Mixture modeling of transcript abundance classes in natural populations

BACKGROUND: Populations diverge in genotype and phenotype under the influence of such evolutionary processes as genetic drift, mutation accumulation, and natural selection. Because genotype maps onto phenotype by way of transcription, it is of interest to evaluate how these evolutionary factors influence the structure of variation at the level of transcription. Here, we explore the distributions of cis-acting and trans-acting factors and their relative contributions to expression of transcripts that exhibit two or more classes of abundance among individuals within populations. RESULTS: Expression profiling using cDNA microarrays was conducted in Drosophila melanogaster adult female heads for 58 nearly isogenic lines from a North Carolina population and 50 from a California population. Using a mixture modeling approach, transcripts were identified that exhibit more than one mode of transcript abundance across the samples. Power studies indicate that sample sizes of 50 individuals will...背景：在遗传漂变（genetic drift）、突变积累（mutation accumulation）与自然选择等进化过程的影响下，种群的基因型与表型会发生分化。由于基因型通过转录过程映射至表型，因此探究上述进化因子如何影响转录层面的变异结构具有重要研究意义。本文旨在分析顺式作用因子（cis-acting）与反式作用因子（trans-acting）的分布模式，及其对种群内个体间存在两类及以上丰度类别的转录本表达的相对贡献。 结果：本研究以黑腹果蝇（Drosophila melanogaster）成年雌性头部组织为实验材料，利用cDNA微阵列（cDNA microarray）开展表达谱分析，所用样本包含来自北卡罗来纳州种群的58个近等基因系（nearly isogenic lines）以及来自加利福尼亚州种群的50个近等基因系。本研究采用混合模型法（mixture modeling approach），鉴定出在样本中呈现多种转录本丰度分布模式的转录本。效力分析（power studies）结果表明，当样本量为50个个体时……