SENP1 and anemia (phenotype): Because global deletion of SENP1 in mice causes anemia and embryonic lethality between E13.5 and postnatal day28, we generated a conditional SENP1 knockout line (SENP1flox/flox; Prrxl1-CreERT2, SENP1 cKO) by crossing a conditional SENP1flox/flox strain with a Prrxl1 tamoxifen-inducible Cre line29.