Liver transcript expression patterns in the sparid striped seabream (Lithognathus mormyrus) upon exposure to cadmium

Changes in hepatic gene expression profiles upon exposures to cadmium applied by feeding or intra-peritoneal injections were identified in the striped sea bream (Lithognathus mormyrus) using cDNA microarray platform. Two groups of four fish were exposed to fed and injected CdCl2, respectively. Additional eight untreated fish were used as a reference group, pooled into 4 hepatic RNA preparations. The isolated hepatic mRNAs were hybridized, after conversion to labeled cDNAs, onto the microarray followed by slide scanning, imaging and analysis. Four parameters: M, meanA, P-value and B were calculated for each unique spot, for both cadmium-fed vs. reference fish (sample1) and cadmium-injected vs. reference fish (sample2). These parameters enable evaluation of hybridization intensity as well as statistical testing of differential expression. Keywords: Response to exposure to cadmium Four biological replicate hybridizations were designed, each composed of labeled hepatic cDNAs of three individual fish, each taken from the two experimental conditions and the reference, respectively. The three cDNAs included in each biological replicate, were dual-hybridized in all three possible alternatives, ending with 12 slides. The two dyes were swaped for each pair of biological replicates to reduce putative dye effects. Graphic presentation of the hybridization scheme is provided as supplementary file.

本研究采用cDNA微阵列（cDNA microarray）技术平台，于条纹鲷（Lithognathus mormyrus）中鉴定了经喂食或腹腔注射暴露于镉后其肝脏基因表达谱的变化。将两组各4尾鱼分别暴露于喂食型与注射型氯化镉（CdCl₂）；另设8尾未处理鱼作为对照，将其肝脏RNA混合为4份制备样品。提取的肝脏mRNA经逆转录为标记cDNA后，与微阵列进行杂交，随后完成玻片扫描、成像与数据分析。针对每个独特探针斑点，分别在喂食镉暴露组vs对照组（样本1）及注射镉暴露组vs对照组（样本2）中，计算M值、meanA值、P值与B值四项参数。上述参数可用于评估杂交信号强度，并对基因差异表达开展统计学检验。关键词：镉暴露应答。本研究设计了4次生物学重复杂交，每次杂交均由3尾个体鱼的标记肝脏cDNA组成，分别取自两种实验处理组与对照组。每次生物学重复包含的3份cDNA，以全部三种可能的配对方式进行双色杂交，最终得到12张芯片。每对生物学重复均交换两种荧光染料，以降低潜在的染料偏倚效应。杂交实验方案的图形展示详见补充材料文件。