Transmission Electron Microscopy to Follow Ultrastructural Modifications of Erythroblasts Upon ex vivo Human Erythropoiesis

DUSSOUCHAUD, ALICE; JACOB, JULIETA; SECQ, CHARLES; VERBAVATZ, JEAN-MARC; MORAS, MARTINA; LARGHERO, JÉRÔME; FADER, CLAUDIO M.; OSTUNI, MARIANO A.; LEFEVRE, SOPHIE D.

Frontiers in Physiology

Frontiers media SA

Año: 2022 vol. 12

Throughout mammal erythroid differentiation, erythroblasts undergo enucleation andorganelle clearance becoming mature red blood cell. Organelles are cleared byautophagic pathways non-specifically targeting organelles and cytosolic content orby specific mitophagy targeting mitochondria. Mitochondrial functions are essential tocoordinate metabolism reprogramming, cell death, and differentiation balance, and alsosynthesis of heme, the prosthetic group needed in hemoglobin assembly. In mammals,mitochondria subcellular localization and mitochondria interaction with other structuresas endoplasmic reticulum and nucleus might be of importance for the removal of thenucleus, that is, the enucleation. Here, we aim to characterize by electron microscopythe changes in ultrastructure of cells over successive stages of human erythroblastdifferentiation. We focus on mitochondria to gain insights into intracellular localization,ultrastructure, and contact with other organelles. We found that mitochondria areprogressively cleared with a significant switch between PolyE and OrthoE stages,acquiring a rounded shape and losing contact sites with both ER (MAM) and nucleus(NAM). We studied intracellular vesicle trafficking and found that endosomes and MVBs,known to be involved in iron traffic and heme synthesis, are increased during BasoE toPolyE transition; autophagic structures such as autophagosomes increase from ProEto OrthoE stages. Finally, consistent with metabolic switch, glycogen accumulation wasobserved in OrthoE stage.