The LSD1 inhibitor RN1 rescues Congenital Dyserythropoietic Anemia type II

Congenital dyserythropoietic anemia type II (CDAII) is an autosomal recessive disease resulting from loss-of-function mutations in SEC23B, which encodes a component of coat complex protein II (COPII) vesicles. We have previously shown that the expression of SEC23A, a paralogous protein for SEC23B, is significantly lower than that of SEC23B in human erythroid cells and that increased SEC23A expression rescues CDAII. In this study, we generated a human erythroid cell line that expresses eGFP from the endogenous genomic locus of SEC23A and performed a small molecule screen to identify compounds that increase the SEC23A-eGFP level. The top compound passing all filters was an LSD1 inhibitor. We validated that LSD1 inhibition with RN1 i) results in increased SEC23A mRNA and protein levels in primary erythroid cells derived from CD34+ human hematopoietic stem and progenitor cells (HSPCs), at doses that do not impair erythroid cell growth or differentiation and ii) rescues the defect resulting from SEC23B deletion in primary human erythroid cells. We validated LSD1 as the target of RN1 by showing that genetic downregulation of LSD1 also led to a profound induction of SEC23A mRNA levels in HPSC-derived erythroid cells. Subsequently, we validated our findings in vivo, demonstrating that deletion of Lsd1 in mouse erythroid cells results in increased Sec23a expression and that RN1 treatment rescues the erythroid defect observed in CDAII mice. Finally, using CUT&RUN, we found that LSD1 occupies a sequence in the SEC23A promoter, which when deleted, results in increased SEC23A expression and rescue of CDAII. These finding suggest that LSD1 occupies the SEC23A promoter, repressing SEC23A transcription and that in the setting of LSD1 inhibition, SEC23A expression is de-repressed, resulting in CDAII rescue. Therefore, using an unbiased screen, we have identified and validated a novel promising therapeutic strategy for CDAII, using a compound that inhibit LSD1 or a genetic approach based on deleting the SEC23A promoter sequence that is occupied by LSD1.