Dntt expression reveals developmental hierarchy and lineage specification of hematopoietic progenitors

Abstract

Intrinsic and extrinsic cues determine developmental trajectories of hematopoietic stem cells (HSCs) towards erythroid, myeloid and lymphoid lineages. Using two newly generated transgenic mice that report and trace the expression of terminal deoxynucleotidyl transferase (TdT), transient induction of TdT was detected on a newly identified multipotent progenitor (MPP) subset that lacked self-renewal capacity but maintained multilineage differentiation potential. TdT induction on MPPs reflected a transcriptionally dynamic, but uncommitted stage, characterized by low expression of lineage-associated genes. Single-cell CITE-Seq indicated that multipotency in the TdT + MPP is associated with expression of the endothelial cell adhesion molecule ESAM. Stable and progressive upregulation of TdT defined the lymphoid developmental trajectory. Collectively, we here identify a new multipotent progenitor within the MPP4 compartment. Specification and commitment are defined by downregulation of ESAM which marks the progressive loss of alternative fates along all lineages.

Induction of whole-body gene deletion via R26-regulated tamoxifen-inducible Cre recombinase activity

“…Double fluorescent Cre reporter mice harboring mTOM/mEGFP transgene are widely used to determine the efficacy of Cre-mediated recombination within floxed genes and lineage tracing studies ( Chandran et al, 2021 ; Forte et al, 2022 ; Klein et al, 2022 ). Thus, we utilized mTOM/mEGFP transgene to assess Cre recombination using green fluorescence and immunohistochemical localization of mEGFP, as end-points for protein expression, and the ratio of mEGFP to mTOM transgene expression, as an end-point for gene expression analysis.…”

Expression of terminal deoxynucleotidyl transferase (TdT) identifies lymphoid-primed progenitors in human bone marrow

“…TdT, terminal deoxynucleotidyl transferase, is functionally intrinsic to VDJ recombination during lymphoid development and has been identified as the characteristic lymphoid gene in previous studies 1,11,23 . Furthermore, a recent study in mice demonstrated high TdT expression in lymphoid-biased MPP4s and CLPs but no expression in GMPs 39 . In contrast, the expression level of TdT in the conventional human GMP compartment was clearly bimodal (Figure 3D) and TdT+ subset had expression level as high as CLPs (Figure S3C).…”

A time and single-cell resolved model of hematopoiesis

“…However, immunophenotyping has limited resolution, and HSPC populations defined by flow cytometry are known to be functionally heterogeneous. This is particularly evident within common myeloid progenitors (CMP) (Paul et al, 2015; Perié et al, 2015) and lymphoid-primed multipotent progenitors (LMPP) (Klein et al, 2022; Nestorowa et al, 2016) as revealed by scRNA-Seq and transplantation experiments. Further high-throughput scRNA-Seq studies charted putative gradual molecular transitions from HSCs toward 8 distinct lineages (Dahlin et al, 2018) including specific stages of erythroid differentiation (Tusi et al, 2018).…”

“…However, immunophenotyping has limited resolution, and HSPC populations defined by flow cytometry are known to be functionally heterogeneous. This is particularly evident within common myeloid progenitors (CMP) (Paul et al, 2015;Perié et al, 2015) and lymphoid-primed multipotent progenitors (LMPP) (Klein et al, 2022;Nestorowa et al, . CC-BY 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”