GTPase tethering membranes through formation of trans-homooligomers and mediating homotypic fusion of endoplasmic reticulum membranes. Functions in endoplasmic reticulum tubular network biogenesis (PubMed:18270207, PubMed:19665976, PubMed:27619977). Interacts with ZFYVE27 (PubMed:23969831). Interacts with REEP5 (PubMed:32075961). Localizes to endoplasmic reticulum tubules and accumulates in punctuate structures corresponding to 3-way junctions, which represent crossing-points at which the tubules build a polygonal network. Expressed in the central nervous system and in dorsal root ganglia neurons. Expressed in peripheral tissues (at protein level). The disease is caused by variants affecting the gene represented in this entry. Belongs to the TRAFAC class dynamin-like GTPase superfamily. GB1/RHD3 GTPase family. GB1 subfamily. Aberrant splicing.