Evaluation of quantitative variation in gene expression.
We investigate the behaviour of the gene-expression rate as a statistical variable using autoradiographic data for 39 transcripts from a heterogeneous set of 80 breast-tissue cultures. Despite standardization, the data distributions of all transcripts showed intervals of normality and intervals of systematic departure from normality which most frequently resulted in a significant skewness and/or kurtosis. Non-normal shapes are attributed to modulation of gene expression. This statistical particularity creates difficulties in the evaluation of differences among specimens. Using classical parametric and non-parametric procedures for normal and non-normal variation, respectively, we demonstrate that large differences in optical density are neither necessary nor sufficient for associating expression rates with biological factors. The transcripts coding for the metalloprotease stromelysin-3 (ST3) and for the receptor to insulin-like growth factors (IGFR) are used as examples and their variation is presented in detail. ST3 expression appeared to be specifically associated with mammary stroma fibroblasts derived from post-radiation fibrosis lesions. IGFR was expressed at higher rates in mammary gland and skin fibroblasts than in mammary epithelial cells and was subject to frequent and strong modulation.
Spanakis
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Institut d'Oncologie Cellulaire et Moléculaire Humaine, Bobigny, France.
Brouty-Boyé
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D
D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D014644:Genetic Variation; D006801:Humans; D053507:Matrix Metalloproteinase 11; D008666:Metalloendopeptidases / Q000235:genetics*; D017451:Receptors, Somatomedin / Q000235:genetics*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D017451:Receptors, Somatomedin; D053507:Matrix Metalloproteinase 11; D008666:Metalloendopeptidases