Paul Riley PhD, BSc
Professor of Molecular Cardiology
As off October 2011, I have moved to the Department of Physiology, Anatomy and Genetics at the University of Oxford to take up the position of Chair of Development and Reproduction and BHF Professor of Regenerative Medicine.
The team members marked below with (*) have moved to Oxford and the other team members are still at ICH
Current team members
* Dr Nicola Smart - BHF Intermediate Basic Science Research Fellow
* Dr Sveva Bollini - Post-doctoral Fellow
* Dr Joaquim Vieira -Post-doctoral Fellow
* Dr Anke Smits - Post- doctoral Fellow
* Dr.
Mark Evans - Lab Manager
* Richard Tyser
Dr. Catherine Risebro - Post-doctoral Fellow
Karina Dube - Research Assistant/PhD student
Chia Yeo - PhD Student
Louisa Petchey - PhD Student
Sara Howard - PhD Student
Gemma Balmer PhD Student
Linda Klotz - PhD Student
Abbygail Shaw - PhD Student
Research interests
We have a broad interest in the transcriptional regulation (Hand1, Prox1) of cardiac morphogenesis and cardiac muscle ultrastructure, towards establishing models of congenital and acquired heart disease.
In
parallel, we are focusing on coronary vasculogenesis and angiogenesis
both during development and in terms of inducing neovascularisation
post-ischaemic heart disease (Thymosin β4).
Recently we have established a British Heart Foundation-funded programme of research to investigate the potential of the epicardium as a source of multipotent cardiovascular stem/progenitor cells in the adult heart capable of initiating myocardial repair and regeneration.
Hand1 regulates cardiomyocyte proliferation versus differentiation in the developing heart
The precise origins of myocardial progenitors and their subsequent contribution to the developing heart has been an area of considerable activity within the field of cardiovascular biology. Much less well understood is how these progenitors are regulated and which signals are responsible for their development. Clearly not only is there a need to identify factors which regulate the transition from proliferation of cardioblasts to differentiation of cardiac muscle, but also factors which maintain an adequate pool of undifferentiated myocyte precursors as a prerequisite to preventing organ hypoplasia and congenital heart disease.
We adopted the inducible Tet-Off system to bring about an in vivo up-regulation of the bHLH transcription factor Hand1, restricted exclusively to Hand1-expressing cells.
This results in significant extension of the heart tube and extraneous looping due to elevated proliferation of cardioblasts in the distal outflow tract.
The activity of Hand1 in this context is independent of further recruitment of extracardiac cells from the secondary heart field and permissive for continued differentiation of adjacent myocardium. Culture studies using ES cell-derived cardiomyocytes, revealed that in a Hand1-null background there is significantly elevated cardiomyocyte differentiation, with an apparent default mesoderm pathway to a cardiomyocyte fate, whereas Hand1 gain of function maintains proliferating precursors resulting in delayed and significantly reduced cardiomyocyte differentiation, mediated by prevention of cell cycle exit, G1 progression and increased cell division.
Thus our work, to-date, identifies Hand1 as a critical cardiac regulatory protein which controls the balance between proliferation and differentiation in the developing heart and fills a significant gap in our understanding of how the myocardium of the embryonic heart is established. Ongoing studies seek to take advantage of the tet-inducible Hand1 model in combination with studies on functional subcellular compartmentalisation of Hand1 (see below) to establish a mechanism as to how Hand1 determines myocardial cell fate in the developing mammalian heart.
Nucleolar release of Hand1 acts as a molecular switch to determine cell fate
In parallel studies we have implicated Hand1 as a molecular switch
in the determination of whether a trophoblast stem cell continues to
proliferate or commits to differentiate. Y2H studies have identified a
novel interaction of Hand1 with I-mfa domain containing protein which
anchors Hand1 in the nucleolus to negatively regulate Hand1 activity.
In Rcho-1 trophoblast stem cells, nucleolar sequestration of Hand1 is
concomitant with sustaining proliferation and renewal, while release of
Hand1 into the nucleus leads to its activation thus committing cells to a
differentiated giant cell fate. Site-specific phosphorylation is
required for nucleolar release of Hand1, as a pre-requisite for
dimerisation and biological function, and this is mediated by the
non-canonical polo-like kinase Plk4 (Sak). Sak is co-expressed in Rcho-1
cells, localizes to the nucleolus in G2 and phosphorylates Hand1 as a
requirement for trophoblast stem cell commitment towards a giant cell
fate. This study defines a novel cellular mechanism for regulating Hand1
as the critical step in a stem cell differentiation pathway.
We now seek to investigate whether nucleolar sequestration and release of Hand1 translates from the trophoblast lineage of the placenta to the developing heart consistent with the findings from the in vivo, tet-inducible over-expression model described above.
