Abstract 10660: Functional Involvements of Heterogeneous Nuclear Ribonucleoprotein A1 in Smooth Muscle Differentiation from Stem Cells in vitro and in vivo
Background: Heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) plays various roles in transcriptional and posttranscriptional modulation of gene expression.
Objective: To investigate the functional impacts of hnRNPA1 on SMC differentiation from stem cells in vitro and in vivo.
Methods and Results: Mouse embryonic stem (ES) cells were cultivated on collagen IV-coated plates and smooth muscle differentiation medium to allow for SMC differentiation. We found that hnRNPA1 gene and protein expression was up-regulated significantly following 3 to 7 days of stem cell differentiation, and co-expressed with SMC differentiation markers in the stem cell-derived SMCs as well as embryonic SMCs of 12.5 days of mouse embryos. In adult mouse tissues/organs, hnRNPA1 expression was strong in aortic SMCs and cardiac cells, but almost undetectable or very low level in small intestines and skeletal muscle. hnRNPA1 knockdown resulted in down-regulation of specific smooth muscle markers and transcription factors, while enforced expression of hnRNPA1 enhanced the expression of these genes. Importantly, knockdown of hnRNPA1 also resulted in impairment of SMC differentiation in vivo. Moreover, we demonstrated that hnRNPA1 could transcriptionally regulate SMC gene expression through direct binding to promoters of SMαA and SM22α genes by using luciferase and chromatin immunoprecipitation assays. We further demonstrated that the binding sites for serum response factor (SRF), a well-investigated SMC transcription factor, within the promoter region of SMαA and SM22α genes was responsible for hnRNPA1-mediated SMαA and SM22α gene expression by using in vitro site-specific mutagenesis and luciferase activity analyses. Finally, we also demonstrated that hnRNPA1 up-regulated myocyte-specific enhancer factor 2C (MEF2C), another smooth muscle transcription factor, gene expression through transcriptional activation.
Conclusions: Our findings demonstrated that hnRNP A1 plays a functional role in SMC differentiation from stem cells in vitro and in vivo. This indicates that hnRNPA1 is a potential modulating target for deriving SMCs from stem cells and cardiovascular regenerative medicine.
- © 2012 by American Heart Association, Inc.