Cell Shape and Interaction Defects in α-Spectrin Mutants of Drosophila melanogaster

• Published in: The Journal of cell biology 1993-12, Vol.123 (6), p.1797-1809
• Main Authors: Lee, John K., Coyne, Robert S., Dubreuil, Ronald R., Lawrence S. B. Goldstein, Branton, Daniel
• Format: Article
• Language: English
• Subjects: Alleles; Amino Acid Sequence; Animals; Base Sequence; Biochemistry. Physiology. Immunology; Biological and medical sciences; Blotting, Southern; Cell membranes; Cells; Chromosome Mapping; Cloning, Molecular; Digestive System - metabolism; Digestive System - ultrastructure; DNA, Complementary - genetics; DNA, Complementary - isolation & purification; Drosophila; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Epithelial cells; Fundamental and applied biological sciences. Psychology; Gamma Rays; Gene Expression - radiation effects; Genetic Complementation Test; Immunoblotting; Insecta; Interstitial cells; Invertebrates; Larva; Larvae; Larval development; Microvilli; Midgut; Molecular Sequence Data; Mutation; Physiology. Development; Polymerase Chain Reaction; Restriction Mapping; Sodium-Potassium-Exchanging ATPase - analysis; Spectrin - analysis; Spectrin - biosynthesis; Spectrin - genetics
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.123.6.1797

We show that the α-spectrin gene is essential for larval survival and development by characterizing several α-spectrin mutations in Drosophila. P-element minigene rescue and sequence analysis were used to identify the α-spectrin gene as the l(3)dre3 complementation group of the Dras-Roughened-ecdysoneless region of chromosome 3. Germ line transformants carrying an α-spectrin cDNA, whose expression is driven by the ubiquitin promoter, fully rescued the first to second instar lethality characteristic of the l(3)dre3 alleles. The molecular defects in two γ-ray-induced alleles were identified. One of these mutations, which resulted in second instar lethality, contained a 37-bp deletion in α-spectrin segment 22 (starting at amino acid residue 2312), producing a premature stop codon between the two EF hands found in this segment. The second mutation, which resulted in first instar lethality, contained a 20 base pair deletion in the middle of segment 1 (at amino acid residue 92), resulting in a premature stop codon. Examination of the spectrin-deficient larvae revealed a loss of contact between epithelial cells of the gut and disruption of cell-substratum interactions. The most pronounced morphological change was seen in tissues of complex cellular architecture such as the middle midgut where a loss of cell contact between cup-shaped cuprophilic cells and neighboring interstitial cells was accompanied by disorganization of the cuprophilic cell brush borders. Our examination of spectrin deficient larvae suggests that an important role of non-erythroid spectrin is to stabilize cell to cell interactions that are critical for the maintenance of cell shape and subcellular organization within tissues.