Our body looks left-right (L-R) symmetric from outside, but visceral organs are L-R asymmetric in terms of their shape, position and size. We are interested in how L-R asymmetry is established during development in various animals including vertebrates and invertebrates.

L-R asymmetry of the body is established early during development. Breaking of L-R symmetry in fish, frog and mouse takes place at the region of the embryo called the left-right organizer (LRO) and involves uni-directional fluid flow generated by motile cilia at the LRO. In the last 10 years , my lab studied how embryos sense the fluid flow. The LRO of mouse embryos possesses another type of cilia, immotile cilia located at its periphery, which sense mechanical force generated by the fluid flow. When immotile cilia sense the flow, Ca2+enters the cell, and stimulates degradation of the target Dand5 mRNA. This Dand5 mRNA degradation occurs only on the left side, generating a molecular asymmetry in the embryo for the first time.

While my lab focused on L-R asymmetry in the mouse, various animals employ different strategies for generating L-R asymmetry. For example, unlike mouse, reptiles and birds break L-R asymmetry without cilia and fluid flow. In snail, L-R symmetry breaking is done at a very early stage, 2nd-3rd cell division, by a mechanism involving actin. However, the later step of L-R asymmetry employs the same set of genes Nodal and Pitx2. In NCBS, my group will study how chick embryos break L-R symmetry without cilia and fluid flow. We also study snail embryos, how the non-conserved symmetry breaking event is connected  to the conserved asymmetric expression of Nodal-Pitx2. Molecular origin of morphological asymmetries is also a very interesting topic.