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Professor John Carroll

Prof John Carroll

Professor of Reproductive Physiology

Associate Dean, Division of Biosciences

j.carroll@ucl.ac.uk Telephone:
Office: 020 7679 7918
(Int: 37918)

How does an oocyte make the transition into an embryo that is capable of developing to term? This is the basic question that research in our lab is aimed at understanding. The first step in this transition is the production of a fertile egg. This requires cell-cell interactions during oocyte growth, progression through the meiotic cell cycle and modifications in the cytoplasm that ensures the egg is capable of responding to the fertilizing sperm. The second step in the transition is fertilization itself. The signal that triggers egg activation is a sperm-induced series of oscillations in intracellular calcium. These oscillations last until the oocyte has completed meiosis and entered the first mitotic cell cycle. This brings us to the third stage, which consists of a series of cell division cycles and the first differentiation event in the embryo. To understand these events we focus on investigating the role of cell signalling by the second messengers, Ca2+ and cAMP. Our approach is to use live cell imaging techniques to monitor Ca2+, cAMP and proteins of interest during meiosis and mitosis. We work in close collaboration with other labs at UCL, in particular Drs Karl Swann and John Parrington. The collaboration provides for a multi-disciplinary approach, incorporating, molecular biology, biochemistry and cell physiology. We hope that the experiments will help us to understand a little more about the causes of infertility and abnormal embryo development while, in a broader context, the oocyte and embryo provide a model system for investigating how mammalian cells divide and differentiate.

Role of cyclic-AMP in oocyte maturation
Mammalian oocytes are held in prophase of the first meiotic division. Meiosis is resumed following a surge of the gonadotrophins LH and FSH. The intracellular signalling pathways involved in meiotic arrest and maturation remain unclear. We are investigating the possible roles of cAMP and Ca2+ in meiotic arrest and resumption.

Initial experiments have shown that in the mouse oocyte FSH and LH do not cause an increase in intracellular Ca2+. However, a strong case can be presented for cAMP being a positive regulator of Gonadotrophin-induced meiotic maturation in mammals. In intact follicles, stimulating an increase in cAMP with gonadotrophins, forskolin or IBMX all lead to GVBD in the oocyte. Until the recent development of a cAMP fluorosensor, FlCRhR, it has not possible to measure cAMP in single living cells in real time. We are using this fluorsensor to clarify the possible roles of cAMP in meiosis.

Calcium releasing mechanisms during meiosis and mitosis
We are investigating the relationship between the spatial organisation of the endoplasmic reticulum (ER) and the generation of Ca2+ transients in the mammalian oocyte and early embryo. As the major intracellular source of free calcium ions, the structure of the ER is of great interest in the study of calium release mechanisms in the developing oocyte. We are using the lipophilic marker DiI to monitor the structure and spatial organisation of the ER during meiosis and the first mitotic cell cycle. We are also using the technique of flash-photolysis to uncage caged inositol-trisphosphate (InsP3) in the mouse oocyte and early embryo in order to test the sensitivity of InsP3-releasable Ca2+ stores during these early cell divisions. In doing this we aim to uncover some clues as to the role of ER organisation in the generation of Ca2+ transients during meiosis and mitosis.


