Endodermal Development and Differentiation

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Ray Dunn


Dr. Ray Dunn obtained his Ph.D. in Cell Biology in 1999 from Vanderbilt University under the supervision of Brigid Hogan, PhD FRS. His thesis described how the TGFb-related growth factor BMP4 controls primordial germ cell formation in the early mammalian embryo. He then completed a post-doctoral fellowship in the laboratory of Elizabeth Robertson, PhD FRS at Harvard University, where he studied the growth factor Nodal and its intracellular effector proteins Smad2 and Smad3 during early axis formation and early germ layer patterning in the mouse. In 2004, he joined ES Cell International Pte Ltd as a Research Scientist in the Diabetes Group, eventually being named Program Manager in 2005. In July 2007, he was appointed as a Principal Investigator in the Institute for Medical Biology and Singapore Stem Cell Consortium.  He also holds an Adjunct Assistant Professor position at the Lee Kong Chian School of Medicine at Nanyang Technological University (NTU).

In life, a single embryonic stem cell gives rise to all the 220 or so specialized cell types that make up the human body. Amongst these, some stem cells will turn into the critical insulin-producing cells of the pancreas, whose loss of function leads to diabetes. Ray's group is investigating how one can mimic this process, starting with cultured human stem cells to generate safe and efficient insulin-producing cells for the treatment of diabetes.

Type I diabetes, which accounts for 5 to 10% of all diagnosed cases, is caused by the autoimmune destruction of the pancreatic beta cells that produce insulin. The focal nature of this pathology makes diabetes an ideal candidate disease for the development of cell replacement therapies. Indeed, recent advances in clinical islet transplantation that draw upon improved islet isolation techniques and immunosuppression regimes, the so-called Edmonton protocol, have been very successful at keeping patients free from insulin dependency for extended, though not indefinite, periods of time. However, the limited supply of donor pancreatic tissue makes this cell therapy approach inadequate to meet the global patient demand for treatment. Intensive research has thus focused on identifying alternative sources of beta cells, of which human embryonic stem cells (hESC) are an appealing choice. By analogy to the behavior of mouse ES cells and given the appropriate culture conditions, hESC can probably form the approximately 220 specialized cell types that comprise the adult human.

In our group, we aim to harness this remarkable lineage potential to generate clinically compliant, functional beta cells that may provide an inexhaustible supply of material for the treatment of type I diabetes. In practice, our experimental design is largely guided by our understanding of mammalian definitive endoderm formation and the inductive interactions and morphogenesis that underlie the emergence of one of its derivatives, the pancreas. At present, we are focusing on the development of a 2D (or "monolayer") protocol that promotes the efficient formation of beta-like cells from hESC after approximately three weeks of in vitro differentiation. In addition, we have embarked on several discovery based strategies including a small molecule library screen to identify factors/pathways that promote beta-cell formation as well as ChIP-on-CHIP and transcriptional profiling studies to reveal novel genes that regulate endoderm formation and specification of early pancreatic progenitors. Lastly, we anticipate building on the groups' strengths in mouse ES cell culture and genetics to validate targets that emerge from these hESC based approaches.


Group Members

Senior Research Fellow Norihiro Tsuneyoshi
Research Fellow Jamie Trott
Postgraduate Student Yunus Alpagu (SINGA)
Senior Research Officer TAN Ee Kim
Research Officer Ong Li Ming, Sheena

