ALTERED GAP JUNCTIONAL COMMUNICATION, INTERCELLULAR SIGNALING, AND GROWTH IN CULTURED ASTROCYTES DEFICIENT IN CONNEXIN43

Astrocytes are characterized by extensive intercellular communication mediated primarily by gap junction channels composed of connexin43. To examine this junctional protein in astrocytic functions, astrocytes w ere cultured from embryonic mice with a null mutation in the connexin4 3 gene (Reaume et al.: Science 267:1831-1834, 1995). Using anti-Cx43 a ntibodies, immunoblotting and immunostaining indicated that homozygous null astrocytes were devoid of Cx43. They are also deficient in inter cellular dye transfer. Astrocytes cultured from heterozygous embryos e xpress significantly lower Cx43 compared to wild type, and their dye c oupling is reduced. Markers of glial differentiation, such as glial fi brillary acidic protein and S100, appeared similar in all genotypes. M easurement of intercellular calcium concentration following mechanical stimulation of confluent astrocytes revealed that the number of cells affected by a rise in intracellular calcium was reduced in homozygous cultures compared to wild type. In fact, the calcium response in homo zygous astrocytes was similar to that observed in wild-type astrocytes in the presence of a gap junction blocker. The growth rate of astrocy tes lacking Cx43 was reduced compared to wild-type astrocytes. These r esults suggest that gap junctional intercellular communication mediate d by Cx43 is not critical for astrocyte differentiation but is likely involved in the regulation of intercellular calcium signaling and cell growth. (C) 1997 Wiley-Liss, Inc.