Acts as guanine nucleotide exchange factor (GEF) for CDC42 and RAC1 small GTPases (By similarity). Through its activation of CDC42 and RAC1, regulates neurite outgrowth in an vitro differentiation system. Mainly located near the cell surface. Widely expressed with highest levels in lung and heart. Expressed at 9.5 dpc in the growing edge of the limb buds and in the developing heart. At 10.5 dpc, strongly expressed at the edge of the limb buds, while expression in the heart maintained. At 11.5 dpc, detected in the apical ectodermal ridge of all 4 limbs, with higher expression in hindlimbs than in forelimbs. By 12.5 and 13.5 dpc, expression pattern more diffused in the limbs. At 13.5 dpc, clearly observed in the developing digits. Up-regulated during differentiation of the N1E-115 neuroblastoma cell line. The DOCKER domain may mediate some GEF activity. Belongs to the DOCK family. Extended N-terminus. Contaminating sequence. Vector contamination at the N-terminus.