Chen Jinhui, Tong Ying, Zhao Shufang, Ma Shanshan, Luo Chen
College of Life Science, Hunan Normal University, Changsha 410081, China.
J Genet Genomics. 2009 Aug;36(8):483-90. doi: 10.1016/S1673-8527(08)60138-1.
Visual system homeobox-1 (vsx1) is important in retinal progenitor proliferation, differentiation, and function maintenance of bipolar cells in vertebrates. Recent study in Xenopus laevis has shown that vsx1 3' untranslated region (3' UTR) can mediate cell-specific translation of vsx1 mRNA in the bipolar cells of the retinal inner nuclear layer (INL). vsx1 is also transcribed at the early developmental stages prior to eye formation and its spatiotemporal expression patterns are conserved in all the examined vertebrates. In order to determine whether the vsx1 3' UTR has a role in regulating the spatiotemporal expression of vsx1 during early embryogenesis, we constructed a vsx1 UTR-controlled green fluorescent protein (GFP) reporter gene system and examined the GFP expression pattern in goldfish, Carassius auratus, at different developmental stages. Our results indicated that both the vsx1 5' UTR and the vsx1 3' UTR remarkably repressed GFP expression at transcription level but did not regulate tissue-specific translation at early developmental stages. GFP protein was ubiquitously expressed in the embryos injected with GFP-sensors containing vsx1 UTRs before 60 h post-fertilization (hpf). From hatching stage (72 hpf) onwards, however, GFP protein was specifically expressed in the bipolar cells of the retinal INL in the vsx1 3'UTR-GFP-sensor embryos, but was still ubiquitously expressed in the embryos injected with GFP-sensor lacking vsx1 3' UTR. These observations showed a significant difference of vsx1 3' UTR-mediated translation between early and late developmental stages and suggested that vsx1 3' UTR might not be involved in regulating the spatiotemporal expression of vsx1 until hatching stage during embryogenesis.
视觉系统同源框-1（vsx1）在脊椎动物视网膜祖细胞增殖、分化以及双极细胞功能维持方面具有重要作用。近期对非洲爪蟾的研究表明，vsx1 3'非翻译区（3'UTR）可介导视网膜内核层（INL）双极细胞中vsx1 mRNA的细胞特异性翻译。vsx1在眼睛形成之前的早期发育阶段也会转录，并且其时空表达模式在所有被检测的脊椎动物中都是保守的。为了确定vsx1 3'UTR在胚胎早期发育过程中是否对vsx1的时空表达具有调控作用，我们构建了一个由vsx1 UTR控制的绿色荧光蛋白（GFP）报告基因系统，并检测了不同发育阶段金鱼（Carassius auratus）中GFP的表达模式。我们的结果表明，vsx1 5'UTR和vsx1 3'UTR在转录水平均显著抑制GFP表达，但在早期发育阶段并不调控组织特异性翻译。在受精后60小时（hpf）之前，注射含有vsx1 UTR的GFP传感器的胚胎中，GFP蛋白普遍表达。然而，从孵化阶段（72 hpf）开始，在vsx1 3'UTR-GFP传感器胚胎中，GFP蛋白特异性表达于视网膜INL的双极细胞中，但在注射缺乏vsx1 3'UTR的GFP传感器的胚胎中仍普遍表达。这些观察结果显示了vsx1 3'UTR介导的翻译在发育早期和晚期阶段存在显著差异，并表明在胚胎发育过程中，vsx1 3'UTR可能直到孵化阶段才参与调控vsx1的时空表达。
