PBX AND Retinoic Acid-dependent Differentiation

描述（由申请人提供）：维甲酸（RA）是维生素A最有效的生物活性形式，在生长、分化、免疫反应、生殖和胚胎发育过程中发挥重要作用。母体维生素A不足和过量都与发育异常有关。RA处理P19胚胎癌细胞导致分化为内胚层或神经元细胞，这取决于培养条件。用RA处理P19细胞后，前B细胞白血病转录因子1（PBX 1）、PBX 2和PBX 3 mRNA水平以及PBX 1/2/3蛋白水平升高。PBX蛋白作为二聚体伴侣与几个HOX蛋白介导的基因表达在发育过程中。这种RA依赖性的PBX 1/2/3表达增加已被证明是P19细胞分化为内胚层细胞和神经元细胞的关键。此外，两个基因，骨形态发生蛋白4（BMP 4）和decornin（DCN）的表达已被证明需要在内胚层细胞分化过程中的PBX 1/2/3表达的RA依赖性增加。提出的研究的目的是阐明在P19细胞分化为内胚层和神经元细胞期间，这种RA依赖性的PBX 1/2/3水平增加的作用。因此，我们计划：（2）确定P19细胞向内胚层细胞和/或神经元细胞的RA依赖性分化是否需要PBX 1/2/3蛋白诱导BMP 4和/或DCN表达;以及（3）鉴定和表征在P19细胞向内胚层和神经元细胞的RA依赖性分化期间的额外的PBX 1/2/3调节基因。这些研究将进一步了解PBX在哺乳动物发育过程中的作用，并进一步阐明分化过程中RA依赖性信号传导途径的细节。

DESCRIPTION (provided by applicant): Retinoic acid (RA), the most potent biologically active form of vitamin A, plays an important role during growth, differentiation, immune response, reproduction, and embryonic development. Both maternal insuffiency and maternal excess of vitamin A are associated with developmental abnormalities. RA treatment of P19 embryonal carcinoma cells causes differentiation to either endodermal or neuronal cells, depending on the culture conditions. Pre-B cell leukemia transcription factor 1 (PBX1), PBX2 and PBX3 mRNA levels, and PBX1/2/3 protein levels are elevated upon treatment of P19 cells with RA. PBX proteins function as dimeric partners with several HOX proteins mediating gene expression during development. This RA-dependent increase in PBX1/2/3 expression has been demonstrated to be critical for differentiation of P19 cells to both endodermal and neuronal cells. In addition, the expression of two genes, bone morphogenetic protein 4 (BMP4) and decornin (DCN) have been shown to require RA-dependent increase in PBX1/2/3 expression during endodermal cell differentiation. The goal of the proposed studies is to elucidation the role of this RA-dependent increase in PBX1/2/3 levels during differentiation of P19 cells to endodermal and neuronal cells. We therefore plan: (1) to further characterize the role of PBX172/3 proteins during differentiation of P19 cells to endodermal, neuronal and cardiac cells; (2) to determine if induction of BMP4 and/or DCN expression by PBX1/2/3 proteins is required for RA-dependent differentiation of P19 cells to endodermal and/or neuronal cells; and (3) to identify and characterize additional PBX1/2/3-regulated genes during RA-dependent differentiation of P19 cells to endodermal and neuronal cells. These studies will further the understanding of the role of PBX during mammalian development and further elucidate the details of one RA-dependent pathway of signaling during differentiation.