PBX AND Retinoic Acid-dependent Differentiation

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、繁殖和胚胎发育。都是母性的 维生素A不足和母亲过量维生素A与发育异常有关。Ra P19胚胎癌细胞的治疗会导致分化为内胚层细胞或神经细胞， 视培养条件而定。前B细胞白血病转录因子1、PBX2和PBX3 RA处理P19细胞后，Pbx1/2/3蛋白水平和mRNA水平均升高。PBX蛋白 在发育过程中与几个HOX蛋白一起发挥二聚体的作用，介导基因的表达。这 RA依赖的Pbx1/2/3表达的增加已被证明是分化的关键 P19细胞转化为内胚层细胞和神经细胞。此外，还有两个基因的表达，骨 形态发生蛋白4(BMP4)和核心蛋白(DCN)被证明需要RA依赖的增加 Pbx1/2/3在内皮细胞分化过程中的表达拟议研究的目标是 阐明这种RA依赖的Pbx1/2/3水平升高在P19细胞分化为 内胚层细胞和神经细胞。因此，我们计划：(1)进一步研究PBX172/3蛋白的作用 在P19细胞分化为内胚层细胞、神经细胞和心肌细胞的过程中；(2)确定是否诱导 P19细胞依赖RA分化需要Pbx1/2/3蛋白表达BMP4和/或DCN 内胚层和/或神经细胞；以及(3)鉴定和表征其他受Pbx1/2/3调控的细胞 视黄酸依赖的P19细胞向内胚层和神经细胞分化过程中的基因。这些研究将 进一步了解PBX在哺乳动物发育中的作用，并进一步阐明细节 分化过程中的一条RA依赖的信号通路。

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.