The function of nonmuscle myosins during oogenesis in Caenorhabditis elegans

Abstract

Oogenesis in C. elegans requires the activity of type II nonmuscle myosins, complexes containing two heavy and four light chains that bind and move actin. Two different complexes are found in the gonad, differing in their heavy chains, (NMY-1 versus NMY-2). These two myosins are redundant during embryonic elongation, and we expected them to also be redundant during oogenesis. Instead, both myosins are required, but their requirement differs at different stages. NMY-2 is required for maintenance and then closure of the ring channels, while both NMY-1 and NMY-2 are required for cytoplasmic streaming. Finally, NMY-1 is required for ovulation. Loss of MLC-4, the regulatory light chain, did not reveal phenotypes other than those seen with the loss of either myosin, meaning that the myosins do not act redundantly during oogenesis. Therefore, the different heavy chains apparently allows differential regulation of separate functions during this process.