Haematopoietic stem cell survival and transplantation efficacy is limited by the BH3‐only proteins Bim and Bmf

Abstract

Anti-apoptotic Bcl-2 family members are critical for the regulation of haematopoietic stem and progenitor cell (HSPC) survival. Little is known about the role of their pro-apoptotic antagonists, i.e. ‘BH3-only’ proteins, in this cell compartment. Based on the analysis of cytokine deprivation-induced changes in mRNA expression levels of Bcl-2 family proteins, we determined the consequences of BH3-only protein depletion on HSPC survival in culture and, for selected candidates, on engraftment in vivo. Thereby, we revealed a critical role for Bim and Bmf as regulators of HSPC dynamics both during early engraftment and long-term reconstitution. HSPCs derived from wild-type donors were readily displaced by Bim- or Bmf-deficient or Bcl-2-overexpressing HSPCs as early as 10 days after engraftment. Moreover, in the absence of Bim, significantly lower numbers of transplanted HSPCs were able to fully engraft radio-depleted recipients. Finally, we provide proof of principle that RNAi-based reduction of BIM or BMF, or overexpression of BCL-2 in human CD34+ cord blood cells may be an attractive therapeutic option to increase stem cell survival and transplantation efficacy.

Long-term serial xenotransplantation of juvenile myelomonocytic leukemia recapitulates human disease in Rag2-/- c-/- mice

“…Contrary to mice transplanted with JMML cells, and in line with previous observations, 33 the human cells found in these mice were predominantly B cells and myeloid differentiation was barely detectable. The mice did not develop organomegaly and their survival after transplantation was no shorter.…”

“…Figure S2. Based on our own previous experience with a xenotransplantation system for healthy human hematopoiesis using the same host strain, 33 we started by using intrahepatic injection of graft cells into newborn mice (1x10 6 viable JMML MNC per mouse) as route of transplantation. To see if the procedure could be simplified and make the model less dependent on the timely birth of pups, we also transplanted 5-week old mice via conventional intravenous injection; these mice received 5x10 6 JMML MNC to compensate for the higher body weight at that age.…”

“…We favored this technique because of an earlier description by Traggiai and the documented suitability for transplantation of healthy cord blood-derived CD34 + cells. 33,38 Adopting an intrahepatic strategy seemed especially appropriate for JMML since it is a disease of early childhood, frequently affects the liver and most probably originates from fetal hematopoietic cells, which appear to be supported better by neonatal than adult tissues. 39,40 In addition, intravenous injection would be technically challenging in newborn mice.…”

Antagonism between MCL-1 and PUMA governs stem/progenitor cell survival during hematopoietic recovery from stress

“…Analysis for R1 and R2 was performed after 8 reconstitution in the context of bone marrow transplantation (competitive: Figure 3B-E; and even noncompetitive: Figure 3F). Given that BIM and PUMA can both antagonize MCL-1 19 and are critical for stress-induced apoptosis of hematopoietic stem/progenitor cells, [20][21][22][23][24] we hypothesized that deficiency in either of these BH3-only proteins would rescue the defects in emergency hematopoiesis caused by loss of 1 allele of Mcl-1.…”

Deregulated cell death and lymphocyte homeostasis cause premature lethality in mice lacking the BH3-only proteins Bim and Bmf

“…6 In addition, both proteins coregulate hematopoietic stem cell dynamics and reconstitution potential in mice, and this role seems conserved in humans. 16 Furthermore, Bim and Bmf share a conserved motif near their N termini that allows interaction with cytoskeletal dynein light chain proteins, suggesting similar regulation. 17 Here, we investigated the short-and long-term consequences of combined deficiency for Bim and Bmf in double-mutant mice.…”