Differences observed between the secretion patterns of the human fetal RPE after REP-1 knock down and peripheral cells from CHM patients could be explained by: (1) the differences in physiology of adult and fetal tissues, (2) the difference in prenylation levels of specific Rab proteins in RPE and other cell types leading to differences in the regulation of secretion in different tissues. The gene discussed is AGFG1; the disease is choroideremia.