A requirement for Zic2 in the regulation of nodal expression underlies the establishment of left-sided identity by Dykes, I, Szumska, D, Kuncheria, L, Puliyadi, R, Chen, C, Papanayotou, C, Lockstone, H, Dubourg, C, David, V, Schneider, J, Keane, T, Adams, D, Brown, S, Mercier, S, Odent, S, Collignon, J, Bhattacharya, S