Mitchell Diana M, Stevens Craig B, Frey Ruth A, Hunter Samuel S, Ashino Ryuichi, Kawamura Shoji, Stenkamp Deborah L
Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America.
Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America; Bioinformatics and Computational Biology Graduate Program, University of Idaho, Moscow, Idaho, United States of America.
PLoS Genet. 2015 Aug 21;11(8):e1005483. doi: 10.1371/journal.pgen.1005483. eCollection 2015 Aug.
The signaling molecule retinoic acid (RA) regulates rod and cone photoreceptor fate, differentiation, and survival. Here we elucidate the role of RA in differential regulation of the tandemly-duplicated long wavelength-sensitive (LWS) cone opsin genes. Zebrafish embryos were treated with RA from 48 hours post-fertilization (hpf) to 75 hpf, and RNA was isolated from eyes for microarray analysis. ~170 genes showed significantly altered expression, including several transcription factors and components of cellular signaling pathways. Of interest, the LWS1 opsin gene was strongly upregulated by RA. LWS1 is the upstream member of the tandemly duplicated LWS opsin array and is normally not expressed embryonically. Embryos treated with RA 48 hpf to 100 hpf or beyond showed significant reductions in LWS2-expressing cones in favor of LWS1-expressing cones. The LWS reporter line, LWS-PAC(H) provided evidence that individual LWS cones switched from LWS2 to LWS1 expression in response to RA. The RA signaling reporter line, RARE:YFP indicated that increased RA signaling in cones was associated with this opsin switch, and experimental reduction of RA signaling in larvae at the normal time of onset of LWS1 expression significantly inhibited LWS1 expression. A role for endogenous RA signaling in regulating differential expression of the LWS genes in postmitotic cones was further supported by the presence of an RA signaling domain in ventral retina of juvenile zebrafish that coincided with a ventral zone of LWS1 expression. This is the first evidence that an extracellular signal may regulate differential expression of opsin genes in a tandemly duplicated array.
信号分子视黄酸（RA）调节视杆和视锥光感受器的命运、分化和存活。在此，我们阐明RA在串联重复的长波长敏感（LWS）视锥视蛋白基因的差异调节中的作用。斑马鱼胚胎在受精后48小时（hpf）至75 hpf用RA处理，然后从眼睛分离RNA进行微阵列分析。约170个基因显示出表达显著改变，包括几种转录因子和细胞信号通路的成分。有趣的是，LWS1视蛋白基因被RA强烈上调。LWS1是串联重复的LWS视蛋白阵列的上游成员，在胚胎期通常不表达。在48 hpf至100 hpf或更长时间用RA处理的胚胎中，表达LWS2的视锥细胞显著减少，而有利于表达LWS1的视锥细胞。LWS报告基因系LWS-PAC(H)提供的证据表明，单个LWS视锥细胞响应RA从表达LWS2转变为表达LWS1。RA信号报告基因系RARE:YFP表明，视锥细胞中RA信号增加与这种视蛋白转换相关，并且在LWS1正常开始表达时对幼虫进行实验性RA信号减少显著抑制了LWS1表达。幼年斑马鱼腹侧视网膜中存在与LWS1表达腹侧区重合的RA信号域，进一步支持了内源性RA信号在调节有丝分裂后视锥细胞中LWS基因差异表达中的作用。这是细胞外信号可能调节串联重复阵列中视蛋白基因差异表达的首个证据。
