Differential Regulation of Retinoic Acid Metabolism in Fanconi Anemia

Fanconi anemia (FA) is a rare genetic disease characterized by heterogeneous congenital abnormalities and increased risk for bone marrow failure and cancer. FA is caused by mutation of any one of 23 genes, the protein products of which function primarily in the maintenance of genome stability. An important role for the FA proteins in the repair of DNA interstrand crosslinks (ICLs) has been established in vitro. While the endogenous sources of ICLs relevant to the pathophysiology of FA have yet to be clearly determined, a role for the FA proteins in a two-tier system for the detoxification of reactive metabolic aldehydes has been established. To discover new metabolic pathways linked to FA, we performed RNA-seq analysis on non-transformed FA-D2 (FANCD2-/-) and FANCD2-complemented patient cells. Multiple genes associated with retinoic acid metabolism and signaling were differentially expressed in FA-D2 (FANCD2-/-) patient cells, including ALDH1A1 and RDH10, which encode for retinaldehyde and retinol dehydrogenases, respectively. Increased levels of the ALDH1A1 and RDH10 proteins was confirmed by immunoblotting. FA-D2 (FANCD2-/-) patient cells displayed increased aldehyde dehydrogenase activity compared to the FANCD2-complemented cells. Upon exposure to retinaldehyde, FA-D2 (FANCD2-/-) cells exhibited increased DNA double-strand breaks and checkpoint activation indicative of a defect in the repair of retinaldehyde-induced DNA damage. Our findings describe a novel link between retinoic acid metabolism and FA and identify retinaldehyde as an additional reactive metabolic aldehyde relevant to the pathophysiology of FA.