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Ring Canals

Ring canals are structures through which intercellular material can pass from the nurse cells to the oocyte of developing Drosophila (and other Dipterans) embryos.  These ring canals are actually arrested cleavage furrows yet rather than contracting and dpepolymerising as they do so as the normal cleavage furrow does, the ring canal increases in every dimention during development of the follicles (Tilney et al, 1996).  A variety of proteins involved in ring canal structure and development have been identified in screens designed for mutants unable to form these structures, some of these mutants ((hu-li tai shao & Kelch) have turned out to be in genes controlling or encoding actin-binding proteins; Adducin,  and Kelch (Robinson et al, 1994) respectively.  Other ABP are known to be constituents of ring canals (table 1).

Protein Function Reference
Adducin binds spectrin to F-actin (Li & Sprading, 1992)
Annilin bundles F-actin (Field, & Alberts, 1995)
Fascin bundles F-actin (Cant et al, 1994)
Filamin cross-links actin & binds to membrane components (Li et al, 1999)
Kelch dimeric bundling (Robinson et al, 1994; Kelso et al, 2002)


Cant, K.,  Knowles, B.A., Mooseker, M.S. & Cooley, L. (1994). Drosophila singed, a fascin homolog, is required for actin bundle formation during oogenesis and bristle extension. J.Cell Biol. 125(2), 369-380.

Field, C.M. & Alberts, B.M. (1995). "Anillin, a contractile ring protein that cycles from the nucleus to the cell cortex." J.Cell Biol. 131, 165-178.

Kelso, R. J., Hudson, A. M. & Cooley, L. (2002) Drosophila kelch regulates actin organization via Src64-dependent tyrosine phosphorylation., J.Cell Biol. 156, 703-713.

Li, M.-g., Serr, M., Edards, K., Ludmann, S., Yamamotot, D., Tilney, L.G., Field, C.M. & Hays, T.S. (1999). " Filamin is required for ring canal assembly and actin organization during Drosophila oogenesis." J.Cell Biol. 146(5), 1061-1074.

Robinson, D. N., Cant, K.  &  Cooley, L. (1994). "Morphogenesis of Drosophila ovarian ring canals." Development 120, 2015-2025.

Robinson, D.N. & Cooley, L. (1996). "Stable intercellular bridges in development: the cytoskeleton lining the tunnel." Trends Cell Biol. 6, 474-479.

Tilney, L.G., Tilney, M.S. & Guild, G.M. (1996). "Formation of actin filament bundles in the ring canals of developing Drosophila follicles." J.Cell Biol. 133(1), 61-74.

Yue, L., & Spradling, A.C. (1992). "hu-li tai shao, a gene required for ring canal formation during Drosophila oogenesis, encodes a homolog of adducin." Genes Dev. 6, 2443-2454.

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