1. Research Background:
How epithelia coordinate cell and tissue structure with growth and metabolic activity to control morphogenesis and homeostasis of tissues is a fundamental question in biology. Altered regulation of epithelial cell/tissue architecture disturbs tissue homeostasis and promotes ageing and ageing-associated diseases, such as cancer and a range of inflammatory diseases. Using the self-renewing epidermis as a paradigm the Niessen laboratory asks how key regulators of the cyto-architecture control the formation and maintenance of epithelial tissues. More specifically, we ask how cell adhesion and polarity integrate with growth and inflammatory pathways to control stem cells, differentiation, tissue integrity and homeostasis in a stratifying epithelium, the epidermis of skin. Furthermore we ask if and how age-associated alterations in molecular regulators of cell architecture alter stem cell behavior and result in skin cancer and skin barrier related diseases.
2. Research questions addresses by the group:
- How do cadherins and polarity signaling pathways regulate the establishment and maintenance of the epidermal skin barrier and how does improper skin barrier function contributes to (age-associated) disease?
- How do core polarity complexes regulate epidermal progenitor cell behavior and cell fate decisions in the mammalian stratifying epithelia?
- How does the insulin/IGF pathway control epidermal morphogenesis, homeostasis and barrier function?
- How do aging and external age accelerators such as UV light affect cell fate decisions and tissue architecture to alter epidermal barrier function?
3. Possible projects:
- How does aging affect epidermal stem cell behavior?
Using different Cre drivers to fluorescently label different epidermal stem cell populations, we will use intra vital microscopy to dynamically follow different epidermal stem cell populations in vivo and ask how aging impacts on activation, localization, division speed and orientation, migration and death of stem cells. These functional data will be linked to proteomic data sets to identify potential molecular candidates that mediate the age-dependent changes in epidermal stem cells.
- Role of polarity and metabolic signals in stem cell aging
We previously found that loss of polarity signaling and its upstream regulator Insulin/IGF-1 results in reduced stem cell numbers and altered stem cell behavior and regenerative responses. We would therefore like to use these two mouse models to examine how these pathways alter stem cell behavior and responses to injury and whether this mimics the behavior of naturally aged stem cells.
- Role of tyrosine kinase receptor signaling in regulation epidermal barrier function.
We recently identified an E-cadherin-mediated mechanical circuit that integrates adhesion, contractile forces and EGFR signaling to drive the polarized organization of junctional tension necessary to build an in vivo epithelial barrier. These results suggest that EGFR integrates regulation of the structural barrier with innate immune barrier function. To address this hypothesis we therefore will inactivate EGFR in different epidermal populations and assess structural barrier functions as well as innate immune responses. We are also developing optogenetic tools to spatiotemporally control tyrosine kinase receptor activity.
4. Applied Methods and model organisms:
All three projects depend on transgenic mouse models, most of which already exist in the lab or are in the process of being generated. Basic analysis of these lines includes histochemistry, immuno histochemistry and high resolution whole mount imaging. In close collaboration with the laboratory of Valentina Greco (Yale University), we have established non-invasive intra vital microscopy (see e.g. Rompolas, Nature, 2012, 2013), which using different fluorescent mouse reporter lines enables revisiting the same stem cell populations within the epidermis. This technique will be used in all 3 projects. In the 3rd project we will also use in vivo imaging on embryos.
Another great advantage of using the epidermis as a paradigm for epithelial renewal and barrier function is not only the obvious ability to easily assess phenotypes but also the ability to isolate and culture epidermal keratinocytes. Projects will use these cultured cells from the different transgenic lines to assess biophysical (traction force and atomic force microscopy, cell stretching) and biochemical parameters and perform life cell imaging in 2d and 3d culture systems. All projects will also make use and /or take advantage of the fact that we have established SILAC and have and will perform proteomics and phospho- proteomics of cells and isolated epidermis of the different mouse models. Finally, when necessary we will perform RNA sequencing and ATAC sequencing to assess overall transcriptional changes and identify potential transcriptional regulators and motifs.
5. Desirable skills and qualifications:
We are looking for a highly scientifically enthusiastic and motivated person who wants to address fundamental molecular cell biology questions with a clear clinical perspectives in an international environment.
Skills and qualifications:
- Experience in high end imaging, mouse genetics and/or bioinformatics
- Ability to work in an international team
- Insulin/IGF-1 controls epidermal morphogenesis via regulation of FoxO-mediated p63 inhibition. Günschmann C, Stachelscheid H, Akyüz MD, Schmitz A, Missero C, Brüning JC, Niessen CM.
Dev Cell. 2013 Jul 29;26(2):176-87. doi: 10.1016/j.devcel.2013.05.017.
- Spatial organization within a niche as a determinant of stem-cell fate. Rompolas P, Mesa KR, Greco V.
Nature. 2013 Oct 24;502(7472):513-8. doi: 0.1038/nature12602. Epub 2013 Oct 6.
- E-cadherin integrates mechanotransduction and EGFR signaling to control junctional tissue polarization and tight junction positioning. Rübsam M, Mertz AF, Kubo A, Marg S, Jüngst C, Goranci-Buzhala G, Schauss AC, Horsley V, Dufresne ER, Moser M, Ziegler W, Amagai M, Wickström SA, Niessen CM.
Nat Commun. 2017 Nov 1;8(1):1250. doi: 10.1038/s41467-017-01170-7.
- MiroshnikovaYA, LeHQ, David Schneider D, ThalheimT, RübsamM, BremickerN, PolleuxJ, KampradN, TarantolaM, WangI, BallandM, NiessenCM, GalleJ, WickströmSA. (2018) A biomechanical network of adhesion forces and cell mechanics couples proliferation and differentiation to drive epidermal stratification. Nature Cell Biology, 20:69-80. doi: 10.1038/s41556-017-0005
- Vorhagen S*, Kleefisch D*, Persa, O-D, Graband, A., SchwickertA, Saynisch M., LeitgesM, Niessen CM+, and IdenS+ (2018) Shared and independent functions of aPKCλ and Par3 in skin tumorigenesis. Oncogene, May 23. doi: 10.1038/s41388-018-0313-1
- E-cadherin binds to desmoglein to facilitate desmosome assembly.
Shafraz O*, Rübsam M*, Stahley SN, Caldara AL, Kowalczyk AP, Niessen CM, Sivasankar S.
Elife. 2018 Jul 12;7. pii: e37629. doi: 10.7554/eLife.37629.
* shared first author, + shared last author