Identification of estrogen-responsive genes in neuroblastoma SK-ER3 cells

To evaluate the role of estrogen receptor in the differentiation of cells of neural origin, we developed a molecular approach aimed at the identification of estrogen target genes by mRNA differential display PCR (ddPCR) in human neuroblastoma SK-ER3 cells. More than 3000 RNAs were examined, a few of which displayed a differential regulation pattern in response to 17 beta-estradiol (E-2). Sequence analysis of three differentially amplified ddPCR products showed homology with the growth-associated nuclear protein prothymosin-alpha (PTMA), the Bcl2-interacting protein Nip2, and one mRNA previously described by others in fetal human brain. Two ddPCR products, referred to as P4 and P10, corresponded to new DNA sequences. Northern analysis confirmed that estrogen treatment of SK-ER3 cells resulted in the upregulation and downregulation of expression of these messages. In particular, PTMA was found to accumulate at both 1 and 17 hr after E-2 treatment, whereas P10 product accumulated only at 1 hr. Conversely, P4, Nip2, and the fetal brain-related mRNAs were significantly decreased by the treatment. Further time course analysis of PTMA and Nip2 mRNAs levels indicated that the hormone exerted a marked biphasic regulatory effect on expression of both messages during the course of cell differentiation. In the present study we report for the first time the identification of a panel of estrogen target genes in neural cells that provide new insights in the molecular mechanism of action of E-2 in cells of neural origin.