Xmab21l3 mediates dorsoventral patterning in Xenopus laevis

► We report the identification of a novel factor, Xenopus mab21-like 3 (Xmab21l3). ► Misexpression of Xmab21l3 promotes dorsal mesoderm formation. ► Misexpression of Xmab21l3 neuralizes ectodermal explants. ► Xab21l3 knockdown inhibits dorsal mesoderm formation. ► Xmab21l3 regulates dorsal fate via BMP/Smad signaling.