We focus on dissecting the roles of the signal transduction pathways during development.
In my lab, two main projects are going on:
The molecular mechanisms of cilia formation during development
The cilium is a small cellular organelle which broadly exists throughout the human body in either motile or immotile form. Motile cilia generate force by beating for directional fluid movement, whereas primary (non-motile) cilia are involved in sensory processes and cellular signaling (Figure 1). Disruption of ciliary structure and/or function in humans causes pleiotropic disorders, called ciliopathies. Although a certain length of motile cilia is important for their normal function, the molecular mechanism that regulates cilia length still remains to be explored.
We recently found that blocking the Smad2/3-dependent TGF-β (Xnr1 and Derrière) pathway in Xenopus embryos shortened motile cilia in several tissues (Figure 2). We further found that the role of TGF-β signaling seems to be independent of known mechanisms that regulate cilia formation including ciliary length control. However, the mechanism that is regulated by TGF-β signaling still remains unknown. To understand the mechanism of ciliary length control, we will analyze this mechanism by using state-of-art technologies such as next generation sequencing and proteomics.
Figure 1. The architecture of motile and primary (immotile) cilia.
Identifying chemical compounds that regulate neuronal differentiation
Stem cell therapy holds considerable promise for the treatment of degenerative diseases. Stem cells are differentiated into required cell types to replace non-functional tissues in degenerative diseases and injuries to functional normal tissues. Stem cell differentiation is regulated by both intrinsic regulators and the extracellular environment, and can be controlled ex vivo by cell culture manipulation with ‘‘cocktails’’ of growth factors, signaling molecules, and/or by genetic manipulation. A challenge to disseminate stem cell therapy is to establish inexpensive and safe methods by which stem cells are differentiated into required cell types. However, purified growth factors are still expensive, and risk of genetic manipulation to recipients with transplantation of these cells is also considerable.
Since human or mouse embryonic stem cells have been hampered by multiple technical challenges, we are using Xenopus embryos for high-throughput screening (HTS) of chemical compound libraries to identify new chemical compounds. We have identified some compounds to control neuronal differentiation (Figure 3).
Figure 2. Knockdown of Xnr1 and Derrière results in short cilia at the GRP. A. Cilia were stained by acetylated α-tubulin antibody. B. Average length of cilia in A.
Figure 3. . Selected chemical compounds. The number is ID of chemical compounds. The pictures are lateral view. b: brain, e: eye.