The connexin43-dependent transcriptome during brain development: importance of genetic background

Use of null mutant mice is a powerful way to evaluate the role of specific proteins in brain function. Studies performed on knockout mice have revealed some unexpected roles of the gap junction proteins (the connexins). Thus, analyses of gene expression in connexin43 (Cx43) null brains indicated that deletion of a single gene (Gja1) induced expression level change of numerous other genes located on all chromosomes and involved in a wide diversity of functional pathways. The significant overlap between alterations in gene expression level, control and coordination in Cx43 knockout and knockdown astrocytes raised the possibility that Gja1 represents a transcriptomic node of gene regulatory networks. However, conditional deletion of Gja1 in astrocytes of two mouse strains resulted in remarkably different phenotypes. In order to evaluate the influence of the genetic background on the transcriptome, we performed microarray studies on brains of GFAP-Cre:Cx43f/f C57Bl/6 and 129/SVEV mice. The surprisingly low number of Cx43 core genes (regulated in all Cx43 nulls regardless of strain) and the high number of differently regulated genes in the two Cx43 CKOs indicate high influence of mouse strain on brain transcriptome. The transcriptomes of WT and Cx43 null brains from both C57Bl/6 and SVEV strains were profiled and compared at perinatal and adult time points to learn more about the strain dependence of the Cx43-null phenotype. For this purpose, differently labeled cDNAs from biological replicas (4 of each genotype) were co-hybridized with Duke MO36K mouse oligonucleotide array spotted with 36k Operon oligonucleotides V4.0.