Insulin-like growth factor 2 modulates murine hematopoietic stem cell maintenance through upregulation of p57

Exp Hematol. 2016 May;44(5):422-433.e1. doi: 10.1016/j.exphem.2016.01.010. Epub 2016 Feb 10.

Abstract

Hematopoietic stem cells (HSC) rely on a highly regulated molecular network to balance self-renewal and lineage specification to sustain life-long hematopoiesis. Despite a plethora of studies aimed at identifying molecules governing HSC fate, our current knowledge of the genes responsible is limited. We have found insulin-like growth factor 2 (IGF2) to be expressed predominantly within long-term HSCs. This study examines IGF2 expression patterns and the effects of the gene in HSCs. Through the overexpression and knockdown of IGF2 within purified HSCs, we report that IGF2 expression increases HSC-derived multilineage colonies in vitro and enhances hematopoietic contribution in vivo on competitive bone marrow transplantation. The effects of IGF2 are mediated by direct upregulation of the CDKi p57, exclusively within long-term HSCs, via activation of the PI3K-Akt pathway. Increased expression of p57 resulted in a concomitant increase in HSCs in the G0/G1 stage of the cell cycle. Analysis of genomic DNA methylation revealed that HSCs exhibited a hypomethylated state within the promoter region of the CDKN1C (p57) gene, providing a potential mechanism for the exclusive effects of IGF2 within HSCs. Our studies indicate a novel role for IGF2 in regulating HSC cell cycle and illustrate potential novel therapeutic targets for hematologic diseases.

MeSH terms

  • Animals
  • Cell Cycle / genetics
  • Cell Lineage / genetics
  • Cell Proliferation / genetics
  • Cells, Cultured
  • Cyclin-Dependent Kinase Inhibitor p57 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p57 / metabolism
  • DNA Methylation
  • Flow Cytometry
  • Gene Expression
  • Hematopoietic Stem Cells / cytology
  • Hematopoietic Stem Cells / metabolism*
  • Insulin-Like Growth Factor II / genetics*
  • Insulin-Like Growth Factor II / metabolism
  • Mice, Inbred C57BL
  • Phosphatidylinositol 3-Kinases / metabolism
  • Promoter Regions, Genetic / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Up-Regulation*

Substances

  • Cdkn1c protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p57
  • Insulin-Like Growth Factor II
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt