Potier, D. | bioRxiv Science

bioRxiv2022

Single-cell analysis of megakaryopoiesis in peripheral CD34+ cells: insights into ETV6-related thrombocytopenia

Expansion of human megakaryoblasts from peripheral blood-derived CD34+ cells is commonly used to characterize inherited or acquired thrombocytopenia and evaluate defects in megakaryocyte (MK) differentiation, MK maturation and proplatelet formation. We applied single-cell RNA sequencing to understand local gene expression changes during megakaryopoiesis (days 6 and 11 of differentiation) in peripheral CD34+ cells from healthy controls and patients with ETV6-related thrombocytopenia. Analysis of gene expression and regulon activity revealed distinct clusters partitioned into seven major cell stages: hematopoietic stem/progenitor cells (HSPC), common-myeloid progenitors (CMP), MK-primed CMP, granulocyte-monocyte progenitors, megakaryocyte-erythroid progenitors (MEP), MK progenitor /mature MK (MKP/MK) and platelets. We observed a subpopulation of MEP that arose directly from HSPC, deviating from the canonical MK differentiation pathway. ETV6 deficiency was characterized by an increase in HSPC, a decrease in MKP/MK, and a lack of platelets. ETV6 deficiency also led to the development of aberrant MEP and MKP/MK cell populations. Genes involved in "mitochondrial" and "DNA repair" pathways were downregulated, while genes involved in "translation" pathways were upregulated. Analysis of patient samples and hematopoietic cell lines transduced with an ETV6 variant revealed increased translation in MK. Ribosomal protein small 6 (RPS6) levels in MK, platelets and peripheral blood mononuclear cells was consistent with the translation findings. Our results provide a framework to understand peripheral CD34+ cell-derived megakaryocytic cultures. Our observations also shed light on ETV6-variant pathology and reveal potential targets for diagnostic and therapeutic purposes. Key points- scRNAseq gain insight into in vitro megakaryopoiesis, identify MK-primed CMP, and a differentiation trajectory that bypasses the CMP. - ETV6 variants led to the development of aberrant MEP and MK cell populations.

bioinformatics↗

bioRxiv2018

Bcl6 promotes neurogenic conversion through transcriptional repression of multiple self-renewal-promoting extrinsic pathways.

During neurogenesis, progenitors switch from self-renewal to differentiation through the interplay of intrinsic and extrinsic cues, but how these are integrated remains poorly understood. Here we combine whole genome transcriptional and epigenetic analyses with in vivo functional studies and show that Bcl6, a transcriptional repressor known to promote neurogenesis, acts as a key driver of the neurogenic transition through direct silencing of a selective repertoire of genes belonging to multiple extrinsic pathways promoting self-renewal, most strikingly the Wnt pathway. At the molecular level, Bcl6 acts through both generic and pathway-specific mechanisms. Our data identify a molecular logic by which a single cell-intrinsic factor ensures robustness of neural cell fate transition by decreasing responsiveness to the extrinsic pathways that favor self-renewal.

neuroscience↗