Modest alterations in Drosophila denticle morphology reveal genetic interactions between actin disassembly proteins...

Building and disassembling actin filaments is essential for the remodeling of the actin cytoskeleton. In large structures, like Drosophila bristles, the loss of function of actin disassembly proteins can lead to smaller and misshapen bundled actin. Here we investigate whether mutant alleles of the disassembly genes twinstar (tsr), flare (flr), and twinfilin (twf) show similar phenotypes in smaller embryonic actin-based denticles. We also examined potential genetic interactions between F-actin disassembly proteins and the molecular motor ck/myosin VIIA, a protein necessary for denticle formation.

Cuticle preparations of late-stage embryos were examined for denticle hook orientation, height, and width. There were mild morphological phenotypes such as loss of hook polarity across the genes. Single mutants for the disassembly genes showed that loss of tsr caused denticles to be longer, loss of twf resulted in shorter denticles, and mutant flr alleles showed varied effects. Double mutants of tsr and twf showed a genetic interaction in widths of denticles while ck was epistatic to twf and flr for width.

These results demonstrate that actin disassembly proteins and ck/myosin VIIA are involved in denticle formation, and the lack of wild type gene function in tsr, twf, flr, and ck causes measurable defects in denticle morphology.