Analysis of the global gene expression profile for pearl oyster, Pinctada maxima, exposed to organotin (tributyltin)(silver-lipped pearl oyster). Series GSE13980.

Bivalves are well known sentinel organism in the detection of environmental pollutants. Bioaccumulation of these contaminants in bivalves often manifests as specific alterations of their biological processes, which are used as biomarkers for environmental pollution. Tributyltin (TBT) is one such pollutant previously used as a biocide in marine antifouling paints, it now causes a number deleterious effects in bivalves leaching out of sediments in marine ecosystems. One effect extensively documented is shell abnormalities, including shell thickening and chambering. Changes in amino acid compositions of the shell matrix are associated with these deformations suggesting that TBT mode of action influences the biological control of shell biomineralization. This environmental toxicant's effect on shell biomineralization was analyzed in this investigation at a transcriptional level in order to elucidate the normal shell biomineralization process. P. maxima animals were exposed to TBT in laboratory conditions and a concentration range for chronic and acute toxicity has been established. Animals exposed to chronic concentrations were analyzed for differential gene expression using PmaxArray 1.0 microarray platform and compared against control animals. Genes indentified as differentially expressed in association with TBT exposure included up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of novel transcripts were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This investigation has used a microarray to determine transcriptional effects of TBT on P. maxima and proposed the involvement of novel components in shell formation, aiding the elucidation of the process.

In order to determine to differential expression profiles for transcripts relevant to TBT exposure, 9 animals treated with TBT 50 ng1-1 were compared to 9 control animals untreated on a dual channel (Cy3 and Cy5) cDNA microarrays. The RNA for the 9 control animals was pooled together for a common reference while the RNA from the 9 treated animals was separated into 3 pooled replicates, each containing RNA from 3 individual animals. Each of the pooled treatment replicates were labeled (Cy3 or Cy5) as was the controls (opposing treatment label) and hybridized to a separate microarray chip, totaling 3 chips. Each chip had duplicate spot grids printed on the left and right of the chip providing technical replication. In total 6 microarrays were challenged and analyzed comprising 3 biological replicates each with 2 technical replicates.

双壳类（Bivalves）是环境污染物检测中广为人知的指示生物（sentinel organism）。此类污染物在双壳类体内的生物富集，往往会表现为其生物过程的特异性改变，这些改变可作为环境污染的生物标志物（biomarker）。三丁基锡（Tributyltin, TBT）便是这类污染物之一，此前曾作为海洋防污涂料中的杀生物剂使用，目前会从海洋生态系统的沉积物中渗出，对双壳类造成诸多有害影响。其中一种被广泛记录的效应是壳体异常，包括壳体增厚与壳腔形成（chambering）。壳基质的氨基酸组成变化与这些畸形相关，这表明三丁基锡的作用方式会影响壳体生物矿化（biomineralization）的生物调控过程。本研究从转录水平分析了这种环境毒物对壳体生物矿化的影响，以阐明正常的壳体生物矿化过程。研究人员在实验室条件下将大珠母贝（Pinctada maxima, P. maxima）暴露于三丁基锡环境中，并确定了其慢性与急性毒性的浓度范围。使用PmaxArray 1.0微阵列（microarray）平台，对暴露于慢性毒性浓度的个体进行差异基因表达分析，并与对照组个体进行比对。经鉴定与三丁基锡暴露相关的差异表达基因包括免疫与解毒相关基因的上调，以及多个壳基质基因的下调。此外还鉴定出了多个全新的转录本（transcript）。研究人员结合三丁基锡毒性与壳体生物矿化过程，探讨了这些基因的潜在作用机制。本研究通过微阵列技术明确了三丁基锡对大珠母贝的转录调控效应，并提出壳体形成过程中存在全新组分的参与，有助于阐明该过程的分子机制。

为明确与三丁基锡暴露相关的转录本差异表达谱，研究人员将9只经50 ng·L⁻¹三丁基锡处理的个体，与9只未处理的对照个体，在双通道（Cy3和Cy5）cDNA微阵列（cDNA microarray）平台上进行比对分析。将9只对照个体的RNA混合作为通用参考样本，而9只处理个体的RNA则被分为3个混合重复样本，每个样本包含3只个体的RNA。每个处理重复样本与对照样本分别用Cy3或Cy5进行标记（处理组与对照组的荧光标记互为反向），并分别杂交至一张微阵列芯片，共计3张芯片。每张芯片的左右两侧均印制了重复的点样网格，以实现技术重复。最终共计完成6张微阵列芯片的杂交与分析，包含3次生物学重复，每次生物学重复对应2次技术重复。