ANALYSIS OF TEMPERATURE SENSITIVE CYK-1 MUTATIONS EFFECT ON MUSCLE DEVELOPMENT ON CAENORHABDITIS ELEGAN SLARVAE

Abstract

Sarcomeres are the most basic unit of muscle cells. Formins are actin regulatory proteins that are important for actin filament polymerization and nucleation, and might be responsible for the actin filamentassembly in sarcomeres. In Caenorhabditis elegans, two formins (CYK-1 and FHOD-1) were found in the body wall muscle (BWM), specifically in the Z-line of sarcomeres. Previously, BWM were analyzed in null cyk-1(ok2300) mutant worms, derived from heterozygous parents, and fhod-1(tm2363) mutantworms, andwere found to have smaller muscles than wild-type worms. Yet, there was still functional CYK-1 present in the worms due to inherited maternal CYK-1. To eliminate this potential source of CYK-1, cyk-1(or596ts) temperature sensitive mutant worms were used to allow for all CYK-1 to be non-functional at 26°C. The focus of this study was to understand the importance of cyk-1on muscle development in C. eleganslarvae. Wild-type, fhod-1(tm2363), cyk-1(or596ts), and fhod-1(tm2363);cyk-1(or596ts) double mutant wormsat L1 larval stage were observed for worm shape and muscle abnormalities. Abnormal worm shapes were observed in fhod-1, cyk-1, and more commonly in fhod-1;cyk-1mutant worms at permissive and restrictive temperatures. Abnormal muscle was observed in both permissive and restrictive temperatures forfhod-1, cyk-1, and fhod-1;cyk-1mutant worms that had abnormal worm shapes, while all worms that had normal body shape usually had normal muscle at both temperatures. Worms were alsotested to determine long-termeffects of cyk-1and fhod-1mutations on muscle development. Worms were held at permissive or restrictive temperatures for various times. Fhod-1and cyk-1mutant worms showed reduced muscle size compared to wild-type, while fhod-1;cyk-1mutant worms displayed a more severelyreduced muscle size. Next, cyk-1orfhod-1were tested to see whether they can rescue muscle cell size after mosaic expressionin a cyk-1(-) or fhod-1(-) mutant worm background. Fhod-1(+) muscle cells showeda significant increase in muscle cell size compared to fhod-1(-) cells, while cyk-1(+) muscle cells showeda non-significant increase in muscle size compared to cyk-1(+/-) cells. This shows cell-autonomousexpressionoffhod-1influencesmuscle growth, while cyk-1expression in another organ might influence muscle development.