Human pluripotent stem cells (PSCs) exist in naive and primed states and provide important models to investigate the earliest stages of human development. Naive cells can be obtained through primed-to-naive resetting, but there are no reliable methods to prospectively isolate unmodified naive cells during this process. Here we report comprehensive profiling of cell surface proteins by flow cytometry in naive and primed human PSCs. Several naive-specific, but not primed-specific, proteins were also expressed by pluripotent cells in the human preimplantation embryo. The upregulation of naive-specific cell surface proteins during primed-to-naive resetting enabled the isolation and characterization of live naive cells and intermediate cell populations. This analysis revealed distinct transcriptional and X chromosome inactivation changes associated with the early and late stages of naive cell formation. Thus, identification of state-specific proteins provides a robust set of molecular markers to define the human PSC state and allows new insights into the molecular events leading to naive cell resetting.

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Cell stem cell, , 1875-9777, , 2017

PMID: 28343983

Aging yeast gain a competitive advantage on non-optimal carbon sources.
Frenk S, Pizza G, Walker RV, Houseley J

Animals, plants and fungi undergo an aging process with remarkable physiological and molecular similarities, suggesting that aging has long been a fact of life for eukaryotes and one to which our unicellular ancestors were subject. Key biochemical pathways that impact longevity evolved prior to multicellularity, and the interactions between these pathways and the aging process therefore emerged in ancient single-celled eukaryotes. Nevertheless, we do not fully understand how aging impacts the fitness of unicellular organisms, and whether such cells gain a benefit from modulating rather than simply suppressing the aging process. We hypothesized that age-related loss of fitness in single-celled eukaryotes may be counterbalanced, partly or wholly, by a transition from a specialist to a generalist life-history strategy that enhances adaptability to other environments. We tested this hypothesis in budding yeast using competition assays and found that while young cells are more successful in glucose, highly aged cells outcompete young cells on other carbon sources such as galactose. This occurs because aged yeast divide faster than young cells in galactose, reversing the normal association between age and fitness. The impact of aging on single-celled organisms is therefore complex and may be regulated in ways that anticipate changing nutrient availability. We propose that pathways connecting nutrient availability with aging arose in unicellular eukaryotes to capitalize on age-linked diversity in growth strategy and that individual cells in higher eukaryotes may similarly diversify during aging to the detriment of the organism as a whole.

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Aging cell, , 1474-9726, , 2017

PMID: 28247585

Tracking the embryonic stem cell transition from ground state pluripotency.
Kalkan T, Olova N, Roode M, Mulas C, Lee HJ, Nett I, Marks H, Walker R, Stunnenberg HG, Lilley KS, Nichols J, Reik W, Bertone P, Smith A

Mouse embryonic stem (ES) cells are locked into self-renewal by shielding from inductive cues. Release from this ground state in minimal conditions offers a system for delineating developmental progression from naive pluripotency. Here we examined the initial transition process. The ES cell population behaves asynchronously. We therefore exploited a short-half-life Rex1::GFP reporter to isolate cells either side of exit from naive status. Extinction of ES cell identity in single cells is acute. It occurs only after near-complete elimination of naïve pluripotency factors, but precedes appearance of lineage specification markers. Cells newly departed from the ES cell state display features of early post-implantation epiblast and are distinct from primed epiblast. They also exhibit a genome-wide increase in DNA methylation, intermediate between early and late epiblast. These findings are consistent with the proposition that naive cells transition to a distinct formative phase of pluripotency preparatory to lineage priming.

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Development (Cambridge, England), , 1477-9129, , 2017

PMID: 28174249

01223 496559

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Latest Publications

Aging yeast gain a competitive advantage on non-optimal carbon sources.

Frenk S, Pizza G, Walker RV

Aging cell
1474-9726: (2017)

PMID: 28247585

Tracking the embryonic stem cell transition from ground state pluripotency.

Kalkan T, Olova N, Roode M

Development (Cambridge, England)
1477-9129: (2017)

PMID: 28174249

International Society for Advancement of Cytometry (ISAC) flow cytometry shared resource laboratory (SRL) best practices.

Barsky LW, Black M, Cochran M

Cytometry. Part A : the journal of the International Society for Analytical Cytology
89 1552-4930:1017-1030 (2016)

PMID: 27813253

The spindle assembly checkpoint works like a rheostat rather than a toggle switch.

Collin P,Nashchekina O,Walker R,Pines J

Nature cell biology
15 1476-4679:1378-85 (2013)

PMID: 24096242

Germline potential of parthenogenetic haploid mouse embryonic stem cells.

Leeb M,Walker R,Mansfield B,Nichols J,Smith A,Wutz A

Development (Cambridge, England)
139 1477-9129:3301-5 (2012)

PMID: 22912412

A high-throughput, flow cytometry-based method to quantify DNA-end resection in mammalian cells.

Forment JV,Walker RV,Jackson SP

Cytometry. Part A : the journal of the International Society for Analytical Cytology
81 1552-4930:922-8 (2012)

PMID: 22893507

A system for imaging the regulatory noncoding Xist RNA in living mouse embryonic stem cells.

Ng K,Daigle N,Bancaud A,Ohhata T,Humphreys P,Walker R,Ellenberg J,Wutz A

Molecular biology of the cell
22 1939-4586:2634-45 (2011)

PMID: 21613549

Oct4 and LIF/Stat3 additively induce Krüppel factors to sustain embryonic stem cell self-renewal.

Hall J,Guo G,Wray J,Eyres I,Nichols J,Grotewold L,Morfopoulou S,Humphreys P,Mansfield W,Walker R,Tomlinson S,Smith A

Cell stem cell
5 1875-9777:597-609 (2009)

PMID: 19951688

Intervertebral disc cell-mediated mesenchymal stem cell differentiation.

Richardson SM,Walker RV,Parker S,Rhodes NP,Hunt JA,Freemont AJ,Hoyland JA

Stem cells (Dayton, Ohio)
24 1066-5099:707-16 (2006)

PMID: 16223853