The Laboratory of Genetics and Physiology (LGP) explores genetic switches and biochemical pathways that control mammalian organogenesis and physiology. In addition, we investigate pathways that control oncogenic transformation in the mammary gland and prostate. We have identified genes, which control cell specification, proliferation, differentiation and death during normal mammary development. Their role is being studied through their deregulated expression in mammary tissue of transgenic animals, and through their deletion from the mouse genome by homologous recombination. Towards this goal, we have established transgenic systems that permit a temporally controlled activation of transgenes, and the tissue-specific and temporally controlled deletion of endogenous genes during development. Current projects include the analysis of the prolactin/Jak2/Stat5 signaling pathway and C/EBPbeta during mammary development and the contribution of the IL6/Stat3/MAPK pathway in mammary gland involution. In 1997 the Laboratory of Genetics and Physiology launched the Mammary Genome Anatomy Project (MGAP) with the goal to identify and understand signaling pathways in normal mammary gland development and neoplastic transformation. In addition, we developed Histobank an online histology atlas and a database for images

1. PrlR/Jak2/Stat5 signaling in mammals
2. Jak/Stat signaling pathways in zebrafish development and physiology
3. The Wnt/beta-catenin pathway in development and tumorigenesis
4. IL6/Stat3/MAPK signaling
5. The role of connexins in epithelial physiology
6. Notch signaling in development and tumorigenesis
7. The role of the transcription factor, C/EBPbeta, in development
8. Gene discovery program

Many cytokines signal through the Jak2/Stat5 pathway and thus control the cell's response to its environment. In the mammary gland, the Jak2/Stat5 pathway is essential for the specification, proliferation, differentiation and possibly survival of mammary epithelium (1-4). Although the signal transducer and activator of transcription Stat5a and Stat5b are highly conserved (5) they play distinct roles in the physiology of the cell. While Stat5a is required for the differentiation of mammary epithelium (2, 6), Stat5b is not reuired (6). While Stat5a is not necessary for the proliferation of mammary epithelium per se, no secretory alveolar epithelium is formed in the combined absence of Stat5a and Stat5b (3). Moreover, the epithelium never specified (3). Since the inactivation of Stat5a and Stat5b genes in the germline results in the loss of certain cell types and in early defects, it is not possible to evaluate its role on later functions, such as differentiation of mammary epithelium and function during lactation.

The same holds true for other cell systems, such as the hematopoietic system. To investigate the role of the Jak2/Stat5 signaling pathway in distinct cell types and different stages of development and physiology, it is necessary to conditionally inactivate these genes. Towards this end we have cloned and characterized the locus that contains the genes encoding Stat5a, Stat5b and Stat3 (7, 8).

Based on this information we have generated targeting vectors and bracketed the Stat5a and 5b genes with loxP sites (Figure 1).

ES cells have been generated that carry a targeted locus and mice are being generated. Mice, which carry conditionally targeted Stat5 genes, and cells derived from these mice, will be used to inactivate Stat5 genes in distinct cell types and during specific time windows using transgenic mice expressing Cre recombinase (e.g ref. 9). In addition, we will use an inducible gene expression system (10) to reconstitute Stat5 expression.

Current investigators: Karen Cui, Wei Tang, Traudl Robinson
Past LGP investigators: Xiuwen Liu, Keiko Miyoshi, Kay-Uwe Wagner, Greg Riedlinger, Brian Bierie
Collaborators: Chu-Xia Deng, Keiko Miyoshi
Past Collaborators: Bernd Groner, Tony Wynshaw-Boris, Lisa Garrett

PubMed search

Relevant references

1. Hennighausen, L. and Robinson, G.W. (2001) Signaling pathways in the mammary gland. Developmental Cell, 1, 467-475.

2. Liu, X., Robinson, G.W., Wagner, K.-U., Garrett, L., Wynshaw-Boris, A. and Hennighausen, L. (1997) Stat5a is mandatory for adult mammary gland development and lactogenesis. Genes and Dev. 11, 179-186

3. Miyoshi, K., Shillingford, J.M., Smith, G.H., Grimm, S.L., Wagner, K.U., Oka, T., Rosen, J.M., Robinson, G.W. and Hennighausen, L. (2001) Signal transducer and activator of transcription 5 (Stat5) controls the specification and proliferation of mammary alveolar epithelium, J. Cell Biol., 155, 531-542.

