Mutation of kri1l causes definitive hematopoiesis failure via PERK-dependent excessive autophagy induction

Abstract

Dysregulation of ribosome biogenesis causes human diseases, such as Diamond-Blackfan anemia, del (5q-) syndrome and bone marrow failure. However, the mechanisms of blood disorders in these diseases remain elusive. Through genetic mapping, molecular cloning and mechanism characterization of the zebrafish mutant cas002, we reveal a novel connection between ribosomal dysfunction and excessive autophagy in the regulation of hematopoietic stem/progenitor cells (HSPCs). cas002 carries a recessive lethal mutation in kri1l gene that encodes an essential component of rRNA small subunit processome. We show that Kri1l is required for normal ribosome biogenesis, expansion of definitive HSPCs and subsequent lineage differentiation. Through live imaging and biochemical studies, we find that loss of Kri1l causes the accumulation of misfolded proteins and excessive PERK activation-dependent autophagy in HSPCs. Blocking autophagy but not inhibiting apoptosis by Bcl2 overexpression can fully rescue hematopoietic defects, but not the lethality of kri1lcas002 embryos. Treatment with autophagy inhibitors (3-MA and Baf A1) or PERK inhibitor (GSK2656157), or knockdown of beclin1 or perk can markedly restore HSPC proliferation and definitive hematopoietic cell differentiation. These results may provide leads for effective therapeutics that benefit patients with anemia or bone marrow failure caused by ribosome disorders.

Molecular mechanisms of ferroptosis and its role in cancer therapy

“…The ER stress responsive genes promote the apoptosis or autophagy process. 46,47 Erastin can also induce ER stress and up-regulates ER stress responsive genes. 5,48,49 The eif2α-ATF4 branch is the major signalling pathway activated by ferroptotic reagents (Figure 1).…”

Engineering Hematopoietic Stem Cells: Lessons from Development

“…Mutants with CHT-specific hematopoietic defects include rumba (deficient in a C2H2 zing finger factor of unknown function) and samba (deficient in a homolog of human augmin complex subunit 3, HAUS3), which show a decrease in HSC number during the early CHT phase and the later expansion phase respectively (Du et al, 2011). A forward genetic screen for definitive hematopoietic mutations performed by Liu and colleagues has identified heterochronic mutants such as kri1l with low numbers of HSPCs in the CHT at days 3 and 5, whereas AGM hematopoiesis was not impaired (Jia et al, 2015). Species-specific hematopoietic differences in models of c-myb deficiency, further highlight the advantage of the zebrafish system.…”

Kri1l: a novel gene that links defective ribosome biogenesis to impaired hematopoiesis through excessive autophagy

“…The recent article in Cell Research published by Dr. Weijun Pan's group at the Institute of Health Sciences, Shanghai Institute for Biological Sciences, revealed that Kri1l, a previously undefined component of rRNA small subunit processome, is required for ribosome biogenesis and HSC development [5]. Their study was performed using zebrafish, which have emerged as a powerful model organism to model human development and disease [6].…”

“…Moreover, the excessive PERK signaling appeared to be responsible for the defect in HSC emergence, since both pharmacologic inhibition of PERK and knocking PERK down using morpholinos, rescued HSC emergence in kri1l mutants. Thus, the defect in ribosome biogenesis in kri1l mutants appears to activate the PERK-EIF2 signaling axis, causing a marked increase in autophagy, which impairs HSC emergence and function and results in failure of definitive hematopoiesis [5].…”

“…The kri1l mutant embryos exhibited severely impaired emergence of definitive HSC (c-myb ? ) in caudal hematopoietic tissue (CHT, equivalent to fetal liver in mammals), thymus, and kidney (equivalent to bone marrow in mammals) [5].…”