Apoptosis (bright green cells) of hair follicle keratinocytes during catagen stage of the hair cycle.

During organ development, pluripotent precursor cells proliferate and expand to undergo progressive series of differentiation steps, finally generating fully differentiated cell types capable off carrying out the functions characteristic for a given organ. In this process, there is a link between cellular proliferation and differentiation because concomitant with the acquisition of differentiation cells usually lose the ability to proliferate. These cellular processes, which are controlled by signals that ultimately affect the regulation of gene expression, can be subverted, causing diseases, including cancer. In fact, cancer cells share many characteristics with undifferentiated cells of a developing organ, including persistent proliferation and suppression of the differentiation program, suggesting that developmental regulatory pathways may be important targets of mutations in cancer.

The long-term goal of the Andersen laboratory is to understand transcriptional control mechanisms that underlie normal development of epidermis, hair follicles and mammary glands, and to use this knowledge to gain insights into carcinogenesis in epithelial tissues. To reach this goal, the laboratory uses a variety of approaches. These include cDNA cloning methods and genomics to identify candidate regulators, mouse genetics to test the function of candidate genes and in vitro studies to understand transcriptional mechanisms.

Currently, research in the Andersen laboratory focuses on the role of two classes of transcriptional regulators: POU homeodomain factors and LIM domain factors. Epidermally expressed POU homeodomain proteins seem to play a role in repressing expression of the keratin 5 and 14 genes, which are normally expressed in undifferentiated keratinocytes but silenced in differentiated cells. Our studies suggest that POU domain factors may interfere with the function of CBP/p300 co-regulators at the core promoter of the keratin 14 gene.

A whole mount preparation of a mammary gland from a 6 wk old mouse. The ductal system is invading the fat pad at this stage and has passed the central lymph node (dark blue structure in the middle). Eventually the ducts will fill in the fat pad.

A major focus of the Andersen laboratory involves investigating the roles of Clim/Nli/Ldb co-activators in stratified epithelia and mammary glands. The Clim proteins were discovered based on their ability to bind to LIM domains of LIM homeodomain factors and confer transcriptional activation by this class of DNA-binding proteins. One member of this family of co-activators, Clim-2, is highly expressed in epithelial cells of the epidermis and internal epithelial linings. We have found that Clims interacts with the LIM only protein, LMO-4, which is expressed in an overlapping manner in epithelial tissues. Intriguingly, the LMO-4 gene belongs to a family of oncogenes.

Using genetic mouse models we have data indicating that this transcriptional complex may be an important regulator of epithelial morphogenesis and homeostasis, including that of the hair follicle morphogenesis and cycling. Presently, we are investigating how the LMO-4/Clim-2 transcriptional complex relates to known signaling pathways involved in epithelial regulation, and how it interacts with DNA-binding proteins. Recently, we have uncovered a new epithelially expressed Grainyhead-like transcription factor, GET-1, which may interact with LMO-4. And, using Affymetrix microarrays and bioinformatics methods, we have been able to link disruption of the LMO-4/Clim-2 complex to distinct molecular alterations in epidermis.

In situ hybridization study showing expresson of GET-1, a novel Grainyhead-like transcription factor, in an e14.5 mouse embryo. This gene is prominently expressed in epithelial linings, including that of the developing epidermis (Ep).

In the mammary gland, expression of the LMO-4 and Clim-2 genes is dramatically upregulated in mammary epithelial cells during midpregnancy – a stage in mammary gland development when epithelial cells are undergoing active proliferation and invasion into the mammary gland fat pad. Therefore, we have hypothesized that the function of the LMO-4/Clim-2 complex may be to promote cellular proliferation and/or invasion. Consistent with this idea, the work of other investigators has shown that the LMO-4 gene is often overexpressed in human breast cancer.

Accumulating evidence suggest that the hair follicle plays important roles in skin carcinogenesis. Some epidermal cancers, especially basal cell carcinoma, may originate from hair follicle cells. In addition, subversion of normal regulators of hair morphogenesis, such as the Wnt and hedgehog pathways, is responsible for skin cancer. We are therefore investigating whether abnormalities in the Clim/LMO transcriptional complex may play a role in epithelial carcinogenesis in epidermis and mammary glands of humans.

Selected Publications:

Andersen, B., Schonemann, M., Flynn, S., Pearse, R., Singh, H., & Rosenfeld, M.G. 1993. Skn-1a and Skn-1i: Two functionally distinct Oct-2-related factors expressed in epidermis. Science 260:78-82.

Andersen, B., Hariri, A., Pittelkow, M.R., & Rosenfeld, M.G. 1997. Characterization of Skn-1a/i POU domain factors and linkage to papillomavirus gene expression. J. Biol. Chem. 272:15905-15913.

Bach, I., Carriere, C., Ostendorff, H.P., Andersen, B., & Rosenfeld, M.G. 1997. A family of LIM domain associated cofactors confer transcriptional synergism between LIM- and Otx homeodomain proteins. Genes & Dev. 11:1370-1380.

Andersen, B., Weinberg, W.C., Rennekampff, O., McEvilly, R., Bermingham, J.R., Hooshmand, F., Vasilyev, V., Hansbrough, J.F., Pittelkow, M.R., Yuspa, S.H., & Rosenfeld, M.G. 1997. Functions of the POU domain genes Skn-1a/i and Tst-1/Oct-6/SCIP in epidermal differentiation. Genes & Dev. 11:1873-1885.

Sugihara, T.M., Bach, I., Kioussi, C., Rosenfeld, M.G. & Andersen, B. 1998. Mouse Deformed epidermal autoregulatory factor 1 recruits a LIM domain factor, LMO-4, and CLIM coregulators. Proc. Natl. Acad. Sci. 95:15418-15423.

Bach, I., Rodriguez-Esteban, C., Carriere, C., Bhushan, A., Krones, A., Rose, D.W., Glass, C.K., Andersen, B., Belmonte, J.C.I. & Rosenfeld, M.G. 1999. RLIM inhibits functional activity of LIM homeodomain transcription factors via recruitment of the histone deacetylase complex. Nature Genetics 22:394-399.

Suzuki, K., Yamanishi, K., Mori, O., Kamikawa, M., Andersen, B., Kato, S., Toyoda, T., & Yamada, G. 2000. Defective terminal differentiation and hypoplasia of the epidermis in mice lacking the Fgf10 gene. FEBS Lett. 8:53-56.

Sugihara, T.M., Kudryavtseva, E., Kumar, V., Horridge, J.J. & Andersen, B. 2001. The POU domain factor Skin-1a represses the keratin 14 promoter independent of DNA binding: possible role for interactions between Skn-1a and CBP/p300. J. Biol. Chem. 276:33036-33044.