The autophagy Protein Atg5 Plays a Crucial Role in the Maintenance and Reconstitution Ability of Hematopoietic Stem Cells

Abstract

Hematopoietic stem cells (HSCs) in bone marrow are pluripotent cells that can constitute the hematopoiesis system through self-renewal and differentiation into immune cells and red blood cells. To ensure a competent hematopoietic system for life, the maintenance of HSCs is tightly regulated. Although autophagy, a self-degradation pathway for cell homeostasis, is essential for hematopoiesis, the role of autophagy key protein Atg5 in HSCs has not been thoroughly investigated. In this study, we found that Atg5 deficiency in hematopoietic cells causes survival defects, resulting in severe lymphopenia and anemia in mice. In addition, the absolute numbers of HSCs and multiple-lineage progenitor cells were significantly decreased, and abnormal erythroid development resulted in reduced erythrocytes in blood of Vav_ Atg5 −/− mice. The proliferation of Lin − Sca-1 + c-Kit + HSCs was aberrant in bone marrow of Vav_ Atg5 −/− mice, and mature progenitors and terminally differentiated cells were also significantly altered. Furthermore, the reconstitution ability of HSCs in bone marrow chimeric mice was significantly decreased in the presence of Atg5 deficiency in HSCs. Mechanistically, impairment of autophagy-mediated clearance of damaged mitochondria was the underlying cause of the HSC functional defects. Taken together, these results define the crucial role of Atg5 in the maintenance and the reconstitution ability of HSCs.

Essential role of autophagy in protecting neonatal haematopoietic stem cells from oxidative stress in a p62-independent manner

“…The Atg5 deletion efficiency was sufficiently high using this system (Supplementary Figure S1 ). Consistent with previous reports 29 , 30 , Atg5 f⁄f ; Vav mice showed severe haematopoietic failure at 7 weeks of age, and most Atg5-deficient mice died presumably because of further progression of haematopoietic failure (Supplementary Fig. S2 ).…”

“…5 c). Consistent with previous reports, granulocyte–macrophage progenitors (GMPs) were reduced significantly 30 , and common myeloid progenitors (CMPs)/megakaryocyte-erythrocyte progenitors (MEPs) were reduced similarly. Additionally, we found that mature B cells in BM were reduced drastically in Atg5 f⁄f ; Vav mice (Fig.…”

“…In our study, alteration of the TMRM level was not apparent at P7 and 3 weeks of age, although an increased mitochondrial mass, TMRM level, and mitochondrial ROS were observed at 7 weeks (Supplementary Fig. S12 ) consistent with previous data 30 . Although we do not have clear evidence of the roles of oxidative stress in defective phenotypes of HSCs in Atg5 f / f ; Vav mice, we assume that the functional change of mitochondria may occur at the perinatal stage.…”

“…Haematopoietic cell-specific Atg5 and Atg7 deletion in the foetal period using the Vav-Cre-loxP system triggers weight loss, severe anaemia, and reduced haematopoietic stem cells (HSCs) of mice and results in death 27 – 31 . In these mice, a mitochondrial status alteration has been observed 30 , 31 . In adult HSCs, for example, autophagy is induced rapidly upon starvation via the FoxO3a-driven gene expression program, which maintains the functionality of HSCs 32 .…”

Exogenous Interleukin-33 Contributes to Protective Immunity via Cytotoxic T-Cell Priming against Mucosal Influenza Viral Infection

“…Then, alveolar macrophages were finally gated with CD11c hi CD11b int , and eosinophils were gated with CD11c int CD11b hi . The analysis of immune cells was performed according to previously described methods [20].…”