Acts as guanine nucleotide exchange factor (GEF) for CDC42 and RAC1 small GTPases. Through its activation of CDC42 and RAC1, may regulate neurite outgrowth (By similarity). Mainly located near the cell surface. Widely expressed. Expressed at low level in spleen, cerebellum, hippocampus and in substantia nigra. The DOCKER domain may mediate some GEF activity. The disease is caused by variants affecting the gene represented in this entry. Belongs to the DOCK family. Truncated N-terminus. Extended N-terminus.