Transcription profiling of mouse Egr-1 knock-outs during development (p30 and p42)

In chicks, the avian homologue of the early growth response protein-1 (ZENK) has been shown to be increased in a special cell type of the retina, the glucagonergic amacrine cells, under conditions that lead to a reduction in eye growth (myopic defocus, recovery of myopia) and decreased under conditions that enhance ocular growth (hyperopic defocus, form-deprivation). The investigation of Egr-1 knock-out mice showed that homozygous knock-out mice with no functional Egr-1 protein developed relative axial myopia at the age of 42 and 56 days, compared to heterozygous- and wildtype Egr-1 knock-out mice. To clarify the role of Egr-1 in the retinal regulation of eye growth, and to get an idea about the biochemical pathways underlying this mechanism, we studied the role of Egr-1 in more detail using Affymetrix microarrays. Experiment Overall Design: Retinal samples of young homozygous Egr-1 knock-out and wildtype mice at the age of 30 days (hm30 and wt30; no difference in axial eye length yet) and 42 days (hm42 and wt42; already a difference in axial eye length of 59 µm) were taken to compare the mRNA expression changes over time between these two genotypes and within the same genotype between the two age groups.在雏鸡中，早期生长反应蛋白1（early growth response protein-1, Egr-1）的禽类同源物ZENK已被证实：在导致眼球生长受抑的条件（近视性离焦、近视恢复）下，其在视网膜特异性细胞类型——胰高血糖素能无长突细胞——中的表达水平升高；而在促进眼球生长的条件（远视性离焦、形觉剥夺）下，其表达水平则显著降低。针对Egr-1敲除小鼠的研究显示，与杂合子及野生型Egr-1敲除小鼠相比，缺乏功能性Egr-1蛋白的纯合子敲除小鼠在出生后42天和56天时会出现相对性轴性近视。为阐明Egr-1在视网膜调控眼球生长中的作用，并解析该机制背后的生化通路，我们采用Affymetrix微阵列（microarrays）对Egr-1的功能开展了更为深入的研究。实验整体设计：我们采集了30日龄（此时纯合子敲除组hm30与野生型组wt30的眼轴长度尚无显著差异）及42日龄（此时两组眼轴长度差异已达59μm，记为hm42与wt42）的幼年纯合子Egr-1敲除小鼠与野生型小鼠的视网膜样本，以对比两种基因型小鼠随时间推移的mRNA表达变化，同时分析同一基因型小鼠在两个年龄组间的mRNA表达差异。