Role of calcium and NFAT signalling in regulating human epidermal stem cell homeostasis
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NESCI would be interested in funding / studentship opportunities for the following proposal.
NESCI are interested in industrial partners who may like to collaborate in one of these fields (for a CASE studentship or other awards), or in anyone who is interested in these areas of research (including other academic groups). For further details, please contact Helen Clamp from NESCI.
Project: Role of calcium and NFAT signalling in regulating human epidermal stem cell homeostasis
Lead: Prof Nick Reynolds and Prof Colin Jahoda
Background: Quiescent stem cells reside in the basal layer of the epidermis and “bulge region” of the hair follicle and through proliferation and differentiation maintain skin tissue homeostasis and function1. Stem cells are also activated during wound healing and dysfunctional control of stem cell proliferation may also contribute to hyperproliferative diseases such as psoriasis. The signals regulating epidermal stem cell quiescence and proliferation are however poorly understood. Calcium ions play an important role in regulating keratinocyte proliferation/differentiation/apoptosis and we have recently shown functional activation of Ca2+/NFAT signalling in epidermal keratinocytes with abnormal activation in psoriatic epidermis1. Moreover, recent evidence indicates that one NFAT isoform NFATc1 regulates epidermal stem cell quiescence and down-regulation of NFATc1 increases stem cell proliferation2 and that spontaneous Ca2+/NFAT signalling may be important in maintaining “stemness” and that Ca2+/NFAT signalling is down-regulated as stem cells differentiate3.
Hypothesis: Ca2+/NFAT signalling plays a key role in regulating epidermal stem cell homeostasis, proliferation and differentiaion
Methods: Culture of normal human keratinocytes on feeder layers in defined medium and isolation of “holoclones”, “meroclones” and “paraclones” for further analysis using live cell confocal imaging of Ca2+ flux using Ca2+ indicator dyes and cells retrovirally transduced with GFP-NFATc1. Spontaneous and agonist-induced Ca2+/NFAT signalling will be analysed and correlated with proliferation, cell cycle progression and differentiation of colonies. Molecular tools are available to block Ca2+ entry and NFAT signalling and the effect of these on stem cell homeostasis will be assessed.
Outcome: increased understanding of signalling mechanisms regulating epidermal stem cell homeostasis.
References:
Waters JM, Richardson GD, Jahoda CA. Hair follicle stem cells. Semin Cell Dev Biol. 2007 18:245-54. Epub 2007 Feb 13.
Ross K, Whitaker M, Reynolds NJ. Agonist-induced calcium entry correlates with STIM1 translocation. J Cell Physiol. 2007 211:569-76
Flockhart RJ, Diffey BL, Farr PM, Lloyd J, Reynolds NJ. NFAT regulates induction of COX-2 and apoptosis of keratinocytes in response to ultraviolet radiation exposure. FASEB J. 2008 Aug 15. [Epub ahead of print]
Al-Daraji WI, Grant KR, Ryan K, Saxton A, Reynolds NJ. Localization of calcineurin/NFAT in human skin and psoriasis and inhibition of calcineurin/NFAT activation in human keratinocytes by cyclosporin A. J Invest Dermatol. 2002 118:779-88.
Horsley V, Aliprantis AO, Polak L, Glimcher LH, Fuchs E. NFATc1 balances quiescence and proliferation of skin stem cells. Cell. 2008 132:299-310.
Kawano S, Otsu K, Kuruma A, Shoji S, Yanagida E, Muto Y, Yoshikawa F, Hirayama Y, Mikoshiba K, Furuichi T. ATP autocrine/paracrine signaling induces calcium oscillations and NFAT activation in human mesenchymal stem cells. Cell Calcium. 2006 39:313-24. Epub 2006 Jan 30.
