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Defective Gap-Junctional Communication Associated with Imaginal Disc Overgrowth and Degeneration Caused by Mutations of the dco Gene in Drosophila

Jursnich, Victoria A. and Fraser, Scott E. and Held, Lewis I., Jr. and Ryerse, Jan and Bryant, Peter J. (1990) Defective Gap-Junctional Communication Associated with Imaginal Disc Overgrowth and Degeneration Caused by Mutations of the dco Gene in Drosophila. Developmental Biology, 140 (2). pp. 413-429. ISSN 0012-1606.

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The lethal(3)discs overgrown (dco) locus of Drosophila melanogaster, located on the third chromosome at cytogenetic position 100A5,6–100B1,2, is necessary for normal development and growth control in the imaginal discs of the larva. Three recessive lethal alleles (dco^2, dco^3, and dco^(18)) in heteroallelic combinations and one allele (dco^3) when homozygous cause the imaginal discs to continue to grow beyond the normal disc-intrinsic limit during an extended larval period. Some degeneration also occurs in the overgrowing discs. The discs overgrow even when transplanted early in their development into wild-type hosts, whereas normal discs stop growth at about the normal final size under such conditions, indicating that the overgrowth is a disc-autonomous effect of the mutations. During overgrowth the imaginal discs retain their single-layered epithelial structure except near regions of degeneration, and they differentiate into disc-appropriate but abnormal adult structures when transplanted into wild-type larval hosts. When the mutant larvae are reared under certain conditions a small percentage develop to the pharate adult stage, and these animals show a characteristic syndrome of abnormalities including swollen leg segments with many extra bristles, small or missing eyes, duplicated antennae and palpi, and separated vesicles of cuticle. A fourth recessive lethal allele (dco^(le88)), when homozygous or in heteroallelic combination with the overgrowth alleles, causes the imaginal discs to degenerate, producing a “discless” phenotype. Gap junction-mediated communication was assayed by observing the intercellular transfer of injected fluorescein complexon (dye coupling). Dye coupling in the imaginal discs of the dco genotypes that cause overgrowth was dramatically reduced at 4 days after egg laying (AEL) compared with wild-type controls. Coupling was more normal although still significantly reduced at 7–8 and 12–14 days AEL. In c43^(hs1), another disc overgrowth mutant, the imaginal disc cells also showed very reduced dye coupling at 4 days and incomplete coupling at 9 days. In contrast, discs from wild-type larvae, two other imaginal disc overgrowth mutants, and a cell death mutant showed extensive dye coupling at all stages tested. Electron microscopic morphometry revealed a reduction in gap-junction length per unit lateral plasma membrane length in dco3dco18 and c43^(hs1) wing discs, although not in dco2dco3, compared with wild-type wing discs. The results suggest that gap-junctional cell communication may be involved in the cell interactions that limit cell proliferation in vivo.

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Fraser, Scott E.0000-0002-5377-0223
Additional Information:© 1990 Academic Press, Inc. Accepted 2 May 1990. We thank Kathleen Matthews and Dr. Thomas Kaufman for drawing our attention to the dco mutants and for providing stocks and unpublished results. We thank Dr. John Merriam for many useful discussions, stocks and unpublished results and Dr. Elizabeth Frayne for help with the epidermal preparations. This investigation was supported by grants from the American Cancer Society (PJB), the Monsanto Company (PJB & JSR) and the National Science Foundation (SEF, LIH).
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American Cancer SocietyUNSPECIFIED
Monsanto CorporationUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20160308-074027025
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ID Code:65173
Deposited By: Ruth Sustaita
Deposited On:08 Mar 2016 17:08
Last Modified:03 Oct 2019 09:44

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