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<strong>EMBL</strong>-EBI<br />

Differentiation and development<br />

Previous and current research<br />

We investigate the cellular and molecular processes underlying mammalian stem cell differentiation,<br />

using a combination of experimental and computational approaches. Embryonic stem (ES)<br />

cells are similar to the transient population of self-renewing cells within the inner cell mass of the<br />

preimplantation blastocyst (epiblast), capable of pluripotential differentiation to all specialised<br />

cell types comprising the adult organism. These cells undergo continuous self-renewal to produce<br />

identical daughter cells, or can develop into specialised progenitors and terminally differentiated<br />

cells. Each regenerative or differentiative cell division involves a decision whereby an individual<br />

stem cell remains in self-renewal or commits to a particular lineage. Pluripotent ES cells can produce<br />

lineage-specific precursors and tissue-specific stem cells, with an accompanying restriction<br />

in commitment potential. These exist in vivo as self-renewing multipotent progenitors localised in<br />

reservoirs within developed organs and tissues. The properties of proliferation, differentiation and<br />

lineage specialisation are fundamental to cellular diversification and growth patterning during organismal<br />

development, as well as the initiation of cellular repair processes throughout life.<br />

Paul Bertone<br />

PhD 2005, Yale University.<br />

At <strong>EMBL</strong>-EBI since 2005.<br />

Group leader since 2006.<br />

Joint appointment with the<br />

Gene Expression and<br />

Developmental Biology Units.<br />

A number of molecular pathways involved in embryonic development have been elucidated, including<br />

those influencing stem cell differentiation. As a result, we know of a number of key transcriptional regulators and signalling molecules<br />

that play essential roles in manifesting nuclear potency and self-renewal capacity of embryonic and tissue-specific stem cells. Despite<br />

these efforts, however, only a small number of components have been identified and large-scale characterisation of cellular commitment and<br />

terminal differentiation to specific cell types remains incomplete. Our research group applies the latest high-throughput technologies to investigate<br />

the functions of key regulatory proteins and their influence on the changing transcriptome. We focus on early lineage commitment<br />

of ES cells, neural differentiation and nuclear reprogramming. The generation of large-scale data from functional genomic and proteomic experiments<br />

will help to identify and characterise the regulatory influence of key transcription factors, signalling genes and non-coding RNAs<br />

involved in early developmental pathways, leading to a more detailed understanding of the molecular mechanisms of vertebrate embryogenesis.<br />

Future projects and goals<br />

A long-term goal of this work is to elucidate accurate models of stem cell differentiation and lineage commitment at various biological levels.<br />

Despite the importance of transcription factors and the interaction of co-factor proteins on the repression and activation of genes, eukaryotic<br />

cells utilise many layers of regulatory control. These range from histone acetylation and methylation events affecting chromatin<br />

accessibility, variations in transcript splicing producing alternate isoforms in certain cell types or conditions, the attenuation of message levels<br />

and/or inhibition of translation by antisense RNAs, and<br />

myriad post-translational modifications affecting protein<br />

function and subcellular localisation. Computational approaches<br />

will be vital for the analysis and integration of<br />

these data in context with existing knowledge.<br />

We eventually wish to characterise the complex interaction<br />

of signalling pathways, gene regulation by key transcription<br />

factors and non-coding RNAs, and chromatin modifications<br />

that function in concert to induce distinct<br />

morphological and physiological outcomes.<br />

Top: Differentiation into neural stem (NS) cells from<br />

neural-rosette structures. A) ES cell primary culture, B, C)<br />

immunostaining for specific surface markers. Bottom: NS<br />

cells express markers characteristic of radial glia,<br />

permitting both accurate identification of differentiation<br />

stages and efficient FACS selection of homogeneous cell<br />

populations for genomic analysis. (Images: Steve Pollard,<br />

University of Cambridge; adapted from Conti et al., 2005).<br />

Selected references<br />

Kind, J. et al. (2008). Genome-wide analysis reveals MOF as a key<br />

regulator of dosage compensation and gene expression in<br />

Drosophila. Cell, 133, 813-828<br />

Kirstetter, P. et al. (2008). Modeling of C/EBPα mutant acute myeloid<br />

leukemia reveals a common expression signature of committed<br />

myeloid leukemia-initiating cells. Cancer Cell, 13, 299-310<br />

65

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