Recent publications

  • Dumollard R, Ward Z, Carroll,J. Duchen MR.(2006) Regulation of redox metabolism in the mouse oocyte and embryo. Development. 2006 Dec 21; [Epub ahead of print] PMID: 17185319 [PubMed - as supplied by publisher]
  • Marangos P, Verschuren EW, Chen R, Jackson PK, Carroll J.(2006) Prophase I arrest and progression to metaphase I in mouse oocytes are controlled by Emi1-dependent regulation of APCCdh1.J Cell Biol. 2007 Jan 1;176(1):65-75. Epub 2006 Dec 26. PMID: 17190794 [PubMed - in process]
  • Halet,G., Tunwell,R., Parkinson,S.J., Carroll,J.(2004) PKCs regulate the temporal pattern of Ca2+ oscillations at fertilization in mouse eggs. Journal of Cell Biology 164(7), 1033-1044. ISSN: 0021-9525 link
  • Larman,M.G., Saunders,C.M., Carroll,J., Lai,F.A., Swann,K.(2004) Cell cycle-dependent Ca2+ oscillations in mouse embryos are regulated by nuclear targeting of PLCzeta. Journal of Cell Science 117, 2513-2521. ISSN: 0021-9533 link
  • Marangos,P., Carroll,J(2004) Fertilization and InsP3-induced Ca2+ release stimulate a persistent increase in the rate of degradation of cyclin B1 specifically in mature mouse oocytes. Developmental Biology 272(1), 26-38. ISSN: 0012-1606 link
  • FitzHarris,G., Marangos,P., Carroll,J.(2003) Cell cycle-dependent regulation of structure of endoplasmic reticulum and inositol 1,4,5-trisphosphate-induced Ca2+ release in mouse oocytes and embryos. Molecular Biology of the Cell 14(1), 288-301. ISSN: 1059-1524 link
  • Marangos,P., Carroll,J.(2004) The dynamics of cyclin B1 distribution during meiosis I in mouse oocytes. Reproduction 128(2), 153-162. ISSN: 1470-1626 link
  • Halet,G., Marangos,P., Fitzharris,G., Carroll,J.(2003) Ca2+ oscillations at fertilization in mammals. Biochemical Society Transactions 31(5), 907-911. ISSN: 0300-5127
  • Halet,G., Tunwell,R., Carroll,J. (2003).(2003) Imaging PIP2 dynamics and PKC activation at fertilization. Journal of Physiology (London) 547P, SA44. ISSN: 0022-3751
  • Marangos,P., Fitzharris,G., Carroll,J.(2003) Ca2+ oscillations at fertilization in mammals are regulated by the formation of pronuclei. Development 130(7), 1461-1472. ISSN: 0950-1991 link
  • Dumollard,R., Carroll,J., Dupont,G., Sardet,C.(2002) Calcium wave pacemakers in eggs. Journal of Cell Science 115(18), 3557-3564. ISSN: 0021-9533 link
  • Halet,G., Tunwell,R., Balla,T., Swann,K., Carroll,J.(2002) The dynamics of plasma membrane PtdIns(4,5)P(2) at fertilization of mouse eggs. Development 130(7), 1461-1472. ISSN: 0950-1991 link
  • Webb RJ, Bains H, Cruttwell C and Carroll J(2002) Gap-juctional communication in mouse cumulus-oocyte complexes: Implications for the mechanism of meiotic maturation. Reproduction 123, 41-52. link
  • Webb,R.J., Marshall,F., Swann,K., Carroll,J.(2002) Ca2+ oscillations at fertilization in mammals are regulated by the formation of pronuclei. Development 130(7), 1461-1472. ISSN: 0950-1991
  • McLay D, Carroll J and Clarke H(2001) The development of of an activity to transfer histones onto sperm chromatin is acquired with meiotic competence during oocyte growth. Dev Biol, 241, 195-206.
  • Carroll J(2001) The initiation and regulation of calcium signalling at fertilization in mammals. Sem in Cell Dev Biol 12, 37-44. link
  • Brind S, Swann K, Carroll J.(2000) Inositol 1,4,5-trisphosphate receptors are downregulated in mouse oocytes in response to sperm or adenophostin A but not to increases in intracellular Ca2+ or egg activation. Dev Biol. 223, 251-265. link
  • Cheung A, Swann K, Carroll J.(2000) The ability to generate normal Ca2+ transients in response to spermatozoa develops during the final stages of oocyte growth and maturation. Hum Reprod. 15, 389-395. link
  • Carroll J(2000) Na+-Ca2+ exchange in mouse oocytes: modifications in the regulation of intracellular free Ca2+ during oocyte maturation. J Reprod Fertil. 118, 337-342. link
  • Bao S, Obata Y, Carroll J, Domeki I, Kono T.(2000) Epigenetic modifications necessary for normal development are established during oocyte growth in mice. Biol Reprod 62, 616-621. link

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