Maintenance of muscle structure, growth and contractility in the developing heart
Impaired cardiac muscle growth and aberrant myocyte arrangement underlie congenital heart disease and cardiomyopathy. We are investigating how cardiac-specific inactivation of the homeobox transcription factor Prox1 results in disruption of the expression and localisation of sarcomeric proteins, gross myofibril disarray and growth retarded hearts. We have demonstrated that Prox1 is required for direct transcriptional regulation of the structural proteins alpha-actinin, N-RAP and Zyxin which collectively function to maintain an actin-a-actinin interaction as the fundamental association of the sarcomere.
Aspects of abnormal heart development and manifestation of a subset of muscular -based disease, have previously been attributed to mutations in key structural proteins. To the best of our knowledge this study is the first demonstration of an essential requirement for transcriptional regulation of sarcomere integrity, in the context of enabling fetal cardiomyocyte hypertrophy, maintenance of contractile function and progression towards inherited or acquired myopathic disease.
Further studies are underway to identify upstream and downstream components of the Prox1 molecular pathway in the context of cardiac muscle development and disease alongside mutation studies on a unique cohort of premature heart failure patients at GOSH.
The role of Thymosin β4 in (cardio-) vascular development
Cardiac failure has a principle underlying aetiology of ischaemic damage arising from vascular insufficiency. The molecules that regulate collateral growth in the ischeamic heart are undoubtedly the same molecules that orchestrate the morphogenetic events of coronary vasculature formation during embryogenesis. We previously identified thymosin β4 (an actin monomer binding protein) as essential for all aspects of coronary vessel development. In this model Tβ4 signals from the developing myocardium to the overlying epicardium to induce vascular progenitors. As part of the same study we revealed Tβ4 can induce adult epicardium to produce endothelial and smooth muscle cells for collateral vessel growth (Smart et al., 2007). We are currently determining whether Tβ4 can stimulate new vessel formation via circulating endothelial progenitors and to investigate cell autonomous vascular roles for Tβ4 in the developing endothelium, epicardium and neural crest lineages.
These studies seek to realize the full potential of Tβ4 both in terms of renewal of regressed vessels at low basal level or sustained neovascularisation following cardiac injury.
Thymosin β4-induced neovascularisation
Previously we showed that Thymosin β4 (Tβ4) promotes coronary vessel formation and collateral growth during development and the migration of vasculogenic precursors from adult epicardium (Smart et al., 2007), offering significant therapeutic potential. However, the feasibility of translating the developmental role of Tβ4 into one of therapeutic angiogenesis in the injured adult heart has not been tested in vivo.
We aim to fully explore the role of Tβ4 in the adult heart, both its normal role in maintenance of a healthy myocardium and vasculature (cardiac homeostasis) and the extent of Tβ4-induced cardioprotection via neovascularisation under pathological conditions (ischaemic injury and hypertension). Furthermore, we intend to define the contribution of the pro-angiogenic cleavage product, AcSDKP, in Tβ4-induced vasculogenesis and in mediating the anti-fibrotic effects of ACE inhibitors.
Crucial to understanding Tβ4 and AcSDKP function, we will identify the receptors and downstream pathways through which they signal. Complete insight into their mechanisms of action is essential for the evolution of more efficient therapies for ischaemic heart disease.
The adult epicardium as a bona fide source of multipotent progenitors
Stimulation of resident cardiac stem cells to replace damaged heart muscle, valves, vessels and conduction fibres holds great therapeutic potential for ischaemic heart disease. We recently identified the epicardium as a novel source of adult multipotent progenitors (EPDCs) which, when activated by Thymosin β4, give rise to vascular cells and cardiomyocytes, and thus have the potential to facilitate neovascularisation and myocardial repair
In
this programme of work we seek to characterise the stem cell-like
phenotype and lineage-potential of EPDCs, the degree of homogeneity in
response to external cues and the plasticity of the epicardium in
contributing to both cardiac homoestasis and endogenous repair. We will
determine the mechanism of activation of adult EPDCs, at a
transcriptional level, and propose a series of siRNA and small molecule
screens for key factors and critical signalling events which will not
only provide insight into EPDC-cell fate determination but may
realistically lead to the identification of novel targets for
regenerative drug discovery.
Funding
British Heart Foundation (Programme Grant, Project Grant and MB/PhD Studentship)
Medical
Research Council (Career Establishment Grant, Project Grant)
Selected bibliography
Links to Research Publications Service for Paul Riley
Contact details
Prof. Paul Riley
Chair of Development and Reproduction;
BHF Professor of Regenerative Medicine Department of Physiology, Anatomy and Genetics Sherrington Building
University of Oxford
South Parks Road
Oxford
OX1 3PT
Tel. +44 (0)1865 282366 (Direct)
Tel. +44 (0)1865 282367 (PA, Emma-Louise Lyon)
Fax. +44 (0)1865 272469
E-Mail: paul.riley@dpag.ox.ac.uk
Page last modified on 10 oct 12 15:30
