title: Gene coexpression analysis in single cells indicates lymphomyeloid copriming in short-term hematopoietic stem cells and multipotent progenitors.
abstract: Progressive restriction to a differentiation pathway results from both activation and silencing of particular gene expression programs. To identify the coexpression and the expression levels of regulatory genes during hematopoietic stem cell (HSC) differentiation toward the T cell branch, we applied a new single-cell RT-PCR technique to analyze the simultaneous expression of 13 genes in 9 functionally purified populations from the bone marrow and the thymus. We report in this paper that Lin(-)Sca1(+)ckit(+) HSCs display, at the single-cell level, a homogeneous and high transcriptional activity as do early thymic progenitors. Moreover, the coexpression of lymphoid and myeloid genes is an early event detected in approximately 30% of short-term HSC and most multipotent progenitors, suggesting novel sources for the generation of early thymic progenitors, common lymphoid progenitors (CLPs), and common myeloid progenitors. Loss of multipotency in Lin(-)Sca1(+)ckit(+) cells directed to the lymphoid branch is characterized by Lmo2 and Gata2 gene expression downregulation. Indeed, highest levels of Gata2 expression are detected only in long-term and short-term HSC populations. Complete shutdown of Pu1 gene expression in all triple-negative (TN)3 stage thymic pre-T cells is indicative of total T cell commitment. Interestingly, this is also observed in 30% of TN2 cells and 25% of CLP in the bone marrow, suggesting a possible initiation of T cell engagement in TN2 and CLP. Also, our strategy highlights similar gene patterns among HSCs and intrathymic progenitors, proposing, therefore, that identical activation signals are maintained until further maturation and generation of CD4 and CD8 coreceptors bearing thymocytes.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unité 591, 156 rue de Vaugirard, F-75730 Paris 15, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Gautreau
authors.forename: Amine
authors.initials: A
authors.lastname: Boudil
authors.forename: Valérie
authors.initials: V
authors.lastname: Pasqualetto
authors.forename: Lamia
authors.initials: L
authors.lastname: Skhiri
authors.forename: Laure
authors.initials: L
authors.lastname: Grandin
authors.forename: Marta
authors.initials: M
authors.lastname: Monteiro
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Jais
authors.forename: Sophie
authors.initials: S
authors.lastname: Ezine
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics* / Q000276:immunology*; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods*; D018507:Gene Expression Regulation, Developmental / Q000276:immunology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D016131:Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D039902:Multipotent Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D022423:Myeloid Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology / Q000378:metabolism