Molecular mechanisms of retinoic acid-mediated control of cellular proliferation and differentiation

利用差异杂交技术，我们分离了20种在RA诱导F9细胞分化过程中表达的cDNA克隆。针对以下两个克隆，我们分析了基因的结构和功能。(1)Rae12：rae 12基因家族编码至少5种不同的14-3-3蛋白成员，其表达在RA介导的F9细胞分化过程中被诱导。我们表明这些成员的表达增强了Raf-1激酶。此外，我们证明了以下几点：i）14-3-3蛋白的过表达增强了MAP激酶级联中的信号转导，导致NIH 3 T3细胞的刺激的细胞增殖和致瘤性转化。ii）14-3-3蛋白的诱导表达增强MAP激酶级联中的信号转导，其在RA介导的F9细胞分化期间起重要作用。(2)rae 28：结构分析cDNA克隆表明rae 28基因是果蝇多形基因的哺乳动物同源物。我们分离了rae 28基因并建立了rae 28基因敲除小鼠。纯合子是致命的，并显示出以下有趣的表型：i）心脏畸形，ii）眼科异常，iii）骨骼异常（后转化），iv）腭裂。

By using the differential hybridization methods, we isolated the 20 kinds of cDNA clones, whose expression is induced during RA-mediated F9 cell differentiation. Focusing on the following two clones, we analyzed the structure and function of the genes.(1) Rae12 : the rae12 gene family encodes at least 5 kinds of different 14-3-3 protein members, whose expression is induced during RA-mediated F9 cell differentiation. We showed the expression of these members enhance the Raf-1 kinase. Furthermore, we demonstrated the following points : i) overexpression of 14-3-3 proteins enhances the signal transduction in the MAP kinase cascade, resulting in the stimulated cellular proliferation and tumorigenic transformation of NIH 3T3 cells. ii) the induced expression of 14-3-3 proteins enhances the signal transduction in the MAP kinase cascade, that plays an important role during RA-mediated F9 cell differentiation.(2) Rae28 : structure analysis the cDNA clone suggested that the rae28 gene is a mammalian homologue of a Drosophila polyhometic gene. We isolated the rae28 gene and established the rae28 knockout mice. The homozygotes are lethal and showed the following intriguing phenotypes : i) heart malformations, ii) ophthalmic abnormalities, iii) skeletal abnormalities (posterior transformation) , iv) cleft palate.