Key findings in 3 systems of inducible knockdown of the Rps19 gene. (A) The doxycycline-inducible mouse described by Jaako et al exhibited reduced hemoglobinization, an increase in mean corpuscular volume (MCV), decreased RBC counts, a decrease in bone marrow cellularity, and evidence of increased p53 activity. Simultaneous administration of L-leucine and doxycycline induction of Rps19 knockdown improved these symptoms. (B) Payne et al relied on morpholino-injected zebrafish embryos that displayed reduced hemoglobin and mTOR activation, alongside defects in development and growth, which were partially ameliorated with leucine treatment. (C) Knockdown of RPS19 in human CD34⁺ cells by Payne et al resulted in differentiation of fewer erythroid cells. In vitro culture with L-leucine resulted in gains in erythroid cell numbers. Professional illustration by Marie Dauenheimer.