The University of Sheffield
Department of Human Metabolism

Dr Neil Chapman, B.Sc.(Hons.), Ph.D., P.G.Cert.H.E., F.H.E.A.

Group Leader and Non-Clinical Lecturer in Reproductive MedicineNeil Chapman

The Department of Human Metabolism,
Academic Unit of Reproductive & Developmental Medicine,
Level 4, The Jessop Wing,
Tree Root Walk,
Sheffield
S10 2SF

Telephone 0114 226 8530
Fax 0114 226 1074
Email n.r.chapman@sheffield.ac.uk





Biography

I joined the University of Sheffield as a Group Leader and Non-Clinical Lecturer in Reproductive Medicine in July 2005. Previous research positions included:

Research Interests and Current Projects

My research interests focus on gene regulation by the nuclear factor kappaB family of transcription factors. I am involved with the following projects:

Research Background: Molecular Biology of Myometrial Function during Pregnancy and Labour

Figure of Pregnant Woman. Reproduced with permission form the Medical Art Service, Munich/Wellcome Images

Importance of Research into Premature Labour:
In the developed world, premature birth complicates 6-10% of pregnancies. As a nation, England has the highest incidence of premature birth in Europe with 42,500 pre-term deliveries recorded in 2003-2004 (Maternity Statistic, England, Department of Health May 2003-2004). In the U.S.A., 500,000 preterm births were recorded in 2003-2004, while hospital charges for 25,000 infant admissions with a primary diagnosis of premature birth totalled $1.9 billion in 2003. Significantly, the incidence of birth before 28 weeks gestation (severely preterm) is increasing with those infants having elevated risks of major long-term mental and physical handicap. Moreover, such infants have a disproportionate effect on health-care budgets world-wide: a recent U.K. estimate of the total cost of preterm birth to the public sector was £2.95 billion. Current tocolytic therapies (treatments used to stop premature myometrial contractions), however, have limited use and are associated with complications for both infant and mother. Since the antenatal health of a baby is seen as a major predictor of adult morbidity, reducing the incidence of premature birth is paramount considering the soaring costs of health care for such adult diseases. Please read the AMR Tiny Lives Charter and the March of Dimes White Paper from the Download box for further information on pre-term birth.

Figure of foetus at birth. Reproduced with permission from the Medical Art Service, Munich/Wellcome Images




The Myometrial Galphas/cAMP/PKA Pathway:
One of the most significant physiological adaptations of the uterus to pregnancy is the development of a relative state of myometrial smooth muscle inactivity termed quiescence. At the onset of labour the state of myometrial quiescence ends and a series of powerful uterine contractions act to expel the infant. There is growing evidence indicating that components of the cyclic AMP (cAMP) signalling pathway are differentially expressed in the human myometrium during pregnancy thereby potentiating the maintenance of uterine quiescence until term. These include calcitonin gene related peptide (CGRP) receptors, chorionic gonadotrophin/LH receptors and the adenylyl cyclase stimulatory G-protein Galphas, whose levels of expression are considerably increased within the myometrium during gestation causing an increased production of cAMP and activation of protein kinase A (PKA); these factors are subsequently reduced in labour. The mechanism by which down-regulation of Galphas expression occurs, however, remains unclear, although recently it was reported that the Galphas promoter was regulated by Sp-like transcription factors requiring phosphorylation by PKA.

Molecular Biology of Myometrial Function
Regulatory networks between cell signalling molecules, transcription factors and DNA ensure cells function normally. One set of transcription factors which govern a wide variety of cellular activities are the nuclear factor kappaB (NF-kappaB) family of proteins. In humans, a number of pro-inflammatory cytokines and inducible factors, associated with the onset of both normal and preterm labour, are regulated by NF-kappaB including TNFalpha, IL-1beta, IL-8 and COX-2 in all gestational tissues examined, including the myometrium. These studies, however, concentrate on well characterised NF-kappaB-responsive promoters in isolation: a poor reflection of the events likely to occur in vivo.

