Cell 149: 1565-1577 Tiki1 Is Required for Head Formation via Wnt Cleavage-Oxidation and Inactivation Xinjun Zhang, Jose Garcia Abreu, Chika Yokota, Bryan T. MacDonald, Sasha Singh, Karla Loureiro Almeida Coburn, Seong-Moon Cheong, Mingzi M. Zhang, Qi-Zhuang Ye, Howard C. Hang, Hanno Steen and Xi He