4. Shillingford, J.M., Miyoshi, K., Robinson, G.W., Grimm, S.L., Rosen, J.M., Neubauer, H., Pfeffer, K. and Hennighausen, L. (2002) Jak2 is an essential tyrosine kinase involved in pregnancy-mediated development of mammary secretory epithelium. Mol. Endo., in press.

5. Liu, X.-W., Goulliaux, F., Robinson, G.W., Groner, B. and Hennighausen, L. (1995) Identification and characterization of STAT5 and a novel homologue (STAT5b) involved in prolactin mediated signal transduction in mouse mammary tissue. Proc. Natl. Acad. Sci.U.S.A. 92, 8831-8835.

6. Teglund, S., McKay, C., Schuetz, E., Van Deursen, J.M., Stravapodis, D., Wang, D., Brown, M., Bodner, S., Grosveld, G and Ihle, J.N. (1998) Stat5a and Stat5b proteins have essential and nonessential, or redundant, roles in cytokine responses. Cell 93, 841-850.

7. Miyoshi, K., Cui, Y.K., Riedlinger, G., Robinson, P., Lehoczky, J., Zon, L., Oka, T., Dewar, K. and Hennighausen, L. (2001) Structures of the mouse and zebrafish Stat3/5 loci: Evolution from Drosophila to zebrafish to mouse. Genomics, 71, 150-155.

8. Cui, Y, Li, M., Walton, K.D., Sun, K., Hanover, J.A., Furth, P.A. and Hennighausen, L. (2001) The Stat3/5 locus encodes novel endoplasmic reticulum and helicase-like proteins that are preferentially expressed in normal and neoplastic mammary tissue. Genomics, 78, 129-134.

9. Wagner, K.-U., Wall, R.J., St-Onge, L., Gruss, P., Garrett, L., Wynshaw-Boris, A., Li, M., Furth, P.A. and Hennighausen, L. (1997) Cre mediated gene deletion in the mammary gland. Nucleic Acids. Res. 25, 4323-4330.

10. Wagner, K.U., McAllister, K., Ward, T., Davis, B., Wiseman, R. and Hennighausen, L. (2001) Spatial and temporal expression of the Cre gene under the control of the MMTV-LTR in different lines of transgenic mice. Transgenic Research, 10, 545-553.

11. Wagner, K-U., Estefania C., Rucker, E., Riedlinger, G, Broussard, C., Schwartzberg, P.L., Siebenlist, U., Hennighausen, L. (2000) Conditional deletion of the bcl-x gene from erythroid cells results in hemolytic anemia and profound splenomegaly. Development, 127, 4949-4958.

12. Furth, P.A., St. Onge, L., Boger, H., Gruss, P., Gossen, M., Kistner, A., Bujard, H. and Hennighausen, L. (1994) Temporal control of gene expression in transgenic mice by a tetracycline responsive promoter. Proc. Natl. Acad. Sci. U.S.A. 91, 9302-9306.

The Jak-Stat signaling pathway is operative not only in mammals but also in other vertebrates and in non-vertebrates. Many of the physiological roles attributed to Jak/Stat signaling in mammals might have been acquired late in evolution, such as its role in lactation. To explore more ancient functions of Stats we are currently adapting zebrafish genetics. As part of this we have cloned several zebrafish genes from the Stat signaling pathway and we are currently exploring their function. Most notably, there is only one Stat5 gene in zebrafish, and based on its sequence and orientation with respect to the Stat3 gene it appears to be the ortholog of Stat5b in mammals.