Control and variability of gene expression in mouse brain and in a neuroblastoma cell line

We used cDNA microarrays to examine the extent to which the expression of individual genes varies in mouse brain and in cultured N2A neuroblastoma cells mRNA extracted from sixC57B1/6J neonatal mouse brains and from four distinct cultures of N2A neuroblastoma cells was cross-hybridized with ten AECOM cDNA microarray chips to determine the individual gene expression variability. A mathematical algorithm reduced the effect of potential sources of variability not associated to the biological material by about 80%. The interval estimates of the standard deviation of individual gene expressionwere determined through chi-square statistics. The newly introduced relative expression variability, defined as the quotient of the middle of the interval estimate of the standard deviation and the mean expression ratio (and its inverse, gene transcription control), was used to rank the most unstably and the most stably transcribed genes. In brains of different animals and in separate cultures of N2A cells, unique sets ofgenes exhibited exceptional stability or were highly variable. Possible implications for such tight or loose transcriptional control are discussed.

Transcriptomic characterization of four classes of cell-cell/cell-matrix genes in brains and hearts of wild type and connexin43 null mice

We have used a highly quantifiable cDNA microarray method to determine the stabilities and expression levels within gene families involved in cell-cell and cell-matrix interactions in neonatal mouse brain and heart. In addition, we have characterized the extent to which deletion of the gap junction protein connexin43 (Cx43) affects these characteristics. Our observations for individual genes revealed a range of differences and variabilities in transcription level among family members; calculation of the genomic patholog (a global measure of gene expression alteration) indicates that these cell interaction genes contribute disproportionately to the overall phenotype. We found significant transcriptomic differences between brain and heart, that deletion of Cx43 considerably decreased gene expression variability and that the average contribution to the pathology of the genes whose encoded proteins are involved in cell-cell or cell-matrix interaction in the Cx43-null mice was about twenty times higher than that of other genes. These findings indicate that gap junction gene expression influences the expression of other genes involved in intercellular and cell-substrate interaction and that expression of these genes is under strong regulatory pressure in the Cx43-null mouse, presumably representing a compensatory response to Cx43 deletion.

[Transcription regulation and coordination of some cell signaling genes in brain and heart of connexin 43 null mouse]

We performed a cDNA microarray study of the transcription regulation and coordination of four gene families whose products are involved in cell-cell and cell-matrix interaction (ADAM, integrin, MMP, TNF) within brain and hearts of wildtype (WT) and connexin43 null (KO) neonatal C57Bl/6j mice. The study revealed that both WT brain and heart exhibit significant correlations among the transcriptions of cell-signaling genes and that depletion of Cx43 regulates both their expression and coordination. Adam8 was identified as the command gene of the group in WT and Mmp2 in KO, while Tnsf6 plays the dominant role in both WT and KO heart. Our results suggest that the functional coordination of cell-signaling proteins may be related to the expression coordination of the corresponding genes presumably to ensure the efficiency of the functional pathways and that intercellular communication modulates cell-cell and cell-matrix interaction.