Functional genomics approaches to study nuclear receptor signaling

Our research focuses on the physiological functions of estrogen receptors (ERs; ERα and ERβ paralogs) and liver X receptors (LXR; LXRα and LXRβ paralogs) particularly in relation to metabolic disease and cancer.

Major technologies

We use functional genomic technologies, including gene expression profiling, global DNA-binding (ChIP on chip) and genotyping, in combination with studies in animal models and human samples.

Project 1: Estrogen signaling and glucose homeostasis

Background and previous results
Mice lacking ERα(ERαKO mice) display a phenotype of type 2 diabetes (T2D). Euglycemic hyperinsulinemic clamps, combined with glucose turnover studies, confirmed the presence of whole body insulin resistance in ERαKO mice. Importantly, in ERαKO mice, the suppression of endogenous glucose output by increased insulin levels is blunted showing the importance of the liver for the observed phenotype.

Future plans
Technologies for global DNA-binding, gene expression profiling, proteomics and metabolomics will be applied to describe signaling from 17-β-estradiol and analogues to phenotype. Different animal models of decreased glucose tolerance are studied.

Project 2: The genome landscape of estrogen receptors ??and β
The goal of this project is to describe the first event in estrogen signaling i.e. the binding of ERs to DNA in the context of intact chromatin.

Background
We were the first to explore differences between the two estrogen receptors, ERα and ERβ, with regard to global DNA-binding. Analysis of bound regions show that regions bound by ERα have distinct properties in terms of genome landscape, sequence features and conservation compared to regions that are bound by ERβ.

Future plans
We will approach the molecular mechanism behind the selectivity observed for ERα and ERβ DNA binding regions. We have recently established a “re-ChIP on chip” assay for binding of ERα-ERβ heterodimers that will allow us to explore interactions between signaling via ERα and ERβ at the level of DNA-binding. Correlating transcript data, including microRNA, with global DNA-binding will reveal important determinants, in addition to ER DNA-binding, for transcript regulation.

Project 3: Estrogen signaling in breast cancer
The goal of this project is to determine the role of the ERβ variant ERβ2 in estrogen signaling in breast cancer cells and responsiveness to anti-estrogen treatment.

Future plans
We will study if, and how, ERβ2 modulates estrogen and antagonist regulated gene networks and global DNA-binding by ERs in breast cancer cells.

The role of ERα in human obesity
The goal of this project is to determine the mechanism of reduced ERα mRNA levels in adipocytes of obese individuals compared with controls that we have described.

Future plans
We will address the mechanism of ERα mRNA down regulation in adipose tissue from obese versus lean individuals.

Recent references

Gao, H., Bryzgalova, G., Hedman, E., Khan, A., Efendic, S., Gustafsson, J.- Å. and Dahlman-Wright, K. (2006) Long-term administration of estradiol decreases expression of hepatic lipogenic genes and improves insulin sensitivity in ob/ob mice: A possible mechanism is through direct regulation of Stat3. Mol Endo, 20, 1287-99.

Dahlman, I., Nilsson, M., Jiao, H., Hoffstedt, J., Lindgren, C.M., Humphreys, K., Kere, J., Gustafsson, J.-Å., Arner, P. and Dahlman-Wright, K. (2006) Liver X receptor gene polymorphisms and adipose tissue expression levels in obesity. Pharmacogenetics and Genomics, 16, 881-9.

Zhao, C., Matthews, M., Tujague, M., Wan, J., Ström, A., Toresson, G., Lam, E., W.-F., Cheng, G., Gustafsson, J.-Å. and Dahlman-Wright, K. (2007) Estrogen receptor (ER) β2 inhibits ERα activity through proteasomal degradation of ERα in human breast cancer. Can Res 67, 3955-62.

Nilsson, M., Dahlman, I., Jiao, H., Gustafsson, J.Å., Arner, P. and Dahlman-Wright, K. (2007) Impact of Estrogen Receptor Gene Polymorphisms and mRNA Levels on Obesity and Lipolysis – a Cohort Study. BMC Med Genet 4, 73-.

Lundholm, L., Zang, H., Lindén Hirschberg, A., Gustafsson, J.-Å., Arner, P., and Dahlman-Wright, K. (2008) Estrogen decreases gene expression of key lipogenic genes in human adipose tissue. Fertility and Sterility 90, 44-8.

Lundholm L., Putnik M., Otsuki M., Andersson S., Ohlsson C., Gustafsson J.-Å. and Dahlman-Wright K. (2008) Effects of estrogen on gene expression profiles in mouse hypothalamus and white adipose tissue: target genes include glutathione peroxidase 3 and cell death-inducing DNA fragmentation factor, alpha-subunit-like effector A. J Endocrinol. 196, 547-57.

Gao, H., Falt, S., Sandelin, A., Gustafsson, J.-Å. and Dahlman-Wright, K. (2008) Genome-wide identification of estrogen receptor α binding sites in mouse liver. Mol. Endocrinol 22, 10-22. I

Liu, Y, Gao, H., Marstrand, T.T., Ström, A., Valen, E, Sandelin , A., Gustafsson, J.-Å. and Dahlman-Wright, K. (2008) The genome landscape of ERα- and ERβ-binding DNA regions. Proc. Natl. Acad. Sci. USA, 19, 2604-9.

Lundholm, L., Bryzgalova, G., Gao, H., Portwood, N., Fält, S., Berndt, K., Dicker, A., Galuska, D., Zierath, J.R. Gustafsson, J.-Å., Efendic, S., Dahlman-Wright, K. and Khan, A. The estrogen receptor alpha-selective agonist PPT improves glucose tolerance in ob/ob mice; potential molecular mechanisms. J. Endocrinology, In press.

Bryzgalova, G., Lundholm, L., Portwood, N., Gustafsson, J.-Å. Khan, A., Efendic, S. and Dahlman-Wright, K. Mechanisms of antidiabetogenic and body weight-lowering effects of estrogen in high fat diet-fed mice. Am J Physiol Endocrinol Metab, In press.

Thesis

M. Nilsson: Estrogen and Liver X Receptors in Human Disease. Thesis, Stockholm Dec 2006.

H. Gao: Estrogen signaling in metabolic disease; A Functional Genomics Approach. Thesis, Stockholm Dec 2006.

L. Lundholm: Molecular Mechanisms of Estrogen Action in Relations to Metabolic Disease. Thesis, Stockholm Dec 2007.