GAP JUNCTION DISTRIBUTION IN THE DROSOPHILA WING DISK MUTANT-VG,MUTANT-I(2)GD, MUTANT-I(3)C43HS1, AND MUTANT-I(2)GL4

The density of gap junctions in 4 D. melanogaster mutants with abnormal wing disc development was determined using quantitative EM and compared with the gap junction density in wild-type wing discs. No appreciable differences relative to wild-type controls were found in the cell death mutant vestigial or in the mildly hyperplastic mutant lethal giant disc which could not be accounted for in terms of altered lateral plasma membrane surface density or as an extension of the gap junction growth which normally occurs during the 3rd larval stage of development in wild-type wing discs. Both the severely hyperplastic mutant l(3)c43hs1 and the neoplastic mutant lethal giant larva have significant reductions in the gap junction surface density, the number of gap junctions, and the gap junction areal fraction of the lateral plasma membrane compared with wild-type controls. These differences cannot be attributed to altered lateral plasma membrane surface densities which are not significantly different from wild-type control wing discs. The reduced gap junction density in severely hyperplastic and neoplastic wing discs suggests that alterations in the number or distribution of gap junctions may be as disruptive to normal growth and development as their complete absence.