半滑舌鳎(Cynoglossus semilaevis)黑色素聚集素受体(MCHR)表达特性及其与无眼侧黑化的关系

Molecular Characterization of MCHR and Its Corelation with Blind-Side Hypermelanosis in Cynoglossus semilaevis

中文关键词: 半滑舌鳎  黑色素聚集素受体  基因克隆  表达调控  无眼侧黑化

英文关键词: Cynoglossus semilaevis  Melanin concentration hormone receptor  Gene cloning  Expression regulation  Hyperpigmentation on blind side

中文摘要:

      利用cDNA末端快速克隆技术(RACE)获得了半滑舌鳎(Cynoglossus semilaevis) 2种黑色素聚集素受体(MCHR1和MCHR2)的cDNA全长序列，并采用定量PCR技术分析了MCHR mRNA的组织表达特性，研究了其与无眼侧黑化程度的关系。结果显示，半滑舌鳎MCHR1 cDNA序列全长为1685 bp，开放阅读框(ORF)长为1080 bp，编码359个氨基酸，与牙鲆(Paralichthys olivaceus)同源性高达83.3%。系统进化分析显示，半滑舌鳎MCHR1与鳉形目、鲽形目和鲈形目鱼类聚为1个小分支。MCHR2 cDNA序列全长为1626 bp，ORF长为1044 bp，编码347个氨基酸，与鲽形目同源性最高达到90%以上。系统进化分析显示，半滑舌鳎MCHR2与鲽形目、鲈形目鱼类聚为1个小分支。MCHR1 mRNA在鳃中表达量最高，而MCHR2 mRNA在有眼侧皮肤中表达量最高，性腺次之。另外，MCHR1和MCHR2 mRNA在其他组织中均检测到表达，这表明半滑舌鳎黑色素聚集素(MCH)可能通过内分泌方式和各组织中的MCHR介导参与生理调控。不同黑化面积表达分析显示，在无眼侧黑化发生早期，脑垂体中MCHR1 mRNA显著升高，在无眼侧50%黑化组达到峰值，皮肤中MCHR1 mRNA在无眼侧10%黑化组显著升高，其后保持较高水平；脑垂体和皮肤中MCHR2 mRNA表达表现出一致的变化趋势，在无眼侧黑化发生早期都达到峰值，其后逐渐下降至相对较低水平。表明MCHR可能直接或通过其他信号通路参与了半滑舌鳎无眼侧黑化性状的调控过程。

英文摘要:

      The full-length cDNA of melanin concentration hormone receptor (MCHR) was isolated from the brain of Cynoglossus semilaevis using RACE (rapid amplification of cDNA ends) method. The spatial and temporal expression patterns of MCHR mRNA in different tissues were analyzed to link with the degree of pigmentation on the blind-side of fish by the quantitative real-time PCR. Results showed that C. semilaevis MCHR1 cDNA sequence was 1685 bp in length and contained a 642 bp of open reading frame encoding 359 amino acids. It shared 83.3% identity with Paralichthys olivaceus. Based on the phylogenetic analysis, C. semilaevis MCHR1 was clustered with the Pleuronectiformes, Cyprinodontiformes and Perciformes species. In addition, C. semilaevis MCHR2 cDNA sequence was 1626 bp in length and contained a 1044 bp of open reading frame encoding 347 amino acids. The identity was more than 90% homology to pleuronectiformes species. C. semilaevis MCHR2 was clustered with the pleuronectiformes and perciformes species based on the phylogenetic analysis. MCHR1 mRNA was mainly expressed in gill and MCHR2 mRNA was primarily expressed in the eye-side skin, followed by gonad. The spatial expression patterns of MCHR mRNA implied that MCHR regulates the physiology of C. semilaevis through endocrine, paracrine and autocrine pathways. Pituitary MCHR1 mRNA level significantly increased during the initial stage of blind-side pigmentation and peaked when fish had 50% pigmentation on the blind-side. By comparison, skin MCHR1 mRNA maintained at high levels during the pigmentation occurring on the blind-side of fish. Both pituitary and skin MCHR2 mRNA levels peaked when fish had about 10% blind-side pigmentation, then significantly decreased as the degree of pigmentation reduced. The results showed that the MCHR is directly or indirectly involved in the regulation of blind-side hypermelanosis in half-smooth tongue sole.