Klusmann, J.-H. | bioRxiv Science

bioRxiv2021

Naked mole-rat hematopoietic stem and progenitors are highly quiescent with an inherent myeloid bias

Naked mole-rats (NMRs) are the longest-lived rodents yet their stem cell characteristics remain enigmatic. Here we comprehensively mapped the NMR hematopoietic landscape and identified unique features likely contributing to longevity. Adult NMRs form red blood cells in spleen and marrow, which is a neotenic trait. A myeloid bias towards granulopoiesis in concert with decreased B-lymphopoiesis defines the marrow composition, resembling fetal leukopoiesis. Very similar to primates, the primitive stem cell compartment is marked by CD34 and THY1. Remarkably, stem and progenitor respiration rates are as low as in human cells, while NMR cells show a strong expression signature for fatty acid metabolism. The pool of quiescent stem cells is higher than in mice, and the cell cycle of hematopoietic cells is prolonged. Our work provides a platform to study immunology and stem cell biology in an animal model of exceptional longevity. TeaserJuvenile features of hematopoiesis shape the blood system of the longest-lived rodent.

cell biology↗

bioRxiv2021

The megakaryocytic transcription factor ARID3A suppresses leukemia pathogenesis

Given the plasticity of hematopoietic stem/progenitor cells, multiple routes of differentiation must be blocked during acute myeloid leukemia pathogenesis - the molecular basis of which is incompletely understood. Here we report that post-transcriptional repression of transcription factor ARID3A by miR-125b is a key event in megakaryoblastic leukemia (AMKL) pathogenesis. AMKL is frequently associated with trisomy 21 and GATA1 mutations (GATA1s), and children with Down syndrome are at a high risk of developing this disease. We show that chromosome 21-encoded miR-125b synergizes with Gata1s to drive leukemogenesis in this context. Leveraging forward and reverse genetics, we uncover Arid3a as the main miR-125b target underlying this synergy. We demonstrate that during normal hematopoiesis this transcription factor promotes megakaryocytic differentiation in concert with GATA1 and mediates TGF{beta}-induced apoptosis and cell cycle arrest in complex with SMAD2/3. While Gata1s mutations perturb erythroid differentiation and induce hyperproliferation of megakaryocytic progenitors, intact ARID3A expression assures their megakaryocytic differentiation and growth restriction. Upon knockdown, these tumor suppressive functions are revoked, causing a dual megakaryocytic/erythroid differentiation blockade and subsequently AMKL. Inversely, restoring ARID3A expression relieves the megakaryocytic differentiation arrest in AMKL patient-derived xenografts. This work illustrates how mutations in lineage-determining transcription factors and perturbation of post-transcriptional gene regulation interplay to block multiple routes of hematopoietic differentiation and cause leukemia. Surmounting this differentiation blockade in megakaryoblastic leukemia by restoring the tumor suppressor ARID3A represents a promising strategy for treating this lethal pediatric disease. Key pointsO_LIRepression of megakaryocytic transcription factor ARID3A by miR-125b synergizes with GATA1s to induce leukemia C_LIO_LIRestoring ARID3A expression relieves megakaryocytic differentiation arrest in megakaryoblastic leukemia C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/440795v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@146c2a7org.highwire.dtl.DTLVardef@9599fdorg.highwire.dtl.DTLVardef@1b0d22borg.highwire.dtl.DTLVardef@1b61447_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