Immortalized connexin43 knockout cell lines display a subset of biological properties associated with the transformed phenotype

Immortalized cells from embryonic connexin43 knockout mice (Cx43(-/-)) and homozygous littermates (Cx43(+/+)) were cloned and characterized to determine whether the absence of Cx43 function would induce observable phenotypic changes. Cells of the Cx43(+/+) clones expressed Cx43 and engaged in gap junctional communication with 10-12 neighboring cells. The Cx43(-/-) cells were devoid of Cx43 and communicated to less than 1 cell. Electrophysiological analysis indicated that the Cx43(-/-) cells communicated through Cx45 channels from 8-80-fold less than did the Cx43(+/+) subclones, which seemed to communicate through Cx43 and Cx45 channels. The Cx43(-/-) clones grew at faster rates and to higher saturation densities, had a more spindly morphology, were more refractile, and adhered less well to the substratum than did the Cx43(+/+) clones. Reintroducing the Cx43 gene into the Cx43(-/-) clones resulted in three subclones that communicated to 3-4 cells. Partial restoration of gap junctional communication in the three subclones was accompanied by reduced growth rates and saturation densities (2-fold compared to that of parental Cx43(-/-) clones) but no reversions in morphology or cell-substratum adhesion. The increased growth rates and saturation densities, altered morphology, and decreased cell adhesion displayed by the Cx43(-/-) clones reflect a subset of the properties of transformed cells. These studies advance the hypothesis that loss of Cx43 function during development may cause cells to acquire a preneoplastic condition.