Michael M. Shen
	Professor Department of Pediatrics UMDNJ-Robert Wood Johnson Medical School Member Cancer Institute of New Jersey Ph.D., 1988, Cambridge University Tel:  [732] 235-3374 Fax: [732] 235-5373 mshen@cabm.rutgers.edu Shen Lab Home Page

EGF-CFC genes, Nodal signaling pathway, embryonic axis formation, TGF-beta signal transduction, prostate induction, cancer progression.

Our laboratory pursues research in the molecular genetics of developmental pathways and their alterations in cancer, using the mouse as a model system. We have been interested in understanding the mechanisms that regulate cell proliferation, pattern formation, and morphogenesis during embryonic development, and how these processes go awry during cancer initiation and progression.

To address the first area, we are pursuing studies of the EGF-CFC gene family, whose members encode novel extracellular proteins that modulate transforming growth factor-beta (TGF-beta) signaling pathways. We have used gene targeting approaches in mice to demonstrate that EGF-CFC genes play essential roles in embryonic axis formation. In particular, Cripto is required for correct orientation of the anterior-posterior (A-P) axis, while Cryptic is necessary for determination of the left-right (L-R) axis. Our studies have also shown essential roles for Cripto in embryonic mesoderm induction and axial midline formation.

Thus, we have found that Cripto mutant embryos lack a primitive streak and embryonic mesoderm, and are instead mostly comprised of anterior neural tissue, resembling a head without a trunk. Notably, markers normally expressed in the anterior visceral endoderm are located distally in Cripto mutants, while early posterior markers are localized proximally. indicating that Cripto is essential for the rotation of a pre-existing proximal-distal asymmetry (corresponding to the prospective D-V axis) into an orthogonal A-P axis. Our results provide strong support for the model that the A-P axis is positioned by coordinated cell movements in the visceral endoderm and epiblast layers.

In contrast, we have demonstrated that Cryptic is required for L-R axis formation in the mouse, and suggests that EGF-CFC activity is necessary for transfer of L-R positional information from the node to the periphery. Thus, Cryptic mutant mice display numerous laterality defects such as randomized abdominal situs and pulmonary right isomerism, while mutant embryos lack expression of L-R asymmetrically expressed genes such as Nodal and Pitx2 in the lateral plate mesoderm. However, asymmetric expression of Nodal around the node is maintained, suggesting that L-R axis specification has initiated at the node, but has not propagated to the periphery. Our results support an interaction of EGF-CFC proteins with the TGF-beta-related factor Nodal and with activin receptors, which we are currently examining using biochemical and cell culture approaches.

In a second area of interest, we are investigating the molecular genetics of prostate development and cancer (in collaboration with Dr. Cory Abate-Shen’s lab). We have been focusing on the role of the Nkx3.1 homeobox gene, which displays restricted expression in the embryonic and adult mouse prostate. We have shown that Nkx3.1 is the earliest known marker of the prostate epithelium, and that it plays a critical role in the normal morphogenesis and function of the prostate. Nkx3.1 mutant mice are viable and fertile, with homozygous males displaying reduced size and ductal branching of the prostate glands, as well as defects in the levels of prostatic secretory proteins.

Moreover, our studies also indicate that Nkx3.1 represents a candidate prostate-specific tumor suppressor gene. Thus, Nkx3.1 homozygous as well as heterozygous mutant mice display prostatic epithelial hyperplasia and dysplasia of increasing severity with advancing age. These lesions in aged mutant mice resemble human prostatic intraepithelial neoplasia (PIN), which is believed to represent the precursor to prostate carcinoma. Furthermore, the Nkx3.1 gene product exhibits tumor suppressor activities in cell culture and in assays for tumor formation in immunodeficient mice. Notably, the human Nkx3.1 ortholog maps to a region of chromosome 8 that undergoes loss of heterozygosity as a frequent and early event in prostate tumors. Our findings show that Nkx3.1 plays a critical role in the normal morphogenesis and function of the prostate, and suggest that the Nkx3.1 mutant mice will be invaluable for molecular studies of cancer progression, for analyses of hormonal carcinogenesis, and for assaying potential pharmacological interventions.

Mislocalized expression of early anterior and posterior markers in Cripto mutant embryos. (Left panel) Expression of Brachyury is normally found in the primitive streak (ps), but is localized to the proximal epiblast in Cripto mutants. (Right panel) Hex is expressed in the anterior visceral endoderm of wild-type embryos, but is found distally in Cripto mutants

Selected Publications1