Homeobox genes encode transcription factors controlling development; however, a number of homeobox genes are expressed postnatally specifically in melatonin-producing pinealocytes of the pineal gland and photoreceptors of the retina along with transcripts devoted to melatonin synthesis and phototransduction. Homeobox genes regulate melatonin synthesis in pinealocytes, but some homeobox genes also seem to be involved in regulation of retinal phototransduction. Due to the lack of photoreceptor models, we here introduce the rat pinealocyte culture as an in vitro model for studying retinal phototransduction. Systematic qPCR analyses were performed on the rat retina and pineal gland in 24 hour in vivo series and on primary cultures of rat pinealocytes: All homeobox genes and melatonin synthesis components, as well as nine out of ten phototransduction genes, were readily detectable in all three experimental settings, confirming molecular similarity between cultured pinealocytes and in vivo retinal tissue. 24 hours circadian expression was mostly confined to transcripts in the pineal gland, including a novel rhythm in arrestin (Sag). Individual knockdown of the homeobox genes orthodenticle homeobox 2 (Otx2), cone-rod homeobox (Crx) and LIM homeobox 4 (Lhx4) in pinealocyte culture using siRNA resulted in specific downregulation of transcripts representing all levels of phototransduction; thus, all phototransduction genes studied in culture were affected by one or several siRNA treatments. Histological colocalization of homeobox and phototransduction transcripts in the rat retinal photoreceptor was confirmed by RNAscope in situ hybridization, thus suggesting that homeobox gene-encoded transcription factors control postnatal expression of phototransduction genes in the retinal photoreceptor.

中文翻译：

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同源框基因编码转录因子在调节光转导中的作用：将原代松果体细胞培养作为光感受器模型

同源盒基因编码控制发育的转录因子；然而，许多同源盒基因在出生后特异性表达在松果体的产生褪黑激素的松果体细胞和视网膜的光感受器中，以及专门用于褪黑激素合成和光转导的转录物。同源盒基因调节松果体细胞中褪黑激素的合成，但一些同源盒基因似乎也参与了视网膜光转导的调节。由于缺乏光感受器模型，我们在这里介绍大鼠松果体细胞培养作为研究视网膜光转导的体外模型。对大鼠视网膜和松果体 24 小时体内系列以及大鼠松果体细胞的原代培养物进行系统性 qPCR 分析：所有同源盒基因和褪黑激素合成成分，以及十分之九的光转导基因，在所有三个实验环境中都很容易检测到，证实了培养的松果体细胞和体内视网膜组织之间的分子相似性。24 小时昼夜节律表达主要局限于松果体中的转录本，包括抑制蛋白的新节律。下垂）。使用 siRNA 在松果体细胞培养中单独敲除同源盒基因 orthodenticle homeobox 2 ( Otx2 )、锥杆同源盒 ( Crx ) 和 LIM 同源盒 4 ( Lhx4 ) 导致代表所有光转导水平的转录物的特异性下调；因此，在培养中研究的所有光转导基因都受到一种或几种 siRNA 处理的影响。RNAscope 原位杂交证实了大鼠视网膜光感受器中同源框和光转导转录物的组织学共定位，因此表明同源框基因编码的转录因子控制视网膜光感受器中光转导基因的出生后表达。