Ohtaka-Maruyama C, Hanaoka F, Chepelinsky A B
Cellular Physiology Laboratory, the Institute for Chemical and Physical Science (RIKEN), 2-1 Hirosawa, Wako, Saitama, 351-01, Japan.
Dev Biol. 1998 Oct 1;202(1):125-35. doi: 10.1006/dbio.1998.8997.
The AP2alpha gene encodes a transcription factor containing a basic, helix-span-helix DNA-binding/dimerization domain, which is developmentally regulated and retinoic acid inducible. Recent reports about AP2alpha null mice indicate that AP2alpha plays an important role in embryogenesis, especially in craniofacial development and midline fusion. Ocular development is also affected in these null mice. As AP2alpha may be involved in transcriptional regulation in the lens, it was important to examine the expression of the AP2alpha gene in the lens. Four AP2alpha mRNA variants have been previously isolated from whole mouse embryos. Variants 1, 3, and 4 are transcriptional activators that are transcribed from different promoters and variant 2 is a repressor lacking the activation domain encoded by exon 2. Using in situ-PCR, we found that AP2alpha is expressed in the lens epithelia but not in the lens fibers. RT-PCR analysis of lens mRNA with amplimers specific for each variant revealed that AP2alpha variants 1, 2, and 3 are expressed in newborn mouse lenses. However, variant 4 is not expressed in the lens. In this report we characterized a novel isoform, which we named variant 5, expressed in the lens and kidney. Variant 5, which is generated by alternative splicing, may function as a repressor due to the partial deletion of the proline-rich transactivation domain encoded by exon 2. This is the first molecular characterization of AP2alpha gene expression in the lens. Our results indicate that two activator and two repressor AP2alpha isoforms may play a role in regulating gene expression in the lens.
AP2α基因编码一种转录因子，该转录因子含有一个碱性的、螺旋-跨度-螺旋DNA结合/二聚化结构域，其表达受发育调控且可被视黄酸诱导。最近关于AP2α基因敲除小鼠的报道表明，AP2α在胚胎发育中起着重要作用，尤其是在颅面发育和中线融合方面。这些基因敲除小鼠的眼部发育也受到影响。由于AP2α可能参与晶状体中的转录调控，因此检测AP2α基因在晶状体中的表达具有重要意义。此前已从整个小鼠胚胎中分离出四种AP2α mRNA变体。变体1、3和4是转录激活因子，它们从不同的启动子转录而来，而变体2是一种缺乏外显子2编码的激活结构域的阻遏物。通过原位PCR，我们发现AP2α在晶状体上皮细胞中表达，但在晶状体纤维中不表达。用针对每种变体的特异性扩增引物对晶状体mRNA进行RT-PCR分析表明，AP2α变体1、2和3在新生小鼠晶状体中表达。然而，变体4在晶状体中不表达。在本报告中，我们鉴定了一种在晶状体和肾脏中表达的新型异构体，我们将其命名为变体5。变体5是通过可变剪接产生的，由于外显子2编码的富含脯氨酸的反式激活结构域部分缺失，它可能作为一种阻遏物发挥作用。这是首次对晶状体中AP2α基因表达进行分子特征分析。我们的结果表明，两种激活型和两种阻遏型AP2α异构体可能在调节晶状体中的基因表达中发挥作用。
