（A）Tsukushi

　Our lab investigates the function of a secretory protein, Tsukushi (TSK) – named so because its expression pattern in the early chicken embryo resembles a ‘Horsetail plant’ (‘Tsukushi’ in Japanese). Tsukushi was generated by Signal sequence trap (SST) cloning and it was first reported by this lab (Ohta et al., Dev. Cell 2004). Tsukushi specifically interacts with molecules belonging to transforming growth factor-beta, Notch and FGF signal cascades, and play important role in development (Ohta et al., Dev. Cell 2004; Ohta et al., Development 2006; Kuriyama et al., Development 2006).

　In the central nervous system of mouse brain, Tsukushi is expressed in lateral-ventricle and hippocamal dentate gyrus. TSK is also found to express in ciliary body, retinal stem cell and olfactory bulb. TSK is responsible for the development, differentiation and proliferation of retinal stem cells and act as Wnt signal inhibitor (Ohta et al., PNAS 2011). TSK is also expected to have similar function in neuronal stem cell (Riyadh et al., in preparation).

　By analyzing TSK knockout mouse, it was found that TSK participates in the neural network formation (Ito et al., BBRC 2010; Hossain et al., Dev. Biol. 2013), hair stem cell development and wound healing of skin (Niimori et al., Dev. Biol. 2012). It is also reported that TSK is responsible for various phenomenon as the extracellular mediator and controls a variety of signal transmission in the extracellular domain.

(1) Expression of Tsukushi in the chicken initial embryo

(2)　Role of Tsukushi in the domain out of the cell