May regulate the intracellular trafficking of RAN. Promotes guanine nucleotide release from RAN and inhibits binding of new GTP. Plays a role in the regulation of the levels of GTP-bound RAN in the nucleus (By similarity). Required for normal expression of the ion channel hcn4 and for normal expression of the cardiac transcription factors nkx2.5, gata4 and hand2 during embryonic development. Required for normal embryonic heart development and normal heart rate (PubMed:26903377). Monomer. Interacts with ran (By similarity). May shuttle between the nucleus and cytoplasm. Detected in one-cell-stage embryos, suggesting maternal expression. Detected in blastomeres at 2.5 to 4 hpf. Ubiquitous in embryos from 6 to 12 hpf. At 24 hpf, expression is ubiquitous, with higher levels of expression in the region of the brain and eyes. At 48 hpf, predominantly expressed in the brain area, but also detected in heart and fins. Morpholino knockdown of the protein causes bradycardia and weakened myocardial contraction. Expression of hcn4 is decreased, and this may be the cause for the decreased heart rate. Morpholino knockdown causes defects in heart looping during embryonic heart development, probably due to the decreased expression of cardiac transcription factors in the anterior lateral mesoderm. Belongs to the MOG1 family.