The total CFC content was similar between all genotypes ( Fig. In these older mice, the PB and BM cellularities were slightly elevated compared with their wild-type age-matched littermates ( Fig. In our care, a small number of RARγ −/− mice have survived to 12 mo of age, which appears to be the maximum lifespan of these mutants. RARγ −/− mice have been reported to exhibit early lethality from unknown causes ( 14). RARγ null BM cells have increased numbers of progenitors RARγ1-transduced cells, with the RARα-transduced cells exhibiting rapid proliferation and differentiation to granulocytes, whereas the RARγ transduced cells exhibited much slower proliferation associated with a much more immature phenotype. Thus, there was a marked difference in the proliferation and differentiation of the RARα- vs. In contrast, cells overexpressing RARγ1 proliferated slowly in culture (comprising <2% of the culture), did not express Gr-1, were negative for all other lineage markers assessed, and expressed high levels of Sca-1 (Fig. At this time point, the RARα-overexpressing cells predominantly expressed the granulocyte marker, Gr-1 (Fig. Both the control and RARα-overexpressing cells proliferated well in culture, comprising >50% of the cells in the cultures at 4 wk (Fig. During the 4 wk of culture, cell viabilities of the GFP + cells within each culture were similar.
48 h after the infection, the transduction efficiencies (GFP + cells) were 8.8% (control), 4.3% (RARα), and 4.5% (RARγ1). To further define the roles of RARα and RARγ1 in HSCs, we used retroviral vector-mediated gene transduction to individually overexpress RARα and RARγ1 ( 15) in 5-fluorouracil pretreated BM and monitored the proliferation and differentiation of the transduced cells during 4 wk of culture in cytokine-containing media (see supplemental Materials and methods). These results, therefore, demonstrate that RARγ is a critical regulator of the balance between HSC self-renewal and differentiation loss of RARγ results in reduced numbers of HSCs as the result of enhanced HSC differentiation, whereas RARγ activation results in HSC self-renewal.
#Self scientific the self science rar serial#
Finally, treatment of cultures of highly enriched populations of hematopoietic precursors/stem cells with ATRA, the natural ligand for RARγ, resulted in increased Notch1 and Hoxb4 expression in these cells accompanied by enhanced HSC self-renewal, as shown by increased potential of ATRA-treated HSCs to repopulate mice after serial transplantation.
#Self scientific the self science rar rar#
In contrast, loss of the other RAR predominantly expressed in hematopoietic cells, RARα, did not result in any hematopoietic defects in the mice and ATRA-treated RARα null HSCs had comparable repopulating activity to wild-type HSCs cultured with ATRA. Furthermore, unlike wild-type HSCs, RARγ null HSCs did not repopulate recipients after 14 d of ex vivo culture with ATRA. Here, we show that loss of RARγ results in reduced numbers of HSCs and increased numbers of more differentiated progenitor cells in the mutant mice. We conclude that the RARs have distinct roles in hematopoiesis and that RARγ is a critical physiological and pharmacological regulator of the balance between HSC self-renewal and differentiation. Finally, pharmacological activation of RARγ ex vivo promotes HSC self-renewal, as demonstrated by serial transplant studies. Furthermore, loss of RARγ abrogated the potentiating effects of all-trans retinoic acid on the maintenance of HSCs in ex vivo culture. Primitive hematopoietic precursors overexpressing RARα differentiate predominantly to granulocytes in short-term culture, whereas those overexpressing RARγ exhibit a much more undifferentiated phenotype. In contrast, RARα is widely expressed in hematopoietic cells, but RARα knockout mice do not exhibit any HSC or progenitor abnormalities. We observe that the retinoic acid receptor (RAR)γ is selectively expressed in primitive hematopoietic precursors and that the bone marrow of RARγ knockout mice exhibit markedly reduced numbers of HSCs associated with increased numbers of more mature progenitor cells compared with wild-type mice. Although several genes influencing HSC self-renewal have been identified, to date no gene has been described that, when activated, enhances HSC self-renewal and, when activated, promotes HSC differentiation. Hematopoietic stem cells (HSCs) sustain lifelong production of all blood cell types through finely balanced divisions leading to self-renewal and differentiation.
0 kommentar(er)
