Distinct and Additive Effects of Long Noncoding RNA-expression and Retinoic Acid-treatment During Neuronal Differentiation of Human Neuroblastoma Cells.

Abstract

Retinoic Acid (RA) induces differentiation and regulates gene expression through three subtypes (α, β, γ) of the nuclear retinoid receptor heterodimer (RAR/RXR), which also function as transcription factors. Earlier, we reported the long intergenic noncoding RNAs (LINC-RBE and LINC-RSAS) induced by All-Trans Retinoic Acid (ATRA) in cultured primary hippocampal neurons from adult rat brain at transcriptional and post-transcriptional levels, respectively. In this study, we report that ~ 25% of the human neuroblastoma (SH-SY5Y) cells were differentiated by 1 µM ATRA-treatment within 72 h showing extension of neurites from spindle-shaped cells demonstrating neuronal differentiation. Expression of RARβ and interferon regulatory factor-1 (IRF-1) mRNAs was significantly upregulated up to 16xfold at 10 h and 2.6xfold at 8 h by 1 µM ATRA-treatment, respectively. This indicated activation of the RA-signaling pathway in these cells. With a transfection efficiency of ~ 40%, overexpression of LINC-RBE and LINC-RSAS caused ~ 34% and ~ 33% inhibition of cell proliferation, respectively, with an increase in cell death and ~ 10% reduction in number of cells in G1-phase of cell cycle. ATRA-treatment alone caused ~ 40% inhibition of cell proliferation, and induced ~ 66% of cells to G1-phase arrest. Combined effect of LINC-RSAS + ATRA further enhanced inhibition of cell proliferation by additional ~ 32%, whereas LINC-RBE, ATRA and LINC-RBE + ATRA showed similar effects indicating distinct effects and mechanisms of their actions. Moreover, overexpression of these lncRNAs led to fourfold increase in genomicDNA breakage/damage in these cells. Thus it showed an unique relationship between lncRNA and RA during neuronal differentiation, most likely involving regulation of gene expression.