p53-Independent Pathways in Diamond Blackfan Anemia

Diamond Blackfan Anemia (DBA) is a rare inherited bone marrow failure syndrome that manifests as a variably penetrant macrocytic anemia, which can spontaneously enter remission for unclear reasons. Rpl5 (uL18) is one of the commonly mutated genes in DBA and is associated with a severe phenotype including morphological defects and reduced likelihood of spontaneous remission. Our previous work established both cellular [mouse embryonic stem (mES) cell] and murine genetic models of Rpl5 haploinsufficiency (Rpl5^{Skax23-Jus/1/+}). Rpl5^{Skax23-Jus/1/+} mutant mice exhibited increased mortality at all ages, reduced fetal liver cellularity, and a block in erythroid differentiation at the CFU-E/proerythroblast stage at E12.5 that started to resolve by E14.5. Newborn mutants are born with macrocytic anemia and the majority exhibited histological evidence of a ventricular septal defect (VSD). In contrast, mutants that survived until weaning lacked anemia and VSD, suggesting that the presence or absence of VSD at E12.5 may identify animals that are more or less likely to spontaneously remit from anemia. Our previous studies demonstrated that Rpl5+/- mES cells have a p53-independent cell cycle defect with a delay in the G2/M transition. Additional preliminary studies indicate that Rpl5 haploinsufficient mES cells also demonstrate no p53 induction and a reduced apoptotic response to oxidative stress. Currently, we are exploring the p53-independent pathways that trigger and/or lead to resolution of anemia in Rpl5^{Skax23-Jus/1/+} mutant mice. We performed RNA-seq to identify, in an unbiased fashion, dysregulated pathways in Rpl5 haploinsufficient E12.5 fetal liver erythroid progenitors. We plan to next validate novel genes and pathways that may drive or predict erythroid failure and spontaneous DBA remission in our model.

Guan:Genentech: Consultancy; Eli Lilly: Consultancy, Honoraria; Roche: Consultancy; Ann Arbor Algorithms: Current holder of stock options in a privately-held company. Engel:Fulcrum Therapeutics: Consultancy; Imago Biosciences: Consultancy, Current equity holder in publicly-traded company; Poseida Therapeutics: Consultancy. Singh:Global Blood Therapeutics, Inc.: Consultancy, Honoraria.