Prep1 (pKnox1) Regulates Mouse Embryonic HSC Cycling and Self-Renewal Affecting the Stat1-Sca1 IFN-Dependent Pathway

Abstract

A hypomorphic Prep1 mutation results in embryonic lethality at late gestation with a pleiotropic embryonic phenotype that includes defects in all hematopoietic lineages. Reduced functionality of the hematopoietic stem cells (HSCs) compartment might be responsible for the hematopoietic phenotype observed at mid-gestation. In this paper we demonstrate that Prep1 regulates the number of HSCs in fetal livers (FLs), their clonogenic potential and their ability to de novo generate the hematopoietic system in ablated hosts. Furthermore, we show that Prep1 controls the self-renewal ability of the FL HSC compartment as demonstrated by serial transplantation experiments. The premature exhaustion of Prep1 mutant HSCs correlates with the reduced quiescent stem cell pool thus suggesting that Prep1 regulates the self-renewal ability by controlling the quiescence/proliferation balance. Finally, we show that in FL HSCs Prep1 absence induces the interferon signaling pathway leading to premature cycling and exhaustion of fetal HSCs.

A tale of TALE, PREP1, PBX1, and MEIS1: Interconnections and competition in cancer

“…VENN diagrams of the DNA‐binding sites of Prep1 ( A ) and Meis1 ( B ). The data derive from ChIP‐seq analysis of total E11.5 mouse embryo trunk , embryonic stem cells , and embryo fibroblasts (MEFs) . The same stringency ( p < 10 −5 ) was applied to the analysis of all data.…”

“…Possibly, the collection of a series of such signatures would allow a better dissection of the gene expression profiles of human tumors. [34], embryonic stem cells [40], and embryo fibroblasts (MEFs) [39]. The same stringency (p < 10 À5 ) was applied to the analysis of all data.…”

“…Hypomorphic Prep1 i/i embryos express very low (about 2%) levels of Prep1 mRNA, die much later, around E17.5 with major deficiency in hematopoietic stem cells; this phenotype is not totally penetrant, as about 25% of the homozygous embryos are born and live an almost normal‐length life . Immunohistochemistry shows the presence of γH2Ax foci in the fetal liver and spleen, indicating DNA damage (unpublished).…”

The genetics and the molecular functions of the PREP1 homeodomain transcription factor

“…However, a Tie-2-Cre mediated hematopoietic and endothelial cell specific deletion of Prep1 (Prep1CKO), did not display any defect in the maintenance or differentiation of hematopoietic cells in fetal livers nor any difference in early B-cell lineage or immature and mature B-cells (Yoshioka et al, 2015). Similarly, fetal livers from Prep1 i/i mice revealed the presence of an increased pool of Lin -Sca1 + c-Kit + progenitor cells at the expense of highly replicative stem cell pool which exhaust rapidly their replicative potential (Modica et al, 2014). However, FL from Prep1CKO mice did not have a significantly higher pool of Lin -Sca1 + c-Kit + cells (Yoshioka et al, 2015) indicating that the relative expression of other TALE proteins or differences due to germline vs somatic expression level can drastically modify the phenotype.…”

“…Hopwever, a mechanism similar to that described by Palmigiano et al, (2018), i.e accumulation of DNA damage, may also be responsible for this phenotype. Other developmental phenotypes observed in various tissues of Prep1 mutant mice are accompanied by defects in cell cycle status and proliferation; hematopoietic stem/progenitor cells (Modica et al, 2014;Yoshioka et al, 2015), thymocytes (Penkov et al, 2005;Penkov et al, 2008) and spermatogonial cells (Kawai et al, 2018). Both in mouse and zebrafish (Ladam et al, 2018) embryos the pre-and a post-gastrulation Prep1 phenotypes may depend on different mechanisms.…”