Abstract 16008: HDAC3 Unconventional Splicing Mediates Stem Cell-Endothelial Differentiation
Background - Our previous studies have demonstrated that histone descetylase 3 (HDAC3) is essential for endothelial differentiation, but it is unknown if HDAC3 isoforms are involved in differentiation/transition of stem cells into endothelial cells.
Methods and Results - In this study, we found that HDAC3 underwent unconventional splicing during stem cell differentiation, embryonic development and mature endothelial cells in response to TGFβ or non-serum medium treatment. Four different splicing variants have been identified, designated as HDAC3α, β, γ and δ, respectively. In these isoforms, the intron 12 is kept as an additional exon and there is recombination between different exons. The insertion of GFP sequence into the intron 12 within the open reading frame demonstrated the natural occurrence of splicing event during embryonic stem cell differentiation. The over-expression of isoform HDAC3α enhanced smooth muscle marker expression in the presence of PDGF in endothelial cells. In vitro study showed that exogenous HDAC3α efficiently reprogrammed endothelial cells into mesenchymal stem/progenitotr cells, expressing CD34, CD133 and alkaline phosphatase in the serum free conditions. Over-expression of HDAC3α in mature endothelial cells induced SMA/FSP1 expression and collagen IV/periostin secretion through enhanced Smad2/3 phosphorylation/nuclear translocation and Snail2 expression, which was independent of TGFβ ligand. However, TGFβ receptor I (ALK5) inhibitor, SB431542, abolished HDAC3α−mediated effects. Co-immunoprecipitation assay showed that HDAC3α associated with Akt and Smad3. In vivo study indicates that HDAC3α isoform not only emerged in the endothelium and colocalized with alpha-smooth muscle actin positive cells in dorsa aorta during vascular development in chick embryo. Knockdown of HDAC3α in embryo resulted in abnormal development of the vasculature.
Conclusion - We provided the first evidence that HDAC3 undergoes unconventional splicing resulting in four isoforms during stem cell differentiation, of which HDAC3α plays a role in endothelial (de)differentiation into stem/progenitors through regulating TGFβ signaling pathway.
- © 2012 by American Heart Association, Inc.