Xi He

Department of Neurology
Children's Hospital
Enders Building, Room 461.2
320 Longwood Avenue
Boston, MA 02115
Tel: (617) 919-2257
Fax: (617) 730-1953
Email: xi.he@childrens.harvard.edu
Web Page: The He Lab Page

We are interested in the signaling mechanisms by the Wnt family of secreted molecules. It has become clear that Wnt proteins are one of about half a dozen major families of conserved signaling proteins that guide embryonic development and adult homeostasis. We primarily focus on Wnt signaling in early vertebrate embryonic patterning, in cell polarity regulation (planar cell polarity and neuronal polarity), and in stem cell and cancer biology. We employ molecular, biochemical, embryological and genetic approaches in several experimental systems, including Xenopus embryos, mammalian and Drosophila cell cultures, and knockout mice.

Wnt/beta-catenin signaling

The canonical Wnt/beta-catenin signaling regulates beta-catenin phosphorylation/degradation and thus beta-catenin-dependent gene expression program. We are interested in understanding the molecular logic of this key developmental signaling pathway, including its dual-receptor system (the Frizzled family and LDL receptor-related proteins, LRP5 and LRP6), the dual-kinase system (CKI and GSK3) for both beta-catenin and the LRP5/6 coreceptors, and the connection from the receptors to beta-catenin regulation.

Wnt signaling in cell polarity

Wnt signaling controls cell polarity, movements and tissue separation during vertebrate gastrulation via distinct signaling pathways, including Rho and Rac GTPases. These pathways are sometimes referred to as planar cell polarity signaling. Wnt/Frizzled signaling also regulates neuronal axon growth/polarity in mice. We are interested in understanding the molecular basis for these perhaps related phenomena.

Wnt signaling in stem cell biology, cancer and diseases

The canonical Wnt/beta-catenin signaling is involved in stem cell regulation, cancer and other diseases such as osteoporosis, as hyperactive beta-catenin signaling leads to tumorigenesis and loss of function of LRP5 results in familial osteoporosis. We are interested in how Wnt signaling interfaces with the self-renewal property of stem cells, and the molecular links between Wnt signaling and human diseases.

References:

• Liu C, Li Y, Semenov M, Baeg G-H, Han C, Tan Y, Zhang Z, Lin X, He X. (2002), Control of beta-catenin phosphorylation/degradation by a dual-kinase mechanism. Cell 108, 837-847.
• He X. (2003). A Wnt –Wnt situation. Developmental Cell 4, 791-797.
• Tamai K, Zeng X, Liu C, Zhang X, Harada Y, Chang Z, He X (2004). A mechanism for Wnt coreceptor activation. Molecular Cell 13, 149-156.
• Zeng X, Tamai K, Doble B, Li S, Huang H, Habas R, Okamura H, Woodgett J and He X. (2005). A dual-kinase mechanism for Wnt coreceptor phosphorylation and activation. Nature 438, 873-877.