GARNL1 is expressed during embryogenesis with E12. During development, GARNL1 expression decreases, persisting at high levels only in neurons of the adult brain. GARNL1 localizes to the cytoplasm where it may play a role regulating GTP hydrolysis of proteins such as Ran and Rap. GARNL1 is imported to the nucleus via dimerization with E12. GARNL1 interacts with the HLH region of E12 and may function to negatively regulate the transcription of E12-dependent downstream target genes. This suggests that at least a portion of the function of GARNL1 is dependent upon its association with E12. GARNL1 may also associate with other HLH proteins and influence a variety of HLH signaling cascades. In adult brain, GARNL1 activity does not involve E12 and therefore it may serve a different function in developed neural tissue.