Structure of the RelA homodimer

NF-kappaB Biology
NF-kappaB, which is rapidly induced by over 400 different stimuli including TNFalpha cytokines and growth factors, is present in virtually every cell type within the body. NF-kappaB can take a number of different forms and is composed of dimeric complexes formed from five distinct subunits (See NF-kappaB Figures; Figure 1 available from the Download Box): RelA (p65), RelB and c-Rel (which contain transactivation domains within their c-termini) and NF-kappaB1 (p105/p50) and NF-kappaB2 (p100/p52) which undergo proteolysis to yield the DNA-binding isoforms, p50 and p52 which lack transactivation domains. Combinations of subunits determine the specificity of transcriptional activation and all have distinct, non-overlapping functions. The consensus NF-kappaB binding site is generally viewed as 5´-GGGRNYYYCC-3´ (where R = A or G; N = A, C, T or G and Y = C or T) although there are a great many functional variations on this and it is estimated that there are in excess of 3000 kappaB sites within the human genome. The figure to the left illustrates the N-terminal domain of the mouse RelA homodimer bound to DNA. This was resolved by Gourisanker Ghosh at the University of California at San Diego (see Chen et al. (1998). Nature Structural Biology 5: 67-73).)



In the majority of unstimulated cell types, NF-kappaB is retained within the cytoplasm in an inactive form, bound to its inhibitor protein, IkappaB (See NF-kappaB Figures; Figure 2 available from the Download Box). NF-kappaB can be activated in at least two ways. In the first, or canonical, pathway, cytokines, such as TNFalpha and IL-1beta, cause phosphorylation of IkappaB kinase (IKK) ultimately releasing p50:RelA and/or p52/RelA heterodimers. The second, non-canonical, pathway utilises IKKalpha-induced phosphorylation and processing of p100 to p52 generating mainly p52:RelB heterodimers which transactivate a different subset of genes. Atypical modes of activation, including that induced by hypoxic insult, stimulate NF-kappaB through methods that often do not rely on degradation of the IkappaB complex. In addition to the variety of homo- and heterodimers formed, these proteins undergo post translational modifications such as phosphorylation and acetylation and can recruit a range of other regulatory proteins and transcription factors to the enhancer/repressor region. Together with the inherent architecture of the enhancer/promoter itself, a number of opportunities therefore arise for highly specific gene expression in response to a given stimulus.

NF-kappaB and the Myometrium
The human myometrium is a complex tissue: previous work in my lab has demonstrated that NF-kappaB expression occurs in a spatio-temporal fashion. As such, it is highly likely that NF-kappaB -regulated genes will be governed in a similar manner to ensure parturition occurs at the correct juncture.

My lab has also defined an association between RelA and the catalytic subunit of PKA in pregnant myometrial homogenates suggesting there may be cross-talk between NF-kappaB and the cAMP/PKA pathways within the myometrium. Significantly, elevation of cAMP and activation of PKA have been shown to inhibit NF-kappaB-mediated transcription in a number of non-myometrial cell lines. This thesis, however, is further complicated by reports detailing an association between RelA and PKA, with PKA being required to activate NF-kappaB DNA-binding in a cAMP-independent fashion. Furthermore, TNFalpha can reduce cAMP levels in cardiac myocytes analogous to that seen in the labouring myometrium. Consequently, my lab work focuses on how inflammatory mediators within the pregnant uterus and decidua work through NF-kappaB to reduce Galphas expression and subsequently induce parturition.

Research Objectives
My group aims to employ the very latest molecular technologies to decipher the molecular and cellular biology of the events which govern human pregnancy and labour. In turn, this will provide a foundation to develop tocolytics which are more effective clinically and safer for both mother and her child.

Research Funding Awarded

Over the last four years I have been either Principal or co-applicant on eight major research grants totalling £1,021,521 from the following sources:

Teaching Interests

My teaching interests include the molecular biology and physiology of parturition and gene regulationn to both undergraduate and post-graduate students. I am involved with the following courses:

Teaching - Undergraduate Medical Curriculum

Teaching - Post-Graduate Studies

Professional Activities and Factors of Esteem

Key Publications

myPublications

Members of the Group

Awards to Group Members

February 2011
Congratulations to Vicky Cookson who successfully defended her theis and was awarded her Ph.D. on February 4th. Well done Dr. Cookson; a fantastic achievement!

April 2010
Congratulations to Sarah Waite, the Senior Research Technician in my group, who has is now a full Member of the Institute of Science and Technology.

September 2009
Congratulations to Vicky Cookson for winning in excess of £3,000 in funding from the Funds for Women Graduates scheme.

May 2009
Congratulations to Vicky Cookson, my first Ph.D. student, who won first prize in the Medical School's third year Ph.D. seminar programme in May 2009: well done, Vicky!