Chia CY, Madrigal P, Denil SLIJ, Martinez I, Garcia-Bernardo J, El-Khairi R, Chhatriwala M, Shepherd MH, Hattersley AT, Dunn NR, Vallier L. GATA6 Cooperates with EOMES/SMAD2/3 to Deploy the Gene Regulatory Network Governing Human Definitive Endoderm and Pancreas Formation. Stem Cell Reports. 2019 Jan 8;12(1):57-70. doi: 10.1016/j.stemcr.2018.12.003. Link
Lovatt M, Yam GH, Peh GS, Colman A, Dunn NR, Mehta JS. Directed differentiation of periocular mesenchyme from human embryonic stem cells. Differentiation. 2018 Jan - Feb;99:62-69. doi: 10.1016/j.diff.2017.11.003 Link
James C, Zhao TY, Rahim A, Saxena P, Muthalif NA, Uemura T, Tsuneyoshi N, Ong S, Igarashi K, Lim CY, Dunn NR, Vardy LA. MINDY1 is a Downstream Target of the Polyamines and Promotes Embryonic Stem Cell Self-Renewal. Stem Cells. 2018 Apr 12. doi: 10.1002/stem.2830 Link
Havlicek S, Shen Y, Alpagu Y, Bruntraeger MB, Zufir NB, Phuah ZY, Fu Z, Dunn NR, Stanton LW. Re-engineered RNA-Guided FokI-Nucleases for Improved Genome Editing in Human Cells. Mol Ther. 2017 Feb 1;25(2):342-355. doi: 10.1016/j.ymthe.2016.11.007. Link
Trott, J, Ee KT, Ong S, Titmarsh DM, Denil SLIJ, Giam M, Wong CK, Wang J, Shboul M, Eio M, Cooper-White J, Cool SM, Rancati G, Stanton LW, Reversade R, Dunn NR. Long-Term Culture of Self-Renewing Pancreatic Progenitors Derived from Human Pluripotent Stem Cells. Stem Cell Reports 2017 8:1675-1688. DOI: 10.1016/j.stemcr.2017.05.019 Link
Ho L, van Dijk M, Chye STJ, Messerschmidt DM, Chng SC, Ong S, Yi LK, Boussata S, Goh GH, Afink GB, Lim CY, Dunn NR, Solter D, Knowles BB, Reversade B. ELABELA deficiency promotes preeclampsia and cardiovascular malformations in mice.Science. 2017 Aug 18;357(6352):707-713. doi: 10.1126/science.aam6607 Link
Mzoughi S, Zhang J, Hequet D, Teo SX, Fang H, Xing QR, Bezzi M, Seah MKY, Ong SLM, Shin EM, Wollmann H, Wong ESM, Al-Haddawi M, Stewart CL, Tergaonkar V, Loh YH, Dunn NR, Messerschmidt DM, Guccione E. PRDM15 safeguards naive pluripotency by transcriptionally regulating WNT and MAPK-ERK signaling. Nat Genet. 2017 Sep;49(9):1354-1363. doi: 10.1038/ng.3922. Link
Dunn NR, Tolwinski NS. Ptk7 and Mcc, Unfancied Components in Non-Canonical Wnt Signaling and Cancer. Cancers (Basel). 2016 Jul 16;8(7). pii: E68. doi: 10.3390/cancers8070068. Link
Bessarab DA, Mathavan S, Jones CM, Ray Dunn N. Zebrafish Rnf111 is encoded by multiple transcripts and is required for epiboly progression and prechordal plate development. Differentiation. 2015 Jan 22. pii: S0301-4681(14)00099-1. doi: 10.1016/j.diff.2014.12.004. [Epub ahead of print] PubMed PMID: 25619648. Link
Teo AK, Tsuneyoshi N, Hoon S, Tan EK, Stanton LW, Wright CV, Dunn NR. PDX1 binds and represses hepatic genes to ensure robust pancreatic commitment in differentiating human embryonic stem cells. Stem Cell Reports. 2015 Apr 14;4(4):578-90. doi: 10.1016/j.stemcr.2015.02.015. Link
Ho L, Tan SY, Wee S, Wu Y, Tan SJ, Ramakrishna NB, Chng SC, Nama S, Sczerbineska I, Chan W, Avery S, Tsuneyoshi N, Ng HH, Gunaratne J, Dunn NR, Reversade B. ELABELA Is an Endogenous Growth Factor that Sustains hESC Self-Renewal via the PI3K/AKT Pathway. Cell Stem Cell. 2015 Sep 16. pii: S1934-5909(15)00365-3. doi: 10.1016/j.stem.2015.08.010. PubMed PMID: 26387754. Link
Young T, Poobalan Y, Tan EK, Tao S, Ong S, Wehner P, Schwenty-Lara J, Lim CY, Sadasivam A, Lovatt M, Wang ST, Ali Y, Borchers A, Sampath K, Dunn NR. The PDZ domain protein Mcc is a novel effector of non-canonical Wnt signaling during convergence and extension in zebrafish. Development. 2014 Sep;141(18):3505-16. doi: 10.1242/dev.114033. PubMed PMID: 25183869. Link
Tsuneyoshi N, Dunn NR. Guards at the gate to embryonic stem cell differentiation. Cell. 2013 Apr 11;153(2):281-3. doi: 10.1016/j.cell.2013.03.037. PubMed PMID: 23582317. Link
