FGD2 is a guanine nucleotide exchange factor that specifically activates CDC42, a member of the Rho family of small GTPases, by catalyzing the exchange of bound GDP for GTP 12. The protein contains a conserved domain architecture including adjacent RhoGEF and PH domains, a second C-terminal PH domain, and a distinctive FYVE domain 1. FGD2 demonstrates complex subcellular localization, concentrating in membrane ruffles and early endosomes, with the FYVE domain mediating endosomal targeting and the C-terminal PH domain directing recruitment to membrane ruffles 2. Functionally, FGD2 overexpression promotes CDC42 activation and elevates JNK1 activity in a CDC42-dependent manner 2. The protein is preferentially expressed in antigen-presenting cells including B lymphocytes, macrophages, and dendritic cells, with expression levels varying during B cell development and being suppressed upon B cell receptor activation 2. This suggests FGD2 plays important roles in leukocyte signaling and vesicle trafficking within immune system cells. Additionally, FGD2 appears to couple actin cytoskeleton dynamics with plasma membrane organization, contributing to cellular processes such as filopodium and lamellipodium formation 3. The gene maps to human chromosome 6.2 1.