In Vivo RNAi Screen Unveils PPARγ as a Regulator of Hematopoietic Stem Cell Homeostasis

Abstract

SummaryHematopoietic stem cell (HSC) defects can cause repopulating impairment leading to hematologic diseases. To target HSC deficiency in a disease setting, we exploited the repopulating defect of Fanconi anemia (FA) HSCs to conduct an in vivo short hairpin RNA (shRNA) screen. We exposed Fancd2−/− HSCs to a lentiviral shRNA library targeting 947 genes. We found enrichment of shRNAs targeting genes involved in the PPARγ pathway that has not been linked to HSC homeostasis. PPARγ inhibition by shRNA or chemical compounds significantly improves the repopulating ability of Fancd2−/− HSCs. Conversely, activation of PPARγ in wild-type HSCs impaired hematopoietic repopulation. In mouse HSCs and patient-derived lymphoblasts, PPARγ activation is manifested in upregulating the p53 target p21. PPARγ and co-activators are upregulated in total bone marrow and stem/progenitor cells from FA patients. Collectively, this work illustrates the utility of RNAi technology coupled with HSC transplantation for the discovery of novel genes and pathways involved in stress hematopoiesis.

Pain and opioid use after reversal of sickle cell disease following HLA‐matched sibling haematopoietic stem cell transplant

“…In this regard, an increased population of adipocytes has been observed in the BM of FA patients and mouse models (Pulliam-Leath et al, 2010), probably as a consequence of FA mesenchymal stem cells preferentially differentiating as adipocytes (Zhou et al, 2017), which appear deleterious for HSC selfrenewal (Naveiras et al, 2009). Moreover, PPARG, a key regulator of adipocyte differentiation and lipid synthesis, is up-regulated in CD34 + cells from FA patients (Sertorio et al, 2017), confirming the deregulation in FA cells of lipid metabolism.…”

Deletion of the Fanconi Anemia C Gene in Mice Leads to Skeletal Anomalies and Defective Bone Mineralization and Microarchitecture

“…PPARγ is an important regulator of the adipogenic program, and overexpression of PPARγ has been detected in FA patient‐derived CD34 + bone marrow cells. Dysregulated PPARγ has been suggested as a contributor to the bone marrow pathology in FA . Many studies have shown that PPARγ and the WNT/β‐catenin pathway antagonizes each other .…”

Altered lipid metabolism could drive the bone marrow failure in fanconi anaemia

“…In this regard, an increased population of adipocytes has been observed in the BM of FA patients and mouse models (Pulliam‐Leath et al , ), probably as a consequence of FA mesenchymal stem cells preferentially differentiating as adipocytes (Zhou et al , ), which appear deleterious for HSC self‐renewal (Naveiras et al , ). Moreover, PPARG , a key regulator of adipocyte differentiation and lipid synthesis, is up‐regulated in CD34 + cells from FA patients (Sertorio et al , ), confirming the deregulation in FA cells of lipid metabolism.…”