Tsuneyoshi, N., Tan, E. K., Sadasivam, A., Poobalan Y., Sumi T., Nakatsuji N., Suemori, H. and Dunn, N.R. 2012. The SMAD2/3 corepressor SNON maintains pluripotency through selective repression of mesendodermal genes in human ES cells. Genes & Dev. 26: 2471-2476.
Teo, A.K.K., Ali, Y., Wong, K.Y., Chipperfield, H., Sadasivam, A., Poobalan, Y., Tan, E.K., Wang, S.T., Abraham, S., Tsuneyoshi, N., Stanton, L.W. and Dunn, N.R. 2012. Activin and BMP4 synergistically promote formation of definitive endoderm in human embryonic stem cells. Stem Cells 30: 631-642.
Young, T., Poobalan, Y., Ali, Y., Wang, S.T., Tan, E.K., Tay, P.E. And Dunn, N.R. 2011. Mutated in Colorectal Cancer (Mcc), a Candidate Tumor Suppressor, Is Dynamically Expressed During Mouse Embryogenesis. Dev Dyn 240: 2166-2174.
Brown S, Teo A, Pauklin S, Hannan N, Cho CH, Lim B, Vardy L, Dunn NR, Trotter M, Pedersen R, Vallier L. 2011. Activin/Nodal signaling controls divergent transcriptional networks in human embryonic stem cells and in endoderm progenitors. Stem Cells 29(8):1176-85.
Teo, A.K.K., S.J. Arnold, M.W.B. Trotter, S. Brown, L.T. Ang, Z. Chng, E.J. Robertson, N.R. Dunn, and L. Vallier. 2011. Pluripotency factors regulate definitive endoderm specification through Eomesodermin. Genes Dev 25, 238-250.
Wong ES, Le Guezennec X, Demidov ON, Marshall NT, Wang ST, Krishnamurthy J, Sharpless NE, Dunn NR, Bulavin DV. 2009. p38MAPK controls expression of multiple cell cycle inhibitors and islet proliferation with advancing age. Dev Cell 17(1): 142-9.
Hentze, H., P.L. Soong, S.T. Wang, B.W. Phillips, T.C. Putti, and N.R. Dunn. 2009. Teratoma formation by human embryonic stem cells: Evaluation of essential parameters for future safety studies. Stem Cell Research 2(3): 198-210.
Dunn, N.R. 2008. Self-renewal made simple. Cell Stem Cell 3, 7-8.
Crook, J.M., T.T. Peura, L. Kravets, A.G. Bosman, J.J. Buzzard, R. Horne, H. Hentze, N.R. Dunn, R. Zweigerdt, F. Chua, A. Upshall, and A. Colman. 2007. The generation of six clinical-grade human embryonic stem cell lines. Cell Stem Cell 1: 490-494.
Phillips, B.P., H. Hentze, W.L. Rust, Q.-P. Chen, H. Chipperfield, E.-K. Tan, S. Abraham, A. Sadasivam, P.L. Soong, S.T. Wang, R. Lim, W. Sun, A. Colman, and N.R. Dunn. 2007. Directed differentiation of human embryonic stem cells into the pancreatic endocrine lineage. Stem Cells Dev 16(4): 561-78.
Crook, J.M., N.R. Dunn, and A. Colman. 2006. Repressed by a NuRD. Nature Cell Bio 8: 212-214.
Rust, W.L., A. Sadasivam, and N.R. Dunn. 2006. Three-dimensional extracellular matrix stimulates gastrulation-like events in human embryoid bodies. Stem Cells Dev 15: 889-904.
Vincent, S.D., N.R. Dunn, R. Sciammas, M. Shapiro-Shalef, M.M. Davis, K. Calame, E.K. Bikoff, and E.J. Robertson. 2005. The zinc finger transcriptional repressor Blimp-1/Prdm1 is required for specification of primordial germ cells in the mouse. Development 132: 1315-1325.
Dunn, N.R., C.H. Koonce, D.C. Anderson, A. Islam, E.K. Bikoff, and E.J. Robertson. 2005. Mice exclusively expressing the short isoform of Smad2 develop normally and are viable and fertile. Genes Dev 19: 152-163.
Chu, G.C., N.R. Dunn, D.C. Anderson, L. Oxburgh, and E.J. Robertson. 2004. Differential requirements for Smad4 in TGFb-dependent patterning of the early mouse embryo. Development 131, 3501-12.
Dunn, N.R., S.D. Vincent, L. Oxburgh, E.J. Robertson, and E.K. Bikoff. 2004. Combinatorial activities of Smad2 and Smad3 regulate mesoderm formation and patterning in the mouse embryo. Development 131, 1717-1728.
Vincent, S.D., N.R. Dunn, S. Hayashi, D.P. Norris, and E.J. Robertson. 2003. Cell fate decisions within the mouse organizer are governed by graded Nodal signals. Genes Dev 17, 1646-1662.