Weiss-Gayet Michèle, Starck Joëlle, Chaabouni Azza, Chazaud Bénédicte, Morlé François
Institut NeuroMyoGène (INMG), Université Claude Bernard Lyon1, Villeurbanne, France.
INSERM U1217, Villeurbanne, France.
PLoS One. 2016 Apr 18;11(4):e0153860. doi: 10.1371/journal.pone.0153860. eCollection 2016.
This study aimed at reinvestigating the controversial contribution of Notch signaling to megakaryocytic lineage development. For that purpose, we combined colony assays and single cells progeny analyses of purified megakaryocyte-erythroid progenitors (MEP) after short-term cultures on recombinant Notch ligand rDLL1. We showed that Notch activation stimulated the SCF-dependent and preferential amplification of Kit+ erythroid and bipotent progenitors while favoring commitment towards the erythroid at the expense of megakaryocytic lineage. Interestingly, we also identified a CD9High MEP subset that spontaneously generated almost exclusively megakaryocytic progeny mainly composed of single megakaryocytes. We showed that Notch activation decreased the extent of polyploidization and maturation of megakaryocytes, increased the size of megakaryocytic colonies and surprisingly restored the generation of erythroid and mixed colonies by this CD9High MEP subset. Importantly, the size increase of megakaryocytic colonies occurred at the expense of the production of single megakaryocytes and the restoration of colonies of alternative lineages occurred at the expense of the whole megakaryocytic progeny. Altogether, these results indicate that Notch activation is able to extend the number of divisions of MK-committed CD9High MEPs before terminal maturation while allowing a fraction of them to generate alternative lineages. This unexpected plasticity of MK-committed progenitors revealed upon Notch activation helps to better understand the functional promiscuity between megakaryocytic lineage and hematopoietic stem cells.
本研究旨在重新探讨Notch信号通路对巨核细胞系发育的有争议的作用。为此，我们将集落分析与对重组Notch配体rDLL1短期培养后的纯化巨核细胞-红系祖细胞（MEP）进行单细胞子代分析相结合。我们发现，Notch激活刺激了Kit+红系和双能祖细胞的SCF依赖性优先扩增，同时有利于向红系分化，而以巨核细胞系为代价。有趣的是，我们还鉴定出一个CD9High MEP亚群，其几乎自发地产生主要由单个巨核细胞组成的巨核细胞子代。我们发现，Notch激活降低了巨核细胞的多倍体化程度和成熟度，增加了巨核细胞集落的大小，并且令人惊讶地恢复了该CD9High MEP亚群产生红系和混合集落的能力。重要的是，巨核细胞集落大小的增加是以单个巨核细胞的产生为代价的，而替代谱系集落的恢复是以整个巨核细胞子代的产生为代价的。总之，这些结果表明，Notch激活能够在终末成熟前延长已向巨核细胞分化的CD9High MEP的分裂次数，同时允许其中一部分产生替代谱系。Notch激活后揭示的已向巨核细胞分化的祖细胞的这种意外可塑性有助于更好地理解巨核细胞系与造血干细胞之间的功能混杂性。
