Cell shape and interaction defects in alpha-spectrin mutants of Drosophila melanogaster.
We show that the alpha-spectrin gene is essential for larval survival and development by characterizing several alpha-spectrin mutations in Drosophila. P-element minigene rescue and sequence analysis were used to identify the alpha-spectrin gene as the l(3)dre3 complementation group of the Dras-Roughened-ecdysoneless region of chromosome 3 (Sliter et al., 1988). Germ line transformants carrying an alpha-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 gamma-ray-induced alleles were identified. One of these mutations, which resulted in second instar lethality, contained a 73-bp deletion in alpha-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.
Lee
J K
JK
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Coyne
R S
RS
Dubreuil
R R
RR
Goldstein
L S
LS
Branton
D
D
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004064:Digestive System / Q000378:metabolism / Q000648:ultrastructure; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D005720:Gamma Rays; D015870:Gene Expression / Q000528:radiation effects; D005816:Genetic Complementation Test; D015151:Immunoblotting; D007814:Larva; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013049:Spectrin / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*
D018076:DNA, Complementary; D013049:Spectrin; D000254:Sodium-Potassium-Exchanging ATPase