Ash1l controls quiescence and self-renewal potential in hematopoietic stem cells
Morgan Jones, … , Sally A. Camper, Ivan Maillard
Morgan Jones, … , Sally A. Camper, Ivan Maillard
Published April 13, 2015
Citation Information: J Clin Invest. 2015;125(5):2007-2020. https://doi.org/10.1172/JCI78124.
View: Text | PDF
Research Article Hematology

Ash1l controls quiescence and self-renewal potential in hematopoietic stem cells

Abstract

Rapidly cycling fetal and neonatal hematopoietic stem cells (HSCs) generate a pool of quiescent adult HSCs after establishing hematopoiesis in the bone marrow. We report an essential role for the trithorax group gene absent, small, or homeotic 1-like (Ash1l) at this developmental transition. Emergence and expansion of Ash1l-deficient fetal/neonatal HSCs were preserved; however, in young adult animals, HSCs were profoundly depleted. Ash1l-deficient adult HSCs had markedly decreased quiescence and reduced cyclin-dependent kinase inhibitor 1b/c (Cdkn1b/1c) expression and failed to establish long-term trilineage bone marrow hematopoiesis after transplantation to irradiated recipients. Wild-type HSCs could efficiently engraft when transferred to unirradiated, Ash1l-deficient recipients, indicating increased availability of functional HSC niches in these mice. Ash1l deficiency also decreased expression of multiple Hox genes in hematopoietic progenitors. Ash1l cooperated functionally with mixed-lineage leukemia 1 (Mll1), as combined loss of Ash1l and Mll1, but not isolated Ash1l or Mll1 deficiency, induced overt hematopoietic failure. Our results uncover a trithorax group gene network that controls quiescence, niche occupancy, and self-renewal potential in adult HSCs.

Authors

Morgan Jones, Jennifer Chase, Michelle Brinkmeier, Jing Xu, Daniel N. Weinberg, Julien Schira, Ann Friedman, Sami Malek, Jolanta Grembecka, Tomasz Cierpicki, Yali Dou, Sally A. Camper, Ivan Maillard

×

Figure 1

Preserved overall fetal and adult hematopoietic output in Ash1lGT/GT mice.

Options: View larger image (or click on image) Download as PowerPoint
Preserved overall fetal and adult hematopoietic output in Ash1lGT/GT mic...
(A) Generation of the Ash1lGT allele by insertion of a splice-acceptor gene trap cassette into the first Ash1l intron. Homozygosity led to >90% reduction in wild-type transcripts in fetal (E15.5) and adult LSK progenitors, as shown by quantitative RT-PCR (qRT-PCR) with primers amplifying cDNA across the exon 1–2 boundary (mean ± SD). (B) qRT-PCR analysis of Ash1l expression normalized to Hprt1 in selected hematopoietic populations (LT-HSC, LSK CD150+CD48– LT-HSCs; MPP, LSK MPPs; HPC1, LSK CD150–CD48+ hematopoietic progenitor cells; HPC2, LSK CD150+CD48+ hematopoietic progenitor cells; myeloid, CD11b+Gr1+ myeloid cells; B cells, B220+AA4.1– B cells; CD4 T cells, TCRβ+CD4+ cells; CD8 T cells, TCRβ+CD8+ T cells) (mean ± SD). (C) Cellularity and percentage of myeloid, erythroid, and B lineage cells in E14.5 wild-type and Ash1lGT/GT (GT) fetal liver (n ≥ 4 per genotype from 2 independent experiments; mean ± SEM). (D) Cellularity and percentage of myeloid, erythroid, and B lineage cells in young adult (6- to 12-week-old) wild-type and Ash1lGT/GT BM (n ≥ 6 per genotype from >2 independent experiments; mean ± SEM). (E) Myeloid colony formation by wild-type and Ash1lGT/GT BM in CFU-GM assays (mean ± SEM, representative of 2 experiments). No statistically significant differences by t test.