Vardimon L, Fox L E, Moscona A A
Proc Natl Acad Sci U S A. 1986 Dec;83(23):9060-4. doi: 10.1073/pnas.83.23.9060.
Glutamine synthetase (GS) is expressed in the neural retina only in Muller glia cells and is inducible with cortisol. A chicken genomic clone that contains at least part of the coding region for the GS enzyme was used to investigate developmental changes in the level of GS mRNA in embryonic chicken retina. A major GS transcript (approximately equal to 3 kilobases) detected by the probe begins to accumulate sharply on day 15 of embryonic development. When cortisol is prematurely supplied to early embryonic retina, it induces precocious accumulation of GS mRNA and of the GS enzyme. At later ages, these effects of cortisol are significantly greater, which suggests that competence to transcribe or stabilize GS mRNA in response to stimulation with cortisol increases with development. Carbonic anhydrase II (CA-II) is expressed in early retina in all the cells, but it becomes later restricted to Muller glia. Using cloned CA-II cDNA, we detected a high level of CA-II mRNA in early retina, followed by a decline due to arrest of CA-II mRNA accumulation in differentiated neurons. As glia cells mature, CA-II mRNA and the enzyme increase to a new high level. Therefore, changes in CA-II gene expression during retina development reflect differentiation-dependent cell-type-specific control of CA-II mRNA accumulation.
谷氨酰胺合成酶（GS）仅在神经视网膜的穆勒胶质细胞中表达，且可被皮质醇诱导。一个包含GS酶至少部分编码区的鸡基因组克隆被用于研究胚胎鸡视网膜中GS mRNA水平的发育变化。探针检测到的一个主要GS转录本（约3千碱基）在胚胎发育第15天开始急剧积累。当皮质醇过早供应给早期胚胎视网膜时，它会诱导GS mRNA和GS酶的早熟积累。在后期，皮质醇的这些作用明显更大，这表明随着发育，响应皮质醇刺激转录或稳定GS mRNA的能力增强。碳酸酐酶II（CA-II）在早期视网膜的所有细胞中均有表达，但后来局限于穆勒胶质细胞。使用克隆的CA-II cDNA，我们在早期视网膜中检测到高水平的CA-II mRNA，随后由于分化神经元中CA-II mRNA积累停止而下降。随着胶质细胞成熟，CA-II mRNA和该酶增加到一个新的高水平。因此，视网膜发育过程中CA-II基因表达的变化反映了CA-II mRNA积累的分化依赖性细胞类型特异